NASA has just released new aerial photographs that show, close-up, an immense, 70-mile long rift in the Larsen C ice shelf in Antarctica. The breach is 300 feet wide and one-third of a mile deep. As it grows, an iceberg the size of Delaware will break off.
When the dark of the Southern Hemisphere winter lifted in August, scientists were shocked to see that the rift in the ice had grown nearly 14 miles. “The growth of this rift likely indicates that the portion of the ice shelf downstream of the rift is no longer holding back any grounded ice,” said Joe MacGregor, IceBridge deputy project scientist and glaciologist at NASA Goddard Space Flight Center.
Ice shelves ride on water and are fed by glaciers and continental ice streams. Cracks and calving are normal, and the loss of a portion of an ice shelf will not contribute to sea level rise as it is already afloat on the ocean. However, an ice shelf such as Larsen C holds back land ice, acting as a buttress. When a shelf disintegrates, the glaciers behind it can flow out to sea, which will directly increase sea level.
Long-term satellite observations show that Antarctic glaciers are rapidly retreating. In West Antarctica, they are losing 23 feet of elevation per year. As they slip away, they add up to 150 billion tons of water to the ocean, raising seas by about a tenth of an inch annually.
In November, Antarctic air temperatures were 3.6 - 7.2 degrees Fahrenheit warmer than normal. Antarctic sea ice set a new record low, as did the Arctic. Antarctic sea ice was a staggering 699,000 square miles below the 1981 to 2010 average. “Antarctic sea ice really went down the rabbit hole this time,” said Ted Scambos, the lead scientist at the National Snow and Ice Data Center. The West Antarctic Ice Sheet could collapse entirely within the next 100 years.
