Estimation of deep-water formation intensity using multi-satellite measurements in the East Sea (Japan sea)

Deep-water formation (DWF) in the East Sea (Japan Sea) can affect the regional meridional overturning circulation via air–sea interactions. Thus, it is important to monitor long-term changes to understand the future regional climate and, thus, marine ecosystem changes associated with DWF. In this study, we propose a new DWF estimation method based on satellite measurements rather than on sparse in situ measurements. First, we estimated the volume of the mixed water (VMW) as a proxy for the intensity of the DWF based on the HYbrid Coordinate Ocean Model (HYCOM) data and examined the VMW signals in satellite measurements of the chlorophyll-a (Chl-a) concentrations and sea-level anomalies (SLA) from January to March for 21 years (1998–2018). When the DWF was intense in the East Sea, Chl-a and SLA decreased. This inverse relationship between the DWF and sea-surface features was much clearer during strong DWF years than during weak DWF years. The decreasing rates of Chl-a and SLA over strong DWF years were −0.0044 mg m−3 and −0.0020 m day−1, respectively. Furthermore, we estimated the VMW from the SLA and Chl-a using a multi-linear regression. These findings will allow us to understand the intensity of the DWF through VMW using multi-satellite measurements alone.