Heat transport variation due to change of North Pacific subtropical gyre interior flow during 1993-2012

Nagano, A, Kizu S, Hanawa K, Roemmich D.  2016.  Heat transport variation due to change of North Pacific subtropical gyre interior flow during 1993-2012. Ocean Dynamics. 66:1637-1649.

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2000s, AGEM, ARGO, cycle intensification, Heat transport, North Pacific subtropical gyre interior flow, ocean, Quasi-decadal timescale variation, sippican, t-7, transport-weighted temperature, tsk, variability, volume, XBT


Applying segment-wise altimetry-based gravest empirical mode method to expendable bathythermograph temperature, Argo salinity, and altimetric sea surface height data in March, June, and November from San Francisco to near Japan (30(ay) N, 145(ay) E) via Honolulu, we estimated the component of the heat transport variation caused by change in the southward interior geostrophic flow of the North Pacific subtropical gyre in the top 700 m layer during 1993-2012. The volume transport-weighted temperature (T (I)) is strongly dependent on the season. The anomaly of T (I) from the mean seasonal variation, whose standard deviation is 0.14(ay)C, was revealed to be caused mainly by change in the volume transport in a potential density layer of 25.0-25.5 sigma (oee integral) . The anomaly of T (I) was observed to vary on a decadal or shorter, i.e., quasi-decadal (QD), timescale. The QD-scale variation of T (I) had peaks in 1998 and 2007, equivalent to the reduction in the net heat transport by 6 and 10 TW, respectively, approximately 1 year before those of sea surface temperature (SST) in the warm pool region, east of the Philippines. This suggests that variation in T (I) affects the warm pool SST through modification of the heat balance owing to the entrainment of southward transported water into the mixed layer.