Friday, April 6, 2012

New paper finds Arctic Ocean warming is from geothermal heat

A paper published today in Geophysical Research Letters titled "The Arctic Ocean warms from below" finds that geothermal heat at the bottom of the Arctic Ocean caused slight warming of 0.004C per year from 1993-2010. The authors find a temperature inversion with higher temperatures at the bottom of the ocean than the interior, which indicates the heat had to arise from geothermal sources; the opposite temperature profile would be expected if the Arctic Ocean was heating from above due to greenhouse gases. Other than the fact that heat rises, the paper throws more water on Trenberth's claim that his 'missing heat' allegedly from greenhouse gases has sunken to the bottom of the ocean.

Key Points
  • The deep water is warming at a measurable rate of ~ 0.0004 {degree sign}C yr-1
  • This heating is not escaping along the basin perimeter
  • A greater fraction of the heat escapes vertically than previously thought
Eddy C Carmack
William James Williams
Sarah Zimmermann
Fiona A. McLaughlin
The old (~450-year isolation age) and near-homogenous deep waters of the Canada Basin (CBDW), that are found below ~2700 m, warmed at a rate of ~0.0004 {degree sign}C yr-1 between 1993 and 2010. This rate is slightly less than expected from the reported geothermal heat flux (Fg ~ 50 mW m-2). A deep temperature minimum Tmin layer overlies CBDW within the basin and is also warming at approximately the same rate, suggesting that some geothermal heat escapes vertically through a multi-stepped, ~300-m-thick deep transitional layer. Double diffusive convection and thermobaric instabilities are identified as possible mechanisms governing this vertical heat transfer. The CBDW found above the lower continental slope of the deep basin maintains higher temperatures than those in the basin interior, consistent with geothermal heat being distributed through a shallower water column, and suggests that heat from the basin interior does not diffuse laterally and escape at the edges.

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