8:00-8:05 - Opening Remarks (JHN-170)
8:05-9:35 - Session 1: Tectonic Processes, from Earthquakes to Mountain Building (JHN-170)
8:05 Shelley Chestler: How does slip occur during low-frequency earthquakes?
8:20 Carolyn Nuyen: A Search for Long-term Slow Slip Along the Cascadia Subduction Zone
8:35 Kelley Hall: Comparisons of Tremor and Slow Slip in Cascadia ETS Events
8:50 Mika Thompson: Sedimentary Basin Amplification in the Puget Sound Region: Observations from Local Earthquakes and 3D Simulations
9:05 Ian Stone: Catalog of Nearshore Seismicity in the Pacific Northwest from the Cascadia Initiative OBS Data
9:20 Sean LaHusen: Quantifying changes in catchment-wide erosion rates following widespread coseismic landsliding in the Seaward Kaikoura Mountains, New Zealand
9:35-9:45 Break
9:45-10:15 - Session 2: Volcanoes and Magma Chamber Dynamics (JHN-170)
9:45 Carl Ulberg: Local Earthquake P-wave Tomography at Mount St. Helens with the iMUSH Broadband Array
10:00 Jill Schleicher: Investigating the plumbing system of Mauna Loa volcano, Hawaii, with crystal populations from the 1868 picrite eruption
10:15-10:25 - Break
10:25-11:10 - Session 3: Leaving Earth: Developments in Cutting Edge Space Technology (JHN-170)
10:25 Paige Northway: Plasma for Propulsion and Composition
10:40 Manuel Azuara Rosales: Air-Breathing Pulsed Plasma Thruster with a Variable Spacing Cathode for Atmospheric Satellite Applications
10:55 Karine Chen: Design and Construction Methods of A Single Stage Rocket Measuring Pressure Dynamics
11:10-11:20 - Break
11:20-12:20 - Session 4: Planetary Science: Dust, Plasma, Extremophiles, and More (JHN-170)
11:20 Owen Lehmer: Early Hydrodynamic Escape Limits Rocky Planets to ≤1.6 Earth Radii
11:35 Steven Sholes: How Many Blue Whales on Mars? Obtaining a Maximum Extant Biomass on Mars using CO Antibiosignatures
11:50 Matt Tilley: Active M-dwarf Effects on an Earth-like Planet in the Habitable Zone
12:05 Chloe Hart: Energetics of Acidianus ambivalens during aerobic growth on sulfur and varying nutrient availability
12:20-1:20 - Lunch Break
1:20-2:05 - Session 5: Future ESS Research (JHN-170)
1:20 Emma Myers: Diving into new active source seismic data offshore Chile
1:35 Ariane Ducellier: Imaging of the oceanic subducting plate from observations of low-frequency earthquakes in Cascadia
1:50 Erik Goosmann: Measuring paleoatmospheric pressure using grain-size distributions of aeolianites
2:05-2:15 - Break
2:15-2:45 - Session 5: Future ESS Research (continued) (JHN-170)
2:15 Sarah Harbert: The Evolution of a Transform Plate Boundary: Thermochronology in the Marlborough Fault System, New Zealand
2:30 Virginia Littell: Tracing the intensity of the Asian Monsoon across the Eocene-Oligocene Transition using oxygen isotopes
2:45-3:00 Session 6: River Response and Processes (JHN-170)
2:45 Sarah Schanz: Multiple paths to straths: re-evaluating strath terrace genesis
3:00-3:30 - Seminar Snacks
3:30-5:00 - Colloquium: Isaac Larson, keynote speaker (JHN-102)
8:15-9:45 - Session 7: Geochemistry and Geochronology: Methods and Applications (JHN-170)
8:15 Landon Burgener: Isotope disequilibrium in soil carbonates from diverse high-elevation and high-latitude environments
8:30 Keith R. Hodson: Reconstructing fluid sources for past episodes of fluid flow along the Moab Fault, Utah
8:45 Nicolas Cuozzo: Understanding Chemical Weathering in Cold, Dry Environments using Magnesium Isotopes
9:00 Yan (Emma) Hu: High-precision measurements of non-traditional stable isotopes by second-generation MC-ICP-MS: challenges and outlooks
9:15 Joel Gombiner: Exploring North American geochronology databases
9:30 Khadijah K. Homolka: Determination of the Small-Scale Sediment Accumulation Rates in Andvord Bay Fjord on the Western Antarctic Peninsula using 210 Pb Geochronology
9:45-9:55 - Break
9:55-10:40 Session 8: Early Earth Evolution (JHN-170)
9:55 Joshua Krissansen-Totton: Early Earth the Exoplanet: Disequilibrium biosignatures in Earth’s atmosphere-ocean system since 4.0 Ga
10:10 Michael Kipp: Nitrogen cycling in the Precambrian: New insights from isotopes and box models
10:25 Matthew C. Koehler: Nitrogen isotopes record transient surface oxygenation in the ~2.7 Ga Jeerinah Formation
10:40-10:50 - Break
10:50-11:35 Session 9: Pre-UW Work (JHN-170)
10:50 Eric Keenan: Observations of M2 Tidal Propagation and Decay along the West Coast of Spitsbergen: New Possibilities for Numerical Model Evaluation
11:05 Mattias Needle: Scaled Physical Experiments of Salt Flow Subparallel to Basement-Involved Normal Faults
11:20 Jana Meixnerova: Hydrocarbon preservation in shales and carbonate concretions of the 1.1 Ga Nonesuch Formation
11:35-12:35 - Lunch Break
12:35-2:20 - Session 10: Tales from the Ice (JHN-170)
12:35 Laura Kehrl: The search for the oldest ice: Allan Hills Blue Ice Area, Antarctica
12:50 Emma Kahle: Some nitty gritty details about measuring diffusion of water isotopes in ice cores
1:05 Brita I. Horlings: Identifying viscosities implicit in current firn-densification models: a step toward a physical-process-based constitutive relation for firn
1:20 Trevor Hillebrand: Delayed deglaciation of Darwin Glacier, Antarctica
1:35 Bradley R. Markle: Non linear water isotope reconstruction
1:50 Alex Huth: Simulating Ice Shelf Response to Potential Triggers of Collapse
2:05 John Erich Christian: Examining transient glacier responses to climate forcing
2:20-2:30 - Break
2:30-3:30 - Poster Session (JHN 100-level Hallway)
Taryn Black: Housing and lifestyle patterns among ESS graduate students
Cassandra Brigham: Investigating the style and tempo of bedrock fault scarp degradation in southern Iceland
Addien Wray: Strange Diets: A Thermodynamic Description of Microbial U(VI) Reduction
Paige Wilson: Environmental Change and Plant Response Across the Cretaceous-Paleogene Boundary in North America: A Study in the Hell Creek Area of NW Montana
William Grimm: Shallow Landslide Susceptibility Study of Magnolia Area, Seattle, WA
Jimmy O'Neil: Design and Development of the “3U Cubesat” Satellite Chassis
Annika N. Horlings: Firn Compaction in Regions of Dynamic Ice Flow
Ari Newman: Validation of high resolution isotope measurements on the South Pole ice core
C. Max Stevens: Evolution of air content in Greenland firn using the UW Community Firn Model
Nancy A. Sackman: Earthquake Relocation near Spirit Lake
Zack McIntire: On the fabric and microstructure of magmatic granular flows
Brittany McManus: Putting Science back in Political Science: Th)e state of science representation in politics
5:00-9:00 - Reception and Closing Ceremony (Vista Cafe)
The movement of tectonic plates drives many processes including mountain building, stress loading and release on faults, and more. This session focuses on a variety of tectonically driven processes including earthquakes (both fast and slow), the evolution of fault systems, and the growth and decay of mountain ranges.
Shelley Chestler (Talk): How does slip occur during low-frequency earthquakes?
Low-frequency earthquakes (LFEs) are tiny, repeating earthquakes that make up tectonic tremor. LFEs occur during slow slip events (SSEs) in subduction zones worldwide (e.g. Japan, Cascadia, the Aleutians, and Mexico) and some strike-slip settings (e.g. the San Andreas Fault) and are thought to be localized asperities that rupture more seismically than the surrounding regions. How much slip occurs during an LFE, and over what area? While we can invert GPS data for the amount of slip and rupture area for SSEs, we cannot directly measure slip and slip area for LFEs. We present three potential models for LFE rupture, (1) where each LFE ruptures the entire LFE family patch, (2) where LFEs rupture small sub-patches within the LFE family patch, and (3) where LFEs slip over small regions within an ductile matrix. Using observations of LFE moment-frequency distributions and relative LFE locations we distinguish between these three models.
Carolyn Nuyen (Talk): A Search for Long-term Slow Slip Along the Cascadia Subduction Zone
We examine GPS data from the PBO and PANGA networks to determine whether or not Cascadia has hosted a long-term slow slip episode (SSE) in the past ~20 years. A preliminary review of the time series data does not reveal any large-scale multi-year transients, such as has been documented in Japan and Alaska where over 5 cm of surface displacement is seen over multiple years. In order to more clearly recognize possible small amplitude long-term SSEs in Cascadia, the GPS data are reduced using two methods. The first method involves cleaning detrended time series GPS data by removing (1) continental water loading terms, (2) transient displacements of known short-term SSEs, and (3) common mode signals that span the network. The second method decomposes raw time series GPS data into trend, seasonal, and remainder components using locally weighted regression analysis. Cleaned GPS data from the first method and the trend component data from the second method are then manually inspected for coherent aberrations between stations. To further identify small amplitude slip events that persist for months-to-years, we invert the time series in Cascadia for fault slip using a principle component analysis-based inversion method. Results from this research have direct implications for Cascadia in terms of moment release, stress redistributions, and seismic cycles. In a broader sense, these results also influence the global knowledge of SSEs by giving a better understanding of the full range of slip modes in Cascadia.
Kelley Hall (Talk): Comparisons of Tremor and Slow Slip in Cascadia ETS Events
The interplay between tremor and slow slip during ETS has implications for the state of stress and friction of a fault. In particular, in regions of the Cascadia Subduction zone where we have no direct measurements of the state of the fault. It has been shown that tremor occurs in a narrow strip along the plate interface, and has been shown to have a relatively distinct up-dip boundary [Wech and Creager, 2008]. However, as shown by Houston (AGU abstract, 2012) and Hall and Houston (AGU abstract 2014), slip inferred from GPS can extend updip of the seismically-detected tremor. Following the methods used on the 2010 ETS event, I used the PANGA GPS to measure the displacement vectors for 71 stations to analyze several large ETS events from 2007 - 2016 in order to look for persistent patterns of slip in comparison to tremor. I implemented Principal Component Analysis to automatically select the direction and magnitude of the maximum displacement vector. I then inverted these GPS displacements for slip, using the Okada formulation of buried rectangular faults in a halfspace with a grid of 8 by 8 km subfaults based on the McCrory slab model. I performed inversions with either 0th or 2nd order Tikhonov regularization. For each event I compared two different inversions, one where slip was allowed on a broad unrestricted regional grid (URI) and a tremor-restricted inversion (TRI) where slip was restricted to grid locations where tremor had been detected. I found that for every ETS event the TRI fit the data significantly worse than the URI. Additionally, it forced the slip to the updip edge of the grid where it reached above 10 cm, which is physically implausible given that this exceeds the slip that can accumulate in an inter-ETS time period. The regional grid inversion indicates that significant slip of 1 to 2 cm occurred 10’s of km updip of the western edge of tremor. This further supports the inference from the 2010 event that in northern Washington, the slow slip during an ETS event extends many kilometers updip of the western edge of tremor. The occurrence of aseismic slow slip updip indicates a possible change if fault properties that discourage the release of seismic energy.
Mika Thompson (Talk): Sedimentary Basin Amplification in the Puget Sound Region: Observations from Local Earthquakes and 3D Simulations
Sedimentary basins in the Puget Sound region, Washington State can increase ground motion intensity and duration of shaking of local earthquakes. Frankel et al. (2009) showed clear evidence of amplification in the Seattle basin due to S-wave focusing, conversion of S-waves to surface waves by the southern basin edge bounded by the Seattle fault zone, and directional dependence of amplification on source location. We calculate spectral ratios from recordings at Pacific Northwest Seismic Network and U.S. Geological Survey stations for local earthquakes with varying magnitudes, depths, and azimuths to compare the amplitudes of seismic waves at basin stations to sites outside the basins. Amplification factors from spectral ratios are plotted on regional maps to study their spatial distribution. We model a set of local earthquakes (M3.7- 6.8) using the 3D finite-difference method and the latest revision of the 3D Cascadia velocity model (Stephenson, 2007), comparing observed and synthetic waveforms up to a frequency of 1 Hz. Preliminary results show peak amplitudes and S-wave and surface wave arrivals are fairly well matched. Synthetics also exhibit complex basin phases we see in observations. The goal of this project is to characterize and model sedimentary basin effects within the Seattle basin in Washington and the Tualatin and Portland basins in Oregon to improve estimates of ground shaking from future large earthquakes in the Pacific Northwest, which is critical for mitigating seismic hazard near major metropolitan centers.
Ian Stone (Talk): Catalog of Nearshore Seismicity in the Pacific Northwest from the Cascadia Initiative OBS Data
We have created a catalog of near-shore seismicity for the coasts of Washington, Oregon, and Northern California using data from the 4-year Cascadia Initiative OBS deployment. With amplitude-based filtration methods, we identified and located 270 earthquakes with epicenters located over, on and under the locked portion of the Cascadia megathrust fault, between the trench and shoreline. 74 of the events were already identified in regional land-based seismic catalogs. These earthquakes were found in regions both previously known and unknown to harbor seismicity. Event locations were found using SVD least-squares methods (Locsat and Hypoinverse), with depths updated from previous work. We quantify the completeness of our catalog by plotting the spatial and time distribution of stations used during event detection. We plan on further populating our catalog through the use of cross-correlation-based detection methods. Our long term goals include using the updated catalog to assess regional land-based seismic networks’ ability to locate offshore seismicity, assessing the ability of OBS networks to monitor seismicity, and ultimately to better understand earthquakes and tectonics along the Cascadia Subduction Zone.
Sean LaHusen (Talk): Quantifying changes in catchment-wide erosion rates following widespread coseismic landsliding in the Seaward Kaikoura Mountains, New Zealand
The 14 November 2016 M 7.8 Kaikoura Earthquake caused intense ground shaking along the northeast coast of the south island of New Zealand, triggering thousands of landslides in the Seaward Kaikoura Mountains. In many high relief mountain ranges around the world, landslides dominate sediment delivery to channels, thereby directly influencing the fluvial system and relief structure in orogens. When triggered by earthquakes, landslides are a widespread and significant agent of erosion, simultaneously swamping catchments with sediment and often damming rivers. Additionally, bedrock landsliding can have a great effect on detrital cosmogenic radionuclide (CRN) derived erosion rates, complicating efforts to quantify these rates in seismically active mountain belts. With a suite of detrital samples having already been collected before the earthquake, we are uniquely poised to answer the following outstanding questions central to the geomorphology and geochronology communities: 1) What effect does coseismic landsliding have on CRN derived basin wide erosion rates? and 2) What is the contribution of periodic but widespread coseismic landslides to erosional mass flux in the Kaikoura Mountains? We will address these questions through comparing detrital 10Be CRN measurements before and after the Kaikoura Earthquake in 8 streams that drain the Seaward Kaikoura Mountains. Results from this study will offer a unique dataset to help improve understanding of erosion processes and rates in the Seaward Kaikoura, and more broadly, how we measure and interpret catchment-wide erosion rates in tectonically active mountain belts in general.
Nancy A. Sackman (Poster): Earthquake Relocation near Spirit Lake
Swarms of earthquakes from 2006 to 2016 were relocated proximal to Mt. St. Helens and Spirit Lake to uncover geologic structure. 293 earthquakes with a depth to approximately 15 kilometers were identified within about a 19 kilometer radius of the crater of Mt. St. Helens. Eighteen seismic stations with 37 channels were used to create waveform data in MATLAB. A frequency range from 2 to 15 Hz was used to examine the seismic events. The waveform arrival times of the P (primary) and S (secondary) waves analyzed were 2 - 2.5 and 4 seconds respectively. A cross correlation function improved the accuracy of the arrival times by comparing the 293 earthquakes with each other. A cross correlation coefficient between 0 and 1 was generated with 0.5 chosen for this study. The cross correlation and lag times of the waveforms were input into a program called hypoDD. Hypo DD or “double difference” is the precise relative relocation of earthquake events. This function takes the difference of two earthquake arrival times and subtracts them from two seismic stations. Preliminary results show 200 earthquakes were relocated to depths over nine kilometers and about 4 kilometers east of Spirit Lake (12 kilometers northeast from the crater of Mt. St. Helens). Further modifications to the input codes are underway and additional iterations will be forthcoming to enhance relocation and identify structure.
What does the inside of a volcano look like? How do magma and crystals move within a magma chamber? This session focuses on a variety of volcano-related topics including magma chamber processes, volcano plumbing systems, as well as imaging and monitoring volcanoes using earthquakes.
Carl Ulberg (Talk): Local Earthquake P-wave Tomography at Mount St. Helens with the iMUSH Broadband Array
We deployed 70 broadband seismometers in the summer of 2014 to image the seismic velocity structure beneath Mount St. Helens (MSH), Washington, as part of the collaborative imaging Magma Under St. Helens (iMUSH) project. Our goal is to illuminate the MSH magmatic system by integrating all portions of the iMUSH experiment, including active- and passive-source tomography, ambient-noise tomography, seismicity, receiver functions, magnetotellurics, and petrology. The broadband array has a diameter of ~100 km centered on MSH with an average station spacing of 10 km, and was deployed through summer 2016. We determine P- and S-wave arrival times and also incorporate picks from the permanent network. There were more than 250 local events during the first year of iMUSH broadband recording, which have provided over 11,000 high-quality arrival times. The iMUSH experiment included 23 active shots in 2014 that were recorded with good signal-to-noise ratios across the entire array. We use the program struct3DP to iteratively invert travel times to obtain a 3-D seismic velocity model and relocate hypocenters. The preliminary 3-D models show low P- and S-wave velocities along the St. Helens seismic zone, striking NNW-SSE of MSH from near the surface to where we lose resolution at 15-20km depth. This seismic zone coincides with a sharp boundary in Moho reflectivity that has been interpreted as the eastern boundary of a serpentinized mantle wedge (Hansen et al, 2016). We speculate that the seismic zone and low wave speeds are related to fluids rising from the eastern boundary of the wedge.
Jill Schleicher (Talk): Investigating the plumbing system of Mauna Loa volcano, Hawaii, with crystal populations from the 1868 picrite eruption
Magmatic crystals respond to the conditions in which they grow, accumulate, and are transported through the magmatic plumbing system of a volcano. Crystals with shared histories define distinct populations by their common compositions, sizes, and morphologies. Magma moving through the crust accumulates multiple populations of crystals through assimilation and magma mixing. Volcanic eruptions sample magma within a reservoir nearly instantaneously; the erupted crystal populations represent not only the state of the reservoir at the time of eruption, but also the conditions at different stages of the magmatic plumbing system. We present preliminary results of whole-rock and crystal variability from the 1868 eruption of Mauna Loa to examine the plumbing system of the volcano. The 1868 eruption concluded a unique sequence of events in Hawaiian history. A summit eruption and series of earthquakes beginning on March 27 culminated in a magnitude 7.9 earthquake, the largest ever recorded in Hawaii. Five days after this earthquake, a picrite (olivine-rich basalt) erupted from the southwest rift zone (SWRZ). Samples from across the flow comprise two groups based on olivine content: picrites, with 30-40% olivine, and basalts, with less than 10%. Point analyses from the cores to rims of olivine crystals demonstrate multiple populations of olivines exist, defined by their compositions and the type of zoning. Olivines within individual populations exist in both the picrites and basalts, which we interpret to result from a combination of crystal accumulation and magma mixing.
Zack McIntire (Poster): On the fabric and microstructure of magmatic granular flows
Magmatic processes are generally governed by multi-phase interactions of silicate liquid, crystals, and bubbles. However, the modes of dissipation and the manner that stress is transmitted are poorly understood. We use a model of a simple but widely applicable gravity current as a means to exemplify the hydrogranular dynamics in crystal-rich magmas. Viscous and lubrication forces are of special interest because they have a dual role in dispersal and mixing in a crystal-rich gravity current. For example, lubrication forces provide an initial apparent yield strength by inducing a negative pore pressure as crystals move apart. However, once the gravity current is underway, lubrication forces reduce the dissipation due to collision and frictional contact.The gravity current is initiated by a combination of toppling and sliding along a well-defined granular fault. This produces three distinct regimes: a quasi-static base, an overlying particle hump that translates in a quasi-plastic fashion by grain-passing and rolling until the angle of repose is reached, and a viscous particle current. The orientation of contacts and force chains are plotted on a rose diagram and fabric tensors are used to quantify the fabrics. The initial force and contact fabric at center of mass has an isotropic distribution. As the plastic flow advances due to gravitational forcing, an anisotropic force and contact fabric emerges with an orientation 45 degrees from sigma 1. The orientation of the contact and force fabric indicates that gravitation forcing of granular material can induce fabric in magmatic systems.
Beyond earth, the solar system hosts a diverse population of orbiting bodies. Some contain rich mineral deposits, others hold key evidence about the origin and evolution of the planets, and a few may harbor extraterrestrial life. This session focuses on emerging space exploration technologies, including new types of rocket fuel, tiny satellites, and sample retrieval from planets, moons, and asteroids.
Paige Northway (Talk): Plasma for Propulsion and Composition
Pulsed Plasma Thrusters (PPT) have been under research in the Advanced Propulsion Laboratory for almost a decade, and have already been flown twice on high altitude balloons. A PPT currently in development will fly on UW CubeSat team's HuskySat-1 in the next two years, which could pave the way for PPT propulsion on future SmallSat missions in Low Earth Orbit (LEO) and beyond. These thrusters are potentially ideal for missions to asteroids, where the PPT arc ablation system could be used in conjunction with a spectrometer to act as a dual propulsion system and composition instrument, using a simlar concept to that of the Laser Induced Breakdown Spectroscopy instrument on the Curiosity Rover. Feasibility and preliminary results are discussed.
Manuel Azuara Rosales (Talk): Air-Breathing Pulsed Plasma Thruster with a Variable Spacing Cathode for Atmospheric Satellite Applications
An Air-Breathing Pulsed Plasma Thruster (AB PPT) with the potential of supporting indefinite flight above the tropopause is currently under development at the Advanced Propulsion Laboratory (APL) at the University of Washington. The advantage of working at high altitudes is that the aircraft is not subject to highly variable weather conditions. With sustained flight at these altitudes, there is the potential for having continuous coverage of a region so that the aircraft acts as an “atmospheric satellite” at significantly reduced altitudes relative to a low Earth orbiting spacecraft. The issue is finding an efficient lightweight propulsion system that can work at the low density of the upper atmosphere. The air-breathing pulsed plasma thruster (AB-PPT) incorporates the innovation of a variable spacing cathode that enables consistent thruster performance over altitudes greater than 60,000 ft. The fact that the system is air-breathing means that no fuel needs to be carried by the aircraft, and with the present system’s design a thrust level of 225 mN/kW can be sustained. Calculations are presented that show that this type of thruster could lead to sustained flight for an atmospheric satellite.
Karine Chen (Talk): Design and Construction Methods of A Single Stage Rocket Measuring Pressure Dynamics
When constructing supersonic rockets, builders must pay close attention to their design and construction methods to ensure that the rocket is capable of withstanding the dramatic pressure changes associated with breaking the sound barrier. This phenomenon is well understood and modeled by aeronautical engineers; however, it can be helpful to understand how pressure impacts individual rocket components for particular builds. Our team constructed a single stage, three-inch rocket capable of flying above thirty thousand feet and speeds well in excess of Mach one to better understand how each of its components experiences stress. A network of five pressure sensors will be employed to study the change in pressure in the nose cone, on the fins, inside and outside the payload section, and between the coupler and motor compartment. These sensors will report to an Arduino, monitoring the flight kinematics of the rocket for referencing the stress anomalies to significant events during flight. The findings of this project can serve to improve future engineering of amateur university rockets, as a more specialized understanding of stress on rocket components will be gathered. This can be used to optimize materials and design to improve rocket performance while maintaining a safe level of durability. Perhaps more importantly, this project will compare the stress experienced by student-built rockets to verified research, checking for congruency in the predicted levels of stress used in simulating rocket performance prior to construction.
Jimmy O'Neil (Poster): Design and Development of the “3U Cubesat” Satellite Chassis
As a response to the NASA Cubesat initiative, students of the Advanced Propulsion Lab at the University of Washington’s Department of Earth and Space Sciences initiated development of the 3U Cubesat in an effort to produce the first 3U CubeSat to feature a pulsed plasma thruster and a reflect array communications system by March 2018. 3U Cubesats are microsatellites with 3 cubes stacked vertically on top of each other. Each cube measures 100 by 100 by 113.5 mm. This is a systems-engineering project requiring interdisciplinary research among various fields and technical backgrounds. As part of the program, the structures team specializes in designing the structural components of the Cubesat using computer aided design (CAD) software such as SolidWorks and testing the vibrational and thermal resistances of the chassis using engineering analysis software such as ANSYS. To ensure mission viability, the structures team is also responsible for developing the hinges and a release mechanism for the solar panel deployment and actuation system. Finally, the structures team is responsible for developing a thermal model of the entire assembly as well as conducting vibrational analysis on the shake table. Various conceptual models were improvised repeatedly in order to fulfill the guidelines of the mission. The current results produced includes a complete CAD model of the 3U Cubesat chassis with all of its components, a conceptual model of the release mechanism and the hinges, and results receive from preliminary thermal models and structural analysis.
What is happening in our galaxy, far, far away? In this session, researchers will share the different ways they are unearthing the mysteries of space, both within the solar system and beyond. Topics include Mars exploration, characterizing the icy moons of the outer solar system, exoplanet modeling, and learning more about life forms that can survive in harsh space environments.
Owen Lehmer (Talk): Early Hydrodynamic Escape Limits Rocky Planets to ≤1.6 Earth Radii
In the past decade thousands of exoplanet candidates and hundreds of confirmed exoplanets have been found. For sub-Neptune-sized planets, those less than ~10 Earth masses, we can separate planets into two broad categories: predominantly rocky planets, and gaseous planets with thick volatile sheaths. Observations and subsequent analysis of these planets show that rocky planets are only found with radii less than ~1.6 Earth radii. No rocky planet has yet been found that violates this limit. We propose that hydrodynamic escape of hydrogen rich protoatmospheres, accreted by forming planets, explains the limit in rocky planet size. Following the hydrodynamic escape model employed by Luger et al. (2015), we modeled the energy limited, XUV driven escape from young planets (less than ~100 Myr in age) around a Sun-like star. With a simple, first-order model we found that the rocky planet radii limit occurs consistently at ~1.6 Earth radii across a wide range of plausible parameter spaces.
Steven Sholes (Talk): How Many Blue Whales on Mars? Obtaining a Maximum Extant Biomass on Mars using CO Antibiosignatures
Mars' atmosphere is characterized by a thermodynamic disequilibrium where substantial concentrations of CO and O2 coexist. The chemical disequilibrium is maintained by photolysis of CO2 and H2O, coupled with hydrogen escape to space, in Mars’ cold, dry, and thin atmosphere. Measured in terms of available Gibbs free energy, this disequilibrium amounts to ~140 J/mol, which is the largest in the Solar System aside from Earth. This untapped free energy constitutes a potential “free lunch” for life. Microbes in habitable environments in diffusive-contact with the atmosphere (e.g. deep subsurface aquifers) could, in principle, exploit this free energy and drive the atmosphere towards equilibrium. CO metabolisms are relatively simple, requiring only CO, water, and catalysis by enzymes possessing a variety of Ni-Fe or Mo active sites, which suggests multiple independent origins. Additionally, ~6% of sequenced microbial genomes contain at least one copy of the enzyme gene, which some argue suggests an ancient metabolism.This disequilibrium may represent an antibiosignature on Mars due to the availability of the simple-to-catalyze free energy from CO. Here, we expand and improve on previous work in 3 main ways: 1) we use updated present-day atmospheric compositions and uncertainties from MSL, 2) we account for ecosystems with multiple different metabolisms, and 3) we test over a broad range of tunable parameters (surface temperature, deposition velocity, and ionospheric fluxes). The results are rigorous constraints on the maximum biomass that could be on Mars today.
Matt Tilley (Talk): Active M-dwarf Effects on an Earth-like Planet in the Habitable Zone
Active M-dwarf stars exhibit high-cadence, high-energy flare events that likely impact the atmospheric equilibrium and surface conditions of Earth-like planets orbiting in the nominal habitable zone. We investigate how repeated electromagnetic and particle radiation events modify the atmosphere using a coupled 1D photochemical and radiative/convective atmospheric model to determine long-term effects of stellar proton events (SPE). A treatment of flare frequency, magnitude, and spectral evolution is motivated by observational results from AD Leonis and Kepler data analysis for the dM4 flare star GJ 1243. The resulting combination of these models indicate repeated EM-only flare activity has uncertain effect on the ozone column depth of the planet, while impacting proton events rapidly destroy the ozone column, which is depleted for long durations. Lacking a significant ozone column, the surface of the planet is likely to be bathed in UV flux, which is detrimental to organic stability.
Chloe Hart (Talk): Energetics of Acidianus ambivalens during aerobic growth on sulfur and varying nutrient availability
While there are several unifying traits for life on Earth, life beyond the Solar System may take different and unrecognizable forms. The need to acquire energy to overcome internal entropy production, however, is a universal characteristic of all living organisms. Understanding bioenergetics and the driving force of growth can provide insight into the evolution of energetic adaptations on Earth, allow one to quantify energy budgets for microbial growth and cell maintenance, and facilitate evaluations of habitability or analogs of life elsewhere. Microbial growth can be modeled by macrochemical equations that describe catabolic and anabolic reactions on a given substrate and not solely rely on standard state calculations. This model was applied to the thermoacidophilic sulfur-oxidizer, Acidianus ambivalens (A. ambivalens), during growth on elemental sulfur to investigate energetic needs under varying nutrient availability. Energetics of A. ambivalens was calculated for recommended growth conditions, designed to enhance growth but is likely inefficient, and two different treatments of oxygen limitation. In all experiments, Gibbs energy of the overall growth reaction was primarily dissipated through the release of enthalpy. When nutrients were unlimited, growth occurred inefficiently by producing a greater amount of heat and lower biomass yields. In oxygen-limited systems, growth was more efficient and resulted in a tighter coupling of energy consumption to biomass production and lower losses of energy through heat. With continued research investigating the thermodynamics of microbial growth, further constraints can be placed on habitability and understanding the driving force of microbial growth and maintenance energy requirements in extreme environments.
What sort of work do Earth and Space Science students plan to do in the future? This session will preview upcoming projects, including research proposals and projects in their infancies. Wild and unorthodox ideas are encouraged!
Emma Myers (Talk): Diving into new active source seismic data offshore Chile
During a seven-week cruise at the end of 2016, a large-scale seismic survey was conducted offshore northern Chile investigating the correlation between crustal heterogeneity and recent seismicity. Prior to the 2014 Pisagua-Iquique M 8.2 earthquake, this roughly 500 km portion of the Peru-Chile subduction zone had not experienced a significant earthquake since 1877. However, slip from the 2014 event did not fill the entire seismic gap or release all accumulated strain as expected. Southward propagation of slip instead terminated at a coincident gravity high and apparent band of relatively low pre-earthquake locking, with complex precursory and aftershock seismicity. The correlation in length scale between fault slip and gravity anomalies suggest geologic controls on local fault slip. To improve the resolution of geologic interpretation, this cruise utilized both a multichannel seismic (MCS) streamer and 69 short-period ocean bottom seismometers (OBS) deployed over the deformation front and incoming Nazca plate. Included in this data set are two longer transects; one transect is oriented along strike of the margin, crossing over the remaining gap and area of slip, while the other is perpendicular to the margin along a ridge on the incoming plate and over the region of greatest slip. Here, I present the initial processing of the perpendicular 2D MCS profile. As a first look, this data marks the beginning for a great deal of potential future work, including detailed imaging of incoming plate structure as well as complexities of the source region of the Pisagua-Iquique earthquake at depth.
Ariane Ducellier (Talk): Imaging of the oceanic subducting plate from observations of low-frequency earthquakes in Cascadia
Hydration and dehydration of minerals in subduction zones play a key role in the geodynamic processes that generate seismicity. Detecting the presence of water in the subducting plate is thus crucial to better understand the seismogenesis and the consequent seismic hazard. Using receiver functions of teleseismic waves in Vancouver Island, Audet et al. (2009) detected a low velocity layer with a sharp negative velocity contrast on top, which they interpret as evidence of high pore-fluid pressure in the upper oceanic crust and a low permeability boundary between the oceanic plate and the continental lithosphere. However, the inversion of the P-wave velocity structure carried out by Preston et al. (2003) in the same area did not display any strong reflector above the Moho that could be the upper boundary of the subducting plate. A considerable amount of low-frequency earthquakes (LFEs) have been observed in the Cascadia region. Due to the convenient location of LFEs on the upper boundary of the subducting plate, the seismic waves that they generate should illuminate well the area around the subducting plate, and allow us to highlight the presence of a low velocity zone. The aim of this research project is thus to use data recorded by seismic arrays in the Olympic peninsula during several events of episodic tremor and slip (ETS), in order to invert for the velocity contrasts associated with the plate interface and the subducting oceanic crust and Moho, and verify the presence of water in the subducting plate.
Erik Goosmann (Talk): Measuring paleoatmospheric pressure using grain-size distributions of aeolianites
The “Faint Young Sun” paradox is the apparent contradiction between standard stellar evolution models predicting a lower solar luminosity during the Archean, and conflicting geologic evidence that the early Earth was warm enough to host abundant liquid water. Proxies suggesting only moderate levels of CO2 in the Archean led to the hypothesis that higher atmospheric pressures of N2 between 1.6-2.4 bar could have sufficiently enhanced greenhouse warming due to pressure broadening effects. However, three independent paleobarometry methods suggest that the Archean atmosphere was equal to, or less than, modern pressure. Unfortunately, large error in these previous methods only provides a range of probable values between 1.1 bar and 0.23 bar. We will attempt to further constrain atmospheric pressure during the Archean by applying a new paleobarometry proxy: grain-size distributions of aeolian dune deposits. Atmospheric pressure is one factor that controls grain size at the saltation-suspension boundary. If the air pressure during the Archean was lower than today, then the maximum grain size capable of being suspended and taken out of the aeolian system should have been larger, leading to coarser aeolian dunes. We will measure grain-size distributions of the 3.2 Ga Moodies Group in South Africa, the oldest known aeolian deposit on Earth, to test this hypothesis. If successful, we will have developed a new proxy for measuring paleoatmospheric pressure, as well as further constrained our measurement of atmospheric pressure during the Archean.
Sarah Harbert (Talk): The Evolution of a Transform Plate Boundary: Thermochronology in the Marlborough Fault System, New Zealand
The Marlborough Fault System (MFS; South Island, New Zealand) is a suite of four transform faults at the boundary between the Australian and Pacific plates. This fault system links the oblique Alpine Fault to the south with the Hikurangi Subduction Zone to the north. The Marlborough faults bound mountain ranges with over 2000m of relief. However, modern GPS velocities show that these faults currently express primarily strike-slip motion. Previous paleomagnetic research suggests that this relief was built during a previous phase of deformation, when at least part of the MFS was oriented more parallel to the subduction zone and was active as a system of thrust faults, before the faults were rotated into their current orientation. Recent research from this department in a limited area of the MFS suggests that differential uplift occurred on two of the MFS faults during the mid-Miocene. Broader regional uplift, unconnected to the faults, occurred across this region by 4-5 Ma, possibly related to the southward propagation of the Hikurangi Subduction Zone. This study addresses the following outstanding questions about the development of this plate boundary using apatite and zircon (U-Th)/He thermochronology. Did all four of the Marlborough faults experience differential uplift during the mid-Miocene? Were the full extents of the Marlborough faults involved in this previous thrusting phase? Has more recent regional uplift occurred across the whole study area, and if so, has it propagated from north to south as the Hikurangi subduction zone has moved south?
Virginia Littell (Talk): Tracing the intensity of the Asian Monsoon across the Eocene-Oligocene Transition using oxygen isotopes
The Modern Asian Monsoon began ~20-25 mya and is primarily caused by temperature differences between the Tibetan Plateau and the Indian Ocean. Recent research on the Eocene Pondaung Formation in Myanmar indicate the presence of a modern-like Asian Monsoon during a greenhouse world ~40 mya. Contrary to modern conditions, the major controls on the Eocene monsoon were likely pCO2 and insolation, since the Himalayas and Tibetan Plateau were younger and did not present a large topographic barrier. The stratigraphic record in Myanmar spans the Eocene-Oligocene Transition (EOT), which presents an opportunity to study how the monsoon responded to a cooling climate and lowering of pCO2. Gastropod and bivalve shells in fossiliferous sections of the Yaw Formation in central Myanmar will be used for stable isotope analysis. Shells will be screened for diagenesis using CL and SEM imaging, and original aragonite specimens will be analyzed for d18O using a mass spectrometer. The oxygen isotope data will serve as a paleoclimate proxy to determine the presence and intensity of the Asian Monsoon during a transitioning climate.
Taryn Black (Poster): Housing and lifestyle patterns among ESS graduate students
Finding housing can be difficult, especially in an unfamiliar city where the newcomer lacks knowledge of appropriate neighborhoods and typical housing rates. I sent an anonymized 28-question survey to current ESS graduate students to assess their housing patterns and related lifestyle characteristics such as commute modes. From the survey results, I mapped the distribution of ESS graduate students throughout Seattle neighborhoods, and typical housing costs for ESS students in each neighborhood. I also analyzed patterns in several of the other survey characteristics. Future work will incorporate external resources such as bus routes and city-wide rent data. The combined survey results and external resources will be summarized into a set of maps and charts that will highlight ESS graduate student housing and lifestyle patterns. This summary will be distributed to current and incoming ESS graduate students to assist with decision-making for moving to or within the Seattle area. The data will also be made available to the ESS department so that it may also be used by others. The survey includes feedback and I will also collect feedback on the summary after it is distributed; if this project proves to be a useful resource then I plan to repeat the survey annually and additionally assess how ESS graduate housing trends change over time.
Cassandra Brigham (Poster): Investigating the style and tempo of bedrock fault scarp degradation in southern Iceland
The study of seismically generated fault scarps has yielded models that determine age of faulting events, rates of movement along faults and recurrence time between earthquakes. However, most of this work has been limited to regolith-mantled scarps, where degradation is governed mainly by diffusive processes. Scarps that occur in fractured bedrock are common throughout the world and the controls over their morphology remain poorly constrained. This study will focus on how the interaction of fault slip and geomorphic processes create and modify basalt-hosted normal fault scarps in Iceland. The ongoing rifting in southern Iceland is marked by Holocene tectono-volcanic systems and characterized by zones of fissures and faults that affect recent lava flows. In multiple sites, a single fault cuts through flows of various ages, providing the opportunity to establish a space-for-time substitution investigating the tempo of scarp degradation along a fault. This study will focus on characterizing the morphology of bedrock scarps of different ages and quantifying the degree to which these scarps have retreated through time by measuring the setback between the trace of the scarp in the youngest lava flows and those that preceded it. In order to do so, structure-from-motion photogrammetry will be used along selected faults in order to create a precise surface model of the scarp. Additionally, samples will be collected for future studies of cosmogenic 36Cl surface exposure ages to constrain the dates of faulting and toppling or other erosive events.
Addien Wray (Poster): Strange Diets: A Thermodynamic Description of Microbial U(VI) Reduction
Uranium contamination from mining activities, nuclear energy and weapons production, and storage of radioactive waste is a problem throughout the world that has resulted in widespread groundwater contamination. Seriously impacted sites include Rifle Colorado, where uranium mining and milling occurred, and an environmentally critical region, the South Columbia Basin, where plutonium production occurred in Hanford, WA. The stimulation of in situ microbes capable of reducing uranium from the soluble U(VI) to the highly insoluble U(IV) is a well-documented reaction that removes uranium from solution. As with any bioremediation effort, its applicability is dependent on stimulating the microbes involved in the desired reaction. For U(VI) reduction, we must quantitatively understand the metabolic processes involved with uranium removal. A fundamental aspect of this understanding is a thorough description of the thermodynamics involved. Already established is the ability of a variety of microbes to reduce U(VI) to U(IV); however, the thermodynamics driving that metabolic process has never been comprehensively described. Additionally, it is important to note that the energetics involved in metabolism are not constant and depend on both the microbe being considered and local geochemical conditions. The purpose of this study is therefore twofold: (1) Describe the thermodynamics of U(VI) reduction for a subset of taxa (Shewanella, Geobacter, Clostridium, and Desulfovibrio), and (2) Compare the relative efficiency of their energetics (as reflected in the thermodynamics of growth) for those taxa under various geochemical conditions. This will dramatically increase our ability to target specific regions and taxonomic groups for bioremediation of groundwater-hosted uranium.
Paige Wilson (Poster): Environmental Change and Plant Response Across the Cretaceous-Paleogene Boundary in North America: A Study in the Hell Creek Area of NW Montana
The goal of this study is to investigate climate change and ecosystem evolution in the Hell Creek (HC) Area of Montana through sedimentological and vegetational proxies. Extensive exposures of the Hell Creek and Fort Union Formations in the HC Area span the Cretaceous-Paleogene (K-Pg) boundary, the mass extinction event at the end of the Cretaceous that killed off non-avian dinosaurs and other lineages. Vertebrate paleontological field research in the HC has been nearly continuous since 1902, and recent work has expanded geochemical analysis in this area. In contrast, the documentation of fossil plants and ancient soils (paleosols) from this area has lagged. Understanding how paleocommunities respond to climate change and diversity crises is crucial for our interpretation of the impact of modern climate change events. I propose to use sedimentological, geochemical, and paleobiological methods to decipher and interpret the signal of climate, vegetational restructuring, and faunal turnover across the K-Pg boundary. To date, we have recovered over 200 leaf specimens from this area, which I intend to significantly expand in summer 2017. These will be used to reconstruct temperature, environment, and vegetation through leaf physiognomy. Additional sediment samples will be selected for suitability in isotope, phytolith, and other proxy methods. Phytolith content can be used as an ecological proxy, while stable and clumped isotopes can be used to infer paleo-temperature (among other environmental variables). Taken together, these lines of evidence would allow me to assess changes in environment and potential correlations between paleofaunal and paleofloral changes across this mass extinction.
Brittany McManus (Poster): Putting Science back in Political Science: The state of science representation in politics
Using the annual congressional roll call data, I have compiled educational and occupational information to identify representation of scientists in the Senate and the House. Without adequate representation, Congress can pass legislation without input from the scientific community who could warn about potential impacts to society. The few proposed bills actually voted on by congress are selected by congressional committees, panels of representatives from the House and/or Senate that are tasked with becoming experts in their specialized group to monitor and recommend bills. Without scientists sitting on specialized committees (e.g. agriculture, nutrition, and forestry; commerce, science, and transportation; energy and natural resources; environment and public works; science, space, and technology), important issues and bills could be overlooked. To help promote scientists to run for office, I have created a simplified guide on how to become a representative based on several publications and have collected resources that offer trainings. Come learn and discuss why the representation of science in congress is important and how to get involved.
This session focuses on rivers, including erosion, restoration, sediment movement, and extreme events such as mega-floods. Topics range from how specific rivers respond to perturbations to the processes that cause or drive rivers to change.
Sarah Schanz (Talk): Multiple paths to straths: re-evaluating strath terrace genesis
Strath terraces record past cycles of fluvial incision and are widely used to infer tectonic rock uplift rates. However, inferred uplift rates can be skewed because of unsteady external forcings such as climate, tectonics, and anthropogenic activity. Yet, previous work connecting forcings with strath formation often relies on temporal correlations and lacks independent evidence linking external forcings to stream variables. Using an exhaustive compilation of published work, we re-analyze findings at a global scale to infer the pathways connecting external forcings with the stream variables that determine bedrock incision, with an emphasis on Holocene strath terraces, for which we have a greater database of climate and seismicity. We find that climate is the most commonly ascribed forcing in our database, with glacial cycles moderating sediment supply and fluvial erosion rates. The timing of incision within glacial cycles varies with no coherent geographic trend and, as an additional complication, Holocene strath terraces indicate that terrace formation can lag a few thousand years behind glacial transitions. The Holocene is also a period with numerous (86 of 190 or 45%) un-ascribed terraces, for which no forcing was determined. We propose a future framework for which to investigate strath terraces, in which the forcing is determined last and more emphasis is placed on the stream variables and pathways to change that variable.
Geochemistry and geochronology serve as windows into the past, providing information on former earth environments and the timing of changes. Analytical techniques such as clumped isotope paleothermometry, OSL dating, carbon-14 dating, thermochronology, cosmogenic nuclide exposure dating, and ice core dating provide some of the best tools for studying the history of earth systems. This session includes both method development and applications.
Landon Burgener (Talk): Isotope disequilibrium in soil carbonates from diverse high-elevation and high-latitude environments
The clumped and stable isotope composition of soil carbonates from high elevation and high latitude sites has the potential to be an important archive of climate change in cold-weather areas. However, recent studies have suggested that soil carbonates at such sites may form cryogenically through freezing of soil water, and that this process may result in isotopic disequilibrium between the soil carbonates and their environment, making them inappropriate for use as a climate proxy. To map out variations in the magnitude of isotopic disequilibrium observed in soil carbonates from different cryogenic environments, we present clumped and stable isotope results for a suite of soil carbonates collected from four cold-climate sites in Antarctica, Chile, Svalbard, and Tibet. Clumped (Δ47) and stable (δ18O, δ13C) isotope values from the Svalbard and Tibet soils are consistent with equilibrium, summer-season carbonate formation, while the Antarctic and Chilean samples show Δ47 depletion, and δ18O and δ13C enrichment. The observed kinetic isotope effects in the Antarctic and Chilean soil carbonates are consistent with disequilibrium carbonate formation via freezing-induced bicarbonate dehydration and dehydroxylation. We suggest that the extremely low soil moisture content and relatively large sediment grain size of the Antarctic and Chilean soils facilitates rapid CO2 degassing during bicarbonate dehydration due to increased pore volume, increasing the magnitude of isotopic disequilibrium. Conversely, the higher soil moisture content and smaller sediment grain size of the Svalbard and Tibet samples decreases pore size, slowing CO2 degassing and inhibiting cryogenic carbonate formation at those sites.
Michael D. Turzewski (Talk): Mega-samples from megafloods: robust statistical treatment of a large-n detrital zircon U-Pb dataset, eastern Himalaya
Extreme megafloods have shaped many landscapes on Earth, but we lack direct observations of these events and we must rely on geomorphic observations or the sedimentary record to understand how they perform geomorphic work on the landscape. The eastern Himalaya provides an excellent opportunity to study the impact of extreme floods because it contains a record of modern landslide-dam outburst floods (10^5 m^3/s), as well as deposits from ancient megafloods (>10^6 m^3/s). Previous work has used detrital zircon U-Pb dating to interpret the provenance of these sediments from a mixture of Tibetan and Himalayan sources, and performed synthetic mixture modeling to constrain the relative proportion of sediment from each source; however, only four megaflood deposits were analyzed (n=450 grains), and recent advances in the statistical treatment of zircon U-Pb datasets indicate the mixture model and its interpretations can be improved. In this study, we present U-Pb ages from seven new megaflood deposits (n=1139), and we perform several statistical techniques to better constrain and interpret the provenance and contribution from upstream sources. We apply a bootstrapping procedure to characterize variability in the age distribution of our full compilation, apply a Bayesian mixture model (BAYESMIX) to determine age components in our distribution, and perform multidimensional scaling (MDS) to estimate the similarity between robust flood deposit samples and potential sources. Combined with geochronological tools such as IRSL dating, these techniques help to constrain the number and source of megafloods, which is crucial to understanding their impact on erosion and deposition in the region.
Keith R. Hodson (Talk): Reconstructing fluid sources for past episodes of fluid flow along the Moab Fault, Utah
Geologic structures exert strong controls on the subsurface migration and storage of fluids such as water and hydrocarbons. Faults present a particular challenge, as they can have a range of effects on local permeability, in some instances acting as barriers to fluid flow and in others acting as conduits. Using carbon, oxygen, strontium and clumped isotopes from fault-hosted carbonate cements, we present a window into the history of structurally controlled fluid-flow along the Moab Fault, Utah. Our data indicate that cementation occurred in multiple episodes, each related to distinct periods of fluid migration with distinct ranges of fluid chemistries. Cements with cool precipitation temperatures (~20 to 40 °C) appear to have precipitated from a marine source fluid, suggesting that they formed near the surface while the region was inundated by the Cretaceous Interior Seaway. Cements precipitated at warmer temperatures (~60 to 100 °C) have a wider range of reconstructed source fluid compositions. Oxygen isotopic compositions for the warm source fluids suggest a mix of meteoric and marine waters, but carbon isotopes are not in the range expected for a marine source. These observations may be explained by the presence of a non-marine, carbon-rich fluid in the system, or may be the signature of isotopic disequilibrium during mineral formation. Together, our data suggest cementation occurred under two distinct environments and precipitated from two source fluid compositions: 1) cool, shallowly circulating cretaceous marine waters and 2) a heterogeneous mix of warm, deeply circulating fluids.
Nicolas Cuozzo (Talk): Understanding Chemical Weathering in Cold, Dry Environments using Magnesium Isotopes
Chemical weathering is evident throughout the frigid, hyperarid Antarctic Dry Valleys; however, little is known about the conditions or rates under which it occurs. Here, chemical weathering processes and rates are reported in ice-cemented permafrost in the Antarctic Dry Valleys using magnesium isotope systematics. This study site is unique since weathering products accumulate and are stored in the ice-cemented permafrost and are not flushed away. Mg isotope mixing curves in the permafrost are from two Mg sources with distinct isotopic signatures: (1) marine aerosols that are captured and deposited by snowfall, and (2) chemical weathering of dolerite. The Mg isotopic composition, soluble salt concentration, ice-content, temperature, and pH along the depth of a 30-meter ice-cemented permafrost core collected in Beacon Valley reveals that chemical weathering occurs up to a depth of 7 meters. Above 7 meters, soils remain frozen and temperatures are above -20°C with seasonal fluctuations. Below 7 meters, the temperature remains below -20°C annually and little to no weathering is evident at these depths. The weathering environment is modeled using chemical thermodynamic programs designed for high brine concentrations, e.g PHREEQC and FREZCHEM, to model the unfrozen water content, as this is likely the primary control on weathering.
Yan (Emma) Hu (Talk): High-precision measurements of non-traditional stable isotopes by second-generation MC-ICP-MS: challenges and outlooks
The advent of Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS) has opened new frontiers in the measurement of stable isotopes of elements that are relatively heavy or bonded predominantly ionically, leading to a rapid growth of a suite of non-traditional stable isotopes (e.g. Li, K, Mg, Cu, Fe, Zn) with diverse applications in the earth and planetary, oceanography and environmental sciences. Here we systematically evaluate a number of instrumental factors that may affect the accuracy of isotopic measurements of these elements on a Nu Plasma II MC-ICP-MS, which is a double-focusing magnetic sector instrument equipped with 16 Faraday detectors. Our results show that mismatches of concentration of element of interest and acid molarity between sample and bracketing standard, as well as matrix element level, can lead to significant analytical artifacts. The influences of these factors also vary for different elements. Furthermore, for Cu and Zn, optimal isotopic measurements are achieved by tuning the instrument for highest mass fractionation stability instead of for maximum sensitivity. High-precision measurements of Li, Mg, Cu and Zn isotopes can be obtained in low-resolution mode whereas Ar based interference on Fe and K isotopes requires pseudo-high resolution mode. For K isotope measurement, the intense 40Ar beam is directed to a dummy cup and formation of 40ArH molecules in the plasma source is further suppressed by reducing the Forward Power. The results from this study provide a guideline for acquiring high-precision data of non-traditional stable isotopes and highlight the new analytical capability of the second-generation MC-ICP-MS.
Joel Gombiner (Talk): Exploring North American geochronology databases
The USGS and NRCAN have both released online geochronology databases in the last 15 years. These databases contain tens of thousand of radiometric ages, spanning potassium-argon (K-Ar), uranium-lead (U-Pb), rubidium-strontium (Rb-Sr), samarium-neodymium (Sm-Nd), and fission track (FT) dating systems. I will focus on the K-Ar and U-Pb data, as the combined USGS-NRCAN dataset contains 23,793 K-Ar ages and 12,572 U-Pb ages, and these dating methods are commonly used in provenance studies. The age databases are extremely useful for provenance work because they provide a data-driven way to characterize sediment sources. I will show an example for glacial lake outburst flood sediments in the Columbia River basin. Histograms of all U-Pb and K-Ar ages in the USGS and NRCAN databases suggest long-period, cyclic crustal formation over the last three billion years. This finding reaffirms previous work on smaller numbers of zircons in river sands.
Khadijah K. Homolka (Talk): Determination of the Small-Scale Sediment Accumulation Rates in Andvord Bay Fjord on the Western Antarctic Peninsula using 210 Pb Geochronology
Little previous research has investigated the spatial variability of sediment accumulation rates in fjords on the Western Antarctic Peninsula (WAP), and no other studies along the WAP have attempted to resolve the small-scale variability of sediment accumulation in an individual fjord. With the rate of temperature rise on the WAP being six times higher than the global average, the effects of modern climate change on glacier dynamics and meltwater production hold particular significance for sediment accumulation rates. In Andvord Bay fjord, Antarctica, modern sediment accumulation rates were determined from 9 kasten cores, and 4 box cores collected throughout the fjord aboard the R/V Nathaniel B. Palmer. A relatively low circulation velocity, and numerous deep basins throughout the fjord create ideal conditions for sediment to accumulate, and be easily cored. Excess 210Pb activity profiles reveal spatially variable sediment accumulation rates throughout the fjord that are on the order of millimeters of accumulation per year. These modern accumulation rates agree with previously determined accumulation rates in polar and subpolar fjords, and are significantly slower than those of temperate tidewater glaciers. The determined excess 210Pb activity profiles provide further insight into the small-scale spatial variability of sediment transport and accumulation in a fjord, and contribute to the subpolar-polar sediment accumulation dataset that is imperative for understanding the effects of modern climate change on the dynamics of glaciers at different latitudes.
How did the Earth and its atmosphere evolve billions of years ago? How did life modify the Earth’s surface environment and vice versa? This session includes both modeling work and geological/geochemical records of the Earth’s distant past, with a focus on the rise of atmospheric oxygen, the advent of carbon and nitrogen cycling, and evidence for early life.
Joshua Krissansen-Totton (Talk): Early Earth the Exoplanet: Disequilibrium biosignatures in Earth’s atmosphere-ocean system since 4.0 Ga
Chemical disequilibrium in planetary atmospheres has been proposed as a generalized method for detecting life on exoplanets. Previous work developed the methodology for calculating thermodynamic disequilibrium, applied it to Solar System atmospheres, and concluded the modern Earth has the largest disequilibrium (2326 J/mol) due to the presence life. Here – motivated by the need for novel early Earth biosignatures – we extend this work by calculating atmosphere-ocean disequilibrium for the Archean and Proterozoic. We use a broad range of proxy- and model-based estimates of early Earth atmosphere and ocean composition as inputs to our disequilibrium calculations. We find (i) thermodynamic disequilibrium has increased over Earth history in step with rise of oxygen, (ii) both the Proterozoic and Phanerozoic may have possessed sizeable, detectable disequilibria due to coexistence of O2, N2, and liquid water, and (iii) there may have been a detectable, biogenic disequilibrium in the Archean due the coexistence of N2, CH4, CO2, and liquid water. We conclude Earth’s atmosphere-ocean system was in disequilibrium throughout its history due to the perturbing influence of the biosphere.
Michael Kipp (Talk): Nitrogen cycling in the Precambrian: New insights from isotopes and box models
Nitrogen is an essential nutrient for all life on Earth, and is the proximately limiting nutrient in the modern ocean. Only some groups of Bacteria and Archaea are able to fix N2 from the atmosphere, leaving the majority of organisms – including all eukaryotes – dependent on a supply of dissolved nitrogen species in the environment. The balance between these two groups of organisms (nitrogen-fixers vs. nitrogen-assimilators) appears to be regulated in the modern ocean by competition-driven feedbacks, and results in a system that is phosphorus-limited on geologic timescales, with proximate nitrogen limitation. The nitrogen isotope record suggests that the bioavailability of dissolved nitrogen species, in particular nitrate (NO3-), has changed over the course of Earth’s history; however, quantitative assessments and linkages to global redox conditions are so far lacking. Here we consider potential differences in the structure of the marine nitrogen cycle during the Precambrian, and model the implications for the prevalence of nitrogen-fixing vs. nitrogen-assimilating organisms, as well as the implications for the sedimentary nitrogen isotope record. We then turn to the Precambrian nitrogen isotope record, and quantitatively assess the prevalence of nitrogen-fixing organisms at different stages in geologic history. We present new nitrogen isotopic data from Paleoproterozoic facies to evaluate the response of the nitrogen cycle to the proposed interval of “oxygen overshoot”. Our results highlight the heterogeneous distribution of fixed nitrogen species in the Precambrian ocean across space and time, and stress the importance of nitrogen fixation for Earth’s early biosphere. The evolution of the nitrogen cycle as controlled by redox and productivity changes likely played a significant role in the evolution of microbial ecosystems and the delayed emergence of eukaryotic life.
Matthew C. Koehler (Talk): Nitrogen isotopes record transient surface oxygenation in the ~2.7 Ga Jeerinah Formation
One of the most active endeavors in Precambrian geochemistry is the effort to constrain the evolution of Earth’s surface redox conditions through time. The Neoarchean in particular (2.8-2.5 Ga) is a period of ambiguous redox proxy data that in the past decade has suggested incipient and dynamic oxygenation on Earth’s surface. The nature and mode of these changes in redox conditions are still poorly understood. Here we present bulk rock and kerogen nitrogen isotope ratios at high stratigraphic resolution from the Jeerinah Formation (2.68 Ga; Fortescue Group, Western Australia) to test for transient changes in surface ocean redox state. We find that both shallow and deep facies of the Jeerinah record positive δ15N excursions, highlighting the onset, persistence, and termination of aerobic nitrogen cycling that requires free O2. This is the oldest high-resolution evidence for “whiffs” of oxygen before the Great Oxidation Event, and represents bidirectional redox evolution of the surface ocean and perhaps the global atmosphere.
Many students completed some exciting projects before joining the UW Earth and Space Sciences Department. In this session, students will share intriguing findings from past work and how that work led to their current research interests.
Eric Keenan (Talk): Observations of M2 Tidal Propagation and Decay along the West Coast of Spitsbergen: New Possibilities for Numerical Model Evaluation
Here we present observations of M2 tidal amplitude and propagation collected by pressure sensors attached to moorings off the west coast of Spitsbergen, in Hornsund, Isfjorden, and the Yermak Plateau. Through harmonic analysis, M2 tidal amplitude is calculated to be 0.50m in Hornsund and Isfjorden, and between 0.34m and 0.42m on the Yermak Plateau. M2 amplitude maximums occur simultaneously at Hornsund and Isfjorden, and 1.3 hours later on the Yermak Plateau. M2 tidal amplitude is shown to decay away from the coast on the Yermak Plateau with maximum amplitude of 0.42m at the mooring nearest to the coast, 0.41m 8km farther away from the coast, 0.37m 48km farther away from the coast, and 0.34m 66km farther out to sea than the nearest shore mooring. These observations agree reasonably well with numerical tidal models and Kelvin wave propagation and amplitude decay theory. However AOTIM-5 modeled M2 amplitudes are shown to be biased low, 0.04m on the west coast of Spitsbergen.
Mattathias Needle (Talk): Scaled Physical Experiments of Salt Flow Subparallel to Basement-Involved Normal Faults
Basement-involved normal faults influence the initial thickness and distribution of synrift salt. Deformation and deposition during and after rifting cause highly ductile salt to flow. I used scaled physical experiments consisting of wet clay, silicone polymer, and rigid blocks to examine the secondary structures that develop in the sedimentary cover above synrift salt that flows subparallel to the strike of basement-involved faults. In the physical experiments, two zones of deformation form within the sedimentary cover: 1) a shear zone with oblique-slip faults that trends (sub)parallel to the strike of the underlying faults; and 2) an extensional domain with normal faults that strike (sub)perpendicular to the flow direction of the ductile unit. An initially thicker ductile unit produces broad domains of deformation at the surface, whereas a thin ductile unit produces deformation directly above the deep structures. When the flow of the ductile unit produces highly oblique extension at depth, the extensional domain has broadly distributed deformation, and the shear zone has a similar orientation to the pre-existing fault. However, with highly oblique shortening at depth, the trend of the shear zone in the cover is not parallel to the strike of the underlying pre-existing fault, and secondary features in the extensional domain are muted in the cover. The latter suggests that the ductile unit subdues the expression of shortening and extensional at the surface. These modeling results suggest that the synrift Argo Salt in the Jeanne d’Arc basin (offshore Newfoundland) flowed parallel to the basin’s long-axis. The salt flow produced secondary structures in the sedimentary cover above the salt including shear zones above basement-involved faults and trans-basin normal faults.
Jana Meixnerova (Talk): Hydrocarbon preservation in shales and carbonate concretions of the 1.1 Ga Nonesuch Formation
One of the most debated events in Earth’s history has been the emergence of complex life. The first unambiguous record of eukaryotes dates back to ~1,600 Ma (Knoll et al., 2006), but the oldest uncontaminated lipid biomarkers diagnostic of Eukaryotes, steranes, were only found at ~850 Ma (Summons et al., 1988). This absence of Eukaryotic molecular fossils throughout the Mesoproterozoic era requires explanation. The 1.1 Ga Nonesuch Formation has been previously described as a location of high organic matter preservation and relatively low thermal maturity. Bitumens of two samples from the Nonesuch Formation, a carbonate concretion and an adjacent shale, have been screened for biomarkers by the means of gas chromatography–mass spectrometry. In contrast to previous studies on the Nonesuch Formation that have not been concerned with careful contamination control, this study found higher thermal maturities based on MPI-1 and MAI values, an absence of any steranes and hopanes, as well as the absence of phytol-derived hydrocarbons such as pristane and phytane. The conspicuous absence of these biomarkers, combined with an isotopic offset between 𝛿13C of kerogen and alkanes in the samples, might point towards intense heterotrophic reworking during the initial biomass deposition. Carbonate concretions from younger shales have been proposed as sites of preferential preservation of organic matter due to protective encapsulation of the molecules inside. However, an enhanced preservation potential of the analyzed carbonate concretion over the surrounding shale could not be confirmed. We suggest that any previous reports of diagnostic biomarkers from the Nonesuch Formation be re-evaluated.
What do ice sheets and ice shelves tell us about the climate of the past and how the climate is changing? How does snow turn into ice, and why do we care? How are the glaciers in our backyard responding to climate change? This session focuses on all things cold and white, from ice sheets to ice crystals.
Laura Kehrl (Talk): The search for the oldest ice: Allan Hills Blue Ice Area, Antarctica
Ice cores provide some of the most detailed, continuous records of paleoclimate available. However, currently these records cover only the past 800 ka of Earth’s history. The Allan Hills Blue Ice Area (AH BIA), Antarctica, has been proposed as a potential drill site to extend the ice-core record further back in time. Previous drilling efforts in AH BIA have recovered stratigraphically disturbed million-year-old ice from a 126-m ice core; this ice is presently the oldest ice recovered from Antarctica. Exposure-age dating of meteorites found in the region suggests that ice older than 1.8 Ma may be present. In this study, we use ground-based radar collected at multiple frequencies (7, 40, 100, and 200 MHz) to map the ice thickness and internal stratigraphy. We determine the age of radar-detected isochrones using age constraints from the ice-core records and tephra layers exposed at the surface. In the ablation zone, the bed rises ~800 m in 2 km, which provides a barrier to flow forcing the ice to flow upwards. Ice that outcrops at the surface has experienced significant strain (~35%) and consequently has a high age gradient (i.e., years per vertical meter). Roughly 5-10 km upstream, the bed is relatively flat, the ice thickness is ~1100 m, and the ice is far less disturbed. We use the age constraints, radar-detected isochrones, and two simple ice flow models to discuss regional ice flow and thereby assess the possibility for a continuous, million-year-old ice-core record at this location.
Emma Kahle (Talk): Some nitty gritty details about measuring diffusion of water isotopes in ice cores
We examine high-resolution water isotope data sets from continous flow analysis (CFA) of the West Antarctic Ice Sheet (WAIS) Divide (WDC) and South Pole (SPC) ice cores. Spectral analysis of water isotope data reveals damping of high-frequency variations associated with diffusive smoothing of the isotopic profile in the firn layer of an ice sheet. This diffusion of water isotope ratios in ice cores can provide information about past firn conditions. The data spectra of windowed sections of CFA data from WDC and SPC show different characteristics as compared with similar discretely-sampled data sets, affecting the estimation of high-frequency damping due to the firn diffusion process. The cause of this spectral difference is not known, but we suggest possible eplanations in the CFA measurement system and in natural firn proceses. Without knowing the origin of this spectral difference, we can still parametrize a method to estimate the extent of diffusion in the spectra. In this study we use a modified method to estimate extent of diffusion in order to efficiently and accurately produce diffusion estimates for full ice core CFA data sets.
Brita I. Horlings (Talk): Identifying viscosities implicit in current firn-densification models: a step toward a physical-process-based constitutive relation for firn
Firn densification rate determines the age of air in bubbles in ice cores, and is a primary uncertainty in conversion of volume changes to mass changes for altimetry surveys of the polar ice sheets. However, most current firn models are empirically tuned to local temperature and accumulation rate because not all physical processes that affect firn densification at the grain scale are adequately understood or measured. With generally fewer tunable parameters than active physical processes, impacts of such missing processes have instead typically been lumped together. As the next step toward developing a microphysical-process-based constitutive relation for firn, effective viscosity is used as the constitutive parameter in eight firn-densification models. Effective viscosity is implicitly identified in each model, and is dependent on factors such as stress, strain rate, temperature, and grain-growth processes. The models are forced with temperature and accumulation rate to find the effective viscosities. Preliminary results indicate that there are major qualitative differences in some of the models’ viscosity definitions, which indicate discrepancies in implicit descriptions of physical processes. Such differences include discontinuous viscosity at the zone 1-2 boundary (at density of 550 kg m-3), and discrepant viscosity trends that potentially indicate lumping of multiple processes. Each firn model describes densification uniquely, and these results confirm that processes are either oversimplified in different ways or are missing in the definitions. Future work will involve developing a viscosity function based explicitly on multiple processes which will help to prioritize future field measurements and lab studies.
Trevor Hillebrand (Talk): Delayed deglaciation of Darwin Glacier, Antarctica
The grounding-line of the Antarctic Ice Sheet in the Ross Embayment retreated >1200 km south of its last maximum extent from 13-2 kyr BP. The long-accepting "swinging gate" model of grounding-line retreat was based on data that implied the grounding-line was established at the mouth of Darwin Glacier >6.8 kyr BP. We present new exposure ages of glacial erratics and bedrock, which show the modern grounding-line was not established at Darwin Glacier until ≤ 2.8 kyr BP, long after glaciers farther south had already reached their modern configurations. This may be due to thickening from convergent flow with Byrd and Mulock Glaciers, and/or stabilizing backstress provided by Minna Bluff. Regional ice dynamics must thus be taken into account when evaluating geologic records of marine ice sheet retreat.
Bradley R. Markle (Talk): Non linear water isotope reconstruction
Stable water isotopes have been the backbone of ice core paleoclimate research for over half a century. Driven by changes to Earth’s water cycle, variability in water isotope records contain information about past temperature changes and have lead to our most detailed knowledge of the Earth’s climate over the last 800,000 years. Water isotopes of polar ice are influenced by temperature at the evaporation site of moisture from the ocean, the temperature at the snow deposition site over icesheets, as well as the temperature history during transport. Multiple water isotope parameters (d18O, dD, and dxs) together with linear scalings based on either modern spatial gradients or linearization from models, allow the reconstruction of temperature history at both the moisture source and the precipitation site. However, even the simplest understanding of the underlying water isotope physics do not lead to linear relationships between the water isotope parameters and temperature. This presents potential problems when extending modern linearizations to temperature reconstructions for the deep past.
Alex Huth (Talk): Simulating Ice Shelf Response to Potential Triggers of Collapse
Ice shelves regulate the flow of grounded ice into the ocean by buttressing the tributary glaciers that feed into them. If an ice shelf weakens or collapses, the tributary glaciers accelerate and transport more ice into the ocean, contributing to sea level rise. Here we develop a finite element ice shelf model that simulates the response of an ice shelf and its tributary glaciers to possible triggers of ice shelf weakening and collapse. We use Larsen C ice shelf as a test case for a larger study that will include several other ice shelves and projections for sea-level rise. The model includes a dual inversion for the basal friction coefficient and the ice viscosity parameter, a constitutive damage law, and level-set methods to track the ice front. For Larsen C, we specifically test if a large impending calving event caused by rifting can be simulated using damage to track rift propagation. We also perform simulations of several potential triggers of ice shelf collapse, including melt ponding, additional calving, and thinning to help diagnose the stability of the ice shelf.
John Erich Christian (Talk): Examining transient glacier responses to climate forcing
The equilibrium sensitivity of a glacier’s length change in response to a climate forcing can be constrained based on its catchment geometry. However, adequately modeling the transient glacier response to climate change must include an appropriate representation of ice dynamics along with realistic boundary conditions and climate forcing. Simplified glacier models (e.g., linear geometric, or shallow-ice approximations) are often used but are potentially less accurate than those that solve for the full stress state in the ice. However, the accuracy of the ice dynamics must be put in context of other uncertainties that accompany real-world settings, such as poorly constrained ice thickness, basal conditions, and uncertainties in climate forcing. We test linear-geometric, shallow-ice flowline, and full-stress ice flow models in response to climate forcings, and compare the inter-model spread to uncertainties in initial conditions and glacier response timescales. These experiments also allow us to explore the basic glacier length response to a gradual warming trend. One fundamental feature is a substantial and persistent disequilibrium with the climate while forcing is underway, implying a large amount of “committed” glacier retreat for many alpine glaciers.
Annika N. Horlings (Poster): Firn Compaction in Regions of Dynamic Ice Flow
Melting terrestrial ice is known to substantially contribute to sea level rise, however contribution of the Antarctic and Greenland Ice Sheets remains largely undetermined. Calculations of ice sheet mass loss from altimetry measurements requires an accurate firn compaction model for the region in order to convert volume changes to mass changes. However, firn compaction remains poorly constrained and gives the greatest error when assessing ice sheet mass loss from altimetry methods because no physically-based constitutive relationship has been established to describe firn compaction. Additionally, dynamic thinning is an important process in many regions but is neglected in firn compaction models because of their 1-dimensional nature. We focus on modeling firn compaction in dynamic regions which exhibit high longitudinal strain such as the shear margins Northeast Greenland Ice Stream. We use eight firn densification models of the Firn Model Intercomparison Experiment (FirnMICE) and implement a simple longitudinal strain definition. The models use different combinations of longitudinal strain and climatic conditions (temperature and accumulation rate) to assess effects on the bubble close-off depth and corresponding depth-integrated porosity of the firn column. The results are subsequently compared to measured firn density depth data of the Northeast Greenland Ice Stream. Depending on the magnitude of the longitudinal strain rate, preliminary results indicate up to a maximum 6 meter decrease in the bubble close-off depth and potentially agree with measured data. Further work will involve improving the longitudinal strain definition in the firn densification models and modeling other dynamic regions in Northeast Greenland and Antarctica.
Ari Newman (Poster): Validation of high resolution isotope measurements on the South Pole ice core
An ice core was drilled at the South Pole in 2015 and 2016 by a research team led by ESS faculty Eric Steig with colleagues from the University of California, Irvine. Measurements of the isotopic composition of water -- the key ice core data used as a paleothermometer -- were measured by ESS graduate student Emma Kahle with Steig and Andrew Schauer at the University of Colorado (CU-Boulder) using a state-of-the-art continuous-flow melting system, coupled to a laser spectroscopy system.The laser spectroscopy system measures not only the traditional deuterium and oxygen-18 concentration, but also the oxygen-17 concentration. These measurements on the South Pole ice core (SPICEcore) therefore are the first-ever continuous measurements of all three stable isotope ratios of water. Because the continuous-flow measurement techniques are novel, is critically important that they be tested against conventional measurements made on discrete samples. To accomplish this, for each of the 1-m long sections of ice measured continuously at CU-Boulder, we sampled 1/2-m long sections and melted them in sealed containers. The samples were then run at UW on our laser spectroscopy instruments, one optimized for deuterium and oxygen-18, the other oxygen-17. Comparisons between the CU-Boulder and UW measurements show good agreement, and allow us to quantify the data quality statistically.
C. Max Stevens (Poster): Evolution of air content in Greenland firn using the UW Community Firn Model
Accurate calculations of ice-sheet mass loss are necessary for estimations of future sea-level rise. Surface-elevation changes are measured by satellite altimetry; however, firn-compaction models are needed to convert measured volume changes into mass changes. Uncertainty in firn-model predictions of density-depth profiles and their evolution remains among the largest contributors to uncertainty in those ice-sheet mass-balance calculations. Using the UW Community Firn Model (CFM), we force an ensemble of published firn models with re-analysis- based temperature and accumulation-rate histories for Greenland (e.g. RACMO), in order to calculate histories of depth-density profiles and depth-integrated porosity (DIP). In order to avoid start-up transients when we compare histories from various models, all of the models go through a spin-up phase in which the density-depth profile “forgets” its initial condition in the past. However, the models cannot completely forget the boundary conditions (i.e. the spin-up climate history). Because the climate of Greenland is not steady, and is not well known in past centuries, uncertainties in this spin-up climate history can propagate into uncertainties when driving the models with modern re-analysis data. Because the models implicitly or explicitly incorporate a range of parameterizations of firn-compaction physics, the models also produce a corresponding range of transient responses to modern re-analysis forcing. We explore the spread of results and range of uncertainty in depth-density profiles and DIP due to (a) spin-up climate uncertainties, and (b) firn-model choice, i.e. incorporated model physics. Model parameters can be adjusted based on comparison with current-day density profiles, but non-uniqueness remains due to uncertain spin-up climate, and incomplete physics in the models. The results illustrate the current diversity among firn-compaction models, and point to a role for firn-compaction models based on constitutive relationships derived using measured strain rates and micro-structural measurements on firn cores.
What causes a slope to be unstable? What is the risk of landslides in the Pacific Northwest and beyond? This session focuses on hillslope processes and landslide hazards.
William Grimm (Poster): Shallow Landslide Susceptibility Study of Magnolia Area, Seattle, WA
Many portions of the Seattle area have moderate to high landslide hazard due to a number of factors. These factors include interbedded permeable (e.g., sand and gravel) and impermeable (e.g., silt and clay) geologic units that were deposited during recent glaciations, oversteepend slopes on lots of bluffs in the area as a result of ice removal, and a high amount of annual precipitation. In the winter of 1996-1997, extreme precipitation events caused lots of landslides throughout the Seattle area, one of which was the Perkins Lane landslide in the Magnolia neighborhood. The Perkins Lane landslide destroyed five homes, but no one was injured. The landslide deposits, along with many other deposits composing the bluffs around Magnolia, are at risk for shallow landsliding. Using a GIS methodology put forth by the Oregon Department of Geology and Mineral Industries (DOGAMI), I created a shallow landslide susceptibility (hazard) map for the Magnolia neighborhood of Seattle. I show that almost all of the bluffs around Magnolia have a moderate to high susceptibility of shallow landslides. Through field verification, I also show that there are some areas in the more densely-populated areas of Magnolia (i.e., away from the bluffs) that have shallow landslide hazard. My results can be used to help inform future infrastructure and building decisions in considering landslide risk in Magnolia and similar areas in Seattle.