[A-OS12] Ocean Science Revealed by Global Observation System

[AOS12-P05] Observed abyssal temperature variability modulated by mesoscale eddies

*Shuya Wang¹, Yusaku Ohta^1,2, Motoyuki Kido³, Fumiaki Tomita^1,3, Ryota Hino² (1.Advanced Institute for Marine Ecosystem Change (WPI-AIMEC), Tohoku University, 2.Graduate School of Science, Tohoku University, 3.International Research Institute of Disaster Science (IRIDeS), Tohoku University)

Keywords:Ocean bottom temperature, Mesoscale eddy

The ocean bottom temperature (OBT) in the Kuril Trench was collected by temperature sensors at three stations on the seafloor for nearly two years, where the water depth is over 7000 m. The observational results indicate low-frequency variability of the OBT with a period longer than one month. Combining the analysis on grided altimetry products, we find that the 60-day lowpassed OBT anomaly shows good consistency with the 60-day lowpassed sea level anomaly (SLA). Specifically, the large positive OBT anomaly is found as an anticyclonic mesoscale eddy stays around the observational stations. Such a long-lived eddy could induce downwelling through isopycnal depression, which is preliminarily evidenced by field CTD observations along the A-line across the eddy. Additionally, the lag correlation between the bandpassed OBT and SLA with a period of 30-60 days is high when the eddy center gets close to the observational sites. Fluctuations of OBT in this band are likely caused by topographic Rossby waves, which are triggered by the interaction between the anticyclonic eddy and the continental slope west of the Kuril Trench. Our results demonstrate the important role of mesoscale eddies in modulating the variability in the abyssal ocean.