Distribution, Seasonality, and Water‐Mass Transformation of Temperature and Salinity Inversions in the Southern Yellow Sea

Abstract

AbstractIn the southern Yellow Sea (SYS) there are temperature and salinity inversions associated with the presence of middepth low temperature and salinity water. Many questions regarding with the inversions, such as the seasonal variation and transformation mechanism, still remain unexplained. In this study, based on hydrographic measurements obtain from 12 cruises within 6‐year (2017–2022), we explored the distribution, seasonality, generation, and transformation mechanism of temperature and salinity inversions in the SYS. Observations reveal widespread temperature and salinity inversions in the Yellow Sea (YS) during both spring and summer. More temperature and salinity inversions are found in spring and summer, respectively. The relative motion between the fresh, cold, high‐dissolved‐oxygen (DO) water at the local shelf/slope and the salty, warm, low‐DO water at the central trough is the key to answering the formation of temperature/salinity inversions. The salinity at the low‐salinity water (LSW) layer increases towards the central YS suggesting the origin of LSW at the local shelf/slope region. Assuming the gain of salinity is caused primarily by vertical diffusion at the upper and lower boundary of the LSW, the propagation speed of the LSW lense is estimated which compares favorably with the magnitude of observed residual currents at the LSW layer. We further note that the depth of subsurface dissolved oxygen maximum agrees well with the LSW layer depth, especially for summer. The influence of the lateral transport of nutrients, and dissolved oxygen on the local biogeochemical environment in the YS is worth further examination.