[en] Greenland's contribution to future sea-level rise remains uncertain and a wide range of upper and lower bounds has been proposed. These predictions depend strongly on how mass loss - which is focused at the termini of marine-terminating outlet glaciers - can penetrate inland to the ice-sheet interior. Previous studies have shown that, at regional scales, Greenland ice sheet mass loss is correlated with atmospheric and oceanic warming. However, mass loss within individual outlet glacier catchments exhibits unexplained heterogeneity, hindering our ability to project ice-sheet response to future environmental forcing. Using digital elevation model differencing, we spatially resolve the dynamic portion of surface elevation change from 1985 to present within 16 outlet glacier catchments in West Greenland, where significant heterogeneity in ice loss exists. We show that the up-glacier extent of thinning and, thus, mass loss, is limited by glacier geometry. We find that 94% of the total dynamic loss occurs between the terminus and the location where the down-glacier advective speed of a kinematic wave of thinning is at least three times larger than its diffusive speed. This empirical threshold enables the identification of glaciers that are not currently thinning but are most susceptible to future thinning in the coming decades.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Felikson, Denis ; Institute for Geophysics, University of Texas at Austin, Austin, United States ; Department of Aerospace Engineering and Engineering Mechanics, University of Texas at Austin, Austin, United States
Bartholomaus, Timothy C.; Institute for Geophysics, University of Texas at Austin, Austin, United States ; Department of Geological Sciences, University of Idaho, Moscow, United States
Catania, Ginny A.; Institute for Geophysics, University of Texas at Austin, Austin, United States ; Department of Geological Sciences, University of Texas at Austin, Austin, United States
Korsgaard, Niels J. ; Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, Reykjavik, Iceland
Kjær, Kurt H.; Centre for GeoGenetics, Natural History Museum, University of Copenhagen, Copenhagen, Denmark
Morlighem, Mathieu ; Department of Earth System Science, University of California, Irvine, United States
Noël, Brice ; Université de Liège - ULiège > Département de géographie > Climatologie et Topoclimatologie ; Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, Netherlands
Van Den Broeke, Michiel; Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, Netherlands
Stearns, Leigh A. ; Department of Geology, University of Kansas, Lawrence, United States
Shroyer, Emily L.; College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, United States
Sutherland, David A. ; Department of Geological Sciences, University of Oregon, Eugene, United States
Nash, Jonathan D.; College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, United States
Language :
English
Title :
Inland thinning on the Greenland ice sheet controlled by outlet glacier geometry
We would like to thank the Polar Geospatial Center for providing theWorldView stereo imagery. This work was funded by NASA Grant NNX12AP50G, by funding from the University of Texas Aerospace Engineering department, and a University of Texas Institute for Geophysics Postdoctoral Fellowship to T.C.B.
Wouters, B., Chambers, D. & Schrama, E. J. O. GRACE observes small-scale mass loss in Greenland. Geophys. Res. Lett. 35, L20501 (2008).
Harig, C. & Simons, F. J. Mapping Greenland's mass loss in space and time. Proc. Natl Acad. Sci. USA 109, 19934-19937 (2012).
Schrama, E. J. O. &Wouters, B. Revisiting Greenland ice sheet mass loss observed by GRACE. J. Geophys. Res. 116, B02407 (2011).
Velicogna, I., Sutterley, T. C. & van den Broeke, M. R. Regional acceleration in ice mass loss from Greenland and Antarctica using GRACE time-variable gravity data. Geophys. Res. Lett. 41, 8130-8137 (2014).
Murray, T. et al. Extensive retreat of Greenland tidewater glaciers, 2000-2010. Arct. Antarct. Alp. Res. 47, 427-447 (2015).
Csatho, B. M. et al. Laser altimetry reveals complex pattern of Greenland ice sheet dynamics. Proc. Natl Acad. Sci. USA 111, 18478-18483 (2014).
Moon, T., Joughin, I., Smith, B. & Howat, I. 21st-century evolution of Greenland outlet glacier velocities. Science 336, 576-578 (2012).
Kjaer, K. H. et al. Aerial photographs reveal late-20th-century dynamic ice loss in northwestern Greenland. Science 337, 569-573 (2012).
Howat, I. M., Joughin, I., Fahnestock, M., Smith, B. E. & Scambos, T. A. Synchronous retreat and acceleration of southeast Greenland outlet glaciers 2000-06 ice dynamics and coupling to climate. J. Glaciol. 54, 646-660 (2008).
Bevan, S. L., Luckman, A. J. &Murray, T. Glacier dynamics over the last quarter of a century at Helheim, Kangerdlugssuaq and 14 other major Greenland outlet glaciers. Cryosphere 6, 923-937 (2012).
Khan, S. A. et al. Sustained mass loss of the northeast Greenland ice sheet triggered by regional warming. Nat. Clim. Change 4, 292-299 (2014).
Enderlin, E. M. et al. An improved mass budget for the Greenland ice sheet. Geophys. Res. Lett. 41, 866-872 (2014).
Price, S. F., Payne, A. J., Howat, I. M. & Smith, B. E. Committed sea-level rise for the next century from Greenland ice sheet dynamics during the past decade. Proc. Natl Acad. Sci. USA 108, 8978-8983 (2011).
Nick, F. M., Vieli, A., Howat, I. M. & Joughin, I. Large-scale changes in Greenland outlet glacier dynamics triggered at the terminus. Nat. Geosci. 2, 110-114 (2009).
Konrad, H. et al. Uneven onset and pace of ice-dynamical imbalance in the Amundsen Sea Embayment,West Antarctica. Geophys. Res. Lett. 44, 910-918 (2017).
Pfeffer,W. T., Harper, J. T. & O'Neel, S. Kinematic constraints on glacier contributions to 21st-century sea-level rise. Science 321, 1340-1343 (2008).
Nick, F. M. et al. Future sea-level rise from Greenland's main outlet glaciers in a warming climate. Nature 497, 235-238 (2013).
Moore, J. C., Grinsted, A., Zwinger, T. & Jevrejeva, S. Semiempirical and process-based global sea level projections. Rev. Geophys. 51, 484-522 (2013).
Korsgaard, N. J. et al. Digital elevation model and orthophotographs of Greenland based on aerial photographs from 1978-1987. Sci. Data 3, 160032 (2016).
Morlighem, M., Rignot, E. &Willis, J. Improving bed topography mapping of Greenland glaciers using NASA's Oceans Melting Greenland (OMG) data. Oceanography 29, 62-71 (2016).
Nye, J. F. The response of glaciers and ice-sheets to seasonal and climatic changes. Proc. R. Soc. A 256, 559-584 (1960).
Pritchard, H. D., Arthern, R. J., Vaughan, D. G. & Edwards, L. A. Extensive dynamic thinning on the margins of the Greenland and Antarctic ice sheets. Nature 461, 971-975 (2009).
Pfeffer,W. T. A simple mechanism for irreversible tidewater glacier retreat. J. Geophys. Res. 112, F03S25 (2007).
van der Veen, C. J. Greenland ice sheet response to external forcing. J. Geophys. Res. 106, 34047-34058 (2001).
Howat, I. M., Negrete, A. & Smith, B. E. The Greenland Ice Mapping Project (GIMP) land classification and surface elevation data sets. Cryosphere 8, 1509-1518 (2014).
Shean, D. E. et al. An automated open-source pipeline for mass production of digital elevation models (DEMs) from very-high-resolution commercial stereo satellite imagery. Int. Soc. Photogramm. 116, 101-117 (2016).
Rignot, E., Box, J. E., Burgess, E. & Hanna, E. Mass balance of the Greenland ice sheet from 1958 to 2007. Geophys. Res. Lett. 35, L20502 (2008).
Noël, B. et al. Evaluation of the updated regional climate model RACMO2.3: summer snowfall impact on the Greenland ice sheet. Cryosphere 9, 1831-1844 (2015).
Cuffey, K. M. & Paterson,W. S. B. The Physics of Glaciers Chap. 11 (Academic, 2010).
Kamb, B. & Echelmeyer, K. A. Stress-gradient coupling in glacier flow: I. Longitudinal averaging of the influence of ice thickness and surface slope. J. Glaciol. 32, 267-284 (1986).
