A giant iceberg, of approximately 100 sq miles in area and with a thickness up to half the height of the Empire State Building, has calved from the Petermann glacier in Greenland, observed by both NASA and ESA satellites. ESA prepared a time-series animation based on Envisat Advanced Synthetic Aperture Radar (ASAR) data from 31 July, 4 August, and 7 August 2010 showing the breaking of the Petermann glacier and the movement of the new iceberg towards Nares Strait.
|The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this natural-color images of Petermann Glacier on 5 August. Click to enlarge.|
The last time such a massive ice island formed was in 1962 when Ward Hunt Ice Shelf calved a 230 square-mile island, smaller pieces of which became lodged between real islands inside Nares Strait. Petermann Glacier spawned smaller ice islands in 2001 (34 square miles) and 2008 (10 square miles). In 2005, the Ayles Ice Shelf disintegrated and became an ice island (34 square miles) about 60 miles to the west of Petermann Fjord.
The Petermann glacier is one of the largest glaciers connecting the Greenland inland ice sheet with the Arctic Ocean. Upon reaching the sea, a number of these large outlet glaciers extend into the water with a floating ice tongue.
The ice tongue of the Petermann glacier was the largest in Greenland, with an extension of about 70 km until early August. This tide-water glacier regularly advances towards the ocean at about 1 km per year. During the previous months, satellite images revealed that several cracks had appeared on the glacier surface, suggesting to scientists that a break-up event was imminent.
In the Envisat radar image taken on 3 August, the ice tongue was still intact but, on 4 August, a large part of the floating ice tongue was separated from the glacier, giving birth to what is currently the largest iceberg in the northern hemisphere. Such a process of detachment, called calving, occurs regularly on the Petermann glacier, with smaller calving events in summer 2008 and 2009. However large calving events are rare, with the last such significant event being documented in 1991 by ESA’s ERS-1 satellite.
The detached iceberg is now floating away from Petermann glacier and will enter into the Nares Strait, which separates Greenland from the Ellesmere Island in Canada.
The Nares Strait connects the Lincoln Sea and Arctic Ocean with the Baffin Bay. The strait is usually navigable by icebreakers during August/September, when sea ice extent is at its minimum after the summer melt period. Envisat ASAR images will be used in the coming days to monitor the movement of the giant iceberg in support of icebreaker navigation.