Marine Matters

How Global Warming Caused Cooling: Dynamic Effects of Thermohaline Circulation

John T. Brosnan III
School of Natural Resources and Environment, University of Michigan, 430 E. University, Ann Arbor, MI 48109-1115;


The currents of the world's oceans form an interconnected conveyor belt known as thermohaline circulation (THC). This belt has its beginnings in the North Atlantic where highly salinized deep-water is formed. This process has been proven to be highly sensitive to temperature changes and fresh-water influxes. THC has a direct impact on the world's climate, and any alteration of North Atlantic deep-water formation can bring about rapid changes in the Earth's mean atmospheric temperatures, and vice versa. Increasing atmospheric carbon dioxide (CO2)(from anthropogenic sources) is highly correlated to greater mean global temperatures, as the Intergovernmental Panel on Climate Change (IPCC) states an increase of 1 C over the past 90 years. Studies have shown increases in CO2 will lead to increases in global temperature and a breakdown of THC. This, in turn, will result in both the decreased ability of the ocean to naturally cycle CO2 and rapid localized climate changes. Findings of these recent studies include abrupt cooling over northwestern Europe, and implicate a positive feedback between increasing CO2 and global climate change. These alterations to the current system will inevitably affects all forms of life on the planet, and could mean disaster for a variety of plant and animal species, both terrestrial and aquatic.

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