Antarctica: Land Glacier began to collapse

(ORDO NEWS) — Sea ice around Antarctica has begun to recover after hitting its lowest point on record in late February 2022. But on a local scale, this transition from melting to freezing can have its own nuances.

For example, near the Land Glacier in West Antarctica, an area of ​​old sea ice broke up as new ice formed in March. Around the same time, part of the ice tongue of the glacier broke off.

Michael Lowe, the analyst at the US National Ice Center who drew attention to these changes, has closely observed this part of the Antarctic coast, known as Maria Byrd Land.

“I’ve been eyeing this area for the past two months when a large area of ​​very old fast ice started to break up,” Lowe said. “When comparing two SAR images taken on different days, I saw that the top of the Lund Glacier was beginning to collapse.”

Changes are also visible in this pair of natural color images taken on February 24 and March 23, 2022 by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA‘s Terra and Aqua satellites, respectively.

The February image shows a huge expanse of sea ice attached to the edge of the coastline, as well as to the ice tongue and icebergs of the Land Glacier.

Lowe explained that this “fast ice” is often in a symbiotic relationship with glaciers and icebergs. Glaciers and icebergs allow sea ice to build up and stably “attach,” he said. “This fast ice then helps anchor these bergs and glaciers as it thickens into old ice over many years.”

But recent studies using satellite observations have shown that fast-growing ice in parts of Antarctica, including off the coast of Maria Byrd Land, has been decreasing since MODIS records began around 2000. However, at the time of the February snapshot, there was still a significant area. By March, most of this old fast ice had broken up.

According to Fraser Christie, a glacier geophysicist at the Scott Institute for Polar Research at the University of Cambridge, the loss of fast ice could have had further consequences.

It is possible that the rapid evacuation of fast ice in February-March, in addition to longer-term losses, contributed to the breakup and eventual collapse of the ice tongue of the Land Glacier, he said.

Christie points to a similar case on the fast flowing Totten Glacier in East Antarctica. There, the loss of seasonal fast ice has caused the glacier front to accelerate by as much as 100 meters per year.

“More and more studies are starting to show the important role of sea ice in thickening and strengthening both ice tongues and ice shelves,” he said.

The March image shows that the icebergs appear to be turning west, in the direction of the remaining sea ice.

Christie explained that icebergs are carried by the Antarctic Coastal Current, which flows west around the continent parallel to the coastline. The Coriolis effect will also affect the flow of the bergs, deflecting them to the left of their path.

The breaking off of icebergs is a natural process for glaciers ending in the ocean. “While there has been a retreat, thinning and acceleration of the Land Glacier in recent years, there is no evidence to suggest that its recent retreat is due to anthropogenic climate change,” Christie said.

“Instead, its behavior most likely reflects the natural life cycle of the current, which is characteristic of all Antarctic ice shelves and marine terminal glaciers.” The last time the glacier lost a similar amount of floating ice was during the Australian winter of 2004.

Another step in the natural life cycle of sea ice is visible in this March image: the growth of new sea ice. Smooth stripes and whirlwinds are “nilas” – young ice, which often forms thin sheets, usually no more than 10 centimeters thick.

(Note that the green-yellow cast is largely the effect of low light and automatic color correction.) New ice that looks streaked lines up with the direction of the surface winds; ice that has a swirling pattern is likely driven by winds and ocean circulation, or “whirlwinds”.

Over the next few winter and summer seasons, scientists will be interested to see what happens to the glacier, icebergs and sea ice off this part of Maria Byrd Land. Lowe added: “We will watch as the bergs that break off the Lund Glacier run aground and allow a new area of ​​old fast ice to form over the next few years, which will stabilize this area.”

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