royal bay glacier retreat – From a Glaciers Perspective

Hindle Glacier comparison in 1989, 2015 and 2017 Landsat images. Red arrow is 1989 terminus, pink arrow the 2015 terminus and red arrow the 2017 terminus location.

South Georgia is south of the Polar Front 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. Hindle Glacier enters Royal Bay on the east coast of South Georgia Island. The British Antarctic Survey (BAS) has been the principal research group examining glacier change on South Georgia Island. Cook et al (2010) and Gordon et al (2008) have emphasized that there is a pattern island wide with many calving glaciers having faster retreat. Gordon et al., (2008) observed that larger tidewater and calving outlet glaciers generally remained in relatively advanced positions from the 1950’s 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. The change in glacier termini position have been documented by Alison Cook at British Antarctic Survey in a BAS retreat map, she identified that 212 of the Peninsula’s 244 marine glaciers have retreated over the past 50 years and rates of retreat are increasing. Here we examine Landsat imagery from 1989 to 2017 to identify the rapid retreat rate. NASA Earth has piggy backed on this assessment, with excellent imagery.

For Ross-Hindle the retreat was minimal from 1960 to 1989 with the glaciers joined In 1989 the glaciers joined 2.5 km from the terminus. The glacier spanned Royal Bay with a 3.2 km wide calving front. By 2002 the glacier front had retreated 800 m, but they were still joined. By 2008 the glaciers had separated due to an additional retreat of 1.4 km. The front was now retreating south up a separate embayment from Ross Glacier. The calving front in 2008 was 1.6 km wide. By 2015 further retreat led to the separation of Hindle from an eastern Tributary at the first prominent headland in the fjord, a 1.6 km retreat in seven years. By 2017 an additional 600 m of retreat had occurred with total retreat of 4.4 km in 28 years. This is a rate of over 150 m/year, which is an exceptional rate. The exceptional retreat rate of Hindle Glacier suggests that Ross Glacier acted as a pinning point stabilizing the terminus reach of the glacier. The low surface slopes in 2017 for the lowest 3 km of the glacier suggest the fjord head is at least 3 km south of the present terminus and the calving retreat will continue until the head of the fjord is reached. This location is close to the origin of the medial moraine that runs right to the glacier front currently. This embayment will open up new areas for Gentoo Penguins and elephant seals to immigrate into. Levy et al (2016) discuss the shift and dispersal of colonies in the region, that climate change is an important driver of.

Map of terminus retreat of Ross and Hindle Glacier from the BAS. Green Pin Locations are Gentoo Penguin colonies.

2002 Landsat image of Hindle Glacier. Red arrow is 1989 terminus and yellow arrow the 2017 terminus location.

Hindle Glacier 2016 Landsat image. Red arrow is 1989 terminus and red arrow the 2017 terminus location.

Location of South Georgia versus atmospheric and ocean circulation features (From South Georgia Future Science).

Landsat Image of Ross Hindle Glacier 1989 left and 2015 right. Something changed.

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. Ross-Hindle Glacier enters Royal Bay on the east coast of South Georgia Island has now separated into the Ross and Hindle Glaciers. Hindle Glacier could do well in a new international Olympic event, “Fastest Retreating Glacier” 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. For Ross-Hindle the retreat was minimal from 1960 to 1989. The change in glacier termini position have been documented by Alison Cook at British Antarctic Survey in a BAS retreat map. By 2008 the glaciers had separated. Here we examine Landsat imagery from 1989 to 2015 to identify recent change.

Region of Hindle Glacier on South Georgia.

BAS map of glacier front change.

In 1989 the glacier extends to the green arrows with a joint terminus that is three kilometers long. This is quite close to the 1960 terminus location. By 2003 the glacier has retreated 800 m with the south side nearly reaching a Point where the Hindle Glacier turns south By 2008 the glaciers have separated, with a further retreat of 1.5 km along the southern margin of Ross Glacier and western margin of Hindle Glacier. Retreat is much less on the northern side of Ross Glacier and the eastern side of Hindle Glacier. By 2015 a new fjord has opened, as Hindle Glacier retreats south 1.7 km on the east margin and 2.1 km on the west side in just seven years.Ross Glacier continues to retreat west with a retreat of 600-700 m since 2008.

In Google Earth by 2010 there is added crevassing near the ice front of Hindle Glacier that indicates an acceleration of the glacier. This suggests the Ross Glacier was impeding its flow previously and that Hindle is in a rapid retreat mode.The rapid recent retreat parallels that of Neumayer Glacier and Twitcher Glacier during the 1989-2014 period. The BAS research effort on glacier front retreat has been documented by Alison Cook . Her comparison of glacier fronts from old aerial photographs and comparing them with satellite images — she identified that 212 of the Peninsula’s 244 marine glaciers have retreated over the past 50 years and that rates of retreat are increasing.