Scientists have uncovered a large expanse of "corrosive" water in the Canadian Arctic that is putting the marine food web at risk.

The waters have been so altered by climate change and melting sea ice that plankton, shellfish and fish may have trouble building their protective shells and skeletons, an international team reports Friday in the journal Science.

The oceanographers have documented a "rapid" drop in the levels of carbonate, a compound used to produce shells and bones, in the top 50 metres of the surface waters of the Beaufort Sea and more northerly Canada Basin over the last decade. The levels are now so low the water is at "corrosive" levels and they warn the "Arctic ecosystem may be risk."

"In actual fact, they'll dissolve the shells," says co-author, Fiona McLaughlin, a research scientist with Fisheries and Oceans Canada.

The Arctic marine system has been hit by what McLaughlin describes as a "triple whammy" - acidification of sea water, stunning rates of ice melt, and upwelling from the deep ocean.

The first is related to the way the world's oceans are growing more acidic because they soak up about a third of the carbon dioxide pumped into the atmosphere through the burning of fossil fuels. The CO2 makes sea water more acidic and decreases the availability of carbonate, which could be potentially catastrophic to marine ecosystems.

McLaughlin says in the Arctic, this acidification process is happening faster than in southern regions because cold water absorbs more CO2 than warm water.

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