30 Jun 2023
 | 30 Jun 2023
Status: this preprint is currently under review for the journal TC.

Evaluating different geothermal heat flow maps as basal boundary conditions during spin up of the Greenland ice sheet

Tong Zhang, William Colgan, Agnes Wansing, Anja Løkkegaard, Gunter Leguy, William Lipscomb, and Cunde Xiao

Abstract. There is currently poor scientific agreement 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 a diversity of opinion in the subglacial geothermal heat flow basal boundary condition employed in different ice-flow models. Here, we employ seven Greenland geothermal heat flow maps in widespread use to 10,000-year spin ups of the Community Ice Sheet Model (CISM). We perform both a fully unconstrained transient spin up, as well as a nudged spin up that conforms to Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) protocol. Across the seven heat flow maps, and regardless of unconstrained or nudged spin up, the spread in basal ice temperatures exceeds 10 °C over large areas of the ice-bed interface. For a given heat flow map, thawed-bedded ice-sheet area is consistently larger under unconstrained spin ups than nudged spin ups. Under the unconstrained spin up, thawed-bedded area ranges from 33.5 to 60.0 % 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. This highlights the direct, and non-trivial, influence of choice of 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 to simulations employing a common heat flow map.

Tong Zhang et al.

Status: open (until 01 Oct 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Tong Zhang et al.

Tong Zhang et al.


Total article views: 376 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
254 108 14 376 10 9
  • HTML: 254
  • PDF: 108
  • XML: 14
  • Total: 376
  • BibTeX: 10
  • EndNote: 9
Views and downloads (calculated since 30 Jun 2023)
Cumulative views and downloads (calculated since 30 Jun 2023)

Viewed (geographical distribution)

Total article views: 365 (including HTML, PDF, and XML) Thereof 365 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
Latest update: 28 Sep 2023
Short summary
The geothermal heat flux determined how much heat enters from the beneath of the ice sheet, and thus impacts the temperature and the flow of the ice sheet. In this study we want to investigate how much geothermal heat flux impacts the initialization of Greenland ice sheet. We use the Community Ice Sheet Model with 2 different initialization methods. We find non-trivial influence of choice of heat flow boundary condition on the ice sheet initializations for further designs of ice sheet modelings.