Evolution Study of the Qingdao Cold Water Mass

The Qingdao Cold Water Mass (QCWM), located in the offshore waters near the Shandong Peninsula, exhibits notable seasonal variability and plays a crucial role in shaping hydrological conditions due to its distinct temperature and salinity structures. This study investigates the evolution of the QCWM in 2014 using cruise observations and the hydrodynamic model FVCOM. The potential evolution mechanisms of QCWM are analyzed, and Lagrangian particle experiments are conducted to explore the source and destination of the QCWM.

The QCWM in 2014 prevails below 20 m near the coast of the Shandong Peninsula. It emerges in April, stabilizes in May, and dissipates by June. Momentum analysis reveals that the anticyclonic circulation near the QCWM area, along with the weakness of the pressure gradient force, including both barotropic and baroclinic components, facilitates the formation and maintenance of the QCWM in spring. The emergence of the Yellow Sea Cold Water Mass (YSCWM) and the frontal circulation at the edges of the YSCWM on the eastern side of the QCWM in late spring, combined with the enhanced westward baroclinic force, destabilizes the QCWM and promotes its dissipation.

A series of Lagrangian particle tracking experiments suggest that the bottom water of the QCWM primarily originates from the local cold waters off the southeastern coast of the Shandong Peninsula. The bottom cold water in the QCWM dissipates locally rather than merging into the YSCWM. Tidal effects may further accelerate this dissipation by enhancing vertical mixing and intensifying the frontal circulation at the edges of the YSCWM.