40% of Antarctica’s ice shelves are shrinking, worrying scientists

“The surprising finding to me was the number of ice shelves that are dramatically and continuously deteriorating,” said Benjamin Davison, lead author of the study. “Many ice shelves, not just the largest ones, are steadily losing mass over time with no sign of recovery.”

Ice shelves are huge floating sections of ice extending from glaciers on Earth. It plays a crucial role in slowing the flow of ice on land into the ocean by essentially acting as a wall and surrounding almost the entire coast of Antarctica. When ice shelves recede or retreat, ice on land can flow into the ocean more quickly and accelerate sea level rise. The Antarctic and Greenland ice sheets are responsible for more than a third of total sea level rise In recent decades.

By analyzing more than 100,000 satellite images from 1997 to 2021, Davison and his colleagues found that 71 out of 162 ice shelves surrounding Antarctica have decreased in size. Nearly 50 of them lost more than 30 percent of their initial mass during those years. The team also found that 29 racks gained mass over the study period, and an additional 62 racks did not change significantly in mass.

Davison, the University of Leeds researcher, said intact ice shelves naturally retreat and grow over time. The ice shelf is constantly flowing and advancing, but it will also lose mass through melting or breaking off, which happens when its front breaks off into the ocean. Then it can pick up ice from the ground and grow again.

Davison said the large portion of ice shelves that are steadily shrinking shows that this natural cycle is halted.

“We see them getting smaller and smaller and smaller for 25 years…often without any sign of any progress or growth during that period,” Davison said. “This is not consistent with what we expect from the natural cycle of the ice shelf.”

The bulk of the shrinking ice shelves are found on the western side of Antarctica, where warmer waters can erode the shelves from below. Almost all of the ice shelves on the western side have seen ice loss.

In West Antarctica, the Getz Ice Shelf experienced some of the heaviest ice losses, losing 1.9 trillion tons of ice over the study period — almost exclusively due to melting at the base of the shelf. The Pine Island Ice Shelf has lost 1.3 trillion tons of ice, a third of which is due to calving.

However, most East Antarctica ice shelves have increased in size or remained the same. The east is not as exposed to warm water as the other side of the continent, Davison said. The area is protected by a strip of cold water on the coast, which helps keep out nearby warm waters. However, the study still shows pockets of shrinking ice shelves, and researchers are still investigating the causes. One theory is that warmer waters on the western side could slowly invade the region, Davison said.

One of the most recent ice shelf collapses in East Antarctica occurred in March 2022. The Conger Ice Shelf — roughly the size of New York City — collapsed completely within a few weeks, possibly caused by a record heatwave in Antarctica that proved to be the most intense on record on record. the world.

Thinning of ice shelves has also been evident in the surrounding environment. Over the 25-year study period, the team estimated that 66.9 trillion tons of fresh water from the ice shelves entered the ocean. Fresh water can dilute saltier ocean water and make it lighter, impairing ocean circulation – a change researchers have found I have already noticed About Antarctica.

Glaciologist Alex Gardner, who was not involved in the research, said the study results confirm previous work looking at ice shelf changes, including his own. for him previous job Calvings increased and caused more ice masses to be lost to the oceans. The new study was also completed Another study This showed how widespread ice shelf thinning is across the continent.

“We now have multiple groups that have come to the same conclusion, which is that when you move away and look at the entire Antarctic ice shelves, you see clear signs of retreat and thinning, signs [that] “This is expected to happen in a warming world,” Gardner said.

Davison said the current ice shelf data set is not long enough for researchers to be able to conclusively link climate change, but he said it would be a “remarkable coincidence” if natural ice shelf variability was much greater. In addition, climate models predict that ice shelves will shrink steadily in a warming world, as noted, eventually Hit a turning point Which could lead to a millennium period of ice sheet disintegration.

But Davison said we don’t need to reach that tipping point before we see an impact on the planet.

“The changes are big and fundamental, even if they are [you] “We can imagine a worse scenario,” Davison said. “Every ice shelf doesn’t need to be essentially gone or gone for it to matter.”