2016 Gala

March 31 - April 1, 2016

Keynote speaker: Wes Thelen (Geophysics '09)

Committee: Joel Gombiner, Adrienne Sorenson, Zack McIntire, Alex Huth

Main website

Schedule

Thursday, March 31

8:50 - 9:00 - Opening Remarks (JHN-170)

9:00 - 9:45 - Session 1: Rivers (JHN-170)

    • 9:00 Sarah Schanz: Investigating the effect of temporally and spatially variable sediment retention on river incision through numerical modeling
    • 9:15 Jonathan Beyeler: Transient fluvial response to alpine deglaciation, Mount Rainier, WA: geomorphic process domains and flux-driven proglacial channel evolution.
    • 9:30 Sarah Harbert: Investigating the role of near-fault relief and vertical uplift in strike-slip landscape development

9:45 - 10:00 - Break

10:00 - 11:00 - Session 2: Subduction (JHN-170)

    • 10:00 Shelly Chestler: Depth depended slow slip processes revealed by low frequency earthquakes
    • 10:15 Yan Hu: Magnesium Isotopic Composition of Subducting Marine Sediments
    • 10:30 Kelley Hall: Spatial and Temporal Relationships between Tremor and Slip in 2010 Cascadia ETS
    • 10:45 Carrie Garrison-Laney: Overview of tsunami potential from landslides in Puget Sound

11:00 - 11:15 - Break

11:15 - 12:00 - Session 3: Dynamic Particles (JHN-170)

    • 11:15 Jillian Schleicher: The mechanics of an open-system magmatic mush intrusion event
    • 11:30 Mike Hay: Effects of random strain perturbations on ice sheet crystal fabric
    • 11:45 Todd Anderson: Vector electric field measurements from the Charged Aerosol Release Experiment II

12:00 - 1:00 - Lunch

1:00 - 1:45 - Session 4: Remote Sensing (JHN-170)

    • 1:00 L.M. Kehrl: A tale of two glaciers: recent observations at Helheim and Kangerdlugssuaq Glaciers, southeast Greenland
    • 1:15 Eric Keenan: Thermal Infrared Remote Sensing of Snow Surface Temperature: Quantifying Snow.s Energy Budgete
    • 1:30 Elena Amador: Spectral Characteristics of dark slope streaks on Mars: A global survey with CRISM

1:45 - 2:00 - Break

2:00 - 2:45 - Session 5: Antarctica (JHN-170)

    • 2:00 Trevor Hillebrand: High frequency radio echo sounding reveals past flow conditions of Crary Ice Rise, Antarctica
    • 2:15 Virginia Littell: Sourcing excess ground ice using water isotopes, Beacon Valley, Antarctica
    • 2:30 Bradley Markle: Moisture transport to West Antarctica constrained by shared water-isotope and ice- impurity variability at millennial to orbital time scales

3:00 - 3:30 - Seminar Snacks

03:30 - 4:30 - Colloquium: Wes Thelen, keynote speaker (JHN-102)


Friday, April 1

9:00 - 10:00 - Session 6: Isotopes (JHN-170)

    • 9:00 Julia Kelson: Quantifying Climate Change During the PETM in Continental North America
    • 9:15 K.R. Hodson: Leaky faults: 50 million years of fluid migration history on the Moab Fault, Utah.
    • 9:30 Landon Burgener: Insights from carbonate clumped isotope thermometry into the climate factors controlling the seasonality of soil carbonate formation
    • 9:45 Austin Steele: Greenland Paleo-temperature Reconstruction Project

10:00 - 10:15 - Break

10:15 - 11:00 - Session 7: Glaciers (JHN-170)

    • 10:15 John Christian: Identifying dynamically-induced variability in glacier mass-balance records.
    • 10:30 Max Stevens: Quantifying firn-model contribution to uncertainty in calculations of ice-sheet mass balance
    • 10:45 David Lilien: Observations During the Quiescent Phase of a Surge-Type Outlet Glacier

11:00 - 12:15 - Lunch

1:30 - 3:00 - Poster Session (JHN 100-level hallway)

    • Mara Page: Investigating Vegetation Changes in Northern Australia during the Late Pleistocene to Holocene
    • Brianna Hunt: Quantitative Oxygen Concentration Data at Depth: The Theory, Methodology, and Application of Optodes.
    • Ashly Padgett: Post-glacial landform sediment diffusivity rates: An alternate dating technique
    • Zi Xian Leong: Movement of the Redbluff Landslide using InSAR and LiDAR Data Sets
    • Khadijah Homolka: Potential for Seawater as a Geostandard for Potassium Isotopes
    • Luke Fisher: Imaging Magma Under St. Helens (iMUSH) Using Cross-Correlation Times of Teleseismic Earthquakes
    • Joel H. Gombiner: Isotope geochemistry of Scabland Flood deposits
    • Katherine Hotchkin: Time Evolution of Geochemical Characteristics in East Molokai, Hawaii
    • Lauren Kowalski: Constraining shallow seawater circulation at the Southern Hydrate Ridge seep system
    • Linnea E. McCann: Isotopic and trace element evidence for basalts with mantle plume affinities in the Cascadia subduction zone
    • Nicolas Cuozzo: Polygonal patterned ground in the Antarctic Dry Valleys and its relation to ice-rich permafrost depth

5:00 - 9:00 - Closing Ceremony (Cafe Vista)

Abstracts by Session

1. Rivers

Sarah Schanz (Talk): Investigating the effect of temporally and spatially variable sediment retention on river incision through numerical modeling

  • Field evidence in several Pacific Northwest streams suggests the loss of in-stream woody debris has reduced sediment retention and triggered river incision in the last century, resulting in incipient strath terrace formation. However, observations of this mechanism are limited to rivers with easily erodible bedrock, recent wood clearing, and a moderate sediment supply, and so the extent to which fluxes in sediment retention impact river incision rates is difficult to determine with field evidence alone. We use a 1-D numerical model to examine the influence of changes in sediment retention on fluvial long profile development over 100,000's of years, and contrast this with changes to sediment supply and water discharge. During periods of low sediment retention, river incision is promoted, leading to the abandonment of straths. Conversely, high sediment retention promotes river widening and strath planation. Our results shed light on the temporal importance of changes in sediment retention and help explain the global increase in strath terrace formation that occurred 2-3 kya. Future work will expand the model to 2-D to better simulate valley widening and strath planation, and will include more accurate climate representations with a storm and wildfire generator.

Jonathan Beyeler (Talk): Transient fluvial response to alpine deglaciation, Mount Rainier, WA: geomorphic process domains and flux-driven proglacial channel evolution

  • Proglacial rivers in deglaciating landscapes are highly dynamic portions of alpine rivers and some of Earth.s most rapidly evolving geomorphic systems due to the variable nature of hydrologic, sediment, and debris inputs under today.s changing climate. Shifting precipitation regimes in the Pacific Northwest are increasing river flood frequencies in winter months, despite lengthening melt seasons. Until recent years, overbank flows (i.e., floods) along glacially-fed rivers in the Cascade Range occurred during melt seasons. Presently many channel networks experience significant floods in response to frequent, low-magnitude winter storms. Driven by warming climate and glacier retreat all of the rivers draining Mount Rainier, WA, are rapidly evolving through paraglacial sedimentation processes. LiDAR differencing along the Carbon and Nisqually Rivers exposes discrete geomorphic processes driving river response to deglaciation post- Little Ice Age (ca. ~1895-1910) that varies systematically along the longitudinal profiles of both rivers. This work shows increasing flood frequencies of rivers draining Mount Rainier National Park (MORA) are largely controlled by the ratio between hydrologic and sediment fluxes, currently driven by transient glaciogenic sediment inputs. We hypothesize that proglacial debris flows from eroding moraines control downstream flooding by rapid deposition in aggrading, widening, and avulsing river channels. Steep headwaters of all MORA rivers are aggrading. However as sediment waves propagate downstream, aggradation is not yet seen along lower-gradient reaches near the park boundaries. The rivers draining Mount Rainier offer an exceptional opportunity to study active paraglacial sedimentation processes, and gain insight into the processes driving transient river response to alpine deglaciation.

Sarah Harbert (Talk): Investigating the role of near-fault relief and vertical uplift in strike-slip landscape development

  • Strike-slip faults create distinctive fluvial landforms, such as offset, diverted, and captured streams, as well as near-fault relief features such as shutter ridges and sag ponds. These landforms have been used to identify faults, assess fault activity and determine slip rates. However, not every active strike-slip fault shows a clear landscape signature of its presence, and strike-slip motion on a fault may not be wholly responsible for the occurrence and form of these features. We use the Channel-Hillslope Integrated Landscape Development model (CHILD) to investigate the effects of vertical uplift and relief across a fault on the production of strike-slip landforms. By varying uplift rates and bedrock erodibility across a modeled strike-slip fault, we consider both how different ratios of vertical to horizontal fault motion affect the landscape and how the presence of landforms such as shutter ridges and sag ponds affect the development of the fluvial network. Of the parameters tested, relief on the downhill side of the fault has the strongest effect on the landscape. When relief is low and shutter ridges are small or not present, offsets are short and stream capture occurs frequently. We compare these results to landscapes in the Marlborough Fault System of New Zealand, where relief downstream of the fault broadly correlates to channel offset length. These results show that the presence of topography or lithologic contrasts can enhance or damp the landscape signature of a strike-slip fault.

2. Subduction

Shelly Chestler (Talk): Depth depended slow slip processes revealed by low frequency earthquakes

  • Using a catalog of low frequency earthquakes beneath the Olympic Peninsula, WA, we study depth dependent slow slip processes in Northern Cascadia. During an ETS event, activity at a given point on the plate interface (i.e. the activity of an LFE family) typically lasts for 3.5 (downdip) to 5 days (updip). Activity generally begins with a flurry of lower-amplitude LFEs lasting 8 hours (downdip) to 20 hours (updip) followed by many short high-amplitude bursts of activity separated by 5 hours or more. Updip families have more bursts (5-10) than downdip families (2-5 bursts). The later bursts often occur during times of encouraging tidal shear stress, while the initial flurries have no significant correlation with tides. Updip LFEs have higher cumulative moment magnitudes that downdip LFEs. While updip LFE families are more active during ETS events that downdip families, they seldom light up between ETS events, which only occur every 12-14 months. On the other hand, downdip LFE families are active much more frequently during the year; the most down-dip families exhibit activity every week or so. Because updip families are rarely active between ETS events, it is possible that little stress is released updip during inter-ETS time periods. Hence during ETS events more stress must be released updip than downdip, consistent with the longer-duration activity and higher amplitudes of updip LFE families.

Yan Hu (Talk): Magnesium Isotopic Composition of Subducting Marine Sediments

  • To characterize the Mg inputs to global subduction zones, we measured .26Mg data for a total of 90 marine sediments collected from 12 drill sites outboard of the world.s major subduction zones. These sediments span a 1.73. range in .26Mg. The detritus-dominated sediments have .26Mg (-0.59 to +0.53) comparable to those of weathered materials on continents (e.g. -0.52 to +0.92), while the calcareous oozes yield .26Mg (as light as -1.20) more similar to the seawater value (-0.83). The negative correlation between .26Mg and CaO/Al2O3 in these sediments indicates the primary control of mineralogy over the Mg isotopic distribution among different sediment types, as carbonates are enriched in light Mg isotopes (-5.10 to -0.40 [5]) whereas clay-rich weathering residues generally have heavier .26Mg. In addition, chemical weathering and grain-size sorting drive sediments to a heavier .26Mg, as indicated by the broad positive trends between .26Mg with CIA (Chemical Index of Alteration) and TiO2/Zr, respectively. Collectively, the arc systems sampled in this study represent ~30% of global arc length and the extrapolated global Mg flux of subducting marine sediments accounts for ~9% of the yearly Mg riverine input with a flux-weighted average .26Mg at -0.26. Subduction of these heterogeneous sediments may not cause significant mantle heterogeneity on a global scale, but the highly variable Mg fluxes and .26Mg of sediments delivered to different trenches are capable of producing local mantle variations. Volcanic rocks sourced from these mantle domains are thus likely to carry a distinct Mg isotopic signal.

Kelley Hall (Talk): Spatial and Temporal Relationships between Tremor and Slip in 2010 Cascadia ETS

  • Slow slip and tremor migrate in tandem along several subduction zones at about 8 km/day in large Episodic Tremor and Slip (ETS) events. These events occur downdip of the locked megathrust, and thus the updip limits of slow slip or tremor provide potential constraints on the the slip budget of subduction zones and on the downdip edge of the locked zone, which inform hazard assessments for major cities including Seattle and Tacoma. As shown by Houston (AGU abstract, 2012) and Hall and Houston (AGU abstract, 2014), the slip inferred from GPS data extended updip of the seismically-detected tremor in the 2010 M6.8 ETS event, as well as in other events. While tremor appears to have a clear updip limit, the updip extent of slow slip is less clear. This also raises questions about spatial variations of the ratio of tremor activity to slip on the fault. We further explore the details of the 2010 event, using the Extended Network Inversion Filter (ENIF) (Segall and Matthews 1997) and tremor locations from the PNSN. Our preliminary results yield a M6.8 event that begins near Seattle on August 8th and propagates mainly to the north with some smaller slip to the south, following the propagation of the tremor. This is consistent with our static inversion results. The initial tremor begins at a depth of ~45 km and migrates up-dip before propagating along strike. There is no resolvable slip from GPS until the tremor has migrated up-dip. The slip pulse nature of the ETS process is clearly imaged, with regions continuing to slip for several days after tremor has passed through, but not for the entire duration of the event. We also find that GPS stations closer to the initiation of the ETS show higher deformation rates than the stations near the end. This suggests a clear progression of slip throughout the event from the initiation to propagation. Similarly, it has been suggested by Ulberg and Creager (AGU Abstract, 2013) that ETSs start with an initiation phase during which tremor amplitudes increase linearly and then a propagation phase where amplitude is highly variable. We plan to explore how this variation in amplitude corresponds to variations in slip. Our goal is to determine how closely tremor activity mimics slip activity, and understand where and why they may manifest differently.

Carrie Garrison-Laney (Talk): Overview of tsunami potential from landslides in Puget Sound

  • Tsunamigenic landslides may be the source two sandy mud layers at Lynch Cove in Hood Canal. The layers, interpreted as tsunami deposits, are dated 730-780, and 110-260 yr B.P. Because of the limitations of radiocarbon dating, correlations between these deposits and Washington coast Cascadia tsunami deposits are dubious. Even a concrete age correlation could not discount tsunamis generated by inland landslides triggered by earthquake shaking. While the age of the 110-260 yr B.P. deposit allows a tentative correlation with the A.D. 1700 earthquake, the 730-780 yr B.P. deposit does not correlate with any Washington coast Cascadia earthquake, so likely has a different source. The Puget Lowland has steep coastal bluffs of failure-prone glacial deposits, and subaerial landslides are common. Historic tsunamigenic landslides include 2.5 meter tsunami from a subaerial landslide that occurred three days after the 1949 M 7.1 Olympia earthquake; a 2 meter wave generated by a subaerial landslide during the 1946 M 7.3 Vancouver Island earthquake; and an oral history of an aseismic subaerial landslide at Camano Head that generated a deadly wave. Submarine landslides and delta failures can also trigger tsunamis. Submarine glacial deposits in narrow deep water fjords are known to be particularly prone to generating submarine landslides. Historic delta failures in Puget Sound include aseismic failure in Commencement Bay in 1894 and 1943, the Duwamish delta in 1986; and delta failure following the 2001 M 6.8 Nisqually earthquake. Examples from Alaska include deadly tsunamigenic submarine landslides triggered by the 1964 M 9.2 Great Alaska earthquake.

3. Dynamic Particles

Jillian Schleicher (Talk): The mechanics of an open-system magmatic mush intrusion event

  • Granular processes play an important role in the dynamics of many earth systems including crystal-rich magma reservoirs, sediment transport in rivers, debris avalanches, glacier flow, and groundwater flow. The mechanics of granular systems are not straight-forward. At low particle concentrations these systems can be considered as single-phase continua, with particle interactions having little influence on the overall dynamics of the system. However, increasing particle concentrations to as little as 30 volume percent can cause jamming, therefore continuum assumptions no longer hold. Forces within a packed bed are not evenly distributed among the particles; at any given instant, only ~30% of particles carry a force exceeding the mean. Additionally, particles bearing the load of the bed from one moment to the next are not constant, and forces transfer to neighboring particles. We present simulated results of an open-system magmatic intrusion into a crystal-rich olivine mush, similar to what may occur in Hawaii. We use a discrete element-computational fluid dynamics method, that resolves particle-scale interactions between particles and the fluid. This method allows us to monitor the evolution of the force network throughout the duration of the intrusion. Initially the probability distribution of the contact forces is proportional to a power law distribution for forces lower than the mean, and an exponential distribution for forces greater than the mean. These distributions vary throughout the intrusion, and the transmission of force through the mush ultimately impacts the processes of fluidization and fabric formation in magmatic systems.

Mike Hay (Talk): Effects of random strain perturbations on ice sheet crystal fabric

  • Crystal-orientation fabrics in polar ice sheets have a strong influence on ice flow due to the plastic anisotropy of ice. Crystal orientations evolve primarily in response to applied strain, but are also affected by temperature, impurities, interactions with neighbors, and other factors. The strain histories of fabrics are generally poorly constrained, and may have varied in unknown ways through time. Nearby layers in ice sheets can also experience different strain histories due to inherent variabilities such as transient flow, or differences in impurities. This means that the continuum ODF itself can be treated as stochastic, because it depends on an effectively-stochastic unknown strain-history. To explore this, we analyze the effects of strain and vorticity variability on the evolution of the continuum ice-crystal ODF. We recast Jeffery.s equation for the evolution of the ODF as a stochastic differential equation, with vorticity and strain perturbed by Gaussian processes. From this, we run a Monte-Carlo ensemble to determine likely bounds of true continuum ODF variability in response to random perturbations of strain and vorticity.

Todd Anderson (Talk): Vector electric field measurements from the Charged Aerosol Release Experiment II

  • The Charged Aerosol Release Experiment (CARE) II, launched in September 2016 from Andoya Space Center, Norway, was designed to study the wave propagation effects of hypersonic dust injection on the ionospheric plasma. Dust is introduced to the ionosphere from many sources, such as from chemical rocket motors, and may disrupt radio frequency wave propagation and excite plasma waves. We present preliminary results from the vector electric field instrument on the CARE II rocket.

4. Remote Sensing

L.M. Kehrl (Talk): A tale of two glaciers: recent observations at Helheim and Kangerdlugssuaq Glaciers, southeast Greenland

  • Marine-terminating glaciers drain about half of the Greenland Ice Sheet. In the early 2000s, many of these glaciers accelerated, thinned, and retreated. Recent studies indicate that this widespread, synchronous retreat likely occurred due to oceanic, rather than atmospheric, warming. This study uses a recently acquired, detailed record of glacier change at Helheim and Kangerdlugssuaq Glaciers, southeast Greenland, to assess the importance of oceanic and atmospheric changes over a much shorter, seasonal timescale. We combine satellite measurements of ice-front position, glacier velocity, and surface elevation from 2008-2016. Despite variations in the ice-front position of >4 km during this time, both glaciers maintained a relatively stable terminus position with no long-term trends. At Kangerdlugssuaq Glacier, the ice-front position varied seasonally, with glacier advance commencing in December and glacier retreat commencing in July. Glacier speed increased both during the winter when the terminus was most-retreated and during the early-summer melt season. In contrast, at Helheim Glacier, glacier retreat and speed-up events occurred at all times of the year. Despite these differences, both glaciers experienced a similar seasonal cycle in surface elevation, with glacier thinning starting in June/July and glacier thickening starting in October/November. We compare the timing of these glacier changes to different climate variables and conclude that both atmospheric and oceanic changes are likely important for driving the observed behavior of Kangerdlugssuaq and Helheim Glaciers over a seasonal timescale.

Eric Keenan (Talk): Thermal Infrared Remote Sensing of Snow Surface Temperature: Quantifying Snow's Energy Budgete

  • Over one sixth of the world's population relies on seasonal snowmelt and glacial runoff for their water resources. With measurable decreases in snow packs and accelerating warming predicted for the next century, quantifying the underlying physical processes describing snow accumulation and melt is critical to making informed water resources decisions. Here we present thermal infrared (TIR) measurements of snow surface temperature collected on the ground and by a small airplane flying over the Tuolumne watershed in Yosemite National Park in February 2016. The plane captured spatial and temporal variations in the temperature of the snow.s surface, while ground measurements provided a reference point to evaluate the aerial measurements' accuracy. TIR measurements provide a diagnostic tool used to assess model representation of many key processes, including snowmelt rates, sensible and latent heat fluxes, and longwave radiation. Moving forward we plan to incorporate our findings into snow models in order to better represent snow pack dynamics.

Elena Amador (Talk): Spectral Characteristics of dark slope streaks on Mars: A global survey with CRISM

  • The formation and fading of low-albedo slope streaks have been observed across the mid- tropical latitudes of Mars since the Viking orbiters. Two explanations have been established for slope streak formation: dust avalanches, and surface .staining. associated with transient brine seeps. The latter formation model was adopted for a class of slope streak termed recurring slope lineae (RSL). Spectral (compositional) data for RSL suggest in some cases spectrally featureless darkening similar to that found for slope streaks in the Olympus Mons Aureole, and most recently, in four instances, transient spectral signatures consistent with hydrated salts have been observed in association with surfaces with active RSL, thus supporting the .wet. formation mechanism. Here, we examine the variability and evolution through time of reflectance spectra of fully resolved slope streaks across Mars and how they may relate to the reported variability of RSL spectra. We find remarkably constant flat/featureless near-IR spectra observed for fully resolved slope streaks across Mars that indicate that these darkened surfaces are .dry., having no excess water/hydration in them with respect to their unaffected adjacent slopes. Similarly flat/featureless near-IR spectral ratios were also reported for RSL, which in some cases appear to show transient spectral absorptions consistent with hydration, strongly arguing in favor of the brine-seepage formation model. The transient nature of these hydration features and the flat/featureless spectral ratios otherwise observed for RSL suggest that within the seasonal timescale of their persistence, RSL may transition to a .dry. phase, in which they remain dark and are spectrally comparable to slope streaks. In addition, while some argue that spectral detection of transient surface hydration in RSL implies a genetic distinction from slope streaks, we argue that: 1) The spectral similarity between slope streaks and RSL during their .dry. phase suggests the opposite, and 2) The chances to capture the implied .wet. phase of slope streak formation are significantly lower given their longer annual- decadal timescales for recurrence on a given slope.

5. Antarctica

Trevor Hillebrand (Talk): High frequency radio echo sounding reveals past flow conditions of Crary Ice Rise, Antarctica

  • Ice rises may act to stabilize fast-flowing sections of the West Antarctic Ice Sheet (WAIS) against the effects of oceanic warming. Thus, it is important to understand the evolution of ice rises in order to make predictions about future WAIS behavior. We used high-frequency radar to conduct high-resolution 3D mapping of basal topography and internal structures at Crary Ice Rise, Antarctica. Echograms reveal a strongly reflecting layer at 200-300 m depth, ubiquitous across the larger ridge of the ice rise. On the ridge axis and the northern flank, the layer contains periodically spaced linear diffractors, aligned subparallel to present divide flow. We hypothesize that this represents a heavily crevassed former ice shelf or shear margin surface that was buried after the first grounding event ~1100 years ago. The orientation of the crevasses indicates a high angle change in flow direction after the ice rise became grounded, consistent with the transition from shelf to divide flow. Strong diffractors are scarce or absent on the southern flank of the main ridge, which could mark the edge of the former shear margin. The strong reflector is absent altogether from the smaller ridge, which is consistent with a more recent, warm-based grounding event. Further processing and integration of other geophysical data collected in the same campaign will be required to test this hypothesis.

Virginia Littell (Talk): Sourcing excess ground ice using water isotopes, Beacon Valley, Antarctica

  • The McMurdo Dry Valleys in Antarctica is a cold desert with a frigid, hyperarid environment. Physical models predict that the sediments should have a net loss of water vapor, but in reality ice-cemented ground is pervasive within decimeters of the surface. Scarce, episodic snowfall is mostly lost to rapid sublimation; however, some water vapor may diffuse into the subsurface and possibly stabilize or form ground ice. This study investigates ice within a 30-m permafrost core that was collected from Beacon Valley in 2008 using a dry coring technique. The entire core is ice rich, ranging from 20-80% water content by weight and is largely composed of weathered sand with some fractured cobbles. The high ice content suggests that the ground surface inflated as the ice formed. Processes leading to the excess accumulation of ice are investigated using .18O and .D. Potential sources of the ice include surface percolation, water vapor diffusion, and accumulation of snow into thermal contraction cracks. Subsamples of the ice-cemented core were cut from its interior, thawed, and the water was collected using a double-bottom centrifuge tube. Isotope analysis was also performed on water samples from hoarfrost collected from the abandoned core holes, snow, and glacier ice in Beacon Valley. The core.s isotope depth profiles will provide information on the origin of the ice and processes that modify it. This site serves as an analog for Mars, where excess ground ice has been confirmed at the Phoenix landing site, and will provide insight on ice accumulation there.

Bradley Markle (Talk): Moisture transport to West Antarctica constrained by shared water-isotope and ice- impurity variability at millennial to orbital time scales

  • Stable isotopes of water as well as a variety of impurities are routinely measured at high resolution in polar ice cores. Water isotope ratios record integrated fractionation processes and are a well-established proxy for ice core site temperature. Changes in the terrestrial impurity content of Antarctic ice are thought to reflect some combination of changes in dust transport, aridity, windiness, and land cover of dust source regions such as South America. Much previous research has focused on changes in the dust source region as the dominant driver of impurity variability through time. In such interpretations, the link between the water isotope and ice-impurity variance is indirect and through the general coupling of disparate aspects of the climate system. However, our analysis suggests that a single mechanism that directly relates .18O and impurity variability is a far more parsimonious explanation for the data. Specifically, we show that the integrated rain-out of precipitation from air masses en route to Antarctica may dominate variations in both .18O and Ca, at millennial to orbital time scales. Cloud formation and rain scavenge airborne impurities, which act as condensation nuclei. Precisely the same condensation processes drive water isotope fractionation. We support our arguments with simple models of isotope fractionation and impurity transport. Such a direct mechanism correctly predicts the logarithmic and inverse relationship between .18O and impurities in ice core records and reconciles the magnitude of impurity concentration changes over large climate shifts for a given range of water isotope variability. It also accounts for the relationship between dust concentration change in ice cores and those at lower latitudes, as archived in marine sediment cores.

6. Isotopes

Julia Kelson (Talk): Quantifying Climate Change During the PETM in Continental North America

  • While the scientific community has generally accepted that modern climate is changing, the ability to quantitatively predict how global climate will respond to an increase in CO2 in the atmosphere respond remains elusive. Ancient events of rapid climate change that are recorded in the record of ancient soils offer the opportunity to empirically constrain how the global climate responds to rapid increases of atmospheric CO2. I will use the record of the Paleocene-Eocene Thermal Maximum in paleosols in Big Bend, Texas to quantify changes in past surface temperature, precipitation, and atmospheric CO2.

K.R. Hodson (Talk): Leaky faults: 50 million years of fluid migration history on the Moab Fault, Utah.

  • The accurate prediction of fluid migration through the Earth.s crust is critical to many research sectors, from energy and resources to environmental remediation and natural hazards. Fault zones complicate the issue, as they can act as either fluid conduits or barriers within the host rock. Predicting the behavior of a specific fault is complex, requiring consideration of both fracture mechanics and the diagenetic effects of the fluids migrating through the fault zone. Studies of fluid flow histories through exhumed faults allow researchers to investigate the processes and conditions associated with structural deformation and diagenesis. Here, we investigate the cementation history of a fault-intersection zone on the Moab Fault, a well-studied fault system within the exhumed reservoir rocks of the Paradox Basin, UT. Stable isotopes, including carbonate clumped isotopes, constrain temperatures of cement formation and source fluid compositions. When combined with petrographic observations, these data allow us to associate cements having different formation temperatures and chemistries with different stages of fault zone evolution. We identify distinct source fluid compositions for the carbonate cements within the fault damage zone, including both marine and meteoric waters. Each is associated with different carbonate precipitation temperatures, luminescence characteristics, and styles of structural deformation. Three phases of carbonate cementation are identified, and appear to record focused fluid flow through the fault zone over a 50 million year period.

Landon Burgener (Talk): Insights from carbonate clumped isotope thermometry into the climate factors controlling the seasonality of soil carbonate formation

  • Due to their ubiquity in the geologic record, soil carbonates preserved in ancient soils have the potential to be an important archive of terrestrial paleoclimate conditions; however, lingering questions regarding seasonal biases in soil carbonate formation, and the exact relationship between soil carbonate formation temperatures and surface air temperatures, have limited the utility of this proxy. We address these questions by comparing C, O, and clumped isotope temperature (T(.47)) data from Holocene soil carbonates to meteorological and in-situ soil monitoring data along a 170 km transect with >4 km of relief in Chile (30 °S). We test the hypothesis that, regardless of soil moisture conditions, soil carbonates from arid regions record warm season biases and form in isotopic equilibrium with soil water and soil CO2. Below 3200 m, precipitation falls as rain and soil carbonate T(.47) values resemble summer soil temperatures. Above 3200 m, precipitation falls as snow and T(.47) values resemble mean annual soil temperatures. Soil carbonates from the highest site yield anomalous .18O, .13C, and T(.47) values indicative of kinetic isotope effects consistent with cryogenic carbonate formation. Our findings (1) highlight the role of the soil moisture regime in modulating the timing of soil carbonate formation, which affects the resulting carbonate T(.47) values; and (2) show that soil carbonates from high elevation or high latitude sites may form under non-equilibrium conditions. These findings underscore the importance of understanding past soil and climate conditions when attempting to reconstruct paleotemperatures using carbonate clumped isotope thermometry.

Austin Steele (Talk): Greenland Paleo-temperature Reconstruction Project

  • Several sediment cores were recovered from Limnaea Sø and Braya Sø, closed-basin lakes in Southwestern Greenland, to reconstruct temperatures during the Holocene epoch (past ~10,000 years). The closed-basin topography makes the lakes ideal for studying changes in evaporation and precipitation, and variations in past lake conditions are recorded by authigenic carbonates in the lake sediments. The sediment cores were analyzed by x-ray, magnetic susceptibility, and bulk density to allow stratigraphic correlation between cores and determine changes in sedimentation rate and lithology. After sectioning, a series of samples taken 20 cm apart were sent for radiocarbon dating, which placed the samples between present day and 9.5 ka(Calendar age). Due to the rate of deposition (~0.1 mm/yr), these sediments were sectioned at 0.5 to 1 cm intervals to achieve ~100 year resolution. 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 .13C and .18O isotopic analysis on the Kiel Carbonate system/isotope ratio mass spectrometer. The .13C and .18O data show periods of abrupt isotopic changes, indicating either a strong change in the hydrologic regime or changes in surface air temperatures. We are analyzing these abrupt periods using novel clumped-isotope paleothermometry to determine whether the isotopic variations are a response to lake temperature variations as previous alkenone analyses indicate, or shifts in precipitation/evaporation patterns.While work from ice cores show relatively stable temperatures during the Holocene epoch, recent lake sediment records have suggested that temperatures may have been more variable than thought. If our results show no significant temperature variations, it will confirm previous interpretations based on .18O 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.

7. Glaciers

John Christian (Talk): Identifying dynamically-induced variability in glacier mass-balance records.

  • Glacier mass balance provides a direct indicator of a glacier's relationship with local climate, but internally-generated variability in atmospheric circulation adds a significant degree of noise to mass-balance timeseries, making it difficult to correctly identify and interpret trends. This study applies .dynamical adjustment. to seasonal mass-balance records to identify and remove the component of variance in these timeseries that is associated with large-scale circulation fluctuations. Mass-balance records are investigated for three glaciers: Wolverine and Gulkana in Alaska, and South Cascade in Washington. North Pacific sea-level pressure and sea-surface temperature fields perform comparably as predictors, each explaining 50-60% of variance in winter balance and 30-40% in summer balance for South Cascade and Wolverine Glaciers. Gulkana glacier, located farther inland, is less closely linked to North Pacific climate variability, with the predictors explaining roughly one-third of variance in winter and summer balance. To investigate the degree to which this variability affects trends, adjusted mass-balance timeseries are compared to those in the raw data, with common results for all three glaciers: winter mass-balance records show no statistically significant trends before or after adjustment, despite the large amount of circulation-related variability. However, the raw summer balance data have statistically significant negative trends that remain after dynamical adjustment. This indicates that these trends of increasing ablation in recent decades are not due to circulation anomalies and are consistent with anthropogenic warming.

Max Stevens (Talk): Quantifying firn-model contribution to uncertainty in calculations of ice-sheet mass balance

  • Snow that falls on ice sheets compacts and becomes glacial ice via an intermediate state called firn. Firn-densification models are needed to correct altimetry-derived estimates of ice-sheet mass balance for firn-air content and transient firn-thickness changes. We have developed the Community Firn Model (CFM) that allows users to run firn-densification physics from a suite of published models. Here, we use the CFM to intercompare firn-model predictions using data from regional climate models. The firn depth-density profiles predicted by the different models vary significantly; for example, the models do not agree in the sign of the change in depth-integrated porosity since 1960 at some sites. Many of the firn-densification models were developed using a steady-state assumption and were tuned for the dry-snow zones of Greenland and Antarctica. Our results help quantify the uncertainty that is introduced by firn-model predictions in estimates of ice-sheet mass balance, and they demonstrate the challenges of using these models to simulate firn density in Greenland.s expanding wet firn and percolation zones.

David Lilien (Talk): Observations During the Quiescent Phase of a Surge-Type Outlet Glacier

  • With fast flow extending 700km inland to near the divide, the Northeast Greenland Ice Stream (NEGIS) is Greenland's largest flow feature. Due to its deep, submarine bedding and large area, NEGIS has the potential to contribute significantly (1.1m) to sea level rise. Dramatic recent changes in velocity and ice-shelf area have been observed in one of its main outlets, though Storstrømmen Glacier, the southernmost of NEGIS.s three outlets, has not accelerated or retreated significantly. Storstrømmen is thought to be a surge-type glacier, a type of glacier characterized by decadal to centennial scale periods of slower movement punctuated by monthly to annual scale accelerated flow. Surge mechanisms, though generally thought to be triggered by changes in basal conditions, remain an area of active research. Observations of a10km calving-front advance from 1978-1984 suggest that Storstrømmen surged at this time. During the surge, the calving-front advance was accompanied by acceleration to at least ten times quiescent-phase speeds. Since 1984, speeds have remained lower and the calving front has slowly retreated. Here we present observations of thickening, deceleration, and calving-front position of Storstrømmen over the last two decades, and investigate the implications for future surge initiation. We discuss possible mechanisms by which Storstrømmen's surges may be initiated and maintained, and speculate on the relation between outlet-glacier surges, Antarctic Ice-Stream activation, and Alaska- and Svalbard-type surges.

8. Posters

Mara Page: Investigating Vegetation Changes in Northern Australia during the Late Pleistocene to Holocene

  • The Madjebebe archaeological site, located in the Northern Territory of Australia, ccontains evidence for first human occupation 50-60 thousand years ago (Roberts et. al. 1990a). Because of the age of this site, Madjebebe has the potential to provide insight into the dispersal of modern homo sapiens out of Africa along the southern arc through Southeast Asia. Clarkson et al. hypothesize that some of the technological changes at the site may be explained by changes to the local environment due to climate change during the Holocene (2014). However, their hypothesis has not yet been tested. Using bulk sediment samples collected at 5 centimeter intervals for the entire 4 meter depth of sediment preserved the site, we will examine the paleovegetation changes that have occurred during the site.s history. Because C4 plants like grasses fixate CO2 through a different pathway than C3 plants such as shrubs and trees, C4 plants are composed of a higher concentration of isotopically heavy 13C relative to C3 plants (DeNiro 1987). The presence of C4 and C3 type plants can be detected through the ratios of 12C/13C that is left behind in the soil (Haslam et al. 2012). Using this technique, we hope to identify shifts in vegetation that occurred at Madjebebe. Our investigation may reveal a correlation between local climate and the patterns of human occupation and technology changes that occurred during the site.s 50 thousand year history. Ultimately, we hope to better understand the conditions that lead to the late pleistocene migration of humans into Northern Australia.

Brianna Hunt: Quantitative Oxygen Concentration Data at Depth: The Theory, Methodology, and Application of Optodes.

  • The presence and concentration of oxygen can control important biological and chemical processes in many environments. Oxygen concentration data is difficult to obtain, particularly in relation to oxygen at depth in primarily anoxic environments, as is experienced in the rhizosphere, the area around plant roots in the soil. Optodes provide a method to obtain quantitative oxygen concentration data at depth that is both high resolution and two dimensional. An optode is an optical interface which provides a cross-sectional view of oxygen at depth. This optode is created by using two chemical dyes, one that luminescence when exposed to a blue light, and one which quenches light in the presence of oxygen. The degree to which the oxygen quenches luminescence is thus indicated by the differences in luminescence throughout the optode. By utilizing these two chemical reactions oxygen concentration is indicated visually under blue light. Photography allows for these images to be captured and processed. The construction of these optodes can be accomplished in individual labs with simple equipment, allowing for wide implementation. This construction involves coating a clear material with the chemical dye and a protective carbon coating. This is followed by calibration and installation. Difficulties have arisen at all stages of this construction process, but valuable data has been obtained from the optodes and it is recommended as a viable procedure with which to gain oxygen concentration data at depth.

Ashly Padgett: Post-glacial landform sediment diffusivity rates: An alternate dating technique

  • Relict post-glacial channels and isostatically raised marine terraces preserved on Whidbey Island, WA are used to constrain the nature and rate of sediment transport operating on the respective slopes since deglaciation, ~15,500 years ago. Accurate surveys of modern stream valley cross-sections profiles and modern wave-eroded bluff profiles are compared to relict landforms that were formed by analogous processes following deglaciation. Diffusivity coefficients (k) are calculated for relict channels and terraces of various scales, precipitation gradients and slope aspects to assess the potential effects of these variables on the sediment transport rate and landform diffusion. Accurately quantifying the diffusivity rate of these relict landforms may provide a valuable dating technique for similar landforms where numerical dating control is absent. The methodology used in this study may also be useful in other climatic settings to constrain sediment transport rates where the initial landform morphology is known, such as glacial moraines.

Zi Xian Leong: Movement of the Redbluff Landslide using InSAR and LiDAR Data Sets

  • The Redbluff landslide, situated at Washington-Oregon state border, is part of the larger Bonneville landslide complex. In 1450 A.D., the Bonneville landslide dammed the Columbia River, but the river eventually breached it. In the present day, only one part of the landslide complex, namely the Redbluff landslide, is still slowly creeping into the Columbia River. It also poses a risk of damaging nearby public infrastructure. Interferometric synthetic aperture radar (InSAR) is a remote sensing technique used to measure millimeter-scale surface deformation. These satellite data are complemented by Light Detection Ranging (LiDAR), which is used to produce high-resolution topography images. Using these observations, I seek to understand how the movement of the Redbluff landslide relates to the surrounding geology and morphology. The downslope landslide movement is computed by back-projecting the line-of-sight InSAR observations onto a downslope vector, as done by previous InSAR glacier studies. ArcGIS software will be used to produce a higher-resolution model of the landslide movement. Furthermore, surface roughness will be computed as a geomorphic proxy of active movement on the slope. I expect that the InSAR surface displacement will show active movement in the regions with highest surface roughness. The InSAR and LiDAR data sets are highly complementary data sets and both help to better characterize landslide hazards along the Columbia River.

Khadijah Homolka: Potential for Seawater as a Geostandard for Potassium Isotopes

  • Non-traditional isotopes have become increasingly important as tracers for geological and environmental processes on earth. Recently, renewed attention has been direct towards potassium (K) isotopes given the abundance of K in the earth and the potential for significant mass-dependent fractionation between 41K and 39K. Seawater has the potential to be an excellent geostandard for K isotope geochemistry because of predicted 41K/39K homogeneity through the water column, and its wide accessibility around the globe. A total of forty-seven, 30 mL samples were collected in July 2015 aboard the R/V Thomas G. Thompson on the VISIONS 2015 Expedition (RSN-OOI) to Axial Seamount on the Juan de Fuca Ridge. Samples were collected from CTD (Conductivity Temperature Depth) casts as well as niskin bottles operated by the Remotely Operated Platform for Ocean Science (ROPOS). Seawater profile samples were taken at several locations from 7 m down to 2890 m. Evaluating the K isotopic composition at each depth and geographic location will determine if the K isotope composition of seawater is homogeneous. In chemical oceanography, there is thought to be a missing sink for K, and it is theorized that clay formation, crustal fractures, or both may remove K from seawater. Because K isotopes likely behave differently during adsorption onto basalt and incorporation into clay, K isotopes may be able to identify if either or both are the missing sink. Determining the feasibility of seawater as a geostandard for K isotopes will further facilitate new research in these and other geochemical topics.

Luke Fisher: Imaging Magma Under St. Helens (iMUSH) Using Cross-Correlation Times of Teleseismic Earthquakes

  • The iMUSH project seeks to determine the architecture of the Mt. St. Helens (MSH) magmatic system. This is a multi-disciplinary project employing passive-source seismic instrumentation, active-source seismic experiments, magnetoteluric installations and petrologic investigations. These data sets will be incorporated into a highly detailed model of the volcanic system. The active-source group has developed high-resolution tomographic images of 3-D, P- and S-wave velocities. Complementary to this is data from the passive-source array, which consists of 70 seismometers within 50 km of MSH. At each station we measure precise relative arrival times of steeply dipping seismic rays from teleseismic (distant) earthquakes following the procedures introduced by VanDecar and Crosson [BSSA, 1990]. I developed a series of Matlab programs to implement this process. In my program every pair of seismograms is cross-correlated to determine differential time offsets. These offsets are inverted to find self-consistent arrival times of the P-wave as it propagates across the array. Challenges included removing noisy seismograms, interactively removing marginal seismograms, identifying and flipping inverted seismograms and resolving numerous metadata inconsistencies. The outcome of this work was a wealth of data about the arrival time across the iMUSH array for teleseismic waves approaching from a variety of azimuths. This information was used to make detailed maps of changes to arrival time at the surface for individual earthquakes and composite maps of how geologic structure may vary with depth. This data will be valuable in tomographic inversions for a full 3-D wave speed model of the MSH volcanic system that is under development by the rest of the iMUSH team. Initial interpretations are consistent with low wave speeds directly beneath MSH and high wave speeds deeper below the surface associated with the subducting Juan De Fuca plate.

Joel H. Gombiner: Isotope geochemistry of Scabland Flood deposits

  • Argon and neodymium isotope geochemistry provide a means of tracking Scabland Flood sediment from source to sink. Analysis of sediment from locations along the flood path and from two marine sediment accumulation sites elucidate patterns of sediment mixing on land, subsequent unmixing at sea, and marine sediment transport pathways. Slackwater deposits in the Tucannon and Willamette valleys are characterized by old K/Ar ages of fine-grained sediment (240-360 Ma), younger 40Ar/39Ar ages of individual micas (mean ages from 70 to 150 Ma), and moderately negative .Nd values (-8.5 to -10.5). Similarly old K/Ar ages and negative .Nd values link glacial outburst flood layers from sediment core MD02-2496 offshore Vancouver Island to the Scabland Floods. This isotopic link shows that Scabland Floods sent plumes of fine-grained sediment >400 km to the north in the Pacific Ocean. A high-resolution geochemical record from MD02-2496 identifies 44 Scabland Flood layers in the core. Sixteen radiocarbon dates spanning the glacial flood interval provide an absolute chronology, showing cyclical deposition with ~50- to 80-year periodicity between ~19.3 and ~14.9 ka. Additionally, 40Ar/39Ar age spectra of individual mica grains from a late Pleistocene Astoria Fan turbidite bed are similar to age spectra from Scabland Flood slackwater deposits, reinforcing the connection between this turbidite sequence and glacial outburst floods.

Katherine Hotchkin: Time Evolution of Geochemical Characteristics in East Molokai, Hawaii

  • Hawaiian volcanoes grow so quickly that only the last few percent of their volcanic history is exposed to sampling. East Molokai volcano is an exception because a giant landslide removed half the volcanic edifice, effectively providing a cross-section through the volcano. This exposure allows us to study the temporal chemical evolution of East Molokai, specifically testing for time-variable contributions of melts from two geochemically distinct types of mantle. We present rare-earth element concentrations and isotope ratios (. Nd, . Hf, 87Sr/86Sr, 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb) for a variety of samples, taken at different elevations, ranging from subaerial to submarine. Previously published data for East Molokai did not include submarine samples or stratigraphic constraints. Preliminary analysis shows that the ratio of La/Lu increases with increasing elevation. The variation of La/Lu with isotope ratios illustrates the mixing of two different chemical types of mantle. Our data are within the same range as that published by Xu et al. (2005, 2007), but ours show regular geochemical trends as a function of stratigraphic position. We suggest that the melt came from two geochemically and petrologically distinct mantle sources that melted at different rates over time within the upwelling mantle plume as reflected in the geochemical variation preserved in the exceptionally exposed section of East Molokai.

Lauren Kowalski: Constraining shallow seawater circulation at the Southern Hydrate Ridge seep system

  • Cold seeps, like Southern Hydrate Ridge (SHR) on the Cascadia margin, are ubiquitous features along continental margins where fluids discharge from the seafloor into the water column. The chemical composition of fluid expelled at seep sites is distinct from the surrounding seawater due to sub-seafloor fluid-rock reactions and biological activity. This altered fluid is important in driving biogeochemical processes that allow diverse biological communities to thrive in these environments. Previous short-term fluid flow studies at SHR and other seep systems have observed upward flow of altered fluids concentrated in regions of bacterial mats and downward flow of seawater-like fluids in regions of clams. To investigate longer-term variability in magnitude and direction of fluid flow at SHR, three continuous-measurement flowmeter/chemical samplers (MOSQUITOs) were deployed over the course of two years in bacterial mats to measure fluid flow rates and solute fluxes. This two-year continuous record of fluid flow shows that the flow rate at SHR is temporally and spatially variable, however there is an unanticipated annual trend of ~20-40 cm/yr of downward fluid flow in regions of bacterial mats. Chloride and sulfate concentration profiles will also be determined from MOSQUITO subsamples in order to examine their fluxes across the sediment-water interface, potential methane hydrate dynamics, and other sources of fluid. This net downward transport of seawater circulation is more constant than previously recognized, it likely plays an important role in controlling the distribution of benthic biological communities, and could be important in marine biogeochemical cycles.

Linnea E. McCann: Isotopic and trace element evidence for basalts with mantle plume affinities in the Cascadia subduction zone

  • Erupted between 4.0 and 0.6 Ma, the Simcoe Volcanic Field of southeastern Washington displays unusually mafic compositions for lavas located within a volcanic arc. Distinct in chemical composition from the mostly andesitic Cascade Range, these lavas resemble Ocean Island Basalts (OIBs) generated by mantle plumes. Our project uses radiogenic isotope and trace element analyses to determine the origins of these unusual basalts in Oregon and Washington. We test the hypothesis that these lavas originated from an enriched mantle component located beneath the Cascadia back-arc. Rare-earth element abundances are typical of OIBs. Our samples show relatively high concentrations of Nb and Ta, indicating an origin outside of normal subduction processes. Most diagnostically, 206Pb/204Pb, 208Pb /204Pb, and 207Pb /204Pb isotope ratios of our samples are similar to the Columbia River and Steens basalts in Eastern Washington and Oregon, two volcanic provinces formed by the Yellowstone Hotspot 16 million years ago. These similarities extend to Nd, where variations in 143Nd/144Nd and 206Pb/204Pb of the Simcoe Basalts are identical to enriched mantle compositions preserved in the Columbia River and Steens Basalts . The results of our Nd, Pb, and trace element analyses suggest the presence of an enriched mantle component in recent volcanism east of the Cascadia volcanic arc.

Nicolas Cuozzo: Polygonal patterned ground in the Antarctic Dry Valleys and its relation to ice-rich permafrost depth

  • Polygonal Patterned Ground (PPG) is a characteristic feature of periglacial landforms and is the hallmark of ice-rich permafrost. Cyclic thermal contractions and expansions of rock, soil, or sediment lead to the typical polygonal patterns with a trough outlined by ridges on either side. One control on the morphology of PPG is the depth to the ice-rich permafrost boundary. Ice-rich permafrost in the Dry Valleys is typically overlain by a layer of dry permafrost of varying thickness causing noticeable changes in the morphology of the polygons. When thermal contraction tension overcomes the tensile strength of the sediment, contraction cracks form and provide stress relief to that region. The peak seasonal stress that drives these fractures occurs at the ice-rich permafrost boundary, with the dry permafrost layer acting as insulation from strong temperature fluctuations. Therefore, a deeper ice-rich permafrost layer will have weaker thermal contraction tension acting on it and low peak seasonal stress. The spacing of cracks, and therefore, the size of polygons, will be related to the order of magnitude of the stress relief of a single crack. Weaker thermal tension will lead to a lower tensile stress relief, allowing for deeper ice-rich boundary layers to have larger polygons (i.e more spacing between cracks). The relationship between polygon size and ice-depth is investigated here for Farnell Valley, a hanging valley on the east side of Beacon Valley. The average size polygons along the length of the two kilometer valley will be compared to hand-measured ice-depths. Large scale polygonal trends will be analyzed using a wavelet analysis to look at spacing between cracks. These results can be interpolated to provide an overall map of ice-rich permafrost depth. Ultimately, this project will test models using real data collected in the field.