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Research
Atmospheric and hydrospheric sciences
202011202011
Future dynamic sea level change in the western subtropical North Pacific associated with ocean heat uptake and heat redistribution by ocean circulation under global warming
Suzuki T, Tatebe H
Sea level, global warming, heat uptake, North Pacific
Thermosteric sea level change (cm) due to the added heat TA (ΔηTA) in the faf-heat experiment and in the case when the area to which the application of heat flux is limited to (b) the subtropical gyre region (4°N–38°N, 100°E–100°W), (c) the subpolar gyre region (38°N–64°N, 100°E–100°W), (d) the southern part of the subtropical gyre (4°N–20°N, 130°E–130°W), and (e) the area excluding the Kuroshio and the Kuroshio Extension recirculation (20°N–35°N,120°E–160°E) for MIROC5.2. Note that the basin average in the North Pacific is subtracted at each grid. The numbers on each figure show the basin average of the North Pacific (NP mean) and the area average of the deviation in the Kuroshio Extension recirculation (KR mean). Contours indicate the climatological DSL in piControl. The solid boxes indicate the area given by heat flux perturbation (b, c), and the dotted box indicates the area excluding the heat flux perturbation (e).
In the present study, the relative importance of ocean heat uptake and heat redistribution on future sea level changes in the western North Pacific has been reconciled based on a set of climate model experiments in which anomalous surface fluxes of wind stress, heat, and freshwater in a warmed climate are separately given to those fluxes in a pre-industrial control simulation. Our findings suggest that the basin-wide ocean heat uptake and resultant heat accumulation by the climatological-mean advection are required to explain the future dynamic sea level (DSL) rise in the western subtropical North Pacific caused by the thermal expansion of subtropical mode water (STMW). At the same time, it has been recognized that the localized heat uptake in association with the wintertime mixed-layer formation around the Kuroshio Extension can be solely attributed to the future STMW change. The thermally induced component is a dominant contribution to the future DSL rise in the western subtropical North Pacific compared to the contributions of wind-induced and halosteric components, which, especially the former, have been reported as a dominant factor resulting from a linear response of the ocean to the northward shift and strengthening of the mid-latitude westerly over the North Pacific in a warmed climate.
