• An East Antarctica ice shelf disintegrated this month following a period of extreme heat in the region, according to scientists.

• Satellite images show the 1,200 square-kilometre Conger Ice Shelf collapsed completely on or around March 15.

• Surrounded by vast oceans and buffered by winds that tend to protect it from large warm-air intrusions, the frozen continent is responding more slowly to climate change than the Arctic, which is warming at three times the rate of the rest of the world.

• In the last century, East Antarctica barely warmed at all, but some regions have been affected and the continent lost an average of 149 billion tonnes of ice per year from 2002 to 2020. 

• Satellite photos show the area had been shrinking rapidly the last couple of years, and now scientists wonder if they have been overestimating East Antarctica’s stability and resistance to global warming that has been melting ice rapidly on the smaller western side and the vulnerable peninsula.

What is ice shelf?

• An ice shelf is a thick, floating slab of ice that forms where a glacier or ice flows down a coastline. While glaciers are defined as large sheets of ice and snow on land, ice shelves are technically part of the ocean.

• Ice shelves take thousands of years to form and act like levees holding back snow and ice that would otherwise flow into the ocean.

• Ice shelves are sometimes referred to as the “safety band” of Antarctica because they buttress the upstream flow of ice from the bordering ice sheet. Little of the Antarctic ice sheet melts at its surface, where snow piles up. Instead, most of the continent loses ice through calving and melting along the underside of the floating ice shelves.

• Because ice shelves already float in the ocean, they do not contribute directly to sea level rise when they break up. However, ice shelf collapse could contribute to sea level rise indirectly. Ice streams and glaciers constantly push on ice shelves, but the shelves eventually come up against coastal features such as islands and peninsulas, building pressure that slows their movement into the ocean. If an ice shelf collapses, the backpressure disappears. The glaciers that fed into the ice shelf speed up, flowing more quickly out to sea. Glaciers and ice sheets rest on land, so once they flow into the ocean, they contribute to sea level rise.

• When an ice shelf like Conger is lost, the grounded ice once kept behind the shelf may start to flow faster as the restraining force of the ice shelf is lost, resulting in more ice tumbling into the ocean.

• The world’s largest ice shelves are the Ross Ice Shelf and the Filchner-Ronne Ice Shelf in Antarctica. The Larsen Ice Shelf in Antarctica broke up into hundreds of small fragments in 1995 and 2002. 

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