High-Resolution Observations Unveil (Sub)Mesoscale Heat Fluxes Shaping Upper-Ocean Heat Content

Abstract

Upper-ocean heat content (UOHC) regulates air–sea exchange and tropical cyclone intensification; however, its variability at (sub)mesoscale remains insufficiently resolved. Here we combine Surface Water and Ocean Topography (SWOT) observations with high-resolution glider sections in the northeastern tropical Pacific to quantify (sub)mesoscale heat exchange mechanisms. Glider observations reveal large UOHC biases in NOAA-ATBD operational products, arising from climatology errors and unresolved (sub)mesoscale variability. Sharp frontal areas exhibit intense vertical heat exchange driven by ageostrophic circulations, Ekman forcing, and enhanced mixing, with magnitudes comparable to air–sea fluxes. These upward heat pathways rapidly connect thermocline anomalies to the surface layer and modulate the warm-core structure of mesoscale anticyclones, thereby regulating the thermal reservoir available for tropical cyclone intensification. Our results demonstrate that resolving (sub)mesoscale frontal dynamics and associated vertical advection is essential for better constraining UOHC, a key input for cyclone-intensity forecasting.

Affiliated Institutions

• Laboratoire de l'Atmosphère et des Cyclones RE
• Center for Scientific Research and Higher Education at Ensenada MX
• Aix-Marseille Université FR
• Laboratoire d’Études en Géophysique et Océanographie Spatiales FR

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