Yamamoto-Kawai, McLaughlin, Carmack, Science 326, Climate change causing 'corrosive' water to affect Arctic marine life

Climate change causing 'corrosive' water to affect Arctic marine life

by Margaret Munro, Canwest News Service, November 19, 2009 -- 

[hat tip to Steve Church]

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.

The remarkable retreat and thinning of the Arctic sea ice has had an even more pronounced impact on the carbonate levels, the team reports. Sea ice contains extremely low levels of the compound, which is squeezed out of the ice as it crystallizes. And melting ice has generated huge volumes of low-carbonate water, diluting and reducing the concentration of the shell-building compound in the top 50 m of water, which are normally the most productive.

McLaughlin recalls how in the late 1980s, the impenetrable ice pack confined the scientists and their icebreaker, CCGS Louis St. Laurent, to the southern Beaufort. In recent summers they have been able to cruise through open water hundreds of kilometres north into the Canada Basin. "It's great for science and being able to explore," she says. "But jeepers, I did not expect in my lifetime for this to occur."

The ice retreat has also led to a third process putting the ecosystem at risk. Winds now howl across open waters once covered by pack ice, and storms can carry deep water up onto the shallow continental shelf in the southern Beaufort, the researchers report. Like melted sea-ice, these deep waters are low in shell-building carbonate.

The corrosive waters are now confined to the Arctic, but they're expected to start flowing into the North Atlantic in about 10 years. "Water doesn't stay in the Arctic forever," says McLaughlin.

She says the findings underscore the urgent need to slow climate change. "What this is saying is that we have to control CO2 emissions," says McLaughlin. "That's the only way that we can stop processes such as acidification of the oceans."

The impact on the ecosystem is not fully understood, but the low carbonate levels now common to the surface waters have been shown by other researchers to dissolve and pit the shells of marine organisms.

The Science report says shell-forming plankton and shellfish in the Arctic are likely already affected. It points to a tiny Arctic pteropod, or sea butterfly, as an important link in the food web. Its larvae normally concentrate in the top 50 m where the changes have been "most profound."

The report is based on measurements taken between 1997 and 2008 by McLaughlin, Michiyo Yamamoto-Kawai and Eddy Carmack at the Federal Institute of Ocean Sciences near Victoria. Thousands of water samples were taken on research cruises on CCGS Louis St. Laurent that covered a huge area about 1,000 km across.

Researchers are now increasing the sampling area in collaboration with Japanese scientists exploring more northern waters. Preliminary results for 2009 show that surface waters low in carbonate are expanding and the scientists expect the levels to keep dropping until multi-year ice melts away completely. Forecasters predict the Arctic could be ice-free in summer by 2030, if not before.

Link to above article:  http://www2.canada.com/topics/technology/science/story.html?id=2242554

Link to abstract from primary source article:  http://climatechangepsychology.blogspot.com/2009/11/m-yamamoto-kawai-et-al-science-326.html