RESEARCH HIGHLIGHT

Climate Change Clues under the Arctic Sea Ice

September 1, 2004

Carbon is the fourth most abundant element in the Universe and is the building block of life. It is the element that anchors all organic substance, from fossil fuels to DNA. Carbon cycles through the land, ocean, atmosphere, and the Earth's interior, mostly in form of CO₂ (carbon dioxide). Nearly all forms of life on Earth depend on the production of sugars, from solar energy and carbon dioxide (photosynthesis) and the metabolism (respiration) of those sugars, to produce the chemical energy that makes growth and reproduction possible.

Carbon dioxide in the atmosphere has been steadily rising, since regular measurements began in 1958, and this tends to warm the earth's surface (greenhouse effect) and change the climate. Climate changes in the Northern Hemisphere have resulted in shrinking sea-ice cover in the summer, increasing time between sea-ice break-up and freeze-up, warming of the Arctic surface, and thawing of permafrost areas. These are all changes that can have an affect on the environment as well as human activity.

Understanding the carbon cycle, the exchange of CO₂ between the atmosphere, ocean and land, is very important because marine (ocean) and terrestrial (land) environments are currently absorbing about half of the CO₂ from fossil-fuel combustion. Until recently, the role of the Arctic Ocean in this CO₂ balance was ignored, as it was thought that sea-ice blocked gas exchange with the atmosphere.

IARC researchers recognize the importance of the carbon cycle in the arctic environment, and are measuring the CO₂ levels near Point Barrow of onshore and offshore wind on fast ice, which is coastal ice or ice attached to a stationary object. They are also measuring pCO₂ (the partial pressure of dissolved CO₂) in sea-ice and under-ice water. To obtain this data, a scientific group led by Dr. Igor Semiletov uses modern instruments and equipment, including a CO₂ tower (Fig.1) that measures CO₂ exchange between the air and sea ice, and a fiber optic sensor that measures pCO₂ pressure in water. Their results have been surprising. They found that the Arctic Ocean sea-ice is an active participant in the CO₂ gas exchange.

They also noticed that concentrations of CO₂ under the sea are different in the spring-summer and fall-winter. Data gathered between February and March, 2003, showed a drastic decline in the level of pCO₂, which may be a result of early marine photosynthesis just after polar sunrise. During these months, the Arctic Ocean may be a significant and uncounted sink of atmospheric CO₂, whereas, in the fall-winter, it can be a source. The data from this research is also important for future use in computer simulations called climate models, which can project climate changes.

CO2 tower on the fast ice near Point Barrow. (Photo by I.Semiletov)

Similar studies are taking place on the Antarctic pack ice by the University de Liege in Belgium. Studying both th Arctic and Southern Oceans can help create a clearer picture of how to predict changes in CO₂ balance and global changes that may result and the broader impacts on society.

The study of CO₂ in arctic sea ice is a very important component in the study of the carbon cycle. In this Arctic "climate kitchen," IARC researchers work to determine the impacts of change in sea ice melt and seasonal length, and their interconnection with other ecological processes on Earth. Their research will help to answer questions about what is taking place both above and below the sea ice. Since carbon is part of every living thing, studying the carbon cycle is important not only for climate researchers, but for ecologists, biologists, and all of us.