A new rift has been forming on Petermann Glacier, Greenland, throughout 2017. An older crack to the right of the new rift also seems to be extending toward the glacier’s center. If this new rift meets up with the older crack, and an iceberg breaks off, it would be Petermann’s third massive iceberg calving since 2010. It also would place the new calving face much farther upstream than the 2010 break.

A close-up image from Sentinel-2A takes advantage of its 10-meter spatial resolution to show the new rift in greater detail. Landsat 8 and Sentinel-2A complement each other by imaging glacial movement and possible calving events.

The prominent vertical line could be from deformation of the ice as it flows over the bedrock farther upstream. The irregular topographic surface of the underlying bedrock could have caused the ice to develop this longitudinal crevasse as it moved over bedrock, resulting in a line being drawn the length of the glacier as it flows. Besides the new rift, other bumps and lines extend from this longitudinal line, which are stress fractures from the glacial movement.

Landsat 8 normally images all Earth landmasses every 16 days. However, at high latitudes, there is considerable overlap because Landsat 8’s orbital tracks converge at the Poles. As a result, this increases the temporal frequency of Landsat 8 coverage over northern Greenland.

Building on this imaging overlap, Landsat 8 takes advantage of long hours of daylight in the Arctic to acquire “nighttime” sunlit images, increasing temporal coverage even more. The two Landsat 8 images were acquired a little over 3 hours apart, one on its descending orbit and one ascending. Having multiple images increases the chances of acquiring more cloud-free images and helps scientists monitor iceberg calving events.