Ancient glacial melting process similar to existing concerns about Antarctica, Greenland

Aug 01, 2011

An analysis of prehistoric "Heinrich events" that happened many thousands of years ago, creating mass discharges of icebergs into the North Atlantic Ocean, make it clear that very small amounts of subsurface warming of water can trigger a rapid collapse of ice shelves.

The findings, to be published this week in , provide historical evidence that warming of water by 3-4 degrees was enough to trigger these huge, episodic discharges of ice from the Laurentide Ice Sheet in what is now Canada.

The results are important, researchers say, due to concerns that warmer water could cause a comparatively fast collapse of ice shelves in Antarctica or Greenland, increasing the flow of ice into the ocean and raising sea levels. One of the most vulnerable areas, the West Antarctic Ice Sheet, would raise by about 11 feet if it were all to melt.

"We don't know whether or not water will warm enough to cause this type of phenomenon," said Shaun Marcott, a postdoctoral researcher at Oregon State University and lead author of the report. "But it would be a serious concern if it did, and this demonstrates that melting of this type has occurred before."

If water were to warm by about 2 degrees under the ice shelves that are found along the edges of much of the West , Marcott said, it might greatly increase the rate of melting to more than 30 feet a year. This could cause many of the ice shelves to melt in less than a century, he said, and is probably the most likely mechanism that could create such rapid changes of the .

To find previous examples of such events, scientists reconstructed past and used computer simulations to re-create what probably happened at various times during Heinrich events of the distant past. It had been known for some time that such events were associated with major climate changes, but less clear whether the events were a reaction to or helped to cause them.

"There is now better evidence that the climate was getting colder prior to the Heinrich events, causing surface ocean waters to cool but actually causing warmer water in the subsurface," Marcott said. "We tried to demonstrate how this warmer water, at depth, caused the base of the ice shelf to warm and collapse, triggering the Heinrich events."

A present-day concern, Marcott said, is that ocean currents could shift and change direction even before overall ocean water had warmed a significant amount. If currents shifted and warmer water was directed toward , more rapid melting might begin, he said.

This study was done by scientists from OSU, the University of Wisconsin, National Center for Atmospheric Research, and the Nanjing University of Information Science and Technology. The lead author was Shaun Marcott, a postdoctoral researcher at OSU. The studies were supported by the National Science Foundation, NASA and other agencies.

Explore further: NASA's HS3 mission spotlight: The HIRAD instrument

Related Stories

Greenland and Antarctic ice sheet melting, rate unknown

Feb 16, 2009

The Greenland and Antarctica ice sheets are melting, but the amounts that will melt and the time it will take are still unknown, according to Richard Alley, Evan Pugh professor of geosciences, Penn State.

Study: Ocean tides once spread massive icebergs

Dec 08, 2004

Connection between changes in ocean circulation and future climate remains a matter of great interest Labrador Sea ocean tides dislodged huge Arctic icebergs thousands of years ago, carrying gigantic ice-rafted debris acr ...

New structure found deep within West Antarctic Ice Sheet

Sep 23, 2004

Ice sheet more susceptible to change than previously thought Scientists have found a remarkable new structure deep within the West Antarctic Ice Sheet which suggests that the whole ice sheet is more susceptible to future ch ...

Recommended for you

NASA's HS3 mission spotlight: The HIRAD instrument

7 hours ago

The Hurricane Imaging Radiometer, known as HIRAD, will fly aboard one of two unmanned Global Hawk aircraft during NASA's Hurricane Severe Storm Sentinel or HS3 mission from Wallops beginning August 26 through ...

Fires in the Northern Territories July 2014

20 hours ago

Environment Canada has issued a high health risk warning for Yellowknife and surrounding area because of heavy smoke in the region due to forest fires. In the image taken by the Aqua satellite, the smoke ...

How much magma is hiding beneath our feet?

21 hours ago

Molten rock (or magma) has a strong influence on our planet and its inhabitants, causing destructive volcanic eruptions and generating some of the giant mineral deposits. Our understanding of these phenomena ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

kivahut
1 / 5 (1) Aug 01, 2011
Yay! I hate glaciers.
Vendicar_Decarian
5 / 5 (1) Aug 01, 2011
Boo. I like drinking water.