Researcher study global warming in Baffin Bay
Are greenhouse gases changing Arctic polynyas?
IQALUIT Marine scientists will sail to an arctic oasis in north Baffin Bay next March to measure the effects of global warming on the Arctic ecosystem.
Among the questions they hope to answer is how polar seas respond to rising levels of atmospheric carbon dioxide, a so-called greenhouse gas.
Canadian researchers are leading the three-year study of the North Water Polynya, considered to be one of the most fertile oceanic regions north of the Arctic Circle.
“This production is possible because it’s open water at a time when everywhere else in the Arctic is under ice cover,” Dr. Christine Michel, a marine biologist with Université de Laval in Quebec City said. “So it is very important from a biological point of view.”
Arctic polynyas serve as feeding, mating, spawning and overwintering grounds for many species of marine birds and mammals. Fish also thrive in these vast expanses of open water, thanks to an abundance of microscopic organisms known as plankton.
The North Water Polynya, hemmed in by Ellesmere and Baffin islands and Greenland, stretches south of Devon Island in January and reaches Bylot Island in June.
“What we know already from previous experiments is that it’s a very productive area in the Arctic,” Michel said.
Polynyas increase in size with global warming
Some scientists predict that polynyas will grow in size and frequency if average global temperatures continue to rise, as they have during the last 50 years.
But exactly how the arctic ecosystem will respond to global warming is not fully understood.
The study, which recieved major funding from Canada’s Natural Sciences and Engineering Research Council, began with an expedition to the North Water Polynya last summer.
Researchers spent several weeks setting up hydrographic instruments which they will use to measure sea currents, salinity, temperature and tides.
“We want to know what are the physical processes that keep the polynya open during the winter,” explained Michel, the study’s co-ordinator.
Using Sir John Franklin
In the second expedition, scheduled to begin in March, 1998, scientists from Canada and seven other countries will spend four months working and living onboard the Canadian Coast Guard icebreaker, the Sir John Franklin.
A wide range of experiments and biological sampling are planned.
Some researchers will look at fish and birds and seals; others will turn their microscopes to much tinier life forms.
Michel herself plans to examine the life-cycle of phytoplankton, in part to estimate the role polynyas play in regulating greenhouse gases associated with global warming.
Phytoplankton essential to food chain
Phytoplankton are microscopic algae that bloom in the arctic sunshine under the ice cover, converting light into food through a process known as photosynthesis. All aquatic food chains depend on them.
“They are very important primary producers in arctic regions,” Michel said.
They may also keep greenhouse gases in check, since inorganic carbon dioxide is incorporated by phytoplankton, and, through photosynthesis, converted into organic matter.
Some scientists speculate that an increase in the absorption of carbon dioxide by phytoplankton could, ultimately, lower global temperatures.
“All organisms produce carbon and there is a transfer of this carbon from one step in the food chain to another, through eating,” Michel said.
Dead and digested organic material tends to sink to the ocean floor, taking the carbon along with it.
“This flux of carbon to the bottom might be very important to regulate the carbon in the atmosphere, because when it goes from the atmosphere to the ocean then sinks to the bottom, it will not go back to the atmosphere,” Michel said.
“So it’s a way to regulate the increase in CO(2) in the atmosphere.”
To this end, sediment traps have been moored to the sea bottom to collect particles sinking from the upper depths. The traps will be reinstalled next summer, to provide a complete two-year record.
In the North Water Polynya, Michel plans to study a species of phytoplankton known as diatoms.
Though individual organisms only range in size from about 10 to 50 one-thousandths of a millimetre in length, diatoms are a critical link in the arctic ecosystem, providing food for animal organisms known as zooplankton, upon which, in turn, fish larvae feed.
A team of scientists led by Dr. Ian Stirling from Environment Canada is also using the expedition to test samples of fish, seals and birds in the polynya for the presence of contaminants.