The seasonal cycle of meridional heat transport at 24°N in the North Pacific and in the global ocean



[1] An improved estimate of the Kuroshio transport and its seasonal variation derived from the World Ocean Circulation Experiment (WOCE) moored current meter array east of Taiwan (referred to as PCM-1) is combined with various wind products and available hydrographic data in the ocean interior to determine the meridional heat transport at 24°N in the North Pacific. The resulting seasonal cycle of meridional heat transport has a minimum heat flux of ∼0 PW in January and February and a broad maximum in the second half of the year, with a peak of 1.1 PW in July and a secondary maximum of 1.0 PW in November. The annual mean heat transport is 0.62 PW, with an uncertainty of 0.2 PW. Of the total heat transport, 0.37 PW is associated with the “overturning” circulation, and 0.25 PW is contributed by the horizontal “gyre” circulation. The Parallel Ocean Program (POP) model simulation of the meridional heat flux at 24°N compares favorably with the observations with regard to both the seasonal variation and the annual mean value. The vertical and horizontal cells are found to contribute about 3/5 and 2/5 of the total heat transport, respectively, and they are confined in the upper ocean on the annual mean and longer timescales. However, for the seasonal variation the vertical cell dominates the variation and involves circulation changes through the entire water column, while the horizontal cell heat flux remains nearly constant year-round. The new estimate of meridional ocean heat flux across 24°N in the Pacific is combined with an updated estimate in the Atlantic at this latitude to yield a total oceanic heat flux across the latitude circle of 24°N of 2.1 ± 0.4 PW, with an annual cycle that ranges from 1.1 PW in February to 2.8 PW in August. This is the first such estimate of the seasonal cycle of the world ocean heat flux across 24°N from direct oceanographic observations.