Multi-year analysis of distributed glacier mass balance modelling and equilibrium line altitude on King George Island, Antarctic Peninsula
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 a...
Main Authors: | , , |
---|---|
Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2018-04-01
|
Series: | The Cryosphere |
Online Access: | https://www.the-cryosphere.net/12/1211/2018/tc-12-1211-2018.pdf |
Summary: | 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 ±1.0 K (100 m)<sup>−1</sup>) 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 km<sup>2</sup> and is glacierized to
93.8 %. Annual discharge from Fourcade Glacier into Potter Cove is
estimated to <mover accent="true"><i>q</i> <mo form="infix">¯</mo> </mover> = 25±6 hm<sup>3</sup> yr<sup>−1</sup> 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. |
---|---|
ISSN: | 1994-0416 1994-0424 |