ProvenanceUnderlying image was public domain image from
http://commons.wikimedia.org/wiki/File:Ocean_currents_1943_Gulf_Stream.jpg
Who got it from:
Section of Ocean Currents and Sea Ice from Atlas of World Maps, United States Army Service Forces, Army Specialized Training Division. Army Service Forces Manual M-101 (1943).
Kim Kastens added red arrow showing net transport of energy from tropics to poles.