[A-OS15] Physical Oceanography (General)

[AOS15-P05] Temporal Variability of Meridional Heat Transport and Ekman Heat Transport in the North Pacific Ocean

*Yukina Fukaumi¹, Kazuyuki Uehara¹ (1.The Graduate School of Science and Technology of Tokai University)

Keywords:heat transport, Ekman transport, North Pacific Ocean

Recently, it reported that the temperature of the western boundary current is increasing at 2-3 times faster than the warming rate of the global ocean (Lixin Wu, 2012). This was suggested by the enhancement of the subtropical western boundary current. In this study, we focus on the Kuroshio Current, which is the western boundary current of the North Pacific subtropical circulation. The heat transport in the ocean by the geostrophic currents and the Ekman heat transport are discussed. The data used were ARMOR3D, a 3D global temperature and salinity data set based on satellite and in-situ observations provided by CMEMS; and JRA55-do, a sea surface ocean model based on JRA55 provided by the Japan Meteorological Agency. The mean net northward volume transport from 0 m to 2000 m on a 25°N for the period 1993-2020 was 52.5 Sv, and the mean northward heat transport was 1.2 PW. The mean net northward Ekman transport over the same latitudinal cross section for the period 1993-2017 was 6.0 Sv, and the mean net northward heat transport was 0.6 PW. The volume transport in the ocean interior due to geostrophic currents is about nine times greater than the Ekman volume transport, while the heat transport is about twice as great. Therefore, it is necessary to discuss ocean heat transport in both the ocean interior and the Ekman layer. Ekman heat transport decreased from 0.8 PW to 0.5 PW from 2012-2014. During the same period, the Ekman transport decreased from 8 Sv to 5 Sv, suggesting that the weakening of the Ekman transport was accompanied by a weakening of the Ekman heat transport. In contrast, the heat transport in the ocean interior increased from 0.8 PW to 1.6 PW and volume transport increased from 40 Sv to 65 Sv. This suggests that, in addition to the enhanced transport in the ocean interior, the increased temperature in the ocean interior also enhanced heat transport. These indicate that the increase and decrease were reversed between the oceanic interior and the Ekman layer during the same period. At the time of our presentation, we plan to discussu the heat transport valiability in the ocean interior and in the Ekman layer in detail.