Abstract
Abstract. The mass budget of the ice caps surrounding the Antarctica Peninsula and, in particular, the partitioning of its main components are poorly known. Here we approximate frontal ablation (i.e. the sum of mass losses by calving and submarine melt) and surface mass balance of the ice cap of Livingston Island, the second largest island in the South Shetland Islands archipelago, and analyse variations in surface velocity for the period 2007–2011. Velocities are obtained from feature tracking using 25 PALSAR-1 images, and used in conjunction with estimates of glacier ice thicknesses inferred from principles of glacier dynamics and ground-penetrating radar observations to estimate frontal ablation rates by a flux-gate approach. Glacier-wide surface mass-balance rates are approximated from in situ observations on two glaciers of the ice cap. Within the limitations of the large uncertainties mostly due to unknown ice thicknesses at the flux gates, we find that frontal ablation (−509 ± 263 Mt yr−1, equivalent to −0.73 ± 0.38 m w.e. yr−1 over the ice cap area of 697 km2) and surface ablation (−0.73 ± 0.10 m w.e. yr−1) contribute similar shares to total ablation (−1.46 ± 0.39 m w.e. yr−1). Total mass change (δM = −0.67 &plusmn 0.40 m w.e. yr−1) is negative despite a slightly positive surface mass balance (0.06 ± 0.14 m w.e. yr−1). We find large interannual and, for some basins, pronounced seasonal variations in surface velocities at the flux gates, with higher velocities in summer than in winter. Associated variations in frontal ablation (of ~237 Mt yr−1; −0.34 m w.e. yr−1) highlight the importance of taking into account the seasonality in ice velocities when computing frontal ablation with a flux-gate approach.
Highlights
According to the recent Fifth Assessment of the Intergovernmental Panel on Climate Change (IPCC, 2013), the mass losses from mountain glaciers and ice caps continue to be one of the largest contributors to sea-level rise, with a share of 27 % of the sum of the estimated contributions over the period 1993–2010, larger than the combined contribution by the Antarctic and Greenland ice sheets of 21 %.The glaciers surrounding the Antarctic mainland cover 18 % of the global glacier area (Pfeffer et al, 2014), but their mass budget is not well understood. Shepherd et al (2012) gave an estimate of the mass budget (1992–2011) for the entire Antarctic Peninsula of −20 ± 14 Gt yr−1, excluding glaciers peripheral to the Antarctic Peninsula
Surface ice velocities derived for Livingston ice cap from feature tracking based on 25 Synthetic aperture radar (SAR) images acquired between October 2007 and March 2011 reveal several fast-flowing outlet glaciers reaching velocities of 250 m yr−1
High values are occasionally observed during the winter and a clear seasonality is not apparent in all basins, velocities tend to be higher during the summer
Summary
According to the recent Fifth Assessment of the Intergovernmental Panel on Climate Change (IPCC, 2013), the mass losses from mountain glaciers and ice caps ( referred to as glaciers) continue to be one of the largest contributors to sea-level rise, with a share of 27 % of the sum of the estimated contributions over the period 1993–2010, larger than the combined contribution by the Antarctic and Greenland ice sheets of 21 %.The glaciers surrounding the Antarctic mainland cover 18 % of the global glacier area (Pfeffer et al, 2014), but their mass budget is not well understood. Shepherd et al (2012) gave an estimate of the mass budget (1992–2011) for the entire Antarctic Peninsula of −20 ± 14 Gt yr−1, excluding glaciers peripheral to the Antarctic Peninsula. Shepherd et al (2012) gave an estimate of the mass budget (1992–2011) for the entire Antarctic Peninsula of −20 ± 14 Gt yr−1, excluding glaciers peripheral to the Antarctic Peninsula. They pointed out that “the spatial sampling of mass fluctuations at the Antarctic Peninsula Ice Sheet is as present inadequate, considering that it provides a significant component of the overall Antarctic Ice Sheet imbalance”. Gardner et al (2013) gave an estimate of −6 ± 10 Gt yr−1 for the mass budget of the glaciers of the Antarctic periphery during 2003–2009, which corresponds to 2 % of global glacier wastage. Hock et al (2009) concluded that these
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