1. Our Frozen Past: Snowball Earth and Ancient Ice
Bradley Markle (Talk): Atmospheric teleconnections between the tropics and high southern latitudes during millennial climate change
- Rapid climate changes, known as Dansgaard-Oeschger (DO) events, are ubiquitous over the last glacial period. DO climate anomalies are propagated globally through climatic teleconnections that are incompletely understood and insufficiently constrained by paleoclimatic data. Here we use a high-resolution deuterium excess record from West Antarctica to show that changes in the moisture sources for Antarctic precipitation occurred in-phase with the DO shifts in Northern Hemisphere (NH) climate and tropical hydrology. These results support the hypothesis that the Southern Hemisphere (SH) storm tracks migrate northwards during NH warm periods, in parallel with the well-established northward migration of the intertropical convergence zone.
Variability in the deuterium excess record also suggests that Southern Ocean sea surface temperatures (SST) followed the pattern of Antarctic surface temperatures -- out of phase with NH climate, as expected from conceptual and numerical models of the ocean bipolar "seesaw" mechanism. Furthermore, using a physically-based definition of the deuterium excess parameter, we show East Antarctic records are highly coherent with the WAIS Divide record, indicating that the SST changes are zonally uniform. Our data demonstrate that both atmospheric and oceanic teleconnections couple climate variations between the NH and SH high latitudes, and constrain the timescales on which they operate.
Adam Campbell (Talk): Ice shadows as refugia for photosynthetic life during Snowball Earth events
- During the Snowball Earth glaciations of the Neoproterozoic, the Earth’s oceans may have been completely covered with ice. Global ice cover, thick enough to block the transmission of light, would have prohibited the survival of photosynthetic eukaryotic organisms living under the ice cover. Fossil records indicate these organisms persisted during the Snowball Earth glaciations. The persistence of these organisms presents a complication to the Snowball Earth theory. If the Earth’s oceans were unable to survive in planet’s ocean during the Snowball Earth events, then in what environments did these organisms survive
Previously, our research has shown that narrow arms of the ocean, analogous to the modern Red Sea, could have been refugia for photosynthetic eukaryotes during Snowball Earth events. We have demonstrated that for a limited range of climate conditions, ice flow into an arm of the sea is restricted sufficiently to allow for the sea to remain partially free from sea-glacier penetration, a necessary condition for these regions to act as a refugia for photosynthetic eukaryotes during a Snowball Earth event. Presently, we demonstrate that thin-ice zones can form on the leeward sides of obstructions in channels. These thin-ice zones, which we call ice shadows, may have acted as refugia for photosynthetic eukaryotes during Snowball Earth events. We test the ability of ice shadows to form in channels where, in the absence of an obstruction, sea-glacier ice would be thick enough to prohibit the transmission of light. We find that ice shadows can form behind obstructions of various sizes and over a range of climate conditions. This research adds to the range of environments where photosynthetic eukaryotes may have survived during the Snowball Earth events.
Trevor Hillebrand (Talk): Holocene deglaciation of the Ross Sea, Antarctica
- A grounded ice sheet filled the Ross Sea of Antarctica at the Last Glacial Maximum (LGM), fed by thickened East Antarctic outlet glaciers in the Transantarctic Mountains. Rapid thinning initiated ~13 ka, and the grounding line retreated >1,200 km through the Holocene. We have mapped and sampled deposits alongside Hatherton and Darwin Glaciers in order to establish the only constraints on the timing of grounding line retreat and the maximum ice thickness in the >700 km between the McMurdo Dry Valleys and Beardmore Glacier. Be-10 exposure ages of glacial erratics and algae radiocarbon ages from deposits alongside Hatherton Glacier suggest that the glacier reached maximum thickness by 8-9 ka, with 250 m of thinning from 9-3 ka at Lake Wellman and 350 m of thinning from 8-5 ka upglacier at Dubris Valley. These fluctuations likely lag changes in the Ross Sea by several hundred to a thousand years. LGM deposits are only present up to 150 m above the modern glacier at the confluence of Darwin Glacier and the Ross Ice Shelf; however, the LGM ice surface was likely hundreds of meters higher than this. Analysis of in-situ C-14 in quartz from bedrock samples will constrain the maximum ice thickness at this site.
Michael Turzewski: Simulations of modern and ancient outburst floods using GeoClaw, eastern Himalaya
Sarah Schanz: Lithologic controls on valley width and strath terrace formation
- We investigated the influence of lithology on strath terrace formation in the Willapa and Nehalem Rivers, Pacific Northwest, and found valley width, and thus terrace formation, is strongly dependent on lithology. In valleys with erosion prone bedrock, valleys were 2-3 times wider than those in erosion resistant bedrock, and multiple flights of strath terraces were well-preserved. In contrast, erosion-resistant bedrock valleys were narrow and confined with discrete and discontinuous strath terraces, if any. This work shows the formation of terraces is dependent on valley width, which in turn is dependent on bedrock erodibility. Furthermore, this work implies ecological diversity in riparian floodplains will vary on a reach- and river-basis dependent on lithology.
Alex Grant: Earthquake-induced landslide hazard mapping in Lebanon
Sean LaHusen: Timing of long runout landslides near Oso, WA and the implications for landscape evolution and natural hazards
- LiDAR bare earth imagery reveals numerous landslide deposits of previously unknown age directly surrounding the March, 2014 Oso landslide in the North Fork Stillaguamish river valley. A quantified surface roughness analysis from this high resolution LiDAR data suggests numerous generations of landslides, while morphology indicates some landslides that are larger than the 2014 Oso landslide and comparably mobile. New radiometric carbon dates from landslide deposits and fluvial terraces has allowed for better temporal constraints on slope failures and river incision, and show that landslide activity has continued through the late Holocene. These results indicate that the Rowan landslide, the largest deposit in the valley, occurred ~650 ybp, suggesting landslides in this area may not be as old as once thought. These catastrophic slope failures, which occur in thick packages of glacial sediment deposited in the Puget Sound during the Last Glacial Maximum, have continued well after the North Fork Stillaguamish river incised through this sediment to its current base level, ~12,000 ybp, and are therefore not exclusively caused by instability from initial river incision following ice retreat. Rather, large and highly mobile slope failures seem to be an ongoing postglacial process in this area, likely caused by river undercutting and exacerbated by high intensity precipitation events. In turn, we hypothesize that these landslides deliver substantial volumes of sediment to the North Fork Stillaguamish river, often drastically shifting the position of the active channel. Over many events and thousands of years, this continual sediment influx may limit long term river incision rates.
3. Environment and Life on Earth and Mars
Susan Wisehart: The effects of increased nitrogen deposition on alpine plants in the Pacific Northwest
- The School of Environmental and Forest Sciences is conducting research on the effects of nitrogen (N) pollution in alpine soils of the Pacific Northwest. This involves fertilization of alpine plots, using 15N-ammonium nitrate, to simulate N deposition. As a part of this project we are interested in how key plant species, which have adapted for normally N limited environments, take up and retain inorganic N with increased N deposition. Recent studies have defined N “critical loads”, the amount of N that will begin changing an ecosystem, for the alpines in Rocky Mountain National Park. Yet, the N “critical load” has not been thoroughly assessed in the Pacific Northwest where pristine alpine ecosystems are handling more pollution with a growing population. To assess the N uptake and storage by plants, we measured the carbon (C) to N ratios in heather (Cassiope mertensiana and Phyllodoce empetriformis) and lupine (Lupinus spp.) tissues from Mt. Rainier, North Cascades, and Olympic National Parks. Samples were collected, dried at 50°C for 48 hours, and manually ground via mortar and pestle. Ground samples were then sent for C, N, and 15N analysis at the U.C. Davis Stable Isotope Laboratory. Low C:N ratios could indicate high N retention rates, while high C:N ratios would be explained by low N retention. Retention of total N, including 15N, could show adaptive ability for plants to retain increased deposition, whereas inability to retain increased N would mark a limitation. Quantifying abilities and limitations of key alpine plants in retaining N will contribute to the definition of N critical loads in the PNW alpine ecosystems, which may ultimately support local pollution control decisions.
Steven Sholes: An anoxic atmosphere on early, volcanically active Mars and its implications for life
- Mars’ modern atmosphere is oxidizing and dominated by the photochemistry of H2O and CO2. Early Mars, however, experienced widespread volcanism, which would have injected gases into the atmosphere such as H2, CO or SO2 that react rapidly with gaseous oxidants. Here, we investigate the effects of volcanic outgassing on the bulk chemistry and redox state of the early martian atmosphere. We find that early Mars could easily have had an anoxic, reducing atmosphere under typical estimates of the amounts of past volcanism. Such an atmosphere is much more conducive to prebiotic chemistry than an oxidizing atmosphere.
We use a modified version of a published 1-D photochemical code. To simulate possible volcanic gas compositions, we varied magmatic oxygen fugacity (fO2), water content (wt% H2O), and pressure of degassing, based on parameter-space established by Gaillard et al. (2013).
The mixing ratios of CO2 and H2O were fixed in the model and we considered how varying fluxes of volcanic SO2, CO, H2, H2S, and S2 would have affected Mars’ atmospheric chemistry. We simulated volcanic emissions by fixing an upward flux for each species that corresponded to volcanic crustal production fluxes ranging 10-4 to 2 km3 yr-1. The model calculated steady-state atmospheric chemistry.
Results suggest that the martian atmosphere was anoxic even at modest levels of volcanic crustal production, ~10-2 to 10-1 km3 yr-1. The average crustal production rate has been estimated as ~0.17 km3 yr-1 over the past 3.8 Ga and other estimates suggest that Mars had volcanism ~5 to 0 km3 yr-1 at 4.1 to 1.0 Ga. Consequently, our calculations suggest that Mars may have experienced long periods of anoxia when volcanic outgassing was sustained.
In the model, at low levels of volcanism (<10-3 km3 yr-1 crustal production rates), the atmosphere is similar to the modern one. As volcanism is ramped up, O2 falls while CO and H2 rise. Finally, the atmosphere reaches full anoxia with negligible O2 where CO and H2 dominate, while carbonyl sulfide (OCS) rises to a ppm level.
The bulk composition of Mars as a whole is more enriched in S than the Earth, and so S plays a far greater role in volcanism. The simulated atmospheres are characterized by the formation of large amounts of sulfate aerosols. In highly reducing atmospheres, elemental polysulfur (S8) aerosols also form. We find that magmatic buffers where S was more stable in the melt would have required more volcanic activity for anoxia. Such buffers are typically drier and, counter-intuitively, have lower fO2. If less S had been outgassed, fewer sulfate aerosols (H2SO4) would have been produced, which consumes less oxygen.
Extensive periods of an anoxic and reducing atmosphere early in Mars’ history (in the early Noachian and periodically through to the mid-Amazonian) could be conducive to an origin of life on Mars. Reducing atmospheres enable prebiotic chemistry, such as atmospheric amino acid synthesis, which has been discussed in the context of possible reducing atmospheres on early Earth.
Higher levels of CO occurs for all simulated mantle buffers. (We assumed a cold dry Mars and thus no major sinks for CO). The CO contributes to the anoxia, and potentially could have provided a substrate for methanogenic metabolism.
Chloe Hart: Thermodynamic analysis of microbial growth during aerobic and anaerobic sulfur metabolism
Paul Sturmer: Transporting BIG Data
- With ever increasing amounts of computing power, practically unlimited storage, and a proliferation of commercially available sensors, transporting data from where it’s gathered to where it’s processed is still problematic. To this end, this talk focuses on the space telecommunication industry. The practical limitations and current trends will be discussed, along with an overview of the development of a high bandwidth CubeSat communication system.
4. Poster Session: Space & Rockets, Geomorphology
Spencer Savage: Langmuir Probe Array for High Power Helicon Plume Analysis
- In order to produce faster missions for future space exploration, humans will need to rely on electric propulsion. One type of spacecraft propulsion engine is the helicon plasma thruster. The high power helicon (HPH) is capable of producing a high density plasma (1017-1018 m-3) and directed ion energies greater than 20 eV that continue to increase tens of centimeters downstream of the thruster. The plasma and propagating wave magnetic field are created from a type ‘R’ helicon antenna, capable of 10-30kA peak-to-peak current, within a 200-800G magnetic field. The electromagnetic wave emitted by the antenna accelerates electrons downstream along magnetic field lines, resulting in a large axial ambipolar electric field, which accelerates the ions. The primary device used to determine the electron temperature, electron density, and electric potential of plasma is called a double Langmuir probe. The Langmuir probe is inserted into the plasma and measures the current and electric potential between the two electrodes. By taking measurements at multiple axial locations, a time of flight velocity for the plasma can be calculated. Five Langmuir probes were constructed horizontally on an aluminum rod which can be moved axially to measure the plasma velocity and density at different positions. The plasma touching probe tips are created from tungsten wire, connected to long copper wires within a ceramic housing.
Nicolas Gutierrez: Hybrid Thermoplastic Graded-Z Radiation Shielding for a Europa CUBEsat Mission
- The Advanced Propulsion Laboratory is designing a 3U CubeSAT to be launched on NASA’s Europa Clipper mission to perform magnetic field readings of the Jovian moon Europa. The main issue with surviving in Jupiter’s orbit is withstanding the high energy and high density radiation fields that exist around the planet, with beta particles being in highest flux. Typically, satellites on Jovian missions are spot shielded with high proton density metals to protect sensitive electronics from radiation induced damage. This study will analyze and test a number of existing graded-z shield compositions and new hybrid thermoplastic graded-z shields. A graded-z shield is a type of passive radiation protection in which layers of material are placed in a gradient from low to high proton density, with a thin final layer of low proton density material. Preliminary calculations show that substituting the aluminum portion of the graded-z shield with crystalline polypropylene will both increase shielding capabilities and lower total shield mass. This new z-shield designed at the UW Advanced Propulsion Lab will have an approximate thickness of 18 mm and is composed of a 12 mm layer of polypropylene, 2 mm of copper, 2 mm of lead, and a final 3 mm of polypropylene. The test itself will be conducted by exposing a custom built Arduino based Geiger counter to a beta particle source (Sr-90 or Th-204) and assessing five test articles: a typical low proton density monolithic shield, two versions of current z-shield designs, a typical high proton density dilithic shield, and the new hybrid thermoplastic z-shield. Due to the non-linearity and complexity of radiation interactions with matter, different shields may be more effective at blocking different particle energies. The results of this study will provide the guidelines for shielding on future CubeSAT missions.
Chayse Aubuchon: Axial Magnetic Field Pulsed Plasma Thruster for CubeSAT Propulsion
- Pulsed Plasma Thrusters (PPT) represent a simple, lightweight, cost effective solution for in-space propulsion onboard small, power-limited spacecraft. PPTs operate by electromagnetic and electrothermal acceleration of a solid propellant, creating a high velocity, low mass exhaust plume. A thruster’s impulse bit is the product of the ablated mass and its velocity. To increase the impulse bit, and therefore the thrust efficiency (exhaust power / input power) of the PPT, an axial magnetic field was added around the discharge chamber region. The addition of a 0.1-1kG field to the thruster will increase the gyromotion of the electrons in the discharge region, which in turn will increase the mass ablation and ionization rate of the thruster, both of which will increase the impulse bit. The field should better confine the expanding gas to prevent perpendicular thermal expansion. Initial perpendicular gyromotion will be converted to parallel axial velocity as the particles travel downstream and into a weaker magnetic field. Current testing with Langmuir probes and a high speed camera will compare varying magnetic field configurations and determine if the applied field adds to the thrusters total thrust efficiency. An electromagnet was chosen over a permanent magnet for laboratory testing to allow for variations to the fields strength and shape.
Karl Mitchell: Super Dart: 3-Stage High-Powered Rocket
- This project aims to use a variety of techniques to create a high performance system for relatively low cost, on a short build schedule. Taking inspiration from several different sounding rocket configurations, the Super Dart aims to achieve an altitude of 32km, and a maximum velocity of 900m/s. Early design inspiration primarily comes from the Loki Super Dart. Designed in the early 1960’s, the Loki sounding rocket consists of a 4.5in diameter booster, which burns out at 5000ft, moving at Mach 5, after which an unpowered 2in dart separates and coasts to 340,000ft due to low drag, high inertia and extreme velocity. Applying the techniques that streamlined the Loki, the SUPER DART is a multistage powered dart. Using two boost stages takes advantage of the exponentially decreasing atmosphere to improve output from the motors, and avoids the difficulty and cost of larger engines. Powering the dart adds more thrust and inertia. To decrease cost from individual components and ensure reliable performance, we use off-the-shelf motors and components. Despite using pre-made components, a significant portion of constructions was left, from fabricating carbon-fiber and Kevlar enforced fins, to integrating motors and building custom electronics. The boost portion of the rocket will deliver 22kN-s of impulse to the rocket, and boost it to 8500m and 600m/s, where the dart will separate. After separation and a brief coast, the dart motor will ignite, providing a final 1000N-s of impulse, coasting to apogee 60s after final burn-out, and 90s after lift-off. To control the flight events, a custom flight computer was designed and implemented. Additional functions acquiring and relaying flight and GPS data in real-time. The Super Dart aims to be the highest and fastest rocket ever launched by the UW, and will be tested at Black Rock, NV. in March 2015.
Erin McLean: Disrupting Rocket Science: 3D Printing High Altitude Rockets
- Traditional manufacturing processes for high altitude rockets are time consuming and vulnerable to a high degree of human error. Currently, in Professor Robert Winglee's Rockets and Instrumentations lab, a rocket and its scientific payload can be built in ten weeks but without a guarantee that the system will have a successful flight. With the rise of 3D printing in the public conscience, and the variety of new printer filaments coming on to market, incorporating additive manufacturing processes into our build cycles could benefit high altitude rocketry research. With 3D printing, we are able to build multiple rocket frames and internal components in a fraction of the time as traditional processes and with fewer hours input by people. For this research project, we are testing the viability of Polyactic Acid (PLA) filament printed rocket airframes for supersonic flights. We are using Kilo print, a large format 3D printer built by the WOOf 3D printing club on the University of Washington campus. The airframe has embedded sensors to record data on stress, strain, flex, and temperature. This data, combined with a flight post-mortem will help us determine if PLA printed rocket components are viable for future flights. The rocket, nicknamed Ctrl+P, will be launched in mid-March from the Black Rock Desert in Nevada. It has an expected top speed of Mach 2.5 and an apogee of 23,000ft. The next phase of our research is to conduct auto-ethnographic surveys to understand how we can incorporate additive manufacturing into our current build processes.
Mariah Danner: Evaluating numerical flood models using high water mark maps of a large historical outburst flood, Eastern Himalaya
- Infrequent high-magnitude releases of dammed water, known as outburst floods, are important to understand due to their hazard to humans and property, as well as their role in shaping landscapes. This importance increases as glacial outburst floods become more frequent in mountainous regions due to climate change and glacial melting, yet numerical models that simulate flood hydraulics and predict hazard have not been rigorously evaluated in mountainous terrain. The 2000 Yigong dam-break-flood in the Eastern Himalaya of Tibet and India is the largest, best documented opportunity to ground truth flood simulations with observations. In this study the flood trimline (high water marks) was mapped to compare to the inundation of Yigong flood simulated using 2D shallow water numerical model. Trimline position was identified by vegetation change observed in two kinds of remote sensing data, GoogleEarth and Landsat imagery. Post-2000 GoogleEarth imagery was used in the southern part of the study region (India), with a total distance of 564 m of trimline being confidently mapped. Results show that mapped trimline positions match the numerical model predictions well. The GoogleEarth imagery also showed the positions of landslides triggered by the flood, indicating the spatial distribution of erosion and landscape modification caused by the flood. Preliminary analysis of 2001 Landsat 7 imagery suggests better resolution and location accuracy for trimline mapping than GoogleEarth, particularly in the Northern region of the study area (Tibet). The most notable benefit of Landsat analysis is the ability to quantitatively isolate vegetation change using specific band widths, thus eliminating subjective interpretation of imagery by the analyst. The good match of mapped trimlines and simulated high water marks validates the numerical model in this region. Our results suggest this modeling approach is promising and applicable to evaluating impacts of floods on hazard and landscape change in other mountainous regions.
Sarah Harbert: Modeling strike-slip-driven stream capture in detachment- and transport-limited fluvial systems
- Rivers respond to tectonics and climate through both gradual and abrupt changes in slope, hydraulic geometry, and planform. At the fast end of the fluvial response spectrum is stream capture, a process by which drainage area, and therefore water and sediment, is rapidly diverted from one catchment into another. Stream capture modifies the topology of drainage networks and has implications for fluvial incision and deposition in sedimentary basins. While stream capture is an important process in landscape evolution, the factors controlling its occurrence are not well understood. We use the Channel-Hillslope Integrated Landscape Development model (CHILD) to investigate the effects of stream size, sediment supply, and drainage divide geometry on stream capture. We model a scenario in which a strike-slip fault forces frequent stream captures by juxtaposing adjacent streams. In a simple scenario, stream captures should occur whenever two streams are juxtaposed, a frequency that depends on the drainage spacing and the fault slip rate. However, our models did not show such regularity. We found that river size and sediment supply both affect the likelihood of stream capture. In more than 90% of stream captures in our model runs, the capturing stream was larger (i.e. had more drainage area) than the captured stream. In model runs in which all of the streams were larger where they cross the fault, stream capture occurred almost twice as often. Finally, fewer stream captures happened when the fluvial system was detachment-limited; nearly twice as many stream captures occurred when fluvial sediment deposition was allowed in the system. Divide geometry also affected the occurrence of stream capture. We found that when the difference in elevations between the streams involved in a capture event is greater, the capture can occur from a greater horizontal distance. We interpret this relationship to mean that stream capture is “easier” when one stream is “perched” high above another. These results indicate that stream capture is affected by many variables other than stream proximity. Comparing these results to field sites will help us to understand the prevalence of stream capture in real-world strike-slip systems and the resulting landscape signature of lateral faulting.
Camille Collett: Understanding the exhumation history of New Zealand's Kaikoura Mountains using low-temperature thermochronometry
- The Kaikoura Mountains (Seaward and Inland) stand high as topographic anomalies in the Marlborough strike-slip fault system, South Island, New Zealand. Understanding when and how these mountains developed is important for unraveling the evolution of the oblique Pacific-Australian plate boundary in this region and for understanding how the topography is related to the adjacent faults. (U-Th)/He low-temperature thermochronology reveals the thermal histories of rocks as they are exhumed towards the surface and is a technique I have been using to begin answering these questions. Apatite helium ages from the Seaward Kaikoura Mountains show recent exhumation (~3 Ma) of the region as a whole (ie. along strike of the adjacent Hope/Jordan faults) while preliminary Zircon helium data show an earlier phase of exhumation (~20 Ma) only observed in the heart of the Seaward Kaikoura Range. This suggests the Seaward Kaikoura (and potentially the Inland Kaikoura) Mountains have undergone an earlier phase of exhumation which may be related to dynamic changes in fault motion over time and the evolution of the oblique plate boundary. Future analysis of samples collected along age-elevation transects during a 2014-2015 field campaign will help reveal the exhumation history of these mountains and provide insight into when and how they developed.
Nikolas Midttun: Deep Springs Normal Fault Facet Morphology: Dependence on Fault Slip Rate and Erosion
- Triangular faceted spurs are a prominent feature of many normal faults around the world. Previous studies have shown that facet geometry is primarily controlled by the slip rate on the normal fault at the facet’s base, and the erosion rate of the facet’s hillslope. This study attempts to determine several geometric properties of the faceted spurs along the southeastern side of Deep Springs Valley. These geometric properties include facet width, height, aspect, slope, area, roughness, and perimeter shape. These variables can then be compared to the slip history of the Deep Springs Valley normal fault, possibly revealing correlations between fault behavior or climate variability and surface geomorphic expression. This study will primarily rely on remotely sensed data and GIS analysis, with the possibility of fieldwork during summer 2015.
Devin Maloney: Geographic Information System (GIS) Analysis of Fluvial and Landslide Geomorphology of the North Fork Stillaguamish River Valley, Washington
- Approximately 17 kilometers (10 miles) of the North Fork Stillaguamish Valley, including the impacts from the Oso Landslide, were analyzed using Geographic Information System (GIS) data. The North Fork Valley is located within Snohomish County, Washington along State Route 530. Historical landslides and the North Fork Stillaguamish River path were digitized using three hillshade layers from 2003 (pre-Hazel Landslide), 2013 (pre-Oso Landslide), and 2014 (post-Oso Landslide) in ArcGIS. Comparative analyses of these three digitized paths were conducted using topographical data obtained from Light Detection and Ranging (LiDAR) and aerial photography. Using overlay analysis, the overlapping area of the river was identified to show where the path remained the same over an eleven year time span. Comparative maps of the topographical data were then created to illustrate where the displacement of the river occurred. The results of the comparison of the 2003 to 2013 data yielded two key discoveries: (1) a small slump occurred altering the path of the river and (2) 610 meters (m) of the river were displaced and relocated 152 m to the northeast. This slump and river displacement occurred prior to the Oso Landslide and raises the question of whether the displacement of rivers can be used as a landslide predictor. GIS is an increasing effective tool that can help answer these questions. However, analyses are currently limited by the lack of historic data, restricting scientific analysis of geomorphic processes. GIS analysis of hillslope stability and river meandering can, and should be used to identify landslide hazard zones. Hazard maps can also educate and inform the public of potential dangers.
Shelley Chestler: Examining tremor propagation patterns using low frequency earthquakes
- Large slow slip events accompanied by seismic tremor, called Episodic Tremor and Slip (ETS) events, occur in the deeper portions of the Cascadia Subduction Zone every 12 to 15 months. The distribution of tremor during these events is strongly heterogeneous. Patches, tens of kilometers in dimension, produce most of the observed tremor (Ghosh et al. 2012). Additionally, there are multiple modes of tremor migration, including the along-strike migration of the tremor front (7-12 km/day), back propagations of tremor, or “rapid tremor reversals” (RTRs) (100-300 km/day), and dip-parallel streaks (25-200 km/hr). We use a 1.5-year catalog of low frequency earthquakes (LFEs) (June 2009 – Sept 2010 and August 2011) to explore the connection between these two key observations beneath the Olympic Peninsula, WA. Low frequency earthquakes, or tiny earthquakes that are depleted in high frequency energy compared to normal earthquakes, occur in rapid succession and generate the continuous tremor signal. Because they can be more precisely located than tremor, they are useful for looking at the finer details of tremor propagation. LFE detections beneath the Olympic Peninsula occur in two patches, each about ten kilometers in diameter, with a ten kilometer gap in between. We examine the interaction between these two patches in order to answer key questions about tremor migration: Does tremor migrate between patches? If so, does tremor propagate faster within a patch or between patches? Finally, do propagation velocities depend on the depth of the patch? The answer to these questions will give insight into the mechanism driving slow slip and its varied migration behaviors.
Carrie Garrison-Laney: Cascadia tsunamis and subduction zone deformation in Puget Sound
- Previous studies of Puget Sound tidal marshes have identified a history of earthquakes, tsunamis, and liquefaction from local fault sources (Bucknam et al., 1992; Sherrod, 2001; Atwater, 1999; Atwater and Moore, 1992; Bourgeois and Johnson, 2001; Martin and Bourgeois, 2012). However, the extent that Cascadia subduction zone deformation and tsunamis affect the Puget Sound region is relatively unknown. I examine two types of evidence of Cascadia earthquakes in Puget Sound tidal marshes: candidate Cascadia tsunami deposits in Puget Sound tidal marshes, and microfossil (diatom) records of vertical land level deformation associated with Cascadia subduction zone earthquake cycles.
A recent tsunami simulation by Pacific Marine Environmental Laboratory (Wei, 2014) of a Cascadia tsunami entering Puget Sound suggests that Cascadia subduction zone tsunamis pose a significant threat to parts of Puget Sound. The model predicts high wave heights in some areas. This model, if supported by new field evidence of tsunami deposits of past Cascadia tsunamis, will significantly change the tsunami hazard estimates for Puget Sound.
Preliminary evidence for two such tsunami deposits has been found at Lynch Cove marsh at the head of Hood Canal. Two sandy mud layers are suggestive of tsunami deposits in their geometry, sediment types, and microfossil content. Radiocarbon dates of these layers yields ages that are within the age ranges of the last two Cascadia earthquakes. Layer A dates between 1685-1850 AD, range that contains the 1700 AD Cascadia earthquake (Satake et al., 1996; Jacoby et al., 1997; Yamaguchi et al., 1997; Atwater et al., 2005). Layer B dates between 1170-1225 AD, a range that overlaps with the penultimate Cascadia earthquake on the outer coast of Washington (Atwater et al., 2004) other regional tsunami deposits (Clague and Bobrowsky, 1994; Williams et al., 2005), Lake Washington turbidites (Karlin et al., 2004), marine turbidites in the Juan de Fuca and Cascadia channels offshore (Goldfinger et al., 2012), and Snohomish river delta tidal marsh subsidence (Bourgeois and Johnson, 2001).
Previous studies have modeled interseismic deformation using constraints of geodetic or tide gauge data. Wang et al.'s (2001) and Wang’s (2007) viscoelastic dislocation models, based in part on GPS data, predict interseismic uplift between 0-1mm/yr, and 1-2mm/yr, respectively, for the Puget Sound region between great earthquakes. Tide gauge records show uplift between 1-2mm/yr for most of the Puget Sound region (Verdonck, 2006). However, GPS and tide gauge datasets document only a portion of interseismic deformation, long after the last earthquake of 1700 AD. Tidal marsh sediments and their corresponding microfossils record long spans of “paleogeodetic” information and the full earthquake cycle between the penultimate and most recent earthquake, making their sea level histories valuable constraints for future models of subduction zone deformation.
My study and statistical analysis of Lynch Cove marsh fossil diatom paleoecology indicates a relative sea level history for Lynch Cove that fluctuates throughout the last 800 years. Separating any subduction zone deformation signal from other potential sources (i.e. local sea level rise, local tectonic source, or sediment compaction) will require further study.
Aaron Brewer: The magnesium isotope composition of volcanic arcs and basalts from large igneous provinces
- While pristine mantle peridotites, MORBs, and OIBs have a homogenous magnesium (Mg) isotope composition (δ26Mg = -0.25±0.07‰), near surface water-rock interaction can cause these rocks to have a heavy composition. If this altered material is added to a magma, at a subduction zone for example, the resulting rock may have a Mg isotope composition that differs from the typical MORB and OIB value even if that rock has not experienced near surface alteration itself. Sixteen unweathered Cascade Volcanic Arc basalts and basaltic andesites and ten Emeishan flood basalts show evidence of crustal input. Both have Mg isotope compositions that vary from mantle values to slightly heavier compositions (as heavy as -0.13±0.07‰) as MgO concentrations decrease (from 8.38 to 1.36 wt%) and K2O concentrations increase (from 0.15 to 2.99 wt%). This trend is best explained by crustal input into the magma either due to subduction of sediments and altered oceanic crust or assimilation of continental crust during magma ascent. Although a significant crustal component will systematically and observably increase the Mg isotope composition of igneous rocks, these effects are small, barely extending beyond the error for mantle values.
6. Flight Plans: Getting to Infinity and Beyond
Ian Johnson: A sulfur propellant pulsed plasma thruster for CubeSAT Operation
- Pulsed Plasma Thrusters (PPTs) have long been considered a leading candidate for small satellite propulsion due to their versatility in size and power as well as inherent simplicity. Propellant for the thruster has traditionally been Teflon, a carbon and fluorine plastic, chosen for its high specific impulse (Isp) and low charring. Recent results show that a 1.6J coaxial PPT with sulfur propellant has an impulse bit of 27uN-sec, twice that of a physically identical Teflon variant. This is believed to be primarily due to the higher total mass bit and higher plasma fraction of sulfur, both consequences of the low melting, boiling, and ionization energies. The higher atomic mass of sulfur leads to a lower plasma exhaust velocity (17km/s), however the higher ionization fraction allows for similar Isp and ΔV capabilities. Three missions are currently under study. (1) Increasing the lifetime of a 3U CubeSAT in a 300km Earth orbit by 50%. (2) Orbit correction for a 3U CubeSAT as a tagalong satellite for the Europa Clipper mission. (3) Primary propulsion for a 6U CubeSAT to complete in the Lunar CubeQuest Challenge. In conjunction with the ESS rocketry and ballooning programs, a number of atmospheric flights are planned for CubeSAT testing over the next three years. Amateur rockets as well as burst balloons can reach altitudes greater than 30km, allowing for short duration testing in a reduced pressure environment. Two such launches will occur in March of 2015, the first to test a 3D printed CubeSAT structure and arduino based control system onboard a single-stage 6” diameter rocket, and the second to test the PPT and arduino based control system flown with a latex zeppelin airship.
Kyler Kelley and Mariah Danner: Quantifying forces acting upon a rocket during sustained supersonic flight
- The importance of understanding the forces which act upon rockets during sustained supersonic flight is unquestionable; rockets which cannot sustain these forces either do not launch or fail ballistically. Though these forces are known, they have yet to be quantified for rockets L2 in size. The goal of our project was to construct a rocket capable of supersonic speeds which collected temperature, flex, and vibration data throughout the flight. The rocket was designed over a two week period using the program OpenRocket to simulate estimated flight velocities, accelerations, and apogees. The most suitable design for the purposes of the experiment was determined to be a two-stage rocket with an M-motor booster and L-motor sustainer, the latter of which’s fins the sensors were embedded into. Over a ten week period the rocket body was constructed using a fiberglass body and fins, with carbon fiber fin overlay to protect against high G-forces. Temperature, flex, and vibration fluctuations on the fins during flight were recorded to a custom built computer board housed within the upper payload section of the rocket. Once flown, the data will be analyzed to determine max stresses undergone by the rocket, as well the duration and timing the stresses. Using the data collected from our sensors we can better understand the forces so in the future we can use materials and construction designs that are better suited for sustained supersonic flight.
Nao Murakami: High-power helicon double gun thruster
- While chemical propulsion is necessary to launch a spacecraft from a planetary surface into space, electric propulsion has the potential to provide significant cost savings for the orbital transfer of payloads between planets. Due to extended wave particle interactions, a plasma thruster that can operate in the 100 kW to several MW power regime can only be attained by increasing the size of the thruster, or by using an array of plasma thrusters. This experiment examines whether simultaneously firing two helicon thrusters side-by-side would have a higher performance than firing a single thruster.
Kristin Poinar: Will meltwater lubrication destroy the Greenland Ice Sheet?
- The Greenland Ice Sheet has the lowest latitude of the earth's three ice sheets, and there is evidence that it was much smaller in size during the Eemian warm period (120 ka). Thus, its stability in today's warming climate is questionable, but the mechanism(s) by which it may vanish are uncertain. One potential cause of collapse is through surface melt enhancing the flow of the ice sheet by lubricating its bottom in new places. This could occur if surface melt were to penetrate down to areas where the bed is currently dry, and thus slow-moving. Catastrophic drainages of supraglacial lakes, which are observed every summer, deliver surface meltwater to the bottom of the ice sheet, but these events currently seem to occur only where the bed is already wet, and thus already relatively fast-flowing. As a warmer climate drives supraglacial lakes to form at higher elevations on the ice sheet that are potentially underlain by dry areas, drainages of these lakes would, in theory, lubricate the bed there and significantly speed ice flow. In this presentation, I address this contemporary concern by evaluating the likelihood of higher-elevation lakes, which are already marching steadily higher on the ice sheet, to drain their water to the underlying bed. This analysis compares satellite imagery of the lakes, observed surface strain rates (which allow lake drainage), and modeled wet / dry areas of the bed. Results suggest that, in fact, higher-elevation meltwater is unlikely to penetrate to the bed in areas where it would affect ice flow. Thus, meltwater lubrication is unlikely to cause the demise of the ice sheet. With this conclusion and similar disarmaments (past ~5 years) of other potential mechanisms that could destroy the ice sheet, it seems likely that the Greenland Ice Sheet will melt over the next few thousand years rather than disintegrate rapidly through ice dynamics.
Michael Hay: Linear stability of coupled anisotropic ice flow and fabric evolution
- Ice in ice sheets and glaciers often has strong plastic anisotropy, in which the flow response of the ice to applied stress is different under different orientations (relative to the applied stress). This can greatly affect ice flow. It may also cause folding of stratigraphic layers or other stratigraphic disturbances, which can affect the interpretation of ice core records.
An individual ice crystal deforms mainly by shear on the basal plane orthogonal to the crystallographic c-axis. Plastic strain in other orientations is around 100 times more difficult. An ice polycrystal with randomly distributed c-axes is plastically isotropic. However, an initially isotropic polycrystal will develop preferred orientations in response to strain, with the c-axes rotating away from axes of principal extension. This can produces non-isotropic fabrics, which can strongly affect ice flow. Therefore, anisotropic flow and fabric evolution form a coupled system.
Folding and boudinage on the meter-scale have been observed hundreds of meters off the bed in ice sheets. Variability of ice fabric may provide an initial seed to allow these disturbances to occur. To investigate this, I am doing a linear perturbation analysis of coupled ice-flow and fabric evolution. This will allow us to determine if it is possible for small amplitude initial perturbations of the fabric to grow into larger disturbances, and affect stratigraphy.
Max Stevens: Model predictions of the physical propeties of polar firn
- Knowledge of the physics of firn-density evolution and gas transport in firn has several important applications in glaciology, including (1) correcting for firn-air content when estimating ice-sheet mass-balance changes from satellite altimetry and (2) determining the ice-age/gas-age difference for paleoclimate interpretations of ice-core records. The firn-physics group at the University of Washington is developing modular and open-source community models describing evolution of firn density, temperature, diffusivity, and other structural properties affecting gas transport. A novel aspect is that the gas model can be coupled to the density model, allowing bubble-close-off depth, lock-in depth, depth-integrated porosity, and effective diffusivity to evolve through time in a consistent way. This feature allows us to investigate how changes in firn physical properties affect gas transport in firn. Here, we compare lock-in and bubble-close-off depths predicted by the firn model to observations from sites in Greenland and Antarctica.
8. Poster Session: Seismology, Cryosphere, Geochemistry, Paleoclimate & Biostratigraphy
Kelley Hall: Slip updip of tremor during the 2012 Cascadia ETS event
- The interplay between tremor and slow slip during ETS has implications for the slip budget of the Cascadia subduction zone. In particular, it can constrain the downdip edge of the locked zone, which informs the hazard assessments for major cities including Seattle, Tacoma, and Vancouver. As shown by Houston (AGU abstract, 2012), slip inferred from GPS extended updip of the seismically-detected tremor in the 2010 M6.8 ETS event. Following the methods used on the 2010 ETS event, we used the PANGA GPS to measure the displacement vectors for 71 stations to analyze a large ETS event in 2012 that extended from Vancouver Island to Southern Washington. We implemented Principal Component Analysis to automatically select the direction and magnitude of the maximum displacement vector. We 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. We performed inversions with either 0th or 2nd order Tikhonov regularization and found that over the 6 weeks of propagation, the 2012 ETS event released moment corresponding to M6.7, in three high-slip regions. We compared two different inversions, one where slip was allowed on a broad regional grid and a tremor-restricted inversion (TRI) where slip was restricted to grid locations where tremor had been detected in the 2012 ETS. We found that the TRI 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. Additionally, the regional grid inversion indicates that 1 to 2 cm of slip 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.
Carl Ulberg: Initiation and propagation phases of northern Cascadia episode tremor and slip events
- Northern Cascadia episodic tremor and slip (ETS) events appear to have distinct initiation and propagation phases. We find that there is a roughly linear increase in tremor amplitude over the first 5-8 days of each ETS event. We observe a corresponding linear increase in the areal distribution of tremor. These episodes typically initiate down dip, and after approximately 5 days have organized and migrated to fill the up-dip/down-dip width of the tremorgenic zone. After this time, tremor amplitudes vary wildly, modulated by tidal stresses, as the tremor propagates along strike in one or both directions at roughly 7-12 km/day, continuing for 3-5 weeks.
In order to estimate tremor amplitude we use three-component seismograms from temporary deployments and permanent stations (Array of Arrays, CAFE, PNSN, TA) to estimate the amplitude of tremor bursts at the source location, using a method similar to Maeda and Obara (JGR, 2009). Source amplitude, or radiated energy rate, is proportional to the root-mean square of band limited (1.5-5.5 Hz) ground velocity for each 5-minute window. Station ground velocities and tremor locations, determined by a waveform envelope cross-correlation method (Wech and Creager, GRL, 2008), are inverted to obtain source amplitude and station statics, taking into account geometrical spreading and attenuation. The result is a catalog of source amplitudes for each of 40,000 tremor locations in northern Cascadia from 2006 to 2011.
Justin L. Brooks: Determining the elastic constants of AN68 plagioclase feldspar by the initiation and measurement of surface acoustic waves by Nd:YAG laser
- This research is in support of Dr. JM Brown’s Elastic Constants of Plagioclase Feldspars. Feldspars make up ~60% of the Earth’s crust. Knowing the elastic response of the constituent parts of the crust is important to predict its response to seismic stimulus. There are two categories of feldspars: Plagioclase feldspars which contain calcium and sodium and Orthoclase feldspars that contain postassium. Plagioclase feldspars represent the continuous branch between anorthite (Ca) and albite (Na) in the Bowen’s Reaction Series. The crystals used in the study are sourced from Plush, Oregon where sunstone, the gem name of this particular Plagioclase Feldspar, is commonly collected. Sunstones contain traces of native copper within the crystal structure causing a reddish shiller which makes them popular as gemstones. However, this characteristic is undesirable for the study so a clear crystal was selected as a sample. Using mass spectrometry, the composition of the specimens was determined to be 68% anorthite which fits well with Dr. Brown’s current research as he has the data for the end members. A clear crystal was broken down to millimeter size to reduce the occurrence of twinning in the specimen. Non-twinned mm size crystals were oriented to desired lattice positions using X-ray diffraction and a robotic goniometer. The crystal was cemented to a round slide and encased in an epoxy plug. This plug was polished using diamond grit until the crystal obtained a mirror finish. 40nm of aluminum was placed upon the crystal/epoxy surface to serve as an interface between the Nd:YAG laser and the crystal. The laser is used to induce and measure surface wave velocities of the 68% anorthite crystal. The importance of this research is that it replaces earlier reported velocities with calculated misfits of ~10%. The determined elastic constants can be used to better understand and interpret the Earth’s crust from collected seismic data.
Ian Lee Rui Jie: Identification, characterization and cataloging of surface features of ice shelves in Dronning Maud Land, Antarctica
- The Antarctic Ice Sheet has been undergoing rapid changes in the past few decades, triggered by the alarming thinning of its ice shelves. This thinning is mostly caused by enhanced basal melting by warm ocean water. However, recent studies have found that melting rates are not spatially uniform, but rather are strongly controlled by the topography of the base of the ice shelf. The topography of the ice-shelf base can often be inferred from the ice-shelf surface. In this research project, I identified, characterized and categorized surface morphological features of the ice shelves in Dronning Maud Land (DML) using RADARSAT-2 satellite imagery. DML has many semi-connected small ice shelves. Due to their sizes and complicated shapes, simple algorithms that are widely used in continent-wide work cannot be applied to these ice shelves. I have processed these new RADARASAT-2 images using speckle filtering and multi-looking methods to enhance image-brightness contrast associated with surface features. The surface features are highly variable between ice shelves, and related to ice-flow fields. These features are digitized and incorporated into the QGIS-operated program Quantarctica 2.0, which is a collection of Antarctic geographical datasets. This project was conducted in winter quarter 2015 as part of larger efforts led by the Norwegian Polar Institute to determine the current status of the DML coast (Ice Shelves, Ice Rises, Outlet Glaciers etc.) in greater detail.
William Medwedeff: A statistical analysis of glacial mass balance data
- There has long been an interest among climate scientists in studying glaciers as indicators of climate change. In particular, glacial length is a commonly reported measurement because it is easy to measure and provides an integrated summary of a glacier's response to the climate. However a trend in the length of a glacier does not provide particularly strong independent evidence of climate change because glaciers respond to both the “noise” of interannual variability as well as the “signal” of real climate change. In fact, previous research has shown that kilometer scale changes in length can be expected as a result of random climate variability alone (Roe & ONeal 2005, Roe 2011). Furthermore even if an actual climate trend does exist, estimates of its magnitude from the trend in glacial length are acutely sensitive to glacier geometry which is often complicated and poorly known. In light of this, we have elected to study glacier mass balance data as it is more closely related to the climate record and has more statistical power to resolve climate change than do glacier length records. We have applied a number of conventional statistical measures to the 127 seasonal mass balance records longer than 5 years that we have identified. In particular, we focus on characterizing the variability and trends observed in the mass balance record. Furthermore, we investigate the significance of mass balance trends and constrain confidence intervals on our statistical results. We find our results to be generally consistent with climate warming, with most of the significant trends appearing in summer records. However, the confidence with which we can report our results is hampered by the limited and geographically biased state of existing mass balance records.
Huong Vo: Spatial distribution of close-off depth, age, and porosity in the Greenland Ice Sheet
- Ice cores from dry snow zones provide a record of Earth’s past climate history and atmospheric composition for up to 800,000 years. In order to interpret ice-core data accurately, scientists must know the difference between the age of the ice and the age of the air trapped within (delta age). In addition, satellite-based measurements of ice-sheet elevation changes must be accompanied by estimates of the air content, or depth-integrated porosity of the firn, in order to infer rates of mass gain or loss. The firn physics group at University of Washington is developing an open source Community Firn Model to simulate firn densification and gas-transport processes. Here, we have used to community model to calculate the spatial distribution of depth and age of the firn at pore close-off, as well as the depth-integrated porosity, using gridded mean- annual temperature and accumulation data for Greenland (Box et al., 2013). Our results can contribute to a better understanding of past climate changes, and knowing the close-off depth and age will provide guidelines for future core sites for investigation of pre-industrial levels of trace gases. Knowing the depth-integrated porosity will allow more accurate mass-loss estimates, and to future sea-level predictions.
Laura Kehrl: What mechanisms control glacier velocity variations at Helheim Glacier, southeast Greenland?
- Marine-terminating outlet glaciers drain about half of the Greenland Ice Sheet. Over the last decade, many of these glaciers have accelerated, thinned, and retreated. This widespread, synchronous response is believed to be due to changes at the ice-ocean boundary. Changes at the ice-ocean boundary (submarine melting, iceberg calving) alter the terminus position and thereby the stress balance. If the glacier retreats into deeper water, more of the driving stress must then be balanced by longitudinal stress gradients and/or basal shear stress, so the glacier speeds up. This study combines satellite observations and numerical ice-flow modeling to investigate velocity variations at Helheim Glacier, southeast Greenland, from 2000-2014. Although Helheim Glacier retreated over 7 km from 2001-2005, its terminus position has been relatively stable since 2007. During terminus variations of more than a few hundred meters, we find velocity variations that extend up to 30 km inland. We use a numerical ice-flow model to investigate how changes at the glacier terminus propagate inland. In particular, we consider whether a coincident change in terminus position and effective pressure (ice overburden pressure minus water pressure) at the glacier bed is necessary to explain our observations. The model experiments will provide additional insight into the mechanisms that control a glacier’s sensitivity to ocean warming.
Nikolas Midttun: Glacial stratigraphy of Possession Point drumlin on south Whidbey Island, WA
- Among the geomorphic features created by continental scale glaciations, drumlins are one of the most prominent and actively studied. Drumlins are highly variable in structure and composition, and the mechanisms behind their formation are not well understood. Detailed mapping of the stratigraphy and internal structure of a drumlin may yield evidence that allows us to piece together the specific depositional and erosional history of that drumlin. This mapping process is made difficult by many drumlins’ complex structure and poor surface exposure. In my study, I am examining the drumlins on the south end of Whidbey Island, in particular, the drumlin situated on the Possession Point peninsula. Possession point provides a unique opportunity to resolve the issue of poor sediment exposure thanks to two properties of the peninsula. First, on top of Possession Point resides a residential neighborhood that has produced a database of approximately twenty well cores with corresponding stratigraphy records. Second, the south and east sides of the drumlin have been eroded back by coastal erosion, possibly revealing internal stratigraphic relationships otherwise not visible. Detailed mapping paired with high-resolution lidar-based digital elevation models from the Pacific Northwest Lidar Consortium will hopefully lead to improved understanding of drumlin formation in the Puget Sound area.
Florence Yuen: Magnesium isotope fractionation in Hainan Island corals and its relationship with sea surface temperature (SST)
- Scientists have been using Sr/Ca ratio, Mg/Ca ratio, δ13C and δ18O as proxies for SST. Because each of these proxies has their weaknesses under certain environmental conditions, it is imperative to search for new proxies to complement existing proxies. My project investigates the relationship between SST and magnesium isotope fractionation in corals as a proxy for gauging paleo temperature. Samples were collected from each annual growth-ring and then powdered before dissolved in concentrated acid. The Mg in the samples was separated by cation exchange chromatography. The values of 26Mg/24Mg and 25Mg/24Mg for each sample will be measured using a multi collector inductively coupled plasma mass spectrometer (MC-ICPMS). If δ26Mg in coral is found to have a direct correlation with SST, then fossil coral could be analyzed to provide a long term record of paleo temperature. Having yet another tool in the paleo thermometer toolbox would help scientists improve on global SST records and better model past and future changes in the climate.global SST records and better model past and future changes in the climate.
Sebastian Belfanti: Searching for subterranean gold ores in Chandalar Mining District, Alaska, using Pb, Sr, and Nd isotopic indicators
- Buried gold deposits in the Brooks Range of northern Alaska have the potential to provide economical sources of gold. Chandalar Mining district was a well-known region for surface, shaft, and placer gold mining throughout the twentieth century, but declined as surface deposits became depleted in the 1960’s. These deposits produced some of the largest orogeny-derived gold nuggets in the world. Preliminary analyses commissioned by Spokane’s Little Squaw Gold Mining Company supports prospects that the area can provide mining opportunities in this century as well. However, the remaining surface deposits are of only moderate value, so we must look below the surface for economically worthwhile ores. In this study, through the analysis of vein minerals collected at the surface and from shallow drill cores, we aim to determine whether unexposed basement in the Chandalar Mining district has characteristics similar to exposed rock in other parts of the Brooks Range that hosts gold mineralization. The district is located on top of an igneous province overlain by a layer of metamorphosed sediment and a sedimentary cap. If isotopic tracers can be used to source samples of hydrothermal veins from shallow core and surface samples to an igneous basement similar to gold-mineralized rocks elsewhere in the Brooks Range, then it is possible that deep drilling to test for mineralization in the igneous basement could be justified. Such mineralization has the potential to support economical sub-surface mining operations. Samples from surface deposits and cores were dissolved and processed using ion-chromatographic column chemistry to separate Pb, Sr, and Nd for isotopic analysis. Isotopic data from these samples are being collected using a Nu-1 mass spectrometer. We will compare these data to published data on gold-mineralized basement from elsewhere in the Brooks Range.
Patrick Watts: Low Temperature Thermal Aqueous Isotopic Fractionation of Magnesium
Sean Lorimor: Greenland Paleotemperature Reconstruction Project
- Several sediment cores were recovered from Limnaea Sø and Braya Sø, closed-basin lakes in Southwestern Greenland, to reconstruct past temperatures during the Holocene epoch (past ~10,000 years). The closed-basin topography make the lakes ideal for studying changes in evaporation and precipitation, and the lake sediments contain authigenic (formed insitu) carbonates which record variations in past lake conditions. {transition needed here} Prior to sectioning, the sediment cores were analyzed by x-ray, magnetic susceptibility, and bulk density to allow stratigraphic correlation between cores and determine changes in sediment input and lithology. The core was sectioned and a series of samples taken 20 cm apart were sent for radiocarbon dating, which placed the samples between present day and 12.5 ka (calendar age). A series of samples were analyzed for total organic carbon, which provided insight into the history of vegetative changes surrounding the lakes. Samples were then prepared for δ13C and δ18O isotopic analysis on the Kiel Carbonate system/isotope ratio mass spectrometer. The δ13C and δ18O data show periods of abrupt isotopic change, which may indicate either strong change in the hydrologic regime and/or surface air temperatures. We are analyzing these periods using clumped-isotope paleothermometry techniques to determine whether the isotopic variations are mainly a response to lake temperature variations. Work from ice cores show relatively stable temperatures during the Holocene epoch; however, recent lake sediment records have suggested that temperatures may have been more variable than previously thought. If our results show no significant temperature variations, it will confirm previous interpretations based on δ18O that large shifts in the hydrologic cycle occurred. The clumped isotope paleothermometry technique will be the first of its kind applied to Greenland lake sediments to produce a temperature reconstruction.
Adrienne Sorenson: Foraminifera: Indicators of pollution effects in Puget Sound, Washington
- The Puget Sound is a part the Salish Sea, a complex estuary and inland waterway that extends 350 km from Olympia, Washington to the northern tip of Vancouver Island, British Columbia. The system is flooded tidally through the Strait of Juan de Fuca bringing cold, oxygen-poor ocean waters from coastal upwelling. Biodiversity is high but because of anthropogenic pollutants, many species are threatened or endangered. Our study is a part of the Puget Sound Foraminifera Project that is investigating the impact of pollutants on benthic ecosystems. Foraminifera are marine microorganisms with CaCO3 or sediment agglutinated shells that preserve in the sediment. They can be used as bio-indicators because they are highly specialized within their habitats, making presence or absence of certain species informative to ecological studies. This project is investigating sediment/water interface conditions in different embayments of Puget Sound using foraminiferal species assemblages at each sample site. Specifically, data was analyzed from Hood Canal, Commencement Bay, Bainbridge Basin and the San Juan Islands. Many of the study locations show a low species diversity and density of foraminifera, as well as a high percentage of partially dissolved calcareous shells. These findings are consistent with an ecosystem that experiences acidification and high anthropogenic nutrient fluxes.