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

August 1, 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: New structure found deep within West Antarctic Ice Sheet

Related Stories

New structure found deep within West Antarctic Ice Sheet

September 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 ...

Study: Ocean tides once spread massive icebergs

December 8, 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 across ...

Greenland and Antarctic ice sheet melting, rate unknown

February 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.

Recommended for you

Don't forget plankton in climate change models, says study

November 26, 2015

A new study from the University of Exeter, published in the journal Ecology Letters, found that phytoplankton - microscopic water-borne plants - can rapidly evolve tolerance to elevated water temperatures. Globally, phytoplankton ...


Adjust slider to filter visible comments by rank

Display comments: newest first

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

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.