Mark Henderson, Science Editor
A new global warming threat to the fragile marine ecosystems of Antarctica has been identified, with the discovery that an increasing number of icebergs are tearing up the sea floor and destroying any life in their way.
The shallow habitats of species such as giant sea spiders, Antarctic worms, sea urchins and corals are facing a growing risk from icebergs, according to research that shows more bergs are floating freely in coastal waters as temperatures rise.
While these near-shore ecosystems have always been pounded by icebergs, crushing the animals and plants that live there, the rate of destruction is increasing as a warmer climate shrinks the winter sea ice that would otherwise lock the bergs in, scientists said. The retreat of coastal glaciers and the collapse of floating ice shelves also mean that more bergs are being shed into the sea, adding to the likelihood of scouring.
The findings, from a team from the British Antarctic Survey (BAS), indicate that the ecological risks of climate change go farther than those posed by rising ocean temperatures.
The findings, from a team from the British Antarctic Survey (BAS), indicate that the ecological risks of climate change go farther than those posed by rising ocean temperatures.
Iceberg scour is a natural phenomenon, and while it is destructive on a local level it often adds to broader biodiversity by clearing spaces for new life to populate. Scientists, however, are concerned that a substantial increase in the rate of scouring could have unpredictable consequences, creating swaths of shallow water in which organisms with longer life-cycles cannot become established. "The whole balance of the ecosystem could be affected, with consequences that are very difficult to predict," said Dan Smale, who led the study.
"The focus of research has all been on rising temperatures, but what has been overlooked is that it isn't just warming of the water that changes the structure of the ecosystem. The distribution of species is likely to be just as important, and that is going to be affected by iceberg scour."
The research, published in the journal Science , has been dedicated to Kirsty Brown, who died in 2003 while conducting fieldwork at the BAS's Rothera Research Station on the Antarctic Peninsula. Ms Brown, 28, who drowned when she was attacked by a leopard seal while snorkling, is named posthumously as one of the authors.
The study was conducted over five years at South Cove, on the Antarctic Peninsula, where temperatures are warming more quickly than anywhere else on the planet, by half a degree celsius each decade. This has led to the collapse of part of the Wilkins Ice Shelf in March, and to the loss of seven other floating shelves over the past 30 years.
The BAS team analysed the effects of these trends on iceberg scour by placing grids of small concrete markers on the seabed, at depths of 5, 10 and 15 metres. These were checked by divers for disturbances caused by iceberg strikes.
Dr Smale said that because sea ice was predicted to shrink further under the impact of global warming, iceberg strike rate was expected to increase.
