2:00 PM - 2:15 PM
[AOS21-02] Interannual variations of temperature and salinity in the Soya Warm Current region over the past 40 years
Keywords:Soya Warm Current, Sea of Okhotsk, Interannual variations, Global warming
The Soya Warm Current (SWC) flows into the Okhotsk Sea through the Soya Strait. The SWC supplies heat and salt into the Okhotsk Sea. Hydrological climatology in this region has been developed in several studies (Itoh and Ohshima, 2000; Ohshima et al., 2017). However, the long-term variations of temperature and salinity in the SWC region have not been investigated.
In this study, we created the updated monthly climatology of temperature and salinity based on accumulated observational data and a new mapping method by Mensah and Ohshima (2023). Using this climatology, we estimated the long-term variations of hydrography in the southwestern part of the Okhotsk Sea, influenced both by the SWC and sea ice. We defined the SWC region as the coastal area whose bottom depth is shallower than 120 m. According to the timeseries of the anomalies, the temperature, salinity, and volume transport are positively correlated with each other, suggesting that these variations originate from the inflow of the SWC. Regarding the long-term variations, the significant warming trend of 1.5 ℃ is identified in the SWC region over the period of 1980-2023. This warming trend was most pronounced at 30 m depth, which suggests that the warming is not due to local interaction with atmosphere but due to the change in the origin water from the Japan Sea. In fact, the timeseries of temperature in the SWC region is correlated with the sea surface temperature in the coastal area of the Japan Sea. Apart from the warming trend in the SWC region, surface layer salinity just offshore of the SWC has decreased mainly in autumn. This salinity decrease suggests changes in the discharge of the Amur River and in the southward current along the Sakhalin shelf.
In this study, we created the updated monthly climatology of temperature and salinity based on accumulated observational data and a new mapping method by Mensah and Ohshima (2023). Using this climatology, we estimated the long-term variations of hydrography in the southwestern part of the Okhotsk Sea, influenced both by the SWC and sea ice. We defined the SWC region as the coastal area whose bottom depth is shallower than 120 m. According to the timeseries of the anomalies, the temperature, salinity, and volume transport are positively correlated with each other, suggesting that these variations originate from the inflow of the SWC. Regarding the long-term variations, the significant warming trend of 1.5 ℃ is identified in the SWC region over the period of 1980-2023. This warming trend was most pronounced at 30 m depth, which suggests that the warming is not due to local interaction with atmosphere but due to the change in the origin water from the Japan Sea. In fact, the timeseries of temperature in the SWC region is correlated with the sea surface temperature in the coastal area of the Japan Sea. Apart from the warming trend in the SWC region, surface layer salinity just offshore of the SWC has decreased mainly in autumn. This salinity decrease suggests changes in the discharge of the Amur River and in the southward current along the Sakhalin shelf.