Warming arctic could teem with life by 2030

Catherine Brahic, New Scientist 8 Jul 09;

"Teeming with life" may not be the description that springs to mind when thinking of the Arctic Ocean, but that could soon change as global warming removes the region's icy lid.

A study of what the Arctic looked like just before dinosaurs were wiped off the planet has provided a glimpse of what could be to come within decades.

Alan Kemp of the UK National Oceanography Centre in Southampton and colleagues used powerful microscopes to inspect cores of mud extracted from the bottom of the Arctic Ocean. They found successive layers of tiny algae called diatoms. The pattern of the layers and the distribution of the diatoms provides strong evidence that the Arctic was free of ice during the summer and, contrary to recent studies, frequently covered in ice during the winter.
Hot summer

Ice-free summers and icy winters are precisely what glaciologists fear could happen in the Arctic within decades. Over the past few years, wind pattern and warm temperatures have been gradually thinning Arctic sea ice, making it less and less likely to survive the summer. Some believe the Arctic could be ice-free during the summer as soon as 2030.

The researchers say that the sheer number of diatoms locked in the mud suggests that when the dinosaurs roamed the Earth the Arctic Ocean was biologically very rich during the summer, on a par with the most productive regions of the Southern Ocean today. Since diatoms are at the very bottom of the food chain, waters rich in diatoms can support a lot of larger life forms as well.

"On the basis of our findings, we can say that it is likely that a future Arctic Ocean free of summer sea ice will also be highly productive," says Kemp. Arctic fauna today is limited by the region's harsh conditions. The ocean is home to very few species of fish – such as the Arctic cod – which in turn support seals, whales and polar bears.
Summer migration

While more diatoms during the summer does not mean that larger animals will spontaneously appear in the Arctic over the coming decades, it could give species that currently live further south an incentive to move into the region by providing them with food. The most likely scenario is one in which larger species migrate to the Arctic in the summer to feed on the enriched summer food chain, then move back south during the dark winters.

"The outcome would depend on organisms at all levels of the food chain moving in to exploit this potential," says Kemp. "What is unpredictable is what species from elsewhere may migrate in to fill the new ecological niches."

A study of fossils and fossilised faeces carried out around Devon Island in the Canadian Arctic, suggested last year that the regions may once have been home to a rich gathering of larger fish and possibly even sharks during the late Cretaceous (Proceedings of the Royal Society B, DOI: 10.1098/rspb.2008.0801). Presumably, these animals would have been supported by Kemp's diatoms.

Journal reference: Nature (DOI: 10.1038/nature08141)