TY - JOUR
T1 - Rapid Submarine Melting Driven by Subglacial Discharge, LeConte Glacier, Alaska
JF - Geophysical Research Letters
Y1 - 2013
A1 - Roman J. Motyka
A1 - Dryer, W. P.
A1 - Jason M Amundson
A1 - Martin Truffer
A1 - Mark Fahnestock
KW - frontal ablation
KW - submarine melting
KW - tidewater glaciers
AB - We show that subglacial freshwater discharge is the principal process driving high rates of submarine melting at tidewater glaciers. This buoyant discharge draws in warm seawater, entraining it in a turbulent upwelling flow along the submarine face that melts glacier ice. To capture the effects of subglacial discharge on submarine melting, we conducted 4 days of hydrographic transects during late summer 2012 at LeConte Glacier, Alaska. A major rainstorm allowed us to document the influence of large changes in subglacial discharge. We found strong submarine melt fluxes that increased from 9.1 ± 1.0 to 16.8 ± 1.3 m d−1 (ice face equivalent frontal ablation) as a result of the rainstorm. With projected continued global warming and increased glacial runoff, our results highlight the direct impact that increases in subglacial discharge will have on tidewater outlet systems. These effects must be considered when modeling glacier response to future warming and increased runoff.
VL - 40
UR - http://dx.doi.org/10.1002/grl.51011
ER -
TY - JOUR
T1 - On the seasonal freshwater stratification in the proximity of fast-flowing tidewater outlet glaciers in a sub-Arctic sill fjord
JF - Journal of Geophysical Research: Oceans
Y1 - 2013
A1 - Mortensen, J.
A1 - Bendtsen, J.
A1 - Roman J. Motyka
A1 - Lennert, K.
A1 - Martin Truffer
A1 - Mark Fahnestock
A1 - Rysgaard, S.
KW - fjord
KW - freshwater sources and their distribution
KW - Greenland Ice Sheet
KW - subglacial freshwater fraction model
KW - subsurface heat sources for glacial ice melt
KW - tidewater outlet glaciers
AB - The Greenland Ice Sheet releases large amounts of freshwater into the fjords around Greenland and many fjords are in direct contact with the ice sheet through tidewater outlet glaciers. Here we present the first seasonal hydrographic observations from the inner part of a sub-Arctic fjord, relatively close to and within 4–50 km of a fast-flowing tidewater outlet glacier. This region is characterized by a dense glacial and sea ice cover. Freshwater from runoff, subglacial freshwater (SgFW) discharge, glacial, and sea ice melt are observed above 50–90 m depth. During summer, SgFW and subsurface glacial melt mixed with ambient water are observed as a layered structure in the temperature profiles below the low-saline summer surface layer (<7 m). During winter, the upper water column is characterized by stepwise halo- and thermoclines formed by mixing between deeper layers and the surface layer influenced by ice melt. The warm (T > 1°C) intermediate water mass is a significant subsurface heat source for ice melt. We analyze the temperature and salinity profiles observed in late summer with a thermodynamic mixing model and determine the total freshwater content in the layer below the summer surface layer to be between 5% and 11%. The total freshwater contribution in this layer from melted glacial ice was estimated to be 1–2%, while the corresponding SgFW was estimated to be 3–10%. The winter measurements in the subsurface halocline layer showed a total freshwater content of about 1% and no significant contribution from SgFW.
VL - 118
UR - http://dx.doi.org/10.1002/jgrc.20134
ER -
TY - JOUR
T1 - Gravity and uplift rates observed in southeast Alaska and their comparison with GIA model predictions
JF - Journal of Geophysical Research
Y1 - 2012
A1 - Tatsuru Sato
A1 - Miura, S.
A1 - Sun, W.
A1 - Sugano, T.
A1 - Jeffrey T. Freymueller
A1 - Chris F. Larsen
A1 - Ohta, Y.
A1 - Fujimoto, H.
A1 - Inazu, D.
A1 - Roman J. Motyka
VL - 117
ER -
TY - JOUR
T1 - A complex relationship between calving glaciers and climate
JF - Eos, Transactions American Geophysical Union
Y1 - 2011
A1 - Post, Austin
A1 - Shad OʼNeel
A1 - Roman J. Motyka
A1 - Streveler, Gregory
KW - climate
KW - glaciers
AB - Many terrestrial glaciers are sensitive indicators of past and present climate change as atmospheric temperature and snowfall modulate glacier volume. However, climate interpretations based on glacier behavior require careful selection of representative glaciers, as was recently pointed out for surging and debris-covered glaciers, whose behavior often defies regional glacier response to climate [Yde and Paasche, 2010]. Tidewater calving glaciers (TWGs)—mountain glaciers whose termini reach the sea and are generally grounded on the seafloor—also fall into the category of non-representative glaciers because the regional-scale asynchronous behavior of these glaciers clouds their complex relationship with climate. TWGs span the globe; they can be found both fringing ice sheets and in high-latitude regions of each hemisphere. TWGs are known to exhibit cyclic behavior, characterized by slow advance and rapid, unstable retreat, largely independent of short-term climate forcing. This so-called TWG cycle, first described by Post [1975], provides a solid foundation upon which modern investigations of TWG stability are built. Scientific understanding has developed rapidly as a result of the initial recognition of their asynchronous cyclicity, rendering greater insight into the hierarchy of processes controlling regional behavior. This has improved the descriptions of the strong dynamic feedbacks present during retreat, the role of the ocean in TWG dynamics, and the similarities and differences between TWG and ice sheet outlet glaciers that can often support floating tongues.
VL - 92
UR - http://dx.doi.org/10.1029/2011EO370001
ER -
TY - JOUR
T1 - An increase in crevasse extent, West Greenland: Hydrologic implications
JF - Geophysical Research Letters
Y1 - 2011
A1 - Colgan, William
A1 - Steffen, Konrad
A1 - McLamb, W. Scott
A1 - Waleed Abdalati
A1 - Rajaram, Harihar
A1 - Roman J. Motyka
A1 - Phillips, Thomas
A1 - Robert S Anderson
KW - crevasses
KW - Greenland
KW - mass balance
KW - velocity
AB - We compare high-resolution 1985 and 2009 imagery to assess changes in crevasse extent in the Sermeq Avannarleq ablation zone, West Greenland. The area occupied by crevasses >2 m wide significantly increased (13 ± 4%) over the 24-year period. This increase consists of an expansion of existing crevasse fields, and is accompanied by widespread changes in crevasse orientation (up to 45°). We suggest that a combination of ice sheet thinning and steepening are responsible for the increase in crevasse extent. We examine the potential impact of this change on the hydrology of the ice sheet. We provide a first-order demonstration that moulin-type drainage is more efficient in transferring meltwater fluctuations to the subglacial system than crevasse-type drainage. As enhanced basal sliding is associated with meltwater “pulses”, an increase in crevasse extent can therefore be expected to result in a net decrease in basal sliding sensitivity. An increase in crevasse extent may also accelerate cryo-hydrologic warming and enhance surface ablation.
VL - 38
UR - http://dx.doi.org/10.1029/2011GL048491
ER -
TY - JOUR
T1 - Reevaluation of the viscoelastic and elastic responses to the past and present-day ice changes in Southeast Alaska
JF - Tectonophysics
Y1 - 2011
A1 - Tatsuru Sato
A1 - Chris F. Larsen
A1 - Miura, S.
A1 - Ohta, Y.
A1 - Fujimoto, H.
A1 - Sun, W.
A1 - Roman J. Motyka
A1 - Jeffrey T. Freymueller
VL - 511
ER -
TY - JOUR
T1 - Submarine melting of the 1985 Jakobshavn Isbræ floating tongue and the triggering of the current retreat
JF - Journal of Geophysical Research
Y1 - 2011
A1 - Roman J. Motyka
A1 - Martin Truffer
A1 - Mark Fahnestock
A1 - Mortensen, J.
A1 - Rysgaard, S.
A1 - I M Howat
VL - 116
ER -
TY - JOUR
T1 - Ice mélange dynamics and implications for terminus stability, Jakobshavn Isbræ, Greenland
JF - Journal of Geophysical Research
Y1 - 2010
A1 - Jason M Amundson
A1 - Mark Fahnestock
A1 - Martin Truffer
A1 - Brown, J.
A1 - M P Lüthi
A1 - Roman J. Motyka
VL - 115
ER -
TY - JOUR
T1 - Tectonic block motion and glacial isostatic adjustment in southeast Alaska and adjacent Canada constrained by GPS measurements
JF - Journal of Geophysical Research
Y1 - 2010
A1 - Elliott, J.L.
A1 - Chris F. Larsen
A1 - Jeffrey T. Freymueller
A1 - Roman J. Motyka
VL - 115
ER -
TY - JOUR
T1 - Volume change of Jakobshavn Isbrae, West Greenland:: 198519972007
JF - Journal of Glaciology
Y1 - 2010
A1 - Roman J. Motyka
A1 - Mark Fahnestock
A1 - Martin Truffer
VL - 56
UR - http://openurl.ingenta.com/content/xref?genre=article&issn=0022-1430&volume=56&issue=198&spage=635
ER -
TY - JOUR
T1 - Terminus dynamics at an advancing glacier: Taku Glacier, Alaska
JF - Journal of Glaciology
Y1 - 2009
A1 - Martin Truffer
A1 - Roman J. Motyka
A1 - Hekkers, M.
A1 - I M Howat
A1 - King, M.A.
VL - 55
UR - http://openurl.ingenta.com/content/xref?genre=article&issn=0022-1430&volume=55&issue=194&spage=1052
ER -
TY - JOUR
T1 - Correspondence: Another surge of Variegated Glacier, Alaska, USA, 2003/04
JF - Journal of Glaciology
Y1 - 2008
A1 - Harrison, W.
A1 - Roman J. Motyka
A1 - Martin Truffer
VL - 54
UR - http://www.ingentaconnect.com/content/igsoc/jog/2008/00000054/00000184/art00019
ER -
TY - JOUR
T1 - Glacier, fjord, and seismic response to recent large calving events, Jakobshavn Isbræ, Greenland
JF - Geophysical Research Letters
Y1 - 2008
A1 - Jason M Amundson
A1 - Martin Truffer
A1 - M P Lüthi
A1 - Mark Fahnestock
A1 - West, M.
A1 - Roman J. Motyka
VL - 35
UR - http://www.agu.org/pubs/crossref/2008/2008GL035281.shtml
ER -
TY - JOUR
T1 - Seasonal fluctuations in the advance of a tidewater glacier and potential causes: Hubbard Glacier, Alaska, USA
JF - Journal of Glaciology
Y1 - 2008
A1 - Ritchie, J.B.
A1 - C S Lingle
A1 - Roman J. Motyka
A1 - Martin Truffer
VL - 54
UR - http://openurl.ingenta.com/content/xref?genre=article&issn=0022-1430&volume=54&issue=186&spage=401
ER -
TY - JOUR
T1 - Flotation and retreat of a lake-calving terminus, Mendenhall Glacier, southeast Alaska, USA
JF - Journal of Glaciology
Y1 - 2007
A1 - Boyce, E.S.
A1 - Roman J. Motyka
A1 - Martin Truffer
VL - 53
ER -
TY - JOUR
T1 - Glacier changes in southeast Alaska and northwest British Columbia and contribution to sea level rise
JF - J. Geophys. Res
Y1 - 2007
A1 - Chris F. Larsen
A1 - Roman J. Motyka
A1 - Anthony A. Arendt
A1 - Echelmeyer, K.A.
A1 - Geissler, P.E.
VL - 112
ER -
TY - JOUR
T1 - Glaciervolcano interactions in the North Crater of Mt Wrangell, Alaska
JF - Annals of Glaciology
Y1 - 2007
A1 - Benson, C.S.
A1 - Roman J. Motyka
A1 - McNUTT, S.
A1 - M P Lüthi
A1 - Martin Truffer
VL - 45
ER -
TY - JOUR
T1 - Hubbard Glacier, Alaska: 2002 closure and outburst of Russell Fjord and postflood conditions at Gilbert Point
JF - Journal of geophysical research
Y1 - 2007
A1 - Roman J. Motyka
A1 - Martin Truffer
VL - 112
ER -
TY - JOUR
T1 - Post Little Ice Age Glacial Rebound in Glacier Bay National Park and Surrounding Areas
JF - Alaska Park Science
Y1 - 2007
A1 - Roman J. Motyka
A1 - Chris F. Larsen
A1 - Jeffrey T. Freymueller
A1 - Echelmeyer, K.A.
VL - 6
ER -
TY - JOUR
T1 - Hazard assessment of the Tidal Inlet landslide and potential subsequent tsunami, Glacier Bay National Park, Alaska
JF - Landslides
Y1 - 0
A1 - Wieczorek, Gerald
A1 - Geist, Eric
A1 - Roman J. Motyka
A1 - Jakob, Matthias
AB - An unstable rock slump, estimated at 5 to 10 × 106 m3, lies perched above the northern shore of Tidal Inlet in Glacier Bay National Park, Alaska. This landslide mass has the potential to rapidly move into Tidal Inlet and generate large, long-period-impulse tsunami waves. Field and photographic examination revealed that the landslide moved between 1892 and 1919 after the retreat of the Little Ice Age glaciers from Tidal Inlet in 1890. Global positioning system measurements over a 2-year period show that the perched mass is presently moving at 3–4 cm annually indicating the landslide remains unstable. Numerical simulations of landslide-generated waves suggest that in the western arm of Glacier Bay, wave amplitudes would be greatest near the mouth of Tidal Inlet and slightly decrease with water depth according to Green’s law. As a function of time, wave amplitude would be greatest within approximately 40 min of the landslide entering water, with significant wave activity continuing for potentially several hours.
VL - 4
UR - http://www.ingentaconnect.com/content/klu/10346/2007/00000004/00000003/00000084
ER -
TY - JOUR
T1 - Hubbard Glacier update: another closure of Russell Fiord in the making?
JF - Journal of Glaciology
Y1 - 0
A1 - Roman J. Motyka
A1 - Lawson, Daniel
A1 - Finnegan, David
A1 - Kalli, George
A1 - Molnia, Bruce
A1 - Anthony A. Arendt
VL - 54
UR - http://www.ingentaconnect.com/content/igsoc/jog/2008/00000054/00000186/art00020
ER -