Abstract

The föhn hypothesis describes the link between the Southern Annular Mode (SAM) positive phase, and the increasing frequency of föhn winds on the leeside of the Antarctic Peninsula. It is theorised that the warm and dry wind conditions prompted surface melting of the Larsen Ice Shelf (LIS) and subsequently contributed to the destabilisation of large sections of the ice shelf. This PhD project investigates the spatial distribution of the föhn events and their impacts over the remainder of the LIS - Larsen C, as part of the NERC funded ‘Orographic Flows and Climate of the Antarctic Peninsula’ (OFCAP) project. Methods have been developed to identify the onset of föhn winds from near-surface observational data and archived output from the Antarctic Mesoscale Prediction System (AMPS). The AMPS archive holds outputs from the Weather Research and Forecast (WRF) model run operationally over the Antarctic by the National Centre for Atmospheric Research, USA . The föhn winds have been identified across the whole of the LIS , however localised features and patterns are present. Furthermore, specific föhn case studies have been run using Polar WRF at 1.5km horizontal resolution. Polar WRF is a polar optimised version of WRF . The occurrence and characteristics of föhn conditions over the LIS will be presented here. Furthermore a comparison of observational and model conditions during the identified föhn conditions will be discussed. A number of the specific case studies analysed in greater detail and modelled with higher resolution Polar WRF will also be presented. Finally, the surface impacts of the föhn conditions will be highlighted.