Trillion tons of Antarctica fell into the sea

Antarctica, the coldest continent on Earth, is known for its remoteness, unique fauna, and frozen ice surface. Around the perimeter of Antarctica, dozens of ice shelves (masses of floating ice fed by glaciers and attached to the land) drift into the Southern Ocean. The two largest ice shelves, the Ross Ice Shelf and the Rhone Ice Shelf, span a combined area of ​​about 350,000 square kilometers (about 135,000 square miles) — an area roughly the size of Venezuela — but the Larsen Ice Shelf in Antarctica, the fourth-largest On the Continent, it has garnered most of the attention over the past 25 years because it is slowly disintegrating. The most recent episode in this saga occurred between July 10 and 12, 2017, when a trillion-metric-ton chunk of ice — possibly needed to hold back much of the remaining shelf — split (i.e., broke off). .

The Larsen Ice Shelf is located on the eastern side of the Antarctic Peninsula and extends into the Weddell Sea. It originally covered an area of ​​86,000 square kilometers (33,000 sq mi), but its footprint has decreased significantly, possibly as a result of warming air temperatures over the Antarctic Peninsula during the second half of the 20th century. In January 1995, the northern section (known as Larsen A) broke up, and a giant iceberg broke off from the middle section (Larsen B). Larsen B declined steadily until February and March 2002, when it, too, collapsed and disbanded. The southern portion (Larsen C) makes up two-thirds of the ice shelf’s original extent, covering an area of ​​about 50,000 square kilometers (19,300 sq mi) alone. Its thickness ranges from 200 to 600 meters (about 660 to 1,970 feet). Sometime between July 10 and July 12, 2017, a section of 5,800 square kilometers (about 2,240 square miles) — about 12% of Larsen C — broke off. Signs of the impending break of Larsen C date back to 2012, when satellite observations detected a steadily growing crack near the Jørge Peninsula at the southern end of the cliff. NASA and European Space Agency satellites tracked the rift as it increased to more than 200 km (124 miles) in length and the massive iceberg broke away from the continent.

Although about 88% of Larsen C remains, many scientists worry that it will collapse like Larsen A and Larsen B, because the loss of such a huge area of ​​the ice front of the shelf could make the rest of the ice shelf less stable. The mass of the cliff, coupled with the fact that it is wedged behind shallow undersea outcroppings, forms a natural dam which significantly slows ice flow into the Weddell Sea. The scientists point out that the part that broke off was not obstructed by rocks, so they are less concerned that the loss of the part that broke off could lead to wholesale break-up of the shelf in the near term. Some scientists even admit that the generated area could grow back to form a new ice dam that reinforces the shelf. However, results from ice calving and glacier flow models predict that the shelf will continue to disintegrate over the course of years and decades.

Calving is a natural process driven in part by seasonal changes in temperature and stresses associated with the build-up of compressive stress on the ice. Some studies claim that the spring and summer foehns (warm, dry gusty winds that periodically descend on the leeward slopes of mountain ranges) also contributed to the weakening of the ice. As investigations into ice shelf dynamics continue, such large iceberg calving events are often viewed as symptoms of climate change associated with global warming. While global warming may play a role in the events of ice shelf detachment, scientists disagree about what role, if any, this phenomenon played in recent developments on the Larsen C surface.

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