Abstract
ABSTRACTTo study subglacial hydrological condition and its influence on the glacier dynamics, we drilled Johnsons Glacier on Livingston Island in the Antarctic Peninsula region. Subglacial water pressure was recorded in boreholes at two locations over 2 years, accompanied by high-frequency ice-speed measurements during two summer melt seasons. Water pressure showed two different regimes, namely high frequency and large amplitude variations during the melt season (January–April) and small fluctuations near the overburden pressure the rest of the year. Speed-up events were observed several times in each summer measurement period. Ice motion during these events substantially contributed to total glacier motion, for example, fast ice flow over 1 week accounted for ~70% of the total displacement over a 25-day long measurement period. We did not find a clear relationship between subglacial water pressure and ice speed. This was probably because subglacial hydraulic conditions were spatially inhomogeneous and thus our borehole data did not always represent a large-scale subglacial condition. Ice temperature measurements in the boreholes confirmed the existence of a cold ice layer near the glacier surface. Our data provide a basis to better understand the dynamic and hydrological conditions of relatively unstudied glaciers in the Antarctic Peninsula region.
Highlights
Glaciers and ice caps on the Antarctic Peninsula and its peripheral islands are affected by rapidly changing climate in the region
Variations observed in the subglacial water pressure confirmed that surface meltwater reaches the bed during the melt season and activates a basal drainage system
High-frequency variations with large amplitudes were observed during the summer melt period, whereas pressure was relatively uniform at a high level during the rest of the year
Summary
Glaciers and ice caps on the Antarctic Peninsula and its peripheral islands are affected by rapidly changing climate in the region. The Antarctic Peninsula experienced rapid atmospheric warming during the second half of the 20th century at a rate of ∼0.5 °C per decade – one of the strongest trends on Earth (e.g. Turner and others, 2009). The spatial pattern of regional glacier changes corresponded with rising ocean temperatures, indicating that ocean forcing acted as a key driver of the glacier retreat, in addition to the atmospheric warming (Cook and others, 2016). Another important process affecting the glaciers is the acceleration of inland ice after the disintegration of ice shelves. Recent studies indicate that the warming trend in the Antarctic Peninsula switched to cooling since the beginning of the 21st century (Turner and others, 2016; Oliva and others, 2017)
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