Under the right meteorological conditions, whales can leave a trail of cool spots on the ocean surface that are detectable in infrared images. When the wind is light and the sun is shining, the surface water warms to produce a thermal gradient in the top few meters of the ocean. Under these conditions, whales swimming near the surface produce a jet of cooler water with each upward motion of the tail fluke. When this jet reaches the surface, it will produce a temperature difference that can persist for several minutes. In this paper, we report the first observations of these thermal footprints; we discovered them in infrared images made by a camera mounted in a light twin-engine airplane. We also describe their formation and dissipation.

Churnside, J., L. Ostrovsky, and T. Veenstra. 2009. Thermal footprints of whales. Oceanography 22(1):206–209, https://doi.org/10.5670/oceanog.2009.20.

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