Something caught the eye of Stef Lhermitte last week, while he was looking through satellite images of the Greenland’s Petermann Glacier. Almost by coincidence he saw a new thin line, as he was going through ESA Sentinel-1 images for research on melt. He checked other satellite images, and saw the line first appear on July 2016, apparently unnoticed until then. In a series of five tweets, Lhermitte shared his discovery, hoping someone might be able to shed some light.
.@Petermann_Ice @AndreasMuenchow @glacier_doc @CopernicusEU @ESA_EO Sentinel-2 satellite time series show this new crack for the first time in July 2016. It has been growing since then. 2/5 pic.twitter.com/5dIiLs8kX9— Stef Lhermitte (@StefLhermitte) April 12, 2017
.@Petermann_Ice @AndreasMuenchow @glacier_doc @CopernicusEU @ESA_EO The internal crack growth is clearly visible in this Sentinel-1 time series, also during polar night. 3/5 pic.twitter.com/AKY2czWFtR— Stef Lhermitte (@StefLhermitte) April 12, 2017
.@Petermann_Ice @AndreasMuenchow @glacier_doc @CopernicusEU @ESA_EO So is ocean forcing playing its role here, similar to the basal crevasses in the center of @AntarcticPIG ? https://t.co/8IDw96BLco 4/5— Stef Lhermitte (@StefLhermitte) April 12, 2017
The final flight
The tweets were noticed by Tom Wagner, head of polar research at NASA, who contacted his colleague Joe MacGregor in Greenland. MacGregor was in Greenland leading a research campaign called Operation IceBridge, which makes low-level flights over Greenland and Antarctica's ice sheets to create 3-D views of the ice.
No images had been made of the area indicated by Lhermitte, but as luck would have it, one final flight was planned over the glacier the next day. As the crack was only a short distance away from the planned trajectory, they flew over that area, confirming the existence of the crack, and at the same time mapping it in greater detail.
A new crack in one of Greenland’s largest glaciers is worrying, especially this newly discovered one, as it lies a great deal further ‘upstream’ in the glacier than other cracks. The further away, the more unstable the underlying layer of ice, should pieces break off.
The glacier acts like a barrier between the ice sheet and the ocean. Retreat of the glacier could lead to more large chunks of ice breaking off into the ocean, causing less ‘resistance’ by the glacier and more melt of land ice, contributing to sea level rise.
The tweets of Lhermitte also drew attention from Washington Post journalist Chris Mooney, who wrote two articles on the topic:
- Scientists just found a strange and worrying crack in one of Greenland’s biggest glaciers (14 April)
- NASA just snapped the first photos of a mysterious crack in one of Greenland’s largest glaciers (15 April)
After that, several other international media outlets picked up on the news, among which the Daily Mail:
- Nasa captures first images of a 'worrying' new crack that has appeared on one of Greenland's largest glaciers (17 April)