Antarctic ecosystem:The march of the penguins is well under way, a forced relocation as a result of climate change, writes Dick Ahlstrom, Science Editor, in San Francisco.
Warming on the Antarctic peninsula is causing a move southwards to keep up with the availability of food.
Alterations to the Antarctic ecosystem due to a warming climate were discussed in a session of the American Association for the Advancement of Science annual meeting, which opened yesterday in San Francisco.
Details of the research were also released yesterday in ScienceExpress, the online version of Science. The key new findings relate to the complex water system that flows beneath the massive ice sheet that covers Antarctica, an elaborate plumbing system that is far more extensive than scientists had realised.
The fear is that changes in this plumbing system caused by climate change could speed up sea level rise.
Yet the climate-related change in Antarctica that will strike a chord with most people relates to the gradual displacement of penguin populations along the Antarctic peninsula. The warming trend there established over the past few decades has already forced penguin populations to migrate south, said Dr Berry Lyons, professor in the School of Earth Sciences and director of the Byrd Polar Research Centre at Ohio State University.
"Researchers are seeing the movement of penguin populations southward down the peninsula as sea ice lessens along its margins," Dr Lyons stated.
"Gentoo and chinstrap penguins are shifting south into areas now populated by adelie penguins, and the adelies are being forced further south, all because of the change in sea ice." The loss of ice has also seen a decline in the availability of krill, a foundation of the Antarctic's food web. This will reduce resources for higher mammals and birds.
The scientists at the meeting were excited by the first analysis of the huge lakes which underlie parts of the Antarctic ice sheet. A full 90 per cent of the world's ice is located in Antarctica, and scientists watch in particular for any climate change-driven alteration to this ice and its potential to cause dramatic sea level rise.
The research describes massive lakes lying underneath two fast-moving rivers of ice, each about one kilometre thick, that carry ice away from the land mass of Antarctica to feed the ice shelves floating on the oceans around the coastline.
The assumption is that the underlying water helps speed along the movement of the ice streams into the sea, making it essential to understand the complex dynamic involved.
"We have found that there are substantial subglacial lakes under ice that's moving a couple of metres per day. It is really ripping along," stated, Dr Robert Bindshadler of Nasa Goddard Space Flight Centre, one of the co-authors of the study.
"It is the fast-moving ice that determines how the ice sheet responds to climate change on a short timescale. We aren't yet able to predict what these ice streams are going to do."
The new findings were made possible by precise elevation measurements taken from Nasa's Ice, Cloud and Land Elevation Satellite (ICESat) from 2003 to 2006 collected over the Whilans and Mercer ice streams in west Antarctica. The streams could be up to 50km wide and two kilometres thick and stretch for hundreds of kilometres back onto the continent.
The presence of the water beneath the streams has been known for some time, but the ICESat has allowed the system to be measured with an accuracy down to a few centimetres.
One of the subglacial lakes measures 10km by 30km and it discharged about two cubic kilometres of water into the ocean in less than three years.
Lead author of the study is Dr Helen Fricker of the University of California San Diego's Scripps Institution of Oceanography and co-authors include Dr Ted Scambos of the National Snow and Ice Data Centre, and Laurie Padman of Earth & Space Research.