17 July, 2008 Press releases

Antarctic worms, sea spiders, urchins and other marine creatures living in near-shore shallow habitats are regularly pounded by icebergs. New data suggests this environment along the Antarctic Peninsula is going to get hit more frequently. This is due to an increase in the number of icebergs scouring the seabed as a result of shrinking winter sea ice. The results are published this week in the journal Science.

Scientists from the British Antarctic Survey (BAS) show how the rate of iceberg scouring on the West Antarctic Peninsula seabed is affected by the duration of winter sea ice, which has dramatically declined (in space and time) in the region over the last few decades due to climate warming. This increase in iceberg disturbance on the seabed, where the majority of all Antarctic life occurs (80%), could have severe effects on the marine creatures living as deep as 500m underwater.

Lead author, Dr Dan Smale from BAS, says:

“It has been suggested previously that iceberg disturbance rates may be controlled by the formation of winter sea ice, but nobody’s been able to go out and measure it before. We were surprised to see how strong the relationship between the two factors is. During years with a long sea ice season of eight months or so, the disturbance rates were really low, whereas in poor sea ice years the seabed was pounded by ice for most of the year. This is because icebergs are locked into position by winter sea ice, so they are not free to get pushed around by winds and tides until they crash into the seabed.”

By using grids of small concrete markers on the seabed at three different depths for five years, BAS SCUBA divers were able to determine the frequency of iceberg scour by counting the number of damaged or destroyed markers annually.

Ice disturbance has been recognised as a driving force in the structure of the Antarctic seabed animal communities. Iceberg scouring damages areas of the seabed creating space for a high diversity of animals to use. However, an increase in iceberg scour with the seabed would affect the type and number of marine creatures found on the seabed and may cause changes in the distributions of key species.

Issued by the British Antarctic Survey Press Office

Athena Dinar, Tel: +44 (0)1223 221414; mobile: 07740 822229 email: amdi@bas.ac.uk

Linda Capper, Tel: ++44 (0) 1223 221448; mobile: 07714 233744 email: lmca@bas.ac.uk

Notes for Editors

Pictures (stills and video) are available from the BAS Press Office as above. These include spectacular photos of marine animals and underwater film sequences of icebergs and divers.

Ice scour disturbance in Antarctic waters by Dan A. Smale, Kirsty M. Brown, David K. A. Barnes, Keiron P. P. Fraser and Andrew Clarke is published in Science.

Author Contacts:

Dr Dan Smale, British Antarctic Survey. Email: dasma@bas.ac.uk mobile: +44 (0)7779 342129.

Dr David Barnes, British Antarctic Survey. Tel: +44 (0)1223 221613; email: dkab@bas.ac.uk

This is a posthumous publication for marine biologist Kirsty Brown who died tragically during fieldwork in the Antarctic in 2003.

Iceberg
An iceberg is a large piece of freshwater ice that has broken off from a snow-formed glacier or ice shelf and is floating in open water.Many factors influence the probability of an iceberg impacting on an area of seabed. These include depth, seabed topography, proximity to an iceberg source, wind direction and tidal regimes.

The Antarctic Peninsula is an area of rapid climate change and has warmed faster than anywhere else in the Southern Hemisphere over the past half century. Climate records from the west coast of the Antarctic Peninsula show that air temperatures in this region have risen by nearly 3°C during the last 50 years — several times the global average and only matched in Alaska.

The Cambridge-based British Antarctic Survey (BAS) is a world leader in research into global environmental issues. With an annual budget of around £45 million, five Antarctic Research Stations, two Royal Research Ships and five aircraft BAS undertakes an interdisciplinary research programme and plays an active and influential role in Antarctic affairs. BAS has joint research projects with over 40 UK universities and has more than 120 national and international collaborations. It is a component of the Natural Environment Research Council.