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April 8, 2004
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Study results published in Nature
Modelling climate change

By Kristin Harris
SPARK Correspondent

Dr. Richard Rivkin
Dr. Richard Rivkin

Global climate is changing due to the burning of fossil fuels and release of carbon dioxide into the atmosphere, which is of obvious scientific and social concern. Dr. Richard Rivkin, a professor at Memorial’s Ocean Sciences Centre, is concerned with the interactions between the upper ocean and the lower atmosphere as it relates to climate warming. One area of his research, carried out as part of an international research team, was recently published in the journal Nature.

Dr. Rivkin’s project focused on the response of the planktonic community to a large-scale iron enrichment of the ocean surface in the eastern Subarctic Pacific. In the study that was reported in Nature, iron was added along with an inert tracer (SF6) to an eight-kilometre-square patch of ocean and the chemistry and biology of the upper ocean was characterized within the iron-enriched patch for about 30 days. Other members of the research team, including Dr. Moire Wadleigh from the Department of Earth Sciences, studied the atmospheric conditions above and surrounding the patch.

Dr. Rivkin’s team observed phytoplankton growth for the first 15 days in response to the addition of iron. However, unlike previous studies, phytoplankton became limited by the supply of silicon and their biomass in the surface declined and was rapidly remineralized back to carbon dioxide near the ocean surface. According to Dr. Rivkin, “although iron did indeed stimulate phytoplankton growth, this study shows clearly that the very little carbon was exported and iron fertilization did not increase the strength of the biological pump. This observations brings into question the scientific validity of geo-engineering proposals to fertilize large areas of the ocean as a means of sequestering carbon dioxide and slowing the rate of climate warming.”

Dr. Rivkin believes that this study will provide information for climate models that make predictions as to how the future ocean will respond to climate change. Predicted climate changes will result in an increase in sea level, increased storm events, and increased wind events. Models predict that a large percentage of the world’s oceans will receive an increased iron supply, due to aeolian (wind delivery) of iron. He states, “the parameterization of the model may not be so simple, because of the potential variability in the response of the ocean to iron deposition, and because silicon seems to be a secondary nutrient factor.” Dr. Rivkin is also part of a Global Analysis Integration Modelling Task Team, which is working on a Dynamic Green Ocean Model. He hopes they will develop, “a more accurate representation of the ocean’s biological system, so we can make more robust predictions of the ocean’s response to climate change.”

The SOLAS (Surface Ocean Lower Atmosphere Study) project, funded by NSERC and CFCAR, is carrying out several research expeditions in both the Atlantic and the Pacific Oceans. The research team in the Pacific was comprised of scientists from Canada, New Zealand, Japan and the USA. Seven graduate students, post-doctoral fellows and research technicians from Dr. Rivkin’s laboratory participated in this project, the results of which are to be published in several oceanographic journals.


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Next issue: April 29, 2004

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