Multi-year analysis of distributed glacier mass balance modelling and equilibrium line altitude on King George Island, Antarctic Peninsula

Abstract

Abstract. The South Shetland Islands are located at the northern tip of the Antarctic Peninsula (AP). This region was subject to strong warming trends in the atmospheric surface layer. Surface air temperature increased about 3 K in 50 years, concurrent with retreating glacier fronts, an increase in melt areas, ice surface lowering and rapid break-up and disintegration of ice shelves. The positive trend in surface air temperature has currently come to a halt. Observed surface air temperature lapse rates show a high variability during winter months (standard deviations up to ±1.0K(100m)-1) and a distinct spatial heterogeneity reflecting the impact of synoptic weather patterns. The increased mesocyclonic activity during the wintertime over the past decades in the study area results in intensified advection of warm, moist air with high temperatures and rain and leads to melt conditions on the ice cap, fixating surface air temperatures to the melting point. Its impact on winter accumulation results in the observed negative mass balance estimates. Six years of continuous glaciological measurements on mass balance stake transects as well as 5 years of climatological data time series are presented and a spatially distributed glacier energy balance melt model adapted and run based on these multi-year data sets. The glaciological surface mass balance model is generally in good agreement with observations, except for atmospheric conditions promoting snow drift by high wind speeds, turbulence-driven snow deposition and snow layer erosion by rain. No drift in the difference between simulated mass balance and mass balance measurements can be seen over the course of the 5-year model run period. The winter accumulation does not suffice to compensate for the high variability in summer ablation. The results are analysed to assess changes in meltwater input to the coastal waters, specific glacier mass balance and the equilibrium line altitude (ELA). The Fourcade Glacier catchment drains into Potter cove, has an area of 23.6 km2 and is glacierized to 93.8 %. Annual discharge from Fourcade Glacier into Potter Cove is estimated to q¯=25±6hm3yr-1 with the standard deviation of 8 % annotating the high interannual variability. The average ELA calculated from our own glaciological observations on Fourcade Glacier over the time period 2010 to 2015 amounts to 260±20 m. Published studies suggest rather stable conditions of slightly negative glacier mass balance until the mid-1980s with an ELA of approx. 150 m. The calculated accumulation area ratio suggests dramatic changes in the future extent of the inland ice cap for the South Shetland Islands.

Brief communication: An ice surface melt scheme including the diurnal cycle of solar radiation

“…The dEBM and two empirical schemes are calibrated and evaluated using the state-of-the-art regional climate and snowpack model MAR (Fettweis et al, 2017) as a reference.…”

“…This new scheme only requires monthly means of temperature and solar radiation as input but implicitly resolves the diurnal cycle of radiation. In a first application on the Greenland Ice Sheet (GrIS) we use a simulation of Greenland's climate of the years 1948 to 2016 with the stateof-the-art regional climate and snowpack model MAR (version 3.5.2 forced with reanalysis data from the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP) for the years 1948-2016, Kalnay et al, 1996;Fettweis et al, 2017) as a reference.…”

Recession and Ice Surface Elevation Changes of Baranowski Glacier and Its Impact on Proglacial Relief (King George Island, West Antarctica)

“…The total area of the island is 1250 km 2 , and almost the entire island is covered by ice caps (Figure 2b). The glacier drains the Warszawa Ice field at its Eastern edge (Figure 2c), where melt The reactions of glaciers, generally in the form of mass loss [18], glacier recession [13], and decreased ice surface elevation [16], have been observed, especially for those located in the South Shetland Islands [18][19][20][21][22][23]. Since 1956, climate warming has been the main factor causing these changes.…”

“…For example, Simoes et al [26] based on the analysis of the transient snow line positioning obtained from remote sensing data claimed that the ELA for the King George Island Ice Cape equaled 300-350 m but Braun et al [55] based on the same method as Simoes et al [26], suggested that for the northern side of KGI it was 250 m. More specifically, Bintanja [56] estimated that for the Ecology Glacier ELA is 100 m. More recent direct observation with the use of stakes done by Sobota et al [24] for Ecology and Sphinx Glacial System (ESGS) suggested that the average ELA in 2012-2013 was 156 m a.s.l. On the other hand, Falk et al [20], based on their own glaciological observation, calculated the average ELA for Fourcad Glacier over the period 2010-2015 and obtained that it was 260 ± 20 m. All of the published studies suggested that since 1980, the ELA for KGI has been rather stable with small negative mass balance [20], but all studies expected further glacial retreat. As the Baranowski Glacier is the closest to ESGS and even being the part of this system, it can be assumed that the ELA of Baranowski Glacier is around 150 m and is presented in Figure 7, this isoline since 1989 rose higher from Siodło and the surface of the glacier started to thin in the following years.…”

“…Since 1956, climate warming has been the main factor causing these changes. Special attention has been paid to the glaciers located within Admiralty Bay [16,19,[24][25][26][27][28][29][30][31] and others that drain the Warszawa Ice field [20,32,33]. The effects of climate change were confirmed, for example, on the Ecology and Sphinx glaciers between 2012 and 2013 in the form of a short-term negative mass balance [24].…”