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Antarctica’s Pine Island Glacier is one of the most closely watched pieces of ice on Earth.

For years, scientists have tracked as chunks of the glacier have broken off, an awe-inspiring event known as “calving” that happens naturally. But it’s happening more often at the Pine Island Glacier, also known as PIG, and it’s got glaciologists worried that climate change is to blame.

“The calving events at Pine Island Glacier are coming more frequently than they used to,” said glaciologist Adrian Luckman from Swansea University in the U.K. in an email.

Glaciologists have raised alarm that a massive new iceberg, designated B-49, may be a result of melting caused by relatively warm water eating away at the ice that surrounds the frozen continent.

B-49 is one of two large icebergs now floating away from Antarctica. It broke away from PIG last week, while the other, a trillion-ton behemoth dubbed A-68, broke away from the Larsen C Ice Shelf, on the east coast of the Antarctic Peninsula, in 2017, scientists say.

Iceberg B-49, is about twice the size of Washington D.C. NASA Earth Observatory

But iceberg A-68, unlike B-49, is probably not a result of a warming climate, said Luckman and other glaciologists.

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Iceberg B-49 covers 40 square miles, while the many smaller icebergs that also broke free on Feb. 9 cover another 80 square miles.

An international scientific team has just completed its first major field season on the giant Thwaites Glacier, about 200 miles from Pine Island Glacier, beside the Amundsen Sea in West Antarctica.

They are trying to learn why glaciers in the region are melting.

We just approached within a couple of miles of the new giant #PineIslandGlacier iceberg B-49 (the white wall behind smaller icebergs and brash ice in the foreground) on @GlacierThwaites @GlacierOffshore cruise #NBP2002 aboard RV Nathaniel B Palmer. pic.twitter.com/xzvoghrz7Z — Robert Larter (@rdlarter) February 12, 2020

“This is a place where we know the ice shelves are thinning quite fast,” said glaciologist Helen Amanda Fricker from the Scripps Institution of Oceanography in San Diego. “It has been identified as an area that is changing rapidly.”

Satellite photographs show Thwaites Glacier and PIG have started flowing faster in recent years, while their edges of floating ice have pulled back toward the land.

“The increased frequency of calving seems to be related to the thinning of the ice tongue,” Luckman said. “This is probably caused by the incursion of warmer waters into the area, which may be related to climate change.”

Glaciers in West Antarctica like the Thwaites and PIG worry scientists because their melting could eventually expose inland glaciers and even more ice, causing a drastic rise in sea levels.

Some recent scientific models predict that Antarctica’s melting alone could cause sea levels to rise by almost 2 feet by 2100.

Iceberg A-68, which covers more than 2,000 square miles, recently left Antarctica’s Weddell Sea, heading for the Southern Ocean.

Several research ships have since tried to study the pristine seabed it covered for thousands of years, but the floating ice in the Weddell Sea has been too heavy for them to get there.

While many icebergs break off from the normal processes of Antarctica’s coastal glaciers flowing into the sea, Luckman said the changes in the west of Antarctica appear to be caused by a warming climate.

“Taken as a whole, the generalized retreat of ice shelves along the Antarctic Peninsula, and especially the thinning elsewhere such as at Thwaites Glacier, shows clearly that climate change is causing accelerating mass loss from Antarctica to the oceans,” he said.