Japan Geoscience Union Meeting 2024

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[J] Oral

A (Atmospheric and Hydrospheric Sciences ) » A-CG Complex & General

[A-CG44] Kuroshio Large Meander

Wed. May 29, 2024 9:00 AM - 10:15 AM 106 (International Conference Hall, Makuhari Messe)

convener:Hatsumi Nishikawa(Japan Agency for Marine-Earth Science and Technology), Hidetaka Hirata(Rissho University), Norihisa Usui(Meteorological Research Institute), KUSAKA AKIRA(National Research and Development Agency, Japan Fisheries Research and Education Agency. Fisheries Resources Institute), Chairperson:Hatsumi Nishikawa(Atmosphere and Ocean Research Institute, University of Tokyo), Hidetaka Hirata(Rissho University), Norihisa Usui(Meteorological Research Institute), KUSAKA AKIRA(National Research and Development Agency, Japan Fisheries Research and Education Agency. Fisheries Resources Institute)

9:45 AM - 10:00 AM

[ACG44-04] Interannual variability of wintertime sea surface heat flux in the Northwest Pacific

*Haruto Fujishima1, Fumiaki Kobashi1, Naoto Iwasaka1 (1.Tokyo University of Marine Science and Technology)

Keywords:Kuroshio Large Meander, Kuroshio Extension, Air-Sea interaction, Heat flux, Sea Surface Temperature

In the Kuroshio-Oyashio Confluence region, where the warm Kuroshio from the south meets the cold Oyashio from the north, the East Asian winter monsoon cools the ocean surface, resulting in significant heat transfer to the atmosphere. Traditionally, mid-latitude oceanic heat release has been attributed to atmospheric variations accompanied with sea surface winds. However, recent arguments suggest that sea surface temperature (SST) plays a primary role in this confluence region. Moreover, the northward shifts and stabilization of the Kuroshio Extension (KE), associated with the Kuroshio Large Meander (KLM) since August 2017, have led to high SSTs offshore northeastern Japan and a reduction in the Oyashio surface area. These changes may have significant impacts on ocean-atmosphere heat transport in the Northwest Pacific. Therefore, this study focuses on turbulent heat flux (THF) in the upstream region of the KE (142-155°E) during winter (DJF) and investigates their variability and its mechanism from 1993 to 2022. Analyzing satellite data, we observed a significant increase in THF and SST in the KE axis region after the extreme northward shift of the KE in 2020. Analysis of SST and horizontal current velocity along the Kuroshio axis off the Boso Peninsula, indicates an increase in the velocity and temperature since around 2019. This suggests that the intensification and warming of the Kuroshio have led to substantial increase in heat release to the atmosphere in the KE region. However, significant increases are not observed in the KOC region or in the KE southern regions. Additionally, the presentation will discuss the relationship between these variables, THF and SST, and atmospheric circulation in the Northwest Pacific, including the influence of fluctuations in the Aleutian Low and jet streams.