Jones Ice Shelf Loss, Antarctica

The Jones Ice Shelf was midway up the west coast of the Antarctic Peninsula. The ice shelf (red arrow) was smaller than other ice shelves that have mostly or substantially disintegrated Wordie Ice Shelf (orange arrow), Larsen B Ice Shelf (pink arrow) or Wilkins Ice Shelf (green arrow). Ant-pen_mapThe British Antarctic Survey (BAS), has been observing the changes in ice shelves around the Peninsula Cook and Vaughan, (2010) and Fox and Vaughan (2005). The BAS noted that the ice shelf had an area of 29 square kilometers in 1980, by 1990 21 square kilometers and 10 square kilometers in 2000 and 2003, gone. Blaicklock Island (C and D) and the Arrowsmith Peninsula (A and B) are now separated by open water in Jones Channel. Cook and Vaughan (2010) also note that this was not the result of a long ongoing retreat, the Jones Ice Shelf expanded 20 % between 1947 and 1978. In the post below there is a sequence of images from Landsat and Google Earth imagery in a sequence as follows, 1989, 1991, 1999, 2009 and 2011. The Ice shelf exists in 1989 and 1991, ending at the orange arrows, which are included in the 2009 and 2011 images as well for comparison. Points A-D are in the same location in each image. The 1999 image indicates a disintegrating Jones Ice Shelf (JIS), with a small ice tongue protruding part way across Jones Sound, the new waterway that has opened. By 2009 the glacier has retreated out of the Jones Channel to the pink arrow and red line in 2011. The eastern terminus retreated 4 km and the western terminus 7 km. The ice shelf loss here is similar in magnitude to Rohss Bay on James Ross Island. jones 1989jones 1991jones tongue gejones 2009jones 2011

Fleming Glacier Acceleration and Retreat, Antarctica

Recent observations indicate that the Fleming Glacier on the Antarctic Peninsula which used to feed the Wordie Ice Shelf is accelerating and thinning even faster(Wendt et al, 2010) This is leading to the production of numerous tabular icebergs from the glacier front as seen below from a 2009 Google Earth image. . A is a rift that is also the ice front toward the upper right. B and C are rifts that will produce future tabular ice bergs. D is an iceberg with an area of just under 1 square kilometer. Wordie Ice Shelf was the northernmost large Ice shelf on the western AP. The ice shelf disintegrated between 1970 and 2000. From an area of 1900 km2 in 1970 to 100 km2 in 2009 as mapped by the British Antarctic Survey. The first image is from the BAS in 1989. Followed by a series of maps illustrating its demise put together by the BAS and USGS The breakup was suggested to have occurred due to a warming trend in the region that began in the 1970’s generating meltwater . There is also thinning and weakening around some of the pinning points where the ice shelf was grounded. This is similar to observations from Wilkins Ice Shelf.
The Wordie Ice Shelf was fed by several major tributary glaciers including the Fleming Glacier.
(Rignot and others (2005) used satellite radar interferometry to observe changes in behavior of Fleming Glacier from 1995 to 2004 identifying a 40-50% increase in glacier velocity from the terminus to 50 km above the terminus and a two meter per year thinning. More recent Airborne thickness data indicate thinning has increased to 3 or 4 m per year in the lower reach of the glacier during the 2004-2008 period (Wendt et al, 2010). Rignot and other (2005) further observed that 6.8 ± 0.3 km3/yr of ice, which is much larger than snow accumulation of 3.7 ± 0.8 km3/yr. This imbalance has certainly increased with acceleration.
Without the presence of a thick, slow moving ice shelf buttressing the Fleming Glacier it has accelerated. Below is a map from Wendt et al (2010) showing the Fleming Glacier former margins. Below that is Google Earth Image showing the nature of the calving front. Notice the tabular ice bergs that have and are about to break off. Below that is an image further up glacier, a nunatak has appeared in mid glacier that is not evident in the 1989 image. As observed for the Jakobshavn and Pine Island Glacier thinning leads to reduced buttressing and increased glacier flow.