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Finding the balance
Science cruise makes strides in studying sea ice ecosystem and its role in global climate processes
Posted December 13, 2007
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One of the key thrusts of the International Polar Year (IPY) is to study the roles the Arctic and Antarctic play in climate change on a global scale.
One of the main components of that interchange is sea ice. In the Arctic, the disappearing ice cover due to warming conditions has garnered considerable attention, partly because of the threat to polar bears. In the Antarctic, the sea ice is no less complex an ecosystem, with perhaps even more complicated questions to answer.
A two-month science cruise aboard the Research Vessel Icebreaker Nathaniel B. Palmer called Sea Ice Mass Balance in the Antarctic (SIMBA) set out in September to characterize an area of that vast ecosystem off the coast of West Antarctica.
A major IPY project, SIMBA joined American and Belgian scientists on an expedition to obtain information about sea ice thickness, its extent and physical and biogeochemical properties in an effort to understand how it evolves and decays. Another key goal was to characterize the interchange between the ocean, atmosphere and the ice.
Other work on the cruise included collecting data on physical oceanography and studying the biological component of this seemingly inhospitable environment.
Photo Credit: Sarah Anderson/PolarTREC
Members of SIMBA take ice cores from the safety of a crane basket.
“One of the things we have to understand about Antarctic sea ice is that it is a major ecosystem,” said Steve Ackley, principal investigator for the project. A professor at the Department of Geological Sciences at the University of Texas San Antonio, Ackley is interested in not only the physics of ice, but also its relationship to the entire ecosystem.
“The interactions between the physics and the biology, while we may attempt to divide these up at the funding level [for individual projects], are not divided up at the fundamental level. The properties of the sea ice are intimately linked in with the biology,” he explained
Sea ice 101Seasonal sea ice nearly doubles the size of Antarctica during the austral winter, and shrinks away by millions of square kilometers during the summer. It is important for a number of reasons, not least of which being a habitat for all manner of critters — from sea algae to shrimp-like krill to penguins and seals.
Sea ice also does its part to help regulate planetary temperatures in various ways. Freezing squeezes the salt out as the water solidifies. The dense and cold, salty water sinks, becoming part of a deep-ocean circulation system that distributes heat around the world. A disruption in this process could decrease the ocean’s ability to absorb carbon dioxide, a greenhouse gas.
The ice also reflects solar radiation much more effectively than open water. When sea ice disappears, solar energy reflected by the ice instead warms the upper ocean. A warmer ocean leads to less ice, which exposes more water, and so on, to create a feedback loop. This is the story currently unfolding in the Arctic.
Noted Ackley, “The relationships between ecosystem, climate and sea ice are no less important in the Antarctic than they are in the Arctic.”