By Chris Mooney
16 December 2016
(Washington Post) – Scientists at institutions in the United States and Australia on Friday published a set of unprecedented ocean observations near the largest glacier of the largest ice sheet in the world: Totten glacier, East Antarctica. And the result was a troubling confirmation of what scientists already feared — Totten is melting from below.
The measurements, sampling ocean temperatures in seas over a kilometer (0.62 miles) deep in some places right at the edge of Totten glacier’s floating ice shelf, affirmed that warm ocean water is flowing in towards the glacier at the rate of 220,000 cubic meters per second.
These waters, the paper asserts, are causing the ice shelf to lose between 63 and 80 billion tons of its mass to the ocean per year, and to lose about 10 meters (32 feet) of thickness annually, a reduction that has been previously noted based on satellite measurements.
This matters because more of East Antarctica flows out towards the sea through the Totten glacier region than for any other glacier in the entirety of the East Antarctic ice sheet. Its entire “catchment,” or the region of ice that slowly flows outward through Totten glacier and its ice shelf, is larger than California. If all of this ice were to end up in the ocean somehow, seas would raise by about 11.5 feet.
“This ice shelf is thinning, and it’s thinning because the ocean is delivering warm water to the ice shelf, just like in West Antarctica,” said Don Blankenship, a glaciologist at the University of Texas at Austin and one of the study’s co-authors. [more]
ABSTRACT: Mass loss from the West Antarctic ice shelves and glaciers has been linked to basal melt by ocean heat flux. The Totten Ice Shelf in East Antarctica, which buttresses a marine-based ice sheet with a volume equivalent to at least 3.5 m of global sea-level rise, also experiences rapid basal melt, but the role of ocean forcing was not known because of a lack of observations near the ice shelf. Observations from the Totten calving front confirm that (0.22 ± 0.07) × 106 m3 s−1 of warm water enters the cavity through a newly discovered deep channel. The ocean heat transport into the cavity is sufficient to support the large basal melt rates inferred from glaciological observations. Change in ocean heat flux is a plausible physical mechanism to explain past and projected changes in this sector of the East Antarctic Ice Sheet and its contribution to sea level.