Antarctica's Ice Sheets Are Melting Faster — And From Beneath

[NickB79]

http://www.npr.org/sections/thetwo-way/2016/10/25/499206005/antarcticas-ice-sheets-are-melting-faster-and-from-beneath

A team from JPL has been studying that grounding line in several places along the edge of the West Antarctic ice sheet. They used radar to look beneath the ice. In particular, overflights have targeted ice shelves along the West Antarctic ice sheet known as the Amundsen Sea Embayment.

They've found that the ice is melting faster than they've ever seen. The researchers believe the cause is warm water circulating beneath the ice shelf. The melting was most pronounced from 2002 to 2009. (The influx of warmer water to the region stalled recently, and the rate of melting seems to have slowed somewhat.)

Khazendar says the more the bottom of the shelves melt, the more ice is exposed to warm water. "It becomes a runaway process," he explains, "which makes it unstable."

Where's the warmer water coming from? The team, whose findings appear in the journal Nature Communications, points to global warming that's heating up the oceans. There's been a spate of research lately showing that Antarctic ice is melting faster than previously thought — and raising global sea levels.

Per another source, the Smith Glacier alone lost almost 1,000 FEET of ice from below in only 7 years!

http://www.gizmodo.com.au/2016/10/the-west-antarctic-ice-sheet-is-wasting-away-fast/

When Khazendar examined changes in the thickness of three glaciers — Smith, Pope and Kohler — he discovered significant thinning near the grounding lines. Smith glacier, in particular, stuck out like a sore thumb: In just seven years, this ice sheet shed 300 to 490m of ice from its underbelly. “What we have observed is rates [of melting] under Smith and other glaciers that are tens of meters per year out of balance,” Khazendar said. “This was really staggering.”

[femmedem]

1. This article describes the abrupt sea level rise this portends:

"...Though such a nightmare melt scenario was recently theoretical, it represented a very real potential near-future event as global temperatures rose into the 1-2 degrees Celsius above 1880s range during recent years. For times in the geological past around 115,000 years ago also produced large glacial melt pulses and related sea level rises of 15-25 feet during periods of similar warmth.

However, direct evidence of such a powerful melt dynamic had not yet been directly observed in Antarctica’s glaciers. Fresh water lenses were developing, rates of glacial loss were quickening. Basal melt rates looked bad. But the kind of tremendous losses necessary to produce rapid sea level rise were not yet fully in evidence..."

More at link