02 Aug 2022
02 Aug 2022
Status: this preprint is currently under review for the journal TC.

The surface energy balance during foehn events at Joyce Glacier, McMurdo Dry Valleys, Antarctica

Marte G. Hofsteenge1,2, Nicolas J. Cullen1, Carleen H. Reijmer2, Michiel van den Broeke2, Marwan Katurji3, and John F. Orwin4,5 Marte G. Hofsteenge et al.
  • 1School of Geography, University of Otago, Dunedin, New Zealand
  • 2Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, The Netherlands
  • 3School of Earth and Environment, University of Canterbury, Christchurch, New Zealand
  • 4Resource Stewardship Division, Alberta Environment and Parks, Canada
  • 5Department of Geography and Planning, Queen’s University, Canada

Abstract. The McMurdo Dry Valleys (MDV) are a polar desert, where glacial melt is the main source of water to streams and the ecosystem. Summer air temperatures are typically close to zero and therefore foehn events can have a large impact on the meltwater production. A 14-month record of automatic weather station (AWS) data on the Joyce Glacier is used to force a 1D surface energy balance model to study the impact of foehn events on the energy balance. AWS data and 1.7 km resolution output of the Antarctic Mesoscale Prediction System (AMPS) are used to detect foehn events at the AWS site. Foehn events at Joyce Glacier occur under the presence of cyclones over the Ross Sea. The location of Joyce Glacier on the leeward side of the Royal Society Range during these synoptic events cause foehn warming through isentropic drawdown. This mechanism differs from the foehn warming through gap-flow that was earlier found for other regions in the MDV and highlights the complex interaction of synoptic flow with local topography of the MDV. Shortwave radiation is the primary control on melt at Joyce Glacier and melt often occurs with subzero air temperatures. During foehn events, melt occurs more frequently and melt rates are enhanced, contributing to 19 % of the total annual melt. Foehn winds cause a switch from a diurnal stability regime in the atmospheric surface layer to a continuous energy input from sensible heat flux throughout the day. The sensible heating during foehn is largely compensated for by extra heat losses through sublimation, and melt rates are enhanced through an additional energy surplus from a reduced albedo.

Marte G. Hofsteenge et al.

Status: open (until 27 Sep 2022)

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Marte G. Hofsteenge et al.

Marte G. Hofsteenge et al.


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Short summary
Foehn winds are warm and dry downslope winds that occur in mountainous areas. In the McMurdo Dry Valleys, foehn winds impact meltwater production of the glaciers, which in turn can have big implications for the fragile ecosystem that is hosted here. With observations and model output we show that foehn winds increase the air and glacier surface temperatures, thereby increasing the occurrence and rates of melt. Foehn winds also impact the atmospheric stability and wind regime of the glaciers.