|The role of ice stream dynamics in deglaciation|
|investigators:||A. Robel and E. Tziperman|
|journal:||JGR Earth Surface|
Does the presence of ice streams enhance deglaciation? If so, this should render certain large ice sheets, those with geometry and basal properties conducive to stream formation, more sensitive to changes in the climatic mass balance input. Based on an idealized PISM configuration, the simulations in this study show that when the ice sheet is large and ice streams are sufficiently developed an upward shift in equilibrium line altitude results in rapid deglaciation, while the same shift applied to an ice sheet without fully-formed ice streams results in continued ice sheet growth or slower deglaciation. Rapid deglaciation in ice sheets with significant streaming behavior is caused by ice stream acceleration and the attendant enhancement of calving and surface melting at low elevations. Ice stream acceleration is ultimately the result of steepening of the ice surface and increased driving stresses in ice stream onset zones, which come about due to the dependence of surface mass balance on elevation.
The 4000 square km ice field in Southeast Alaska is well-known and accessible since its outlets are in the suburbs of the Alaska state capital, Juneau. But climate data for the area are sparse.
Those model runs that agreed well with observations for 1971 to 2010 generated volume and area losses of more than half by 2099. While co-author Regine Hock (UAF) is quoted as saying “The massive icefield that feeds Alaska’s Mendenhall Glacier may be gone by 2200 if warming trend predictions hold true,”, the authors emphasize that spatially-distributed mass balance measurements and improved climate projections that resolve the local temperature and precipitation patterns are essential to solidifying these predictions.
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The Paleoclimate Dynamics section at Alfred-Wegener-Institut invites applications for a position as a
with a background in ice sheet or climate modelling for the DFG-project “Global sea level change since the Mid Holocene” (SPP 1889).
Background and tasks:
The aim of this project is to study the evolution of polar ice sheets of the last 6000 years and to estimate the role of climate – ice sheet interactions. Combining climate and ice sheet simulations of different resolution, the project particularly focusses on the ice sheets' mass balance and on ice shelf – ocean interactions under natural and anthropogenic climate change.
The postdoc’s duties will include set-up, supervision, and analysis of climate and ice sheet (PISM) simulations as well as publication in peer-reviewed journals.
The successful candidate should have a PhD in glaciology, atmospheric sciences, oceanography or related sciences and should have a background in either ice sheet or climate modelling.
The position is limited to 3 years, starting August 1st, 2016 or later. The salary will be paid in accordance with the German Tarifvertrag des öffentlichen Dienstes (TVöD Bund), salary level 13. The place of employment will be Bremerhaven.
For further information:
PISM is jointly developed at the University of Alaska, Fairbanks (UAF) and the Potsdam Institute for Climate Impact Research (PIK). For more about the team see the UAF Developers and PIK Developers pages.
UAF developers, who are in the Glaciers Group at the GI, are supported by NASA's Modeling, Analysis, and Prediction and Cryospheric Sciences Programs (grants NAG5-11371, NNX09AJ38C, NNX13AM16G, NNX16AQ40G) and by NSF grants PLR-1603799 and PLR-1644277.