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Data on ice loss in the Arctic Ocean can be misleading

barber_ing (Ingressbilde)

Multiyear ice in the Arctic is heavily decayed and shrinking rapidly. Estimates of when we may first experience an ice-free summer in the Arctic Ocean are constantly being revised. These were the key points of Dr David Barber's plenary talk this morning.

"Scientists spend a lot of energy discussing the ‘squiggly line' generated by satellite data on sea ice extent," Dr. Barber told the audience, showing a graph from the National Snow and Ice Data Center. "But extent alone does not reflect the real condition of the sea ice. I think we are all looking forward to getting reliable data on thickness from CryoSat. Because what really matters is the condition and thickness of the multiyear ice."

"We are losing 70 000 square kilometres of sea ice every year. That adds up to 2.5 million square kilometres over the last 30 years. The reality is even worse," continued Dr Barber. "Even though the extent of the sea ice  - both the winter maximum and the summer minimum - increased in 2008 and 2009, the amount of multiyear ice continued to decline rapidly."

Dr. David Barber.Photo: John Petter Reinertsen/ Samfoto
Dr. David Barber.
Appearances can be deceptive
"Last summer we studied sea ice recovery in the Southern Beaufort Sea aboard the research vessel Amundsen. We expected to be stopped at some point by thick multiyear ice, but the Amundsen, only ice classed to break ice 1.2 metres thick, was able to continue at full speed. We realised that the ice was rotten."

Dr Barber and his team saw swells penetrating far into the Beaufort Gyre and breaking up huge ice sheets. Normally, the ice should be too strong for this to happen.

"We also observed that melt pond formation on the multiyear ice had continued all the way through the ice, leaving separate chunks of multiyear ice. When the freeze started, a thin layer - only about 5 cm - of first-year ice formed across the surface, and the combination was mistaken by the radar for multiyear ice." This means that some of the data on the extent of multiyear ice are misleading.

Two ways of knowing

Dr Barber has headed one of the largest IPY projects, the Circumpolar Flaw Lead System Study, involving 370 studies and scientists from 27 nations. The project has been groundbreaking in that traditional Inuit knowledge has been brought together with scientific knowledge. This is the concept of combining "two ways of knowing", as Dr Barber explained.

"To the peoples of the North, climate change is not just a theoretical concept. It directly affects their livelihoods. Often they become the last line of defence for the environment, and we must be cautious when we explore the opportunities the retreating ice gives us to utilise natural resources," said Dr Barber, explaining that there is concern about an "Arctic Gold Rush". "We can come under pressure to produce scientific results that can facilitate the exploitation of natural resources."

Dr Barber explained that sea ice controls heat, light and momentum  in the Arctic. He added that we should take an ecological approach to whole system, "I like to compare the sea ice and tropical rainforests."

Little-known mechanisms

He continued by describing some little-known mechanisms. "We need to look at the sea ice as part of the whole hydrological system. The effect of cyclones varies with the time of year. When they bring snow in cold weather, this insulates the multiyear ice and prevents it from growing as thick during the winter. The winds also bring momentum to the surface, churning it up and delaying ice formation in autumn."

There are also feedback mechanisms we know little about.  "We used to think that sea ice was an impermeable slab that prevented the release of CO2 from the ocean. It turns out that the ice is in fact permeable and there is an active exchange of CO2 between the ocean and the atmosphere."

Last updated: 14.06.2010