Weddel Glacier is on the southeast coast of South Georgia Island. It terminates in Beaufoy Cove just north of Gold Harbor.The change in glacier terminus position has been documented by Alison Cook at British Antarctic Survey in a BAS retreat map. In 1958 it reached within 400 m of the coast at the outlet of Beaufoy Cove. Gordon et al., (2008) observed that larger tidewater and sea-calving valley and outlet glaciers generally remained in relatively advanced positions until the 1980s. For Weddel Glacier the retreat was rapid from 1960 to 1974 and was slow from 1992-2003. Here we examine Landsat imagery from 1989 to 2015 to visualize and update this change.
Google Earth Image
BAS map of glacier terminus position
In 1989 the glacier terminates near the tip of a peninsula, red arrow in each image. The calving front extends southeast, orange dots. At the yellow arrow the glacier fills a small side valley adjacent to the main glacier. At the purple arrow is a small extension of the main icefall flowing down the bedrock step.
In 2002 there is only minor retreat at the red and yellow arrow, but thinning has led to the small extension of the main icefall being almost cutoff by bedrock. By 2015 the glacier has retreated 200-300 meters from the 1989 position and the main terminus is narrower. At the yellow arrow the side valley no longer has ice. At the purple arrow this is just bedrock now, there is no glacier extension flowing down the bedrock step. A close up the icefall in a 2009 Google Earth image indicates both the extensive crevassing but also the lack of glacier ice at the purple arrow, where an extension of the icefall formerly flowed. A Google Earth closeup of the terminus indicates that only a small section is still in contact with Beaufoy Cove in 2009, with land exposed at the orange arrows. This glacier is almost not tidewater and has terminated in shallow water since 1989, which helps explain a slower rate of retreat. The glacier has thinned more rapidly than it has retreated in the last 25 years. The retreat rate is less than nearby Bertrab Glacier, Konig Glacier and Neumayer Glacier on the same coast of South Georgia.
Landsat Image 1989
Landsat image 2002
Landsat image 2015
Google Earth icefall image
Google Earth 2009 image
Bertrab Glacier is on the east coast of South Georgia Island. The change in glacier terminus position has been documented by Alison Cook at British Antarctic Survey in a BAS retreat map. In 1958 it reached the coast in Gold Harbor. Gordon et al., (2008) observed that larger tidewater and sea-calving valley and outlet glaciers generally remained in relatively advanced positions until the 1980s. For Bertrab Glacier the retreat was minimal from 1958 to 1989. Since 1989 a whole new embayment has opened. Here we examine Landsat imagery from 1989 to 2015 to visualize and update this change.
BAS Glacier Front map 1958-2007.
Google Earth image
In 1989 the southern arm of the glacier extends to the shoreline of the barrier beach system in Gold harbor, Red arrow. The northern arm extends around to the edge of a very green region, suggesting well developed vegetation, hence no real retreat for sometime. By 2002 a lake has formed at the northern arm terminus and it has retreated 400 m. The southern arm has retreated across a new embayment ending near the yellow arrow, though the exact position is obscured by cloud. In 2011 the southern terminus has retreated up a slope from the edge of the embayment, yellow arrow. In 2015 there are no longer two arms to the glacier. The glacier terminates near the edge of the new embayment. The retreat is 700 m on the northern arm and 1000 m for the southern end since 1989. The glacier no longer reaches the water limiting calving. The glacier also ends on moderate slope. This should lead to a reduced retreat in the near future. The 2015 picture is from Jan.15, so there is still two months left in the melt season. The retreat is similar to that of Ross Hindle Glacier , Konig Glacier and Neumayer Glacier on the same coast of South Georgia, and faster than for neighboring Weddel Glacier. Like on Stephenson Glacier, Heard Island the new embayment does offer new potential habitat for penguins and seals.
1989 Landsat image
2002 Landsat image
2011 Landsat image
2015 landsat image
Purvis Glacier is on the norteastern coast of the island, terminating on land near Possession Bay. The British Antarctic Survey (BAS) has mapped many aspects of the island including glacier front changes. Their mapping indicated below shows that the Purvis Glacier terminus was on the coastline in 1974. Here we examine Landsat imagery from 1999 to 2014 to identify more recent changes. Cook et al (2010) quantified the change in these maps noting that 97% of the 102 coastal glacier retreated between the 1950’s and today.
BAS map of Glacier change.
Google Earth image
In 1999 the proglacial lake, red arrow, that the glacier terminated in was 300 m wide, indicating a retreat of 300-400 m since 1974. By 2002 the proglacial lake had expanded to a width of 600 m, exposing a peninsula at Point A. By 2013 the proglacial lake had expanded to 1050 m, further exposing the peninsula at Point A. By March 1, 2014 Landsat imagery indicates a retreat of 1100 m since 1974, with most of that retreat occurring since 1979. A closer look at the glacier from Google Earth highlights the issue. The glacier is fed by relatively low lying snowfields with quite limited areas above 500 m. Sugden, Clapperton and I in a 1989 paper identified the snowline a short distance from here at 400 to 450 m. As the 2011 Google Earth image indicates the remaining snowcover at the end of the melt season is minimal, too little to sustain this glacier (Pelto, 2010). Further a look at the terminus indicates the stagnant nature of the terminus region that will lead to continued retreat, blue arrows note ablation holes in the glacier that do not develop when a glacier is actively moving. The low slope and stagnant nature should preserve an excellent glacial geologic landscape.
The glacier is behaving in the same fashion as other land terminating glaciers Heaney Glacier and Konig Glacier. The retreat is less than that of calving glaciers on the island Neumayer Glacier and Ross-Hindle Glacier.
1999 Landsat image
2002 Landsat image
2013 Landsat image
2014 Landsat image
Google Earth image
Herz Glacier is on the southeast coast of South Georgia Island. The terminus change of this tidewater glacier ending in Iris Bay was completed by the British Antarctic Survey for the 1960-2007 period (Gordon et al, 2008). The map below indicates the slow retreat from 1960-1988 and a more rapid retreat since. Here we examine imagery from Google Earth and Landsat to examine terminus change from 1989-2010. In each image the red arrow indicates the location of the terminus in 2009-2010 the yellow arrow the 1989 terminus position. The first image is the Google Earth image from 2010, followed by the 1989, 2000 and 2009 Landsat images. The terminus on the north side of the fjord has retreated 1.8 km in the 20 year period and the terminus on the south side has retreat 2.2 km. The overall 2 km retreat is a rate of 100 meters/year and is 20 % of the total glacier length. This is an exceedingly cloudy region and imagery from 2011 and 2012 does not provide a clear observation of the terminus. The retreat of this glacier is less dramatic than that of Neumayer Glacier or Ross Hindle Glacier further north on the coast.
South Georgia sits amidst the furious if not screaming fifties latitude belt, the circum Antarctic westerlies. This region is famous for the endless march of storms parading around Antarctica. The island is south of the Antarctic Convergence, preventing any truly warm season from persisting. The cool maritime climate leads to numerous glaciers covering a majority of the island and quite low equilibrium line altitudes. Sugden, Clapperton and Pelto (1989-sorry no good link to this paper, one of the first I worked on), 1989 noted the ELA of Neumayer Glacier at 550 m. The tidewater glaciers of South Georgia in general maintained fairly advanced positions unitl 1980. Gordon et al., (2008) observed that larger tidewater and sea-calving valley and outlet glaciers generally remained in relatively advanced positions until the 1980s. After 1980 most glaciers receded; some of these retreats have been dramatic and a number of small mountain glaciers will soon disappear. Neumayer Glacier is one of the large tidewater glaciers on South Georgia. Maps from the British Antarctic Survey (BAS) and satellite imagery are used here to assess the changes in this glacier terminus position. A view of the entire glacier in 2006 from Google Earth, from beyond its calving terminus, indicates indicates the glacier remains vigorous with extensive crevassing at the calving front and extensive snowcover above the ELA. The BAS has a mapping function that provides glacier front positions since early in the 20th century. For Neumayer Glacier the 1938 position is 3.5 km down fjord from the 2006 position. There was essentially no retreat up to 1974 and limited retreat up to 1993. . In 2004 and 2009 NASA provided two images of Neumayer Glacier indicating retreat from 2004 when the glacier extended to the down fjord edge of a tributary glacier from the south. By 2009 the glacier has retreated upglacier of this now former tributary, this retreat is 1300 m. Landsat Image from 1999 to 2014 indicates retreat of 4800 m from the red to the green arrow , this is 320 m/year. The glacier appears to have retreated into a deeper section of the fjord then where it ended from 1970-2002. This will enhance calving from the glacier, and promote additional mass loss and retreat. This retreat will impact Konig Glacier which is connected to the Neumayer Glacier. Calving rate increases with water depth and the degree of glacier. Pelto and Warren (1991) provided an expanded version of the relationship first quantified by Brown and others (1982). In the you would have never guessed it category, is the glacier retreat has been an aid to the rat population, as the glacier tongues used to corner populations.