Satellites observe glacier committing "ice piracy"

Previously , this activity was thought to have been occurring over hundreds or even thousands of years. However, high-resolution satellite observations reveal that a massive glacier has been cutting ice from its slower-moving neighbour for less than 18 years.

Researchers from the University of Leeds in England say it is unprecedented that this change in ice flow direction can be directly observed in Antarctica in such a short period of time, and that their discovery represents an important step towards better understanding the future of Antarctica and its contribution to sea level rise.

Their findings were published in the journal The Cryosphere, Europa Press reported on Thursday.

A study led by the University of Leeds shows the acceleration of seven ice streams in West Antarctica. One of them almost doubled its speed (87%) at the ice-ocean boundary between 2005 and 2022, and three accelerated between 60% and 84% during the same period.

Six of these currents reached average speeds of more than 700 meters per year in 2022, the equivalent of advancing the length of seven football fields in a year - a remarkably fast pace for ice.

The team used satellite data to measure the change in ice speed in the Pope, Smith and Kohler (PSK) region of West Antarctica.

Scientists found that ice flows have accelerated by an average of 51 percent since 2005 at baseline, the point where glaciers and ice shelves begin to float.

Baselines demonstrate the instability of the ice sheet, as changes in its position reflect an imbalance with the surrounding ocean and affect continental ice flow.

However, the research team discovered one particularly shocking fact. In stark contrast to the widespread acceleration observed between 2005 and 2022 across all other glaciers in the region, ice flow at Kohler West has decreased by 10%.

The largest change in speed was observed at the neighboring Kohler East Glacier as well as the Smith West Glacier, which were flowing about 560 m/year faster in 2022 than in 2005.

Currently, several glaciers around Antarctica are responding to climate change by flowing more rapidly into the ocean.

When a glacier's flow speeds up, its ice stretches and thins at the same time, but the Kohler West Ice Stream slows down.

"We believe that the observed slowdown at Kohler West Glacier is due to the redirection of ice flow to its neighbor, Kohler East. This is due to the large change in the slope of the Kohler West surface, likely caused by the very different thinning rates of the neighboring glaciers," said lead author Heather L. Selley, a senior author of the study.

As the Kohler East Ice Stream flows and thins more rapidly as it moves forward, it absorbs or 'steals' ice from the Kohler West. This is effectively an act of 'ice piracy', where ice flow is redirected from one glacier to another, and the accelerating glacier is essentially 'stealing' ice from its slowing neighbor.

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