Meridional Overturning Circulation in the Indian Ocean: Toward the understanding of multi decadal variability in climate

2022 Fiscal Year Final Research Report

• Project/Area Number: 18K03750
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17020:Atmospheric and hydrospheric sciences-related
• Research Institution: Japan Agency for Marine-Earth Science and Technology
• Principal Investigator: Nagura Motoki 国立研究開発法人海洋研究開発機構, 地球環境部門(大気海洋相互作用研究センター), 主任研究員 (10421877)
• Project Period (FY): 2018-04-01 – 2023-03-31
• Keywords: インド洋 / 循環 / 波動 / 水塊

Outline of Final Research Achievements

This study examined various phenomena such as temperature and salinity variations in water masses, temporal variations in a basin-wide circulation, and waves on intraseasonal to interannual timescales near the equator and at southern midlatitudes in the Indian Ocean. This study uses the most of devices available in this field, i.e., in-situ observations from Argo profiling floats and a current profiler, satellite measurements of sea surface height, an ocean dataset that assimilates these observations, a simple ocean model, and a sophisticated ocean general circulation model. The phenomena were specified and described using observations. Their causes and generation mechanisms were identified by numerical experiments. The predictability of the detected phenomena was discussed using simple numerical experiments.

Free Research Field

海洋物理

Academic Significance and Societal Importance of the Research Achievements

研究によって得られた成果から、水塊の沈み込みを通じた海洋による熱の取り込み、インド洋の循環と太平洋の風系変動の関連、インド洋の亜表層の流れの変動、亜表層を伝播する波動、オーストラリア沿岸の海面高度変動の予測可能性、赤道波の成因を明らかにした。これらの現象は海洋内部の貯熱量や循環による熱輸送、およびそれらの経年的な変化に関わっている。研究成果から特定された時間スケールは経年から十年規模であり（周期が7~15年程度）、これらの周期の気候変動の理解に貢献すると考えられる。