A 1.1-trillion-ton iceberg has broken off Antarctica, and scientists say it's one of the largest ever recorded

Antarctica has shed an iceberg that's big enough to fill Lake Erie more than two times.
It weighs about 1 trillion metric tons.
It may be the third-largest iceberg recorded since satellites began taking photos of Earth.
Human activity most likely isn't responsible for this event, but carbon emissions are driving other changes to Antarctic ice.

The image is a bit fuzzy, but to scientists it's unmistakable: One of the largest icebergs ever recorded has broken free of Antarctica.

A crack in an Antarctica's Larsen C ice shelf is responsible for calving the colossal new iceberg, which has roughly the area of Delaware state and more than twice the volume of Lake Erie.

Researchers noticed the distinctive rift in Antarctica's ice in 2010, and it had grown rapidly since 2016. The iceberg calved as early as Monday, researchers said.

"Breaking news! The iceberg has fully detached from Larsen C - more details to follow soon," Martin O'Leary a glaciologist at Swansea University, wrote in a tweet early Wednesday morning for the Antarctic research program Project Midas.

A NASA Earth-observing satellite called Modis was among the first to photograph the colossal ice block freed of Antarctica's grasp.

Based on the image above, and another created by Adrian Luckman, also a glaciologist at Swansea University and a Project Midas member, it appears the iceberg has largely stayed intact.

That size could make it the third-largest iceberg recorded since satellite measurements began, according to a tweet last Thursday by The Antarctic Report.

In a Wednesday blog post, Luckman and O'Leary said it was "one of the biggest ever recorded" at a weight of roughly 1 trillion metric tons, or 1.1 trillion tons, and said its name would most likely be dubbed A68.

"The calving of this iceberg leaves the Larsen C Ice Shelf reduced in area by more than 12%, and the landscape of the Antarctic Peninsula changed forever," they said.

The ice block's area is roughly comparable to the US state of Delaware. But CryoSat — Europe's ice-monitoring satellite — recently took the most precise measurements to date of its thickness, allowing scientists to gauge its volume.

Days before the iceberg broke free, Noel Gourmelen, a glaciologist at the University of Edinburgh, and his colleagues estimated that it would be about 620 feet (190 meters) thick and harbor some 277 cubic miles (1,155 cubic kilometers) of frozen water.

Gourmelen and the European Space Agency on July 5 released this 3D animation that shows the iceberg's dimensions:

And here's Lake Erie for a size comparison:

Scientists previously said they weren't sure what would happen after the iceberg's breakaway, since such large calvings are rarely seen.

"It could, in fact, even calve in pieces or break up shortly after. Whole or in pieces, ocean currents could drag it north, even as far as the Falkland Islands," Anna Hogg, a glaciologist at the University of Leeds, said in a July 5 press release by the ESA.

Those islands lie more than 1,000 miles away from Larsen C in Antarctica.

This illustration of hundreds of icebergs' paths, from 1999 through 2010, shows how that drift might play out before it melts.

An ice block thousands of years in the making

The Larsen C ice shelf is one of the largest such shelves in Antarctica.

According to a tweet from Project Midas, "most of the ice that calves off fell as snow on the ice shelf in the past few hundred years, but there's an inner core that's a bit older."

Project Midas announced in early June that satellite images showed the rift had split, turned north, and begun moving toward the Southern Ocean.

Luckman, who has closely monitored the ice shelf with his colleagues at Project Midas, previously released an animation of the rift's rapid growth (below).

It shows how the rift "jumped" as it sliced through bands of weak ice and slowed when it met stronger, thicker ice. The ocean is shown in emerald green (top right), the Larsen C ice shelf is the light blue patch, and the glacier behind it is depicted in white.

The final frame shows an image of the rift's tip breaking in multiple directions — a sign of imminent calving of the iceberg.

A close-up from the ESA's Copernicus satellite more clearly showed the chaos of the crack's tip on Thursday:

Are humans behind this?

The iceberg won't noticeably raise sea levels, since it was already floating in the ocean as part of Larsen C and displacing water. But Luckman and O'Leary previously said that once Larsen C lost its iceberg, the rest of the shelf "will be less stable than it was prior to the rift."

Put another way: There's a very slim chance that new iceberg could cause the entire Larsen C ice shelf, and an ancient glacier behind it, to slowly disintegrate and fall into the sea.

The chaos wouldn't be unprecedented. In 2002, a neighboring ice shelf called Larsen B collapsed and broke up in the Southern Ocean. This animation captures that event unfolding from January 31 through April 13, 2002:

Some scientists think that if and when Larsen C and its accompanying glacial ice eventually collapse, sea levels may rise by up to 4 inches.

But experts on Antarctic ice say that such a loss is exceedingly unlikely and would be due mostly to natural processes.

"Large calving events such as this are normal processes of a healthy ice sheet, ones that have occurred for decades, centuries, millennia — on cycles that are much longer than a human or satellite lifetime," Helen Amanda Fricker, a glaciologist who studies Antarctic ice for the Scripps Institution of Oceanography, wrote in The Guardian last month. "What looks like an enormous loss is just ordinary housekeeping for this part of Antarctica."

But Fricker warned that we shouldn't be complacent about climate change, which is being driven mostly by human activity.

"Antarctic ice shelves overall are seeing accelerated thinning, and the ice sheet is losing mass in key sectors of Antarctica," she said. "Continuing losses might soon lead to an irreversible decline."

: In a previous version of this story, we misstated the iceberg's volume as comparable to that of Lake Michigan. The iceberg's size is closer to double the volume of Lake Erie.