Satellite spots massive Manhattan-sized iceberg as it splits from Greenland glacier

1
474
Jakobshavn glacier calving
This optical image of Jakobshavn glacier in western Greenland, acquired by Sentinel-2A on 16 August 2015, offers a valuable perspective of the scale of the calving event that took place between 14 and 16 August. The contour indicates the area of ice lost between images acquired on 6 and 16 August. All-weather radar images from the Sentinel-1A satellite provide a year-round view of glacier dynamics. Credit: Copernicus Sentinel data (2015)/ESA

The European Space Agency’s Sentinel-1A satellite has captured what is pegged as one of the most significant calving events on record – splitting of Manhattan-sized iceberg from Greenland glacier.

The event, which says says took place between August 14 and 16, the Jakobshavn glacier in western Greenland lose a massive chunk of ice measuring 12.5 sq km. The Sentinel-1A satellite has managed to capture radar images of the glacier before and after this shedding event the new face of the glacier has been pushed inland by several kilometres.

According to ESA estimates, the glacier lost a total area of 12.5 sq km. Assuming the ice is about 1400 m deep, this equates a volume of 17.5 cubic km – which could cover the whole of Manhattan Island by a layer of ice about 300 m thick. The history of this last calving event is also revealed in images taken by Sentinel-2A on 6 and 16 August.

Other similar events have been documented where the glacier parted with 7 sq km of ice, both earlier this year and back in 2010.

Jakobshavn glacier is of particular importance from the scientific context because it drains 6.5 per cent of the Greenland ice sheet, producing around 10 per cent of its icebergs. Putting this in numbers, this drainage and iceberg formation amounts for 35 billion tonnes of ice that calve every year.

Scientists have been studying the Jakobshavn glacier for over 250 years now and the information collected during this period has enabled scientists to develop understanding of the importance of ice streams and glaciers in climate change, icecap glaciology, and how they affect sea level.

ESA chasing glacier retreat
Radar images from Sentinel-1A captured the Jakobshavn glacier in western Greenland before and after a massive calving event, which took place between 14 and 16 August 2015. The image composite includes different Sentinel-1A images from 27 July, and 13 and 19 August. The red, green and blue indicate the position of the calving front and other dynamic features on each respective date. Credit: Copernicus Sentinel data (2015)/ESA

ESA notes that the icebergs that get formed, like the latest one, are often so massive that they are not able to float away. Because of this, they tend to remain stuck on the bottom in shallower areas of the fjord for years at a time until they melt enough to disperse, break into pieces or are pushed out by icebergs coming up from behind.

ESA’s Sentinel-1A, which is an all-weather satellite, day-and-night radar imaging mission and Sentinel-2A, which carries a multispectral imager, are the first two satellites in Europe’s Copernicus programme. Sentinel-3 mission, which is yet to be launched, will add further complementary measurements for operational applications and scientific purposes.