james ross island glacier retreat – From a Glaciers Perspective

Coley Glacier terminus comparsion in Landsat images from 2000 (red arrows) and 2016 (yellow arrow) indicating a retreat of 2 km along the western side and 1 km along the eastern side. Purple dots indicate the transient snowline and the purple arrow an area of debris exposed with glacier thinning.

Coley Glacier is a tidewater glacier on the northeast side of James Ross Island near the tip of the Antarctic Peninsula. Davies et al (2012) observed that 90% of the glaciers of the Northern Antarctic Peninsula including James Ross Island retreated from 1988-2001 and 79% from 2001-2009. They further observed that the rapid shrinkage of tidewater glaciers on James Ross Island would continue due to their low elevation and relatively flat profiles. Rohss Bay Glacier is one example of this having retreated 15 km from 1999-2009 (Glasser et al, 2011). Barrand et al (2013) note a strong positive and significant trend in melt conditions in the region, driving the retreat.

Coley Glacier in 2000 had a relatively straight calving front running across the embayment. The front represents the joining of four tributary glaciers. The snowline was generally below the top of the escarpment just west of Point C, the elevation of this lower glacier reach is below 200 m. This fits the low elevation low slope criteria noted by Davies et al (2012). By 2016 the glacier has developed a concave glacier front with the northern tributary almost separating the retreat ranges from 2 km on the west side to 1 km on the east side. The snowline is above the escarpment at 400 m. A comparison below of 2001 and 2015 indicates that the snowline in 2015 was also near 400 m and above the escarpment. A map of the region from the USGS (Ferigno et al.,2006) illustrates the retreat from the 1960’s to 2000. Nývlt et al (2010) reported on the retreat and changes on two glaciers on the north side of James Ross Island.

Coley Glacier terminus comparison in Landsat images from 2001 and 2015. Red arrows is the 2000 terminus and yellow arrows the 2016 terminus. Purple dots indicate the transient snowline and the purple arrow an area of debris exposed with glacier thinning.

COASTAL-CHANGE AND GLACIOLOGICAL MAP OF THE TRINITY PENINSULA AREA AND SOUTH SHETLAND ISLANDS, ANTARCTICA: 1843–2001

USGS (Ferigno et al.,2006)

In January 1995 the Prince Gustav Ice Shelf connecting James Ross Island to the Antarctic Peninsula collapsed (Glasser et al 2011). One of the principal glaciers feeding the iceshelf was the outlet glacier from Rohss Bay on James Ross Island. By 1999 this outlet glacier terminus was at the outlet of Rohss Bay. From 1999 to 2009 Rohss Bay opened up as the Rohss Bay glacier retreated 15 km. This retreat represents part of the extensive ice loss, 490 square kilometers for the island from 1988-2009 Davies et al (2011). From 1988-2001, 91 of 100 glaciers on the island examined by Davies et al (2011) retreated. Imagery from the field work by the LARISSA project in the region provides excellent context for the region. A combination of Landsat and Google Earth Imagery from 1999, 2000, 2008 and 2010 illustrates this change in a sequence below. The margin is indicated in each case as is an unnamed island by an arrow at the southwest end of Rohss Bay. Most of the ice loss was the breakup of a floating ice shelf in the bay. Glasser et al (2011) provide a sequence from 2002-2006 that illustrates most of the retreat occurring in this five year period. Currently most of the floating ice of the bay has been lost and retreat should slow down considerably. The ice was lost not through surface melting, but via calving. The typical sequence for ice shelf collapse is thinning from basal and surface melt increases, that leads to weakening and destabilization of the iceshelf, expansion of rifting and then breakup. The retreat on James Ross Island is also observed on the island to the north Vega Island.