Meeting Documents

Global Anomalous Water Mass Budgets for Marine Heatwaves in ECCOv4r4

Abstract

Marine heatwaves (MHWs) and their impacts are emerging as a critical research frontier in the context of global warming. Previous studies have largely attributed the mechanisms of MHWs using mixed-layer heat budgets, yet such approaches face limitations in linking total heat content changes to underlying diabatic and adiabatic thermodynamic processes, and they cannot readily be extended to the subsurface interior ocean. As an alternative, water mass analysis provides a powerful framework to quantify the roles of surface fluxes, advection, and mixing in shaping warm water variability. One difficulty is that existing implementations are restricted to absolute temperature budgets, while MHW detection is often based on temperature anomalies relative to a seasonal climatology.

In this study, we develop a novel theoretical framework for anomalous water mass transformation budgets that directly addresses the evolution of temperature anomalies associated with MHWs. Leveraging the physically consistent and perfectly closed budgets of the ECCOv4r4 state estimate, we then quantify the diabatic and adiabatic drivers of anomalously warm water masses during MHW events globally. Our results demonstrate that the anomalous water mass budget provides new mechanistic insights into the formation and decay of MHWs, bridging the gap between process-based heat budget studies and event-based anomaly analysis.