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.
Environmental changes in the northern Antarctic Peninsula provide a sensitive local indicator of climate warming. A consequence of these changes is the activation of surface and subsurface hydrological cycles in areas where water, in colder conditions, would remain frozen. This paper analyses the effects of hydrological cycle activation at Cape Lamb, Vega Island. The conclusions are based on hydrochemistry and isotope interpretation of 51 representative water samples from precipitation, streams, lakes, ice, snow and groundwater. Based on these results relationships between the different components of the hydrological cycle are proposed. This paper highlights the important contribution of groundwater to surface water chemistry, the disconnection of the lakes from the overall flow, the lack of an ocean spray signature in surface water and groundwater and the significant influence of windblown dust in the composition of the analysed waters.
Although the relationship between surface air temperature and glacial discharge has been studied in the Northern Hemisphere for at least a century, similar studies for Antarctica remain scarce and only for the past four decades. This data scarcity is due to the extreme meteorological conditions and terrain inaccessibility. As a result, the contribution of glacial discharge in Antarctica to global sea-level rise is still attached with great uncertainties, especially from partly glaciated hydrological basins as can be found in the Antarctic Peninsula. In this paper, we propose a simplified model based on the Monte Carlo method and Fourier analysis for estimating discharge in partly glaciated and periglacial hydrological catchments with a summer melt period. Our model offers the advantage of scarce data requirements and quick recognition of periglacial environments. Discharge was found to be highly correlated with surface air temperature for the partially glaciated hydrological catchments on Potter Peninsula, King George Island (Isla 25 Mayo). The model is simple to implement and requires few variables to make most versatile simulations. We have obtained a monthly simulated maximum flow estimates between 0.74 and 1.07 m s for two creeks (South and North Potter) with a very good fit to field observations. The glacial mean monthly discharge during summer months was estimated to 0.44±0.02 m s for South Potter Creek and 0.55±0.02 m s for North Potter Creek.This article is part of the theme issue 'The marine system of the West Antarctic Peninsula: status and strategy for progress in a region of rapid change'.
Glaciers and ice sheets export significant amounts of silicon (Si) to downstream ecosystems, impacting local and potentially global biogeochemical cycles. Recent studies have shown Si in Arctic glacial meltwaters to have an isotopically distinct signature when compared to non-glacial rivers. This is likely linked to subglacial weathering processes and mechanochemical reactions. However, there are currently no silicon isotope (δ 30 Si) data available from meltwater streams in Antarctica, limiting the current inferences on global glacial silicon isotopic composition and its drivers. To address this gap, we present dissolved silicon (DSi), δ 30 Si DSi , and major ion data from meltwater streams draining a polythermal glacier in the region of the West Antarctic Peninsula (WAP; King George Island) and a cold-based glacier in East Antarctica [Commonwealth Stream, McMurdo Dry Valleys (MDV)]. These data, alongside other global datasets, improve our understanding of how contrasting glacier thermal regime can impact upon Si cycling and therefore the δ 30 Si DSi composition. We find a similar δ 30 Si DSi composition between the two sites, with the streams on King George Island varying between-0.23 and +1.23 and the Commonwealth stream varying from-0.40 to +1.14. However, meltwater streams in King George Island have higher DSi concentrations, and the two glacial systems exhibit opposite DSi-δ 30 Si DSi trends. These contrasts likely result from differences in weathering processes, specifically the role of subglacial processes (King George Island) and, supraglacial processes followed by in-stream weathering in hyporheic zones (Commonwealth Stream). These findings are important when considering likely changes in nutrient fluxes from Antarctic glaciers under climatic warming scenarios and consequent shifts in glacial thermal regimes.
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 ±1.0 K/100 m), and a distinct spatial heterogeneity
Abstract. There is only a small number of recent publications discuss glacial runoff in Antarctica and even fewer of them deal with the groundwater flow discharge. This paper focuses on the groundwater flow aspects and is based on a detailed study performed on a small hydrological catchment, informally called Potter Basin, located on King George Island (KGI; Isla 25 de Mayo), South Shetland Islands, at the northern tip of the Antarctic Peninsula. This region has experienced drastic climatological changes within the past five decades. The basin is representative for the rugged coastline of the Northern Antarctic Peninsula, and is discussed as a case study for possible future evolution of similar basins further to the South. A conceptual hydrogeological model has been defined using vertical electrical soundings (VES), geological and hydrogeological surveying methods, geomorphological interpretation based on satellite imagery, permeability tests, piezometric level measurements, meteorological, geocryological and glaciological data sets. The transmissivities of the fluvial talik aquifer and suprapermafrost aquifer range from 162.0 to 2719.9 · 10−5 m2 s−1, and in basaltic fissurated aquifers from 3.47 to 5.79 · 10−5 m2 s−1. The transmissivities found in the active layer of hummocky moraines amount to 75.23 · 10−5 m2 s−1, in sea deposits to 163.0 · 10−5 m2 s−1, and in the fluvioglacial deposits they were observed between 902.8 and 2662.0 · 10−5 m2 d−1. Finally, the groundwater flow discharge was assessed to 0.47 m3 s−1 (only during January and February), and the total groundwater storage was estimated to 560 000 m3. This data can be used to adjust the local glacial mass balance and to improve the understanding of coastal sea water processes in Potter Cove and their effects on the local marine biota, as a consequence of the global climate change.
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