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Exceptionally high heat flux needed to sustain the Northeast Greenland Ice Stream
The Northeast Greenland Ice Stream (NEGIS) currently drains more than 10 % of the Greenland Ice Sheet area and has recently undergone significant dynamic changes. It is therefore critical to accurately represent this feature when assessing the future contribution of Greenland to sea level rise. At present, NEGIS is reproduced in ice sheet models by inferring basal conditions using observed surface velocities. This approach helps estimate conditions at the base of the ice sheet but cannot be used to estimate the evolution of basal drag in time, so it is not a good representation of the evolution of the ice sheet in future climate warming scenarios. NEGIS is suggested to be initiated by a geothermal heat flux anomaly close to the ice divide, left behind by the movement of Greenland over the Icelandic plume. However, the heat flux underneath the ice sheet is largely unknown, except for a few direct measurements from deep ice core drill sites. Using the Ice Sheet System Model (ISSM), with ice dynamics coupled to a subglacial hydrology model, we investigate the possibility of initiating NEGIS by inserting heat flux anomalies with various locations and intensities. In our model experiment, a minimum heat flux value of 970 mW m−2 located close to the East Greenland Ice-core Project (EGRIP) is required locally to reproduce the observed NEGIS velocities, giving basal melt rates consistent with previous estimates. The value cannot be attributed to geothermal heat flux alone and we suggest hydrothermal circulation as a potential explanation for the high local heat flux. By including high heat flux and the effect of water on sliding, we successfully reproduce the main characteristics of NEGIS in an ice sheet model without using data assimilation.
- Jet Propulsion Lab United States
- Jet Propulsion Laboratory United States
- National Aeronautics and Space Administration United States
- California Institute of Technology United States
- University of Oslo Norway
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Åkesson, H., Morlighem, M., Nisancioglu, K., Svendsen, J., and Mangerud, J.: Atmosphere-driven ice sheet mass loss paced by topography: Insights from modelling the south-western Scandinavian Ice Sheet, Quaternary Sci. Rev., 195, 32-47, https://doi.org/10.1016/j.quascirev.2018.07.004, 2018.
Alley, R. B., Pollard, D., Parizek, B. R., Anandakrishnan, S., Pourpoint, M., Stevens, N. T., MacGregor, J., Christianson, K., Muto, A., and Holschuh, N.: Possible Role for Tectonics in the Evolving Stability of the Greenland Ice Sheet, J. Geophys. Res.-Earth, 124, 97-115, https://doi.org/10.1029/2018JF004714, 2019.
Artemieva, I. M.: Lithosphere thermal thickness and geothermal heat flux in Greenland from a new thermal isostasy method, Earth-Sci. Rev., 188, 469-481, https://doi.org/10.1016/j.earscirev.2018.10.015, 2019.
Asay-Davis, X. S., Cornford, S. L., Durand, G., Galton-Fenzi, B. K., Gladstone, R. M., Gudmundsson, G. H., Hattermann, T., Holland, D. M., Holland, D., Holland, P. R., Martin, D. F., Mathiot, P., Pattyn, F., and Seroussi, H.: Experimental design for three interrelated marine ice sheet and ocean model intercomparison projects: MISMIP v. 3 (MISMIP +), ISOMIP v. 2 (ISOMIP +) and MISOMIP v. 1 (MISOMIP1), Geosci. Model Dev., 9, 2471- 2497, https://doi.org/10.5194/gmd-9-2471-2016, 2016. [OpenAIRE]
Aschwanden, A., Bueler, E., Khroulev, C., and Blatter, H.: An enthalpy formulation for glaciers and ice sheets, J. Glaciol., 58, 441-457, https://doi.org/10.3189/2012JoG11J088, 2012.
Aschwanden, A., Fahnestock, M., and Truffer, M.: Complex Greenland outlet glacier flow captured, Nat. Commun., 7, 10524, https://doi.org/10.1038/ncomms10524, 2016.
Beyer, S., Kleiner, T., Aizinger, V., Rückamp, M., and Humbert, A.: A confined-unconfined aquifer model for subglacial hydrology and its application to the Northeast Greenland Ice Stream, The Cryosphere, 12, 3931-3947, https://doi.org/10.5194/tc-12-3931- 2018, 2018.
Bondzio, J. H., Morlighem, M., Seroussi, H., Kleiner, T., Rückamp, M., Mouginot, J., Moon, T., Larour, E. Y., and Humbert, A.: The mechanisms behind Jakobshavn Isbrae's acceleration and mass loss: A 3-D thermomechanical model study, Geophys. Res. Lett., 44, 6252-6260, https://doi.org/10.1002/2017GL073309, 2017.
Box, J.: Greenland monthly surface mass balance 1840-2012, Zenodo, https://doi.org/10.5281/zenodo.3359192, 2019.
Christianson, Knut, Peters, Leo E., Alley, Richard B., Anandakrishnan, Sridhar, Jacobel, Robert W., Riverman, Kiya L., Muto, Atsuhiro, Keisling, Benjamin A.:Dilatant till facilitates ice-stream flow in northeast Greenland, Earth Planet. Sc. Lett., 401, 57-69, https://doi.org/10.1016/j.epsl.2014.05.060, 2014.
- Jet Propulsion Lab United States
- Jet Propulsion Laboratory United States
- National Aeronautics and Space Administration United States
- California Institute of Technology United States
- University of Oslo Norway
- University of Bergen Norway
- UNIVERSITETET I BERGEN Norway
- University of Bergen, Department of Earth Sciences Norway
- California Institute of Technology, Jet Propulsion Laboratory United States
- Jet Propulsion Laboratory, California Institute of Technology, NASA, Pasadena, CA United States
- University of Bergen, Bjerknes Centre for Climate Research Norway
- Jet Propulsion Laboratory (JPL) California Institute of Technology United States
The Northeast Greenland Ice Stream (NEGIS) currently drains more than 10 % of the Greenland Ice Sheet area and has recently undergone significant dynamic changes. It is therefore critical to accurately represent this feature when assessing the future contribution of Greenland to sea level rise. At present, NEGIS is reproduced in ice sheet models by inferring basal conditions using observed surface velocities. This approach helps estimate conditions at the base of the ice sheet but cannot be used to estimate the evolution of basal drag in time, so it is not a good representation of the evolution of the ice sheet in future climate warming scenarios. NEGIS is suggested to be initiated by a geothermal heat flux anomaly close to the ice divide, left behind by the movement of Greenland over the Icelandic plume. However, the heat flux underneath the ice sheet is largely unknown, except for a few direct measurements from deep ice core drill sites. Using the Ice Sheet System Model (ISSM), with ice dynamics coupled to a subglacial hydrology model, we investigate the possibility of initiating NEGIS by inserting heat flux anomalies with various locations and intensities. In our model experiment, a minimum heat flux value of 970 mW m−2 located close to the East Greenland Ice-core Project (EGRIP) is required locally to reproduce the observed NEGIS velocities, giving basal melt rates consistent with previous estimates. The value cannot be attributed to geothermal heat flux alone and we suggest hydrothermal circulation as a potential explanation for the high local heat flux. By including high heat flux and the effect of water on sliding, we successfully reproduce the main characteristics of NEGIS in an ice sheet model without using data assimilation.