Larsen Ice Shelf Breakoff: Our Future in Ice

Candice Gaukel Andrews July 25, 2017 0

On Antarctica’s west side, average annual temperatures have risen 5 degrees Fahrenheit since 1950—a rate that is several times faster than that for the rest of the planet. ©Christopher Michel, flickr

A gigantic iceberg has just broken off from Antarctica’s massive Larsen C Ice Shelf. The berg began its independent life sometime in the middle of July 2017.

And it’s huge. The 2,200-square-mile iceberg weighs a trillion tons (twice the volume of Lake Erie) and is nearly the size of Delaware. Named A68, it has changed the outline of the Antarctic Peninsula forever.

Some scientists believe the event is part of a natural cycle of iceberg calving. Others say it is due primarily to climate change. Almost all, however, have concluded that the breakoff will play a major role in what comes next for the ice shelf, the continent of Antarctica, our coastal cities and the future inhabitants of planet Earth.

The glaciers going and the waters rising

The ice shelves at the tip of the Antarctic Peninsula have been changing dramatically in recent decades, as illustrated in this composite satellite photo showing the historic ice extent prior to calving events. ©NASA Earth Observatory

The Larsen Ice Shelf is situated along the northeastern coast of the Antarctic Peninsula, one of the fastest-warming places on the globe. Catching the powerful winds and ocean currents that endlessly swirl around Antarctica, the peninsula gets slammed with warm air and water from farther north.

And that air and water is getting warmer all the time. Most of the heat trapped by our fossil fuel emissions since the Industrial Revolution began in the 19th century has gone into the ocean. Intensified circumpolar winds and currents have driven this warmer water from offshore onto Antarctica’s continental shelf and under the floating ice. Because of that, average annual temperatures on Antarctica’s west side have risen nearly 5 degrees Fahrenheit since 1950—a rate that is several times faster than that experienced by the rest of the planet—and the winters have warmed an astonishing 9 degrees. Sea ice now forms only four months a year instead of seven.

From north to south, the segments of the Larsen Ice Shelf are called Larsen A (the smallest), Larsen B and Larsen C, which is one of the largest ice shelves in the region, spanning approximately 21,000 square miles. Farther south, is Larsen D and the much smaller Larsens E, F and G.

In 2002, the Larsen B Ice Shelf partially collapsed. ©Oregon State University

In the past three decades, two large sections of Larsen A and B have collapsed. The Larsen A Ice Shelf disintegrated in January 1995. In 2002, the Larsen B sector partially collapsed, sending forth 1,250 square miles of ice that was 720 feet thick, an area comparable to Rhode Island. In 2015, a study concluded that the remaining Larsen B ice shelf will disintegrate by 2020, based on observations of faster flow and rapid thinning of glaciers in the area.

Our warmer air and warmer water currents helped trigger the collapses of Larsen A and Larsen B. While warm currents ate away the underside of the shelf, warmer air helped meltwater ponds to form on the surface of ice shelf. The ponds then drained into crevasses; and acting like a multitude of wedges, they levered the shelf apart. As the shelves vanish, the glaciers they once stabilized rush into the ocean, accelerating two to nine times their original speed.

For now, the best estimates suggest that Antarctica will shed enough ice to raise global sea levels by 1.5 to 3.5 feet by 2100, depending on how quickly humans continue to pump out greenhouse gases. Add in rapidly melting glaciers in Greenland and in other parts of the world, and sea level could rise seven feet by 2100. That would mean that the Earth’s coastal cities—such as Copenhagen, Los Angeles, New York and Shanghai, along with dozens of others—would need to be abandoned.

The future floating into focus

Antarctica’s melting is reshaping the White Continent—and the world’s future. ©Liam Quinn, flickr

The most imminent danger from A68 is the threat to ships in the region. Now that it has separated from the Larsen C Ice Shelf, it will be more vulnerable to climate impacts. If the iceberg breaks into smaller pieces, ocean currents could push them north. Scientists will be tracking A68’s integrity and path through the Southern Ocean in order to predict its trajectory.

In addition to that, however, glaciologists will be monitoring the flow of the glaciers behind the ice shelf. They expect that a new zone will be created, where calving happens more frequently. For example, a summary of a scientific workshop compiled last year by the National Snow and Ice Data Center warns, “A significant retreat of the Thwaites Glacier system [located in West Antarctica in the Amundsen Sea embayment to the south] would trigger a wider collapse of most of the West Antarctic Ice Sheet.” That entire ice sheet contains enough water to raise global sea level by more than 10 feet in a matter of decades to centuries.

A68 is not only a physical iceberg, it’s the tip of a much larger, proverbial one: the beginning of an entire continent reshaping itself and the fulcrum of the world’s future.

Here’s to finding your true places and natural habitats,

Candy

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