A synthesis of the basal thermal state of the Greenland Ice Sheet.
The basal thermal state of an ice sheet (frozen or thawed) is an important control upon its evolution, dynamics and response to external forcings. However, this state can only be observed directly within sparse boreholes or inferred conclusively from the presence of subglacial lakes. Here we synthesize spatially extensive inferences of the basal thermal state of the Greenland Ice Sheet to better constrain this state. Existing inferences include outputs from the eight thermomechanical ice-flow models included in the SeaRISE effort. New remote-sensing inferences of the basal thermal state are derived from Holocene radiostratigraphy, modern surface velocity and MODIS imagery. Both thermomechanical modeling and remote inferences generally agree that the Northeast Greenland Ice Stream and large portions of the southwestern ice-drainage systems are thawed at the bed, whereas the bed beneath the central ice divides, particularly their west-facing slopes, is frozen. Elsewhere, there is poor agreement regarding the basal thermal state. Both models and remote inferences rarely represent the borehole-observed basal thermal state accurately near NorthGRIP and DYE-3. This synthesis identifies a large portion of the Greenland Ice Sheet (about one third by area) where additional observations would most improve knowledge of its overall basal thermal state.
Institute for Geophysics, The University of Texas at Austin, Austin, Texas, USA.
Joseph A
JA
MacGregor
Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, USA.
Mark A
MA
Fahnestock
Institute for Geophysics, The University of Texas at Austin, Austin, Texas, USA; Dept. of Geological Sciences, The University of Texas at Austin, Austin, Texas, USA.
Ginny A
GA
Catania
Geophysical Institute, University of Alaska Fairbanks, Fairbanks, Alaska, USA.
Andy
A
Aschwanden
U.S. Geological Survey, Denver, Colorado, USA; Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado, USA.
Gary D
GD
Clow
Dept. of Earth and Space Science and Engineering, York University, Toronto, Canada.
William T
WT
Colgan
Center for Remote Sensing of Ice Sheets, The University of Kansas, Lawrence, Kansas, USA.
S Prasad
SP
Gogineni
Dept. of Earth System Science, University of California, Irvine, California, USA.
Mathieu
M
Morlighem
Cryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA.
Sophie M J
SM
Nowicki
Center for Remote Sensing of Ice Sheets, The University of Kansas, Lawrence, Kansas, USA.
John D
JD
Paden
Fluid Dynamics Group, Los Alamos National Laboratory, Los Alamos, New Mexico, USA.
Stephen F
SF
Price
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA.
Hélène
H
Seroussi