The Arctic Ocean warms from below

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°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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