Vertical Structures of Marine Heatwaves in the South China Sea: Characteristics, Drivers and Impacts on Chlorophyll Concentration

Marine heatwaves (MHWs) are characterized as extreme ocean warming events, which have multifaceted impacts on marine ecosystems. The warming of the ocean associated with MHWs can extend into the deep ocean. In the study, five main types of MHWs in the South China Sea (SCS) are identified with various vertical structures, including shallow, surface-extension-reversed, surface-extension-intensified, deep, and surface-extension-intensified-reversed. Different types of MHWs have different spread patterns and depths. Shallow and surface-extension-reversed MHWs are common in coastal areas, and surface-extension-intensified MHW events often occur in deep areas. The vertical structures of MHWs are affected by ocean dynamical processes, particularly vertical processes and horizontal heat advection. These MHWs can alter ocean chlorophyll concentration to varying degrees and locations, contingent on their vertical thermal profiles. Furthermore, an analysis of the impacts of a long-lived MHW event in the SCS in 2020 revealed that the MHWs could alter chlorophyll concentration. These results help to better understand the physical drivers of localized MHWs and their potential impacts in the context of climate change.