%0 Journal Article %J Geophysical Research Letters %D 2015 %T Subglacial discharge at tidewater glaciers revealed by seismic tremor %A Bartholomaus, Timothy C %A Amundson, Jason M %A Walter, Jacob I %A O'Neel, Shad %A West, Michael E %A Chris F. Larsen %B Geophysical Research Letters %G eng %0 Journal Article %J Geophysical Research Letters %D 2015 %T Surface melt dominates Alaska glacier mass balance %A Chris F. Larsen %A Burgess, E %A Arendt, AA %A O'Neel, S %A Johnson, AJ %A Kienholz, C %B Geophysical Research Letters %V 42 %P 5902–5908 %G eng %0 Journal Article %J Alaska Park Science %D 2014 %T Alaska National Park glaciers: what do they tell us about climate change? %A Loso, M.G. %A Arendt, A. %A Chris F. Larsen %A Murphy, N. %A Rich, J. %B Alaska Park Science %V 12 %P 18–25 %G eng %0 Journal Article %J Journal of Geophysical Research: Solid Earth %D 2013 %T Active tectonics of the St. Elias orogen, Alaska, observed with GPS measurements %A Elliott, Julie %A Jeffrey T. Freymueller %A Chris F. Larsen %K Alaska %K geodesy %K St. Elias orogen %K tectonics %K Yakutat block %X We use data from campaign and continuous GPS sites in southeast and south central Alaska to constrain a regional tectonic block model for the St. Elias orogen. Active tectonic deformation in the orogen is dominated by the effects of the collision of the Yakutat block with southern Alaska. Our results indicate that  37 mm/yr of convergence is accommodated along a relatively narrow belt of N-NW dipping thrust faults in the eastern half of the orogen, with the present-day deformation front running through Icy Bay and beneath the Malaspina Glacier. Near the Bering Glacier, the collisional thrust fault regime transitions into a broad, northwest dipping décollement as the Yakutat block basement begins to subduct beneath the counterclockwise rotating Elias block. The location of this transition aligns with the Gulf of Alaska shear zone, implying that the Pacific plate is fragmenting in response to the Yakutat collision. Our model indicates that the Bering Glacier region is undergoing internal deformation and could correspond to the final stage of offscraping and accretion of sediments from the Yakutat block prior to subduction. Predicted block motions at the western edge of the orogen suggest that the crust is laterally escaping along the Aleutian fore arc. %B Journal of Geophysical Research: Solid Earth %P n/a–n/a %G eng %U http://dx.doi.org/10.1002/jgrb.50341 %R 10.1002/jgrb.50341 %0 Journal Article %J Earth and Planetary Science Letters %D 2013 %T Does calving matter? Evidence for significant submarine melt %A Timothy C. Bartholomaus %A Chris F. Larsen %A Shad OʼNeel %B Earth and Planetary Science Letters %V 380 %P 21 - 30 %G eng %U http://www.sciencedirect.com/science/article/pii/S0012821X13004408 %R http://dx.doi.org/10.1016/j.epsl.2013.08.014 %0 Journal Article %J Nat Commun %D 2013 %T Flow velocities of Alaskan glaciers %A Evan W. Burgess %A Richard R. Forster %A Chris F. Larsen %B Nat Commun %V 4 %G eng %U http://dx.doi.org/10.1038/ncomms3146 %R 10.1038/ncomms3146 %0 Journal Article %J Geophysical Research Letters %D 2013 %T Low-frequency radar sounding of temperate ice masses in Southern Alaska %A Eric Rignot %A Mouginot, J. %A Chris F. Larsen %A Gim, Y. %A Kirchner, D. %K Alaska %K bed topography %K glaciology %K mass balance %K radar %K thickness %X We present the Warm Ice Sounding Explorer (WISE), a low-frequency (2.5 MHz) radar for the sounding of temperate ice. WISE deployment in southern Alaska in 2008 and 2012 provides comprehensive measurements of glacier thickness, reveals deep valleys beneath glaciers and the full extent of zones grounded below sea level. The east branch of Columbia Glacier is deeper that its main branch and remains below sea level 20 km farther inland. Ice is 1000 m deep on Tazlina Glacier. On Bering glacier, two sills separate three deep bed depressions (>1200 m) that coincide with the dynamic balance lines during surges. The piedmont lobe of Malaspina Glacier and the lower reaches of Hubbard Glacier are entirely grounded below sea level 40 and 10 km, respectively, from their termini. Knowledge of ice thickness in these regions helps better understand their glacier dynamics, mass balance, and impact on sea level. %B Geophysical Research Letters %P n/a–n/a %G eng %U http://dx.doi.org/10.1002/2013GL057452 %R 10.1002/2013GL057452 %0 Journal Article %J Journal of Glaciology %D 2013 %T Mass balance in the Glacier Bay area of Alaska, USA, and British Columbia, Canada, 1995–2011, using airborne laser altimetry %A Johnson, Austin J %A Chris F. Larsen %A Murphy, Nathaniel %A Anthony A. Arendt %A Zirnheld, S Lee %B Journal of Glaciology %V 59 %P 632–648 %G eng %N 216 %R 10.3189/2013JoG12J101 %0 Journal Article %J Annals of Glaciology %D 2013 %T The propagation of a surge front on Bering Glacier, Alaska, 2001–2011 %A Turrin, James %A Richard R. Forster %A Chris F. Larsen %A Sauber, Jeanne %X Bering Glacier, Alaska, USA, has a ∼20 year surge cycle, with its most recent surge reaching the terminus in 2011. To study this most recent activity a time series of ice velocity maps was produced by applying optical feature-tracking methods to Landsat-7 ETM+ imagery spanning 2001–11. The velocity maps show a yearly increase in ice surface velocity associated with the down-glacier movement of a surge front. In 2008/09 the maximum ice surface velocity was 1.5 ± 0.017 km a–1 in the mid-ablation zone, which decreased to 1.2 ± 0.015 km a–1 in 2009/10 in the lower ablation zone, and then increased to nearly 4.4 ± 0.03 km a–1 in summer 2011 when the surge front reached the glacier terminus. The surge front propagated down-glacier as a kinematic wave at an average rate of 4.4 ± 2.0 km a–1 between September 2002 and April 2009, then accelerated to 13.9 ± 2.0 km a–1 as it entered the piedmont lobe between April 2009 and September 2010. The wave seems to have initiated near the confluence of Bering Glacier and Bagley Ice Valley as early as 2001, and the surge was triggered in 2008 further down-glacier in the mid-ablation zone after the wave passed an ice reservoir area. %B Annals of Glaciology %V 54 %P 221-228 %G eng %U http://www.ingentaconnect.com/content/igsoc/agl/2013/00000054/00000063/art00024 %R doi:10.3189/2013AoG63A341 %0 Journal Article %J Geophysical Research Letters %D 2013 %T Summer melt regulates winter glacier flow speeds throughout Alaska %A Evan W. Burgess %A Chris F. Larsen %A Richard R. Forster %K Alaska %K Ice Dynamics %K Mountain Glaciers %K Offset Tracking %K Sub-Glacial Hydrology %K Winter %X Predicting how climate change will affect glacier and ice sheet flow speeds remains a large hurdle towards accurate sea level rise forecasting. Increases in surface melt rates are known to accelerate glacier flow in summer, whereas in winter, flow speeds are believed to be relatively invariant. Here we show that wintertime flow speeds on nearly all major glaciers throughout Alaska are not only variable but are inversely related to melt from preceding summers. For each additional meter of summertime melt, we observe an 11% decrease in wintertime velocity on glaciers of all sizes, geometries, climates and bed types. This dynamic occurs because inter-annual differences in summertime melt affect how much water is retained in the sub-glacial system during winter. The ubiquity of the dynamic indicates it occurs globally on glaciers and ice sheets not frozen to their beds and thus constitutes a new mechanism affecting sea level rise projections. %B Geophysical Research Letters %G eng %U http://dx.doi.org/10.1002/2013GL058228 %R 10.1002/2013GL058228 %0 Journal Article %J Journal of Geophysical Research %D 2012 %T Calving seismicity from iceberg–sea surface interactions %A Timothy C. Bartholomaus %A Chris F. Larsen %A Shad OʼNeel %A West, M. %B Journal of Geophysical Research %V 117 %P F04029 %G eng %R 10.1029/2012JF002513 %0 Journal Article %J Journal of Geophysical Research %D 2012 %T Gravity and uplift rates observed in southeast Alaska and their comparison with GIA model predictions %A Tatsuru Sato %A Miura, S. %A Sun, W. %A Sugano, T. %A Jeffrey T. Freymueller %A Chris F. Larsen %A Ohta, Y. %A Fujimoto, H. %A Inazu, D. %A Roman J. Motyka %B Journal of Geophysical Research %V 117 %P B01401 %G eng %0 Journal Article %J The Cryosphere Discuss %D 2012 %T Surge dynamics on Bering Glacier, Alaska, in 2008–2011 %A Evan W. Burgess %A Richard R. Forster %A Chris F. Larsen %A M Braun %B The Cryosphere Discuss %V 6 %P 1181–1204 %G eng %R 10.5194/tc-6-1251-2012 %0 Journal Article %J Tectonophysics %D 2011 %T Reevaluation of the viscoelastic and elastic responses to the past and present-day ice changes in Southeast Alaska %A Tatsuru Sato %A Chris F. Larsen %A Miura, S. %A Ohta, Y. %A Fujimoto, H. %A Sun, W. %A Roman J. Motyka %A Jeffrey T. Freymueller %B Tectonophysics %V 511 %P 79–88 %G eng %R 10.1016/j.tecto.2010.05.009 %0 Journal Article %J Geology %D 2010 %T Glacier microseismicity %A West, M. %A Chris F. Larsen %A Martin Truffer %A Shad OʼNeel %A LeBlanc, Laura %X We present a framework for interpreting small glacier seismic events based on data collected near the center of Bering Glacier, Alaska, in spring 2007. We find extremely high microseismicity rates (as many as tens of events per minute) occurring largely within a few kilometers of the receivers. A high-frequency class of seismicity is distinguished by dominant frequencies of 20–35 Hz and impulsive arrivals. A low-frequency class has dominant frequencies of 6–15 Hz, emergent onsets, and longer, more monotonic codas. A bimodal distribution of 160,000 seismic events over two months demonstrates that the classes represent two distinct populations. This is further supported by the presence of hybrid waveforms that contain elements of both event types. The high-low-hybrid paradigm is well established in volcano seismology and is demonstrated by a comparison to earthquakes from Augustine Volcano. We build on these parallels to suggest that fluid-induced resonance is likely responsible for the low-frequency glacier events and that the hybrid glacier events may be caused by the rush of water into newly opening pathways. %B Geology %V 38 %P 319-322 %G eng %U http://geology.gsapubs.org/content/38/4/319.abstract %R 10.1130/G30606.1 %0 Journal Article %J Journal of Geophysical Research %D 2010 %T Gravity measurements in southeastern Alaska reveal negative gravity rate of change caused by glacial isostatic adjustment %A Sun, W. %A Miura, S. %A Tatsuru Sato %A Sugano, T. %A Jeffrey T. Freymueller %A Kaufman, M. %A Chris F. Larsen %A Cross, R. %A Inazu, D. %B Journal of Geophysical Research %V 115 %P B12406 %G eng %R 10.1029/2009JB007194 %0 Journal Article %J Journal of Geophysical Research %D 2010 %T Iceberg calving as a primary source of regional-scale glacier-generated seismicity in the St. Elias Mountains, Alaska %A Shad OʼNeel %A Chris F. Larsen %A Rupert, N. %A Hansen, R. %B Journal of Geophysical Research %V 115 %P F04034 %G eng %R 10.1029/2009JF001598 %0 Journal Article %J Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences %D 2010 %T Recent and future warm extreme events and high-mountain slope stability %A Huggel, C. %A Salzmann, N. %A Allen, S. %A Caplan-Auerbach, J. %A L Fischer  %A Haeberli, W. %A Chris F. Larsen %A Schneider, D. %A Wessels, R. %B Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences %V 368 %P 2435–2459 %G eng %R 10.1098/rsta.2010.0078 %0 Journal Article %J Journal of Geophysical Research %D 2010 %T Tectonic block motion and glacial isostatic adjustment in southeast Alaska and adjacent Canada constrained by GPS measurements %A Elliott, J.L. %A Chris F. Larsen %A Jeffrey T. Freymueller %A Roman J. Motyka %B Journal of Geophysical Research %V 115 %P B09407 %G eng %R 10.1029/2009JB007139 %0 Journal Article %J Journal of oceanography %D 2009 %T Accurate ocean tide modeling in southeast Alaska and large tidal dissipation around Glacier Bay %A Inazu, D. %A Tatsuru Sato %A Miura, S. %A Ohta, Y. %A Nakamura, K. %A Fujimoto, H. %A Chris F. Larsen %A Higuchi, T. %B Journal of oceanography %V 65 %P 335–347 %G eng %0 Journal Article %J Journal of Geodynamics %D 2008 %T Earth tides observed by gravity and GPS in southeastern Alaska %A Tatsuru Sato %A Miura, S. %A Ohta, Y. %A Fujimoto, H. %A Sun, W. %A Chris F. Larsen %A Heavner, M. %A Kaufman, AM %A Jeffrey T. Freymueller %B Journal of Geodynamics %V 46 %P 78–89 %G eng %0 Journal Article %J Journal of Glaciology %D 2008 %T Recent glacier mass changes in the Gulf of Alaska region from GRACE mascon solutions %A Scott B Luthcke %A Anthony A. Arendt %A Rowlands, D.D. %A J J McCarthy %A Chris F. Larsen %B Journal of Glaciology %V 54 %P 767–777 %G eng %0 Journal Article %J J. Geophys. Res %D 2007 %T Glacier changes in southeast Alaska and northwest British Columbia and contribution to sea level rise %A Chris F. Larsen %A Roman J. Motyka %A Anthony A. Arendt %A Echelmeyer, K.A. %A Geissler, P.E. %B J. Geophys. Res %V 112 %P F01007 %G eng %0 Journal Article %J Alaska Park Science %D 2007 %T Post Little Ice Age Glacial Rebound in Glacier Bay National Park and Surrounding Areas %A Roman J. Motyka %A Chris F. Larsen %A Jeffrey T. Freymueller %A Echelmeyer, K.A. %B Alaska Park Science %V 6 %P 36–41 %G eng