Abstract
Abstract. Warm, dry föhn winds are observed over the Larsen C Ice Shelf year-round and are thought to contribute to the continuing weakening and collapse of ice shelves on the eastern Antarctic Peninsula (AP). We use a surface energy balance (SEB) model, driven by observations from two locations on the Larsen C Ice Shelf and one on the remnants of Larsen B, in combination with output from the Antarctic Mesoscale Prediction System (AMPS), to investigate the year-round impact of föhn winds on the SEB and melt from 2009 to 2012. Föhn winds have an impact on the individual components of the surface energy balance in all seasons and lead to an increase in surface melt in spring, summer and autumn up to 100 km away from the foot of the AP. When föhn winds occur in spring they increase surface melt, extend the melt season and increase the number of melt days within a year. Whilst AMPS is able to simulate the percentage of melt days associated with föhn with high skill, it overestimates the total amount of melting during föhn events and non-föhn events. This study extends previous attempts to quantify the impact of föhn on the Larsen C Ice Shelf by including a 4-year study period and a wider area of interest and provides evidence for föhn-related melting on both the Larsen C and Larsen B ice shelves.
Highlights
In July 2017, an iceberg of approximately 6000 km2 calved off the Larsen C Ice Shelf (Hogg and Gudmundsson, 2017), located on the eastern side of the Antarctic Peninsula (AP).Some decades earlier, in 1997 and 2002, the more northerly Larsen A and B ice shelves collapsed almost entirely
The collapse of Larsen A and B was facilitated by a process known as hydrofracture, whereby ice is weakened due to drainage of surface meltwater into crevasses and increased pressure from ponds of standing meltwater forming on the ice shelf surface (Scambos, 2004; Robel and Banwell, 2019)
Föhn winds have been observed over the whole Larsen C Ice Shelf and are most frequent at the foot of the AP mountains (Elvidge et al, 2015; Turton et al, 2018; Wiesenekker et al, 2018)
Summary
In 1997 and 2002, the more northerly Larsen A and B ice shelves collapsed almost entirely This rapid disintegration had been preceded by a series of iceberg calving events in previous years, which caused the calving front to recede beyond a compressive arch that provided stability to the ice shelves (Doake et al, 1998). Surface melt is projected to increase strongly on Larsen C in the coming century (Trusel et al, 2015; Bell et al, 2018).
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