October 17, 2012
Study Finds Polar Ice Sheet Melt Influenced By Underwater Landscape
Brett Smith for redOrbit.com - Your Universe Online
As average global temperatures rise, climatologists are scrambling to see how this development might affect polar ice sheet melt, which could potentially result in a dangerous rise in sea levels.
In studying the polar ice sheets around Antarctica, a group of British researchers has found that the shape of water channels beneath the ice can have a strong effect on ice behavior, temporarily hiding indications of its retreat.
A report on the group´s findings, which was recently published in the journal Nature Geoscience, showed how the researchers were able to create a groundbreaking model that replicated the activity of an Antarctic ice sheet over a 10,000-year period.
"Our research shows that the physical shape of the channels is a more important factor in controlling ice stability than was previously realized,” said the report´s lead author Stewart Jamieson, from the Department of Geography at Durham University.
“Channel width can have a major effect on ice flow, and determines how fast retreat, and therefore sea-level rise, can happen,” he said.
Jameison added that the landscape beneath the ice sheet can mitigate the melting forces generated by warmer climate and oceanic shifts.
"Our results suggest that during an overall phase of retreat an ice stream can appear almost stable when in fact, in the longer-term, the opposite may be the case,” he said."Getting a clearer picture of the landscape beneath the ice is crucial if future predictions of change in the ice-sheets and sea level are to be improved."
By examining the seafloor in Marguerite Bay, located in the Antarctic Peninsula, the researchers were able to notice a pattern of ice sheet recession that occurred 13,000 years ago, which included several periods where the retreat slowed or paused.
Using a computer model, the team was able to accurately recreate the retreat pattern indicated by the geophysical evidence on the seafloor. The model showed that the ice sheet tended to drag on the sides of the channel where it became narrower, resulting in the slowing or stopping of the ice´s retreat.
The researchers concluded that these bottlenecks in the channels beneath the ice caused this mitigation of the ice melt. These findings are a slight departure from the prevailing theory on ice sheet melt which asserts that the topography of the underlying channels determines the rate at which the ice melts.
"We can see from our simulations and from new maps of the ocean floor that these bottlenecks occur in the same place as pauses or slowdowns in past ice retreat,” said co-author Andreas Vieli, from the Department of Geography at Durham University.
“This means we should look more closely at the shape of the bed underneath Greenland and Antarctica to better understand how ice might retreat in the future,” he said.
"Knowledge of the factors influencing stability and retreat of ice streams is of particular concern because significant portions of the West Antarctic and Greenland ice sheets are currently losing mass that contributes significantly to sea-level rise,” added co-author Claus-Dieter Hillenbrand, from the British Antarctic Survey.
“Our model results help to explain the apparently time-transgressive retreat of ice streams around Antarctica following the last ice age."