The impact of Föhn conditions across the Antarctic Peninsula on local meteorology based on AWS measurements

Föhn winds are warm, strong, downslope winds on the lee side of mountains, which can last from several hours to a few days. Recently Föhn conditions over the ice shelves on the eastern side of the Antarctic Peninsula (AP) mountains have attracted particular interest in the polar science community. Here, on the Larsen Ice Shelves (LIS) they provide atmospheric conditions for significant warming over the ice shelf which are thought to have clearly contributed to the collapse of Larsen A and B ice shelves in 1995 and 2002 respectively. We examine the representation of Föhn conditions as observed by measurements at an Automatic Weather station (AWS) located on Cole Peninsula (CP) on the east of the AP mountain range in 2011. We introduce criteria to identify Föhn conditions and analyse the meteorological conditions at the AWS location with regard to the influence of Föhn overall, and on a seasonal and monthly basis. We consult two cases to highlight the seasonally different effects Föhn can have. We also compare our findings with data obtained in other studies, for example an AWS in a comparable location at Flask Glacier (FG). Measurements obtained at a crest AWS on the Avery Plateau (AV), and the analysis of conditions upstream using the Froude number help to put observations at CP into a wider context. Most importantly our data show that Föhn conditions can raise the air temperature to above freezing, and thus trigger melt/sublimation even in winter.

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