Articles | Volume 11, issue 6
The Cryosphere, 11, 2411–2426, 2017
The Cryosphere, 11, 2411–2426, 2017

Research article 01 Nov 2017

Research article | 01 Nov 2017

Observationally constrained surface mass balance of Larsen C ice shelf, Antarctica

Peter Kuipers Munneke1, Daniel McGrath2,3, Brooke Medley4, Adrian Luckman5, Suzanne Bevan5, Bernd Kulessa5, Daniela Jansen6, Adam Booth7, Paul Smeets1, Bryn Hubbard8, David Ashmore8, Michiel Van den Broeke1, Heidi Sevestre9, Konrad Steffen10, Andrew Shepherd7, and Noel Gourmelen11 Peter Kuipers Munneke et al.
  • 1Institute for Marine and Atmospheric research, Utrecht University, Utrecht, the Netherlands
  • 2Geosciences Department, Colorado State University, Fort Collins, CO, USA
  • 3U.S. Geological Survey, Alaska Science Center, Anchorage, AK, USA
  • 4Cryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
  • 5Geography Department, College of Science, Swansea University, Swansea, UK
  • 6Alfred Wegener Institute Helmholtz-Centre for Polar and Marine Research, Bremerhaven, Germany
  • 7School of Earth and Environment, University of Leeds, Leeds, UK
  • 8Centre for Glaciology, Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, UK
  • 9Department of Geography and Sustainable Development, University of St Andrews, St Andrews, UK
  • 10Swiss Federal Research Institute WSL, Birmensdorf, Switzerland
  • 11School of Geosciences, University of Edinburgh, Edinburgh, UK

Abstract. The surface mass balance (SMB) of the Larsen C ice shelf (LCIS), Antarctica, is poorly constrained due to a dearth of in situ observations. Combining several geophysical techniques, we reconstruct spatial and temporal patterns of SMB over the LCIS. Continuous time series of snow height (2.5–6 years) at five locations allow for multi-year estimates of seasonal and annual SMB over the LCIS. There is high interannual variability in SMB as well as spatial variability: in the north, SMB is 0.40 ± 0.06 to 0.41 ± 0.04 m w.e. year−1, while farther south, SMB is up to 0.50 ± 0.05 m w.e. year−1. This difference between north and south is corroborated by winter snow accumulation derived from an airborne radar survey from 2009, which showed an average snow thickness of 0.34 m w.e. north of 66° S, and 0.40 m w.e. south of 68° S. Analysis of ground-penetrating radar from several field campaigns allows for a longer-term perspective of spatial variations in SMB: a particularly strong and coherent reflection horizon below 25–44 m of water-equivalent ice and firn is observed in radargrams collected across the shelf. We propose that this horizon was formed synchronously across the ice shelf. Combining snow height observations, ground and airborne radar, and SMB output from a regional climate model yields a gridded estimate of SMB over the LCIS. It confirms that SMB increases from north to south, overprinted by a gradient of increasing SMB to the west, modulated in the west by föhn-induced sublimation. Previous observations show a strong decrease in firn air content toward the west, which we attribute to spatial patterns of melt, refreezing, and densification rather than SMB.

Short summary
How much snow falls on the Larsen C ice shelf? This is a relevant question, because this ice shelf might collapse sometime this century. To know if and when this could happen, we found out how much snow falls on its surface. This was difficult, because there are only very few measurements. Here, we used data from automatic weather stations, sled-pulled radars, and a climate model to find that melting the annual snowfall produces about 20 cm of water in the NE and over 70 cm in the SW.