When Land Ice Meets Sea Ice
acquired April 21, 2018 download large image (5 MB, JPEG, 4032x3024)

On April 21, 2018, pilots guided NASA’s P-3 research aircraft over glaciers along Greenland’s eastern coast, with walls of ice-carved fjords rising on each side. The flight to map land ice along the Geikie Peninsula was part of Operation IceBridge—NASA’s long-running airborne mission to monitor polar ice.

But the view suddenly changed where the glaciers reach the sea. As the plane looped around for another run up one of eight glaciers targeted for this day, an iceberg caught the eye of Linette Boisvert, a sea ice scientist at NASA’s Goddard Space Flight Center. She took this photograph from an altitude of 1500 feet (500 meters) over Scoresby Sound while flying west toward Vestfjord Glacier.

Icebergs start as land ice—snow that has accumulated on land and, over the course of many years, has been compacted into ice. When this glacial ice flows downstream and reaches the sea, cracks in the ice are widened as warm water and air melt the ice from below and above, respectively. When these cracks become large enough, pieces break off like fingernail clippings and drift into the water as icebergs. Boisvert’s berg was trapped in sea ice—the frozen seawater that floats around on the ocean.

While the sea ice looks like it could prevent this berg from moving, it was not completely still. According to Boisvert, the patterns in the fractured sea ice were likely caused by the iceberg rotating or by part of it breaking off. If part of the iceberg broke, it would fall onto the sea ice and then into the ocean. The impact would cause the ice to break up in the circular pattern on one side, “like ripples in a pond when a stone is thrown into it.”

That’s not too hard to do; it was first-year sea ice, and therefore thin, flat, and easily broken. Areas of open water between the fractured sea ice had already begun to refreeze. Other small bergs, possibly those that had broken off from the main berg and caused the broken up pattern, are drifting around in the mix. Such a mixture of sea ice and iceberg pieces is called mélange—a French word that means “mixed.”

“This iceberg was in an area during our flight that we termed ‘polar bear highways’ because there were so many polar bear tracks on the surface of the sea ice and snow, looping around icebergs and linking one iceberg to another,” Boisvert said. “These openings in the ice are ideal places for seals to come out of the water and rest, and for polar bears to hunt. Although there were no visible tracks around this iceberg, it might be visited by polar bears as it makes it way to out to the Atlantic Ocean.”

acquired April 27, 2018 download large image (8 MB, JPEG, 3974x2980)

On April 27, Boisvert snapped another photograph of icebergs encased in broken sea ice. The second photograph showcases all ice types in the fjord of the Kangerdlugssuaq Glacier, as well as the glacier front (top-right). Notice the pond of meltwater atop the iceberg in the center of the image.

“These images capture the complexity in which land ice and sea ice interact in the Arctic climate system,” Boisvert said. “Studying these interactions is very important for understanding changes in some glacier termini and outflow, and sea ice thickness and compaction in the context of climate change...thus reminding us that all ice types matter.”

Photographs by Linette Boisvert, NASA’s Goddard Space Flight Center/Operation IceBridge. Story by Kathryn Hansen.

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When Land Ice Meets Sea Ice

May 13, 2018
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