A Multidecadal Analysis of Föhn Winds over Larsen C Ice Shelf from a Combination of Observations and Modeling

Jasper Wiesenekker,Michiel Van Den Broeke,C Smeets,Peter Kuipers Munneke

doi:10.3390/atmos9050172

Abstract

The southward progression of ice shelf collapse in the Antarctic Peninsula is partially attributed to a strengthening of the circumpolar westerlies and the associated increase in föhn conditions over its eastern ice shelves. We used observations from an automatic weather station at Cabinet Inlet on the northern Larsen C ice shelf between 25 November 2014 and 31 December 2016 to describe föhn dynamics. Observed föhn frequency was compared to the latest version of the regional climate model RACMO2.3p2, run over the Antarctic Peninsula at 5.5-km horizontal resolution. A föhn identification scheme based on observed wind conditions was employed to check for model biases in föhn representation. Seasonal variation in total föhn event duration was resolved with sufficient skill. The analysis was extended to the model period (1979–2016) to obtain a multidecadal perspective of föhn occurrence over Larsen C ice shelf. Föhn occurrence at Cabinet Inlet strongly correlates with near-surface air temperature, and both are found to relate strongly to the location and strength of the Amundsen Sea Low. Furthermore, we demonstrated that föhn occurrence over Larsen C ice shelf shows high variability in space and time.

Highlights

Multiple ice shelves fringing the Antarctic Peninsula (AP) east coast have recently collapsed in quick succession, namely Prince Gustav (January 1995), Larsen A (January 1995) and Larsen B (February 2002) [1,2,3]
We have assessed föhncharacteristics characteristics asas recorded by AWS18, located in Cabinet Inlet (CI) on ice shelfC ice föhn recorded by AWS18, located inLarsen
Local föhn events were identified based on three criteria, namely wind shelf in the Antarctic Peninsula

Summary

Introduction

Multiple ice shelves fringing the Antarctic Peninsula (AP) east coast have recently collapsed in quick succession, namely Prince Gustav (January 1995), Larsen A (January 1995) and Larsen B (February 2002) [1,2,3]. Since ice shelves buttress grounded glaciers upstream [4], their disintegration has led to acceleration of tributary glaciers and subsequent sea-level rise [1,5,6,7]. The collapse of these ice shelves was preceded by the formation of meltwater ponds [2,8]. The warming trend is partially explained by changes in the atmospheric circulation around the AP [12]. The dominant mode of circulation in the Southern Hemisphere (SH), the SH Annular

Methods

Results

Conclusion