Scientists’ shock at rate of vanishing sea ice
Scientists returning from Antarctica say an ‘‘astonishing’’ lack of sea ice could herald major changes in the marine ecosystems around the icy continent.
An international research team aboard the Niwa vessel Tangaroa spent six weeks installing instruments and carrying out experiments in the Ross Sea to help their understanding of the climate, atmospheric and oceanographic processes in the region and how they influence the marine ecosystem.
But they were shocked at the scarcity of sea ice – with the coverage on the oceans around Antarctica this summer the second lowest since satellite records began back in the 1970s.
The lowest level was recorded last year and, while the pattern does not indicate a trend, scientists say the expected long-term predictions of less ice could trigger huge changes to the marine ecosystem.
Speaking from the Tangaroa after it docked in Wellington yesterday, voyage leader and Niwa marine ecologist Dr David Bowden said: ‘‘We planned this voyage knowing it was late in the season and that we might not be able to get where we wanted to go because of ice, but it has been almost completely ice-free.
‘‘A lot of the ecology of the Ross Sea and the whole of the Antarctic marine system is tied up with ice.
‘‘The animals and plant life in the sea to a greater or lesser extent is all dependent on sea ice, so if we end up with no sea ice it’s going to be a very different ecological system than we have now.’’
One species that is highly dependent on sea ice for survival is krill, a crustacean that forms a key part of the food chain for everything from Adelie penguins and seabirds to whales.
‘‘Less ice, less krill – it will have a knock-on for the rest of the system there,’’ Bowden said.
‘‘There are also animals that are dependent on sea ice for resting. Crab eater seals we know very little about, but in a normal year we would expect to sea a lot of them holed up on ice floes.
‘‘With no sea ice there is less food for them because they feed on krill as well, and there is less habitat generally.
‘‘So there will be changes certainly, but from a single voyage like this all we can do is gather data, which becomes one piece of the jigsaw puzzle.’’
While he could not categorically blame climate change for the loss of coverage, Bowden said more work is needed to understand the impact it has in the polar regions.
During the expedition, the 23-strong team of scientists examined everything from microbial production in plankton to the distributions of seabed fauna, krill and whales, and collected data to help determine whether the objectives of the newly-established Ross Sea marine marine protection area are being achieved.
They also established an experiment to examine the movement of extremely cold water from the Ross Sea towards the tropics that acts as a regulating system on the global circulation of the oceans.
Meanwhile, University of Canterbury researchers have found a catastrophic loss of snow and ice on the Rolleston Glacier in Arthur’s Pass National Park from the extremely hot summer.
Dr Heather Purdie said the glacier had lost nearly all the snow accumulated over the previous year, as well as snow from earlier years.
‘‘This is likely the most negative mass balance year ever recorded on this glacier.
‘‘The only snow left on the Rolleston Glacier was snow that had avalanched down onto the glacier from the surrounding mountain peaks.
‘‘Without this avalanche input, the glacier would have had no snow left at all.’’