TY - JOUR
T1 - Evaluating different geothermal heat-flow maps as basal boundary conditions during spin-up of the Greenland ice sheet
AU - Zhang, Tong
AU - Colgan, William
AU - Wansing, Agnes
AU - Løkkegaard, Anja
AU - Leguy, Gunter
AU - Lipscomb, William H.
AU - Xiao, Cunde
N1 - Publisher Copyright:
© 2024 Copernicus GmbH. All rights reserved.
PY - 2024/1/26
Y1 - 2024/1/26
N2 - There is currently poor scientific agreement on whether the ice-bed interface is frozen or thawed beneath approximately one third of the Greenland ice sheet. This disagreement in basal thermal state results, at least partly, from differences in the subglacial geothermal heat-flow basal boundary condition used in different ice-flow models. Here, we employ seven widely used Greenland geothermal heat-flow maps in 10g000-year spin-ups of the Community Ice Sheet Model (CISM). We perform two spin-ups: one nudged toward thickness observations and the other unconstrained. Across the seven heat-flow maps, and regardless of unconstrained or nudged spin-up, the spread in basal ice temperatures exceeds 10gC over large areas of the ice-bed interface. For a given heat-flow map, the thawed-bed ice-sheet area is consistently larger under unconstrained spin-ups than nudged spin-ups. Under the unconstrained spin-up, thawed-bed area ranges from 33.5g% to 60.0g% across the seven heat-flow maps. Perhaps counterintuitively, the highest iceberg calving fluxes are associated with the lowest heat flows (and vice versa) for both unconstrained and nudged spin-ups. These results highlight the direct, and non-Trivial, influence of the heat-flow boundary condition on the simulated equilibrium thermal state of the ice sheet. We suggest that future ice-flow model intercomparisons should employ a range of basal heat-flow maps, and limit direct intercomparisons with simulations using a common heat-flow map.
AB - There is currently poor scientific agreement on whether the ice-bed interface is frozen or thawed beneath approximately one third of the Greenland ice sheet. This disagreement in basal thermal state results, at least partly, from differences in the subglacial geothermal heat-flow basal boundary condition used in different ice-flow models. Here, we employ seven widely used Greenland geothermal heat-flow maps in 10g000-year spin-ups of the Community Ice Sheet Model (CISM). We perform two spin-ups: one nudged toward thickness observations and the other unconstrained. Across the seven heat-flow maps, and regardless of unconstrained or nudged spin-up, the spread in basal ice temperatures exceeds 10gC over large areas of the ice-bed interface. For a given heat-flow map, the thawed-bed ice-sheet area is consistently larger under unconstrained spin-ups than nudged spin-ups. Under the unconstrained spin-up, thawed-bed area ranges from 33.5g% to 60.0g% across the seven heat-flow maps. Perhaps counterintuitively, the highest iceberg calving fluxes are associated with the lowest heat flows (and vice versa) for both unconstrained and nudged spin-ups. These results highlight the direct, and non-Trivial, influence of the heat-flow boundary condition on the simulated equilibrium thermal state of the ice sheet. We suggest that future ice-flow model intercomparisons should employ a range of basal heat-flow maps, and limit direct intercomparisons with simulations using a common heat-flow map.
UR - http://www.scopus.com/inward/record.url?scp=85184039399&partnerID=8YFLogxK
U2 - 10.5194/tc-18-387-2024
DO - 10.5194/tc-18-387-2024
M3 - Article
AN - SCOPUS:85184039399
SN - 1994-0416
VL - 18
SP - 387
EP - 402
JO - Cryosphere
JF - Cryosphere
IS - 1
ER -