Understanding Subsurface Marine Heatwaves

Seminar by Shujing Zhang from University of Tasmania

02 July 2024
KST 14:00 – 15:00

The Seminar is being held in Room 1010 (Jasmin) – Integrated mechanical engineering building. Click here for the campus map.

Marine heatwaves (MHWs), the prolonged extreme ocean warming events, occur not only at the ocean surface but also extensively in the global subsurface ocean. In the subsurface, as depths increase, the influence of air-sea fluxes diminishes, and oceanic processes become more significant. Given the lack of a heat source in the ocean interior and the presence of complex subsurface ocean processes, two main questions about the causes of subsurface MHWs arise: where does the heat of subsurface MHWs come from, and how do ocean processes drive subsurface extreme temperature changes? To investigate these questions, we implemented a spice-heave framework to analyze observed subsurface MHWs in the upper 2000m of the ocean since 2004. By examining temperature and salinity changes along isobars and isopycnals, we differentiated temperature changes due to water-mass property changes (“spice”) from changes due to the dynamic movement of isopycnals (“heave”). Through a seasonal synthesized analysis of spice and heave, we identified various potential dominant ocean processes driving local subsurface MHWs at different layers in the upper 2000m of the ocean. To explore the different regional drivers for subsurface MHWs, we applied the framework to several MHW hotspots in different ocean dynamical zones, including the northeast Pacific, eastern equatorial Pacific, East Australian Current extension, and Antarctic Circumpolar Current regions.