Greenland Refrozen

Greenland Refrozen

It won’t be until summertime that a significant amount of melt shows up across the Greenland Ice Sheet. For now, most indications of meltwater ponds and lakes are leftovers from past seasons that have since refrozen.

These photographs were snapped during research flights for NASA’s Operation IceBridge—now in its final year after a decade of airborne missions to map polar ice. The first photograph, shot by Jeremy Harbeck on April 16, 2019, shows part of a frozen meltwater lake in the Lambert Land region of northeastern Greenland, between the Zachariæ Isstrøm and 79N glaciers.

“It looks like the edge of a deep-blue colored, frozen meltwater lake with stress fractures in it, next to what is very likely permafrost,” said Harbeck, a sea ice scientist at NASA’s Goddard Space Flight Center. “The lake looks to be, at the very least, a semi-permanent feature and very likely is liquid water in the summer.”

The second image was acquired on April 18, 2019, with the Continuous Airborne Mapping by Optical Translator (CAMBOT) system. The system takes downward-looking images throughout a flight, which can later be used by scientists to interpret other data. This image shows part of large, frozen lake on Storstrømmen Glacier, about 200 kilometers (120 miles) south of the first image. This lake also thaws in summertime, which is why it shows up as blue ice.

Lakes atop a glacier, or “supraglacial lakes,” are somewhat stable in terms of their location, according to Joe MacGregor, NASA project scientist for Operation IceBridge. The lake on Storstrømmen is visible in satellite data at least as far back as May 2012. On occasion, water in lakes like this can drain away through a vertical shaft known as a “moulin.” Scientists initially wondered if the dark circular area on the right side of this image could be a moulin, but closer inspection suggested it is just a deeper part of the lake.

The third photo shows a refrozen melt pond with more muted color. Jim Yungel, an engineer based at NASA’s Wallops Flight Facility, was flying with the IceBridge mission on April 17, 2019, when he shot the image over Petermann Glacier in northwestern Greenland. The pond, which was likely liquid during the previous melt season, now appears to be well frozen and covered with snow. Winds have cleared away some snow, exposing part of the frozen surface.

It remains to be seen when each of these frozen features will melt again. Conditions on the Greenland Ice Sheet can change from day to day as weather conditions change. You can follow melt conditions here and here.

Some photographs from the IceBridge mission, notably those from the CAMBOT system, will be part of a data set eventually released by the National Snow and Ice Data Center. Others are simply beauty shots, taken by the scientists and engineers who have observed some spectacular scenery over the past decade. Both data and the photos helped prevent a gap in polar ice measurements in the years between the end of the ICESat satellite mission in 2009 and the launch of ICESat-2 in 2018.

Photos and image interpretation courtesy of Jeremy Harbeck, Joe MacGregor, and Jim Yungel; NASA’s Operation IceBridge mission. Story by Kathryn Hansen.

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