Warming ocean water undercuts Antarctic ice shelves

[OKIsItJustMe]

http://www.colorado.edu/news/releases/2016/03/14/warming-ocean-water-undercuts-antarctic-ice-shelves

[font face=Serif][font size=5]Warming ocean water undercuts Antarctic ice shelves[/font]

March 14, 2016

[font size=4]This is a joint release of the National Snow and Ice Data Center, CIRES, the University of Colorado Boulder and Scripps Institution of Oceanography.[/font]

[font size=3]“Upside-down rivers” of warm ocean water threaten the stability of floating ice shelves in Antarctica, according to a new study led by researchers at the University of Colorado Boulder’s National Snow and Ice Data Center. The study highlights how parts of Antarctica’s ice sheet may be weakening due to contact with warm ocean water.

“We found that warm ocean water is carving these 'upside-down rivers,’ or basal channels, into the undersides of ice shelves all around the Antarctic continent. In at least some cases these channels weaken the ice shelves, making them more vulnerable to disintegration,” said Karen Alley, a Ph.D. student in CU-Boulder’s Department of Geological Sciences and lead author of an analysis published today in Nature Geoscience.

…

The team also used satellite laser altimetry, which measures the height of an ice shelf surface with high accuracy, to document how quickly some of the channels were growing. The data show that growing channels on the rapidly melting Getz Ice Shelf in West Antarctica can bore into the ice shelf base at rates of approximately 10 meters (33 feet) each year.

The mapping shows that basal channels have a tendency to form along the edges of islands and peninsulas, which are already weak areas on ice shelves. The team observed two locations where ice shelves are fracturing along basal channels, clear evidence that basal channel presence can weaken ice shelves to the point of breaking in vulnerable areas.

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http://dx.doi.org/10.1038/NGEO2675

[Doctor_J]

1. Uh oh

The stuff's about to hit the fan

[OKIsItJustMe]

2. It will probably hit the fan some time…

I don’t think I would say, “it’s about to…”

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2675.html

[font face=Serif][font size=5]Impacts of warm water on Antarctic ice shelf stability through basal channel formation[/font]

Nature Geoscience (2016) doi:10.1038/ngeo2675
Received 02 July 2015 | Accepted 10 February 2016 | Published online 14 March 2016

[font size=4]Antarctica’s ice shelves provide resistance to the flow of grounded ice towards the ocean. If this resistance is decreased as a result of ice shelf thinning or disintegration¹, acceleration of grounded ice can occur, increasing rates of sea-level rise. Loss of ice shelf mass is accelerating, especially in West Antarctica, where warm seawater is reaching ocean cavities beneath ice shelves². Here we use satellite imagery, airborne ice-penetrating radar and satellite laser altimetry spanning the period from 2002 to 2014 to map extensive basal channels in the ice shelves surrounding Antarctica. The highest density of basal channels is found in West Antarctic ice shelves. Within the channels, warm water flows northwards, eroding the ice shelf base and driving channel evolution on annual to decadal timescales. Our observations show that basal channels are associated with the development of new zones of crevassing, suggesting that these channels may cause ice fracture. We conclude that basal channels can form and grow quickly as a result of warm ocean water intrusion, and that they can structurally weaken ice shelves, potentially leading to rapid ice shelf loss in some areas.[/font]

[font size=3]…[/font][/font]

Looking at the illustrations, things don’t look good for the West Antarctic Ice Sheet (WAIS.)