March 7, 2016
Lewis Glacier (S) and Sunshine Glacier (S) on Coronation Island in 1990 and 2015. Red arrow is 1990 terminus location and yellow arrow the 2015 terminus location.
Sunshine and Lewis Glacier are tidewater glaciers on the south side of Coronation Island in the South Orkney Islands. This is an area of excessive cloud cover leading to few available satellite images illustrating glacier change. A map of the glaciers from the British Antarctic Survey indicates they had nearly filled the embayments. The BAS maintains a research base on Signy Island (SG) that faces directly across the Orwell Bight to Sunshine Glacier. Coronation Island is extremely windy with the prevailing westerly wind averaging about 14 knots, at Signy Station with gales recorded on about 60 days each year. The Signy Station research focuses mainly on marine mammals and birds, with elephant seals, chinstrap, Adelie and gentoo penguins being most common.
Map of Coronation Island indicating Lewis Glacier (L), Sunshine Glacier (S) and the BAS Signy research station (SG)
View across Orwell Bight from Signy Island to Sunshine Glacier with the BAS Research vessel James Clark Ross in view during November 2015. (From BAS)
In 1990 Lewis Glacier had an east-west calving front extending from the last prominent east-west oriented ridge on the west side of the glacier. Sunshine Glacier extended well beyond the end of prominent ridge on the west edge of the glacier. By 2005 in the Google Earth image below Lewis Glacier had retreated in the center of the glacier more than on the west end. By 2013 Lewis Glacier had retreated to a second prominent east west trending ridge. Sunshine Glacier had retreated beyond the prominent ridge on the west by 2005. From 2005 to 2013 additional retreat occurred along the east side of Sunshine Glacier. The terminus on the east side of Sunshine Glacier is now adjacent to a series of nunataks comprising a ridge extending east from the glacier. Retreat of Lewis Glacier from 1980 to 2015 averaged 900 m across the 3 km wide calving front. Sunshine Glacier retreated 1100 m from 1990 to 2015 across the 3.5 km wide calving front. Both glaciers have relatively flat regions within one kilometer of the calving front which are prone to continued calving retreat. The glaciers are encased in sea ice much of the year protecting the calving front, but the summer climate is maritime with temperatures typically above freezing and the area relatively ice free. Today the region is also accessed by Oceanwide Expeditions. The retreat is similar to that of nearby on Endurance Glacier on Elephant Island and many retreating glaciers on South Georgia Island. .
Google Earth images from 2005 and 2013 indicating the 1990 (red arrows) and 2015 terminus locations (yellow arrows).