Interannual-decadal variations in the Yellow Sea cold water mass in summer during 1958–2016 using an eddy-resolving hindcast simulation based on OFES2

In the Yellow Sea, a large volume of cold water with temperature below 10 °C exists in the bottom layer in summer and affects the regional circulation, climate and marine ecosystem. Here, we investigated in detail the interannual-decadal variations in the summer Yellow Sea Cold Water Mass (YSCWM) using six decades (1958–2016) of a quasi-global eddy-resolving hindcast simulation, which was validated with observations. Results indicated that volume and mean temperature of the YSCWM were 0.52×1012–4.10 × 1012 m3 (2.22 × 1012 m3 on average) and 8.53–9.32 °C (8.94 °C on average). The YSCWM was dominated by interannual-decadal variations with a weakly warming and shrinking trend. The YSCWM volume (mean temperature) had larger (smaller) average values and varied more significantly during the two periods of 1958–1988 and 2005–2016 than during 1989–2004. Interannual-decadal variations in the summer YSCWM agreed with those in February temperature in the Yellow Sea, which were primarily caused by net surface heat flux variations, with a minor but negative contribution from heat exchange with the East China Sea through the northward Yellow Sea warm current and southward coastal currents. Winter net surface heat flux variations were dominated by latent heat flux and sensible heat flux, both of which resulted from combined effects of the Siberia High, Western Pacific pattern and Arctic Oscillation through controlling sea surface wind speed and air temperature over the Yellow Sea. The current study provided a more complete picture and in-depth understanding of changes in the summer YSCWM responding to large-scale climate change and variabilities during the past six decades.