Interannual-to-interdecadal variability of the Yellow Sea Cold Water Mass in 1967–2008: Characteristics and seasonal forcings

We identified characteristics of interannual-to-interdecadal variability of the Yellow Sea Cold Water Mass and examined mechanisms to generate variability using the Korea Oceanographic Data Center dataset. Regional/background variables (sea level pressure (SLP), surface air temperature (SAT), and sea surface temperature (SST)) and five climate indices were used to explore the linkage to seasonally-differential forcings. The first EOF mode (53%) represents warming/cooling over the entire bottom cold water with the dominant periods of 2–7 and 10–20 years. Three cold and two warm events occur in 1967–2008. The variability preliminarily attributes to previous winter surface forcings; however, summer surface forcings intensify bottom cold water temperature anomaly (BWTa) induced in the previous winter and also trigger a new anomaly, especially in the cold event after 1996. Cold events relate to the winter forcing (strengthening of the Siberian High, the Aleutian Low, East Asian Jet Stream, Pacific Decadal Oscillation, and Arctic Oscillation) and the summer forcing (increased SLP in the Asian continent and the Aleutian Islands and increased SST in the Kuroshio and the Alaskan Current). In both seasons, SST and SAT anomalies on the tropical to subtropical western North Pacific are strongly correlated to BWTa; however, mechanisms are different.

Research highlights
► Examine interannual-to-interdecadal variability in a three-dimensional view.
► Explain spatio-temporal relationship between upper layer and bottom cold water.
► Discover Seasonal forcing to drive the variability comprehensively.
► Reveal both concurrent and delayed connections to the climate factors.
► A new scenario using summer forcings for the variability of the bottom cold water.