Basin‐Scale Marine Heatwave Types in the Gulf of Mexico: Wind–Humidity Controls on Latent Heat‐Loss Suppression and Ocean‐State Modulation of Vertical Thermal Structure

Abstract Marine heatwaves (MHWs) in the Gulf of Mexico (GoM) have become more frequent and intense, yet the mechanisms governing basin‐scale events remain incompletely understood. EOF–k‐means clustering of event‐mean sea surface temperature anomalies (SSTA) during 1982–2024 identifies four recurrent, seasonally dependent spatial regimes: two stronger, longer cold‐season regimes and two weaker, shorter warm‐season regimes. Despite distinct seasonal occurrence and large‐scale backgrounds, all four types share an onset‐stage regional forcing characterized by near‐surface moistening, weakened winds, suppressed upward latent heat loss, and positive net surface heat input. Latent heat‐loss suppression provides the largest positive surface‐flux contribution (58%–68%) across all types, but its controls vary seasonally: led by humidity‐gradient in cold season types, whereas led by wind‐speed in warm‐season types, with shortwave radiation contributing up to 26% of the positive net surface heat‐flux anomaly. The spatial SSTA pattern is already partly established before formal onset and increasingly resembles the peak pattern as onset approaches, while pre‐onset ocean‐state anomalies show no robust association with additional start‐to‐peak surface amplification. Vertically, inner‐shelf warming extends through much of the shallow water column, whereas outer‐shelf warming is more surface‐intensified; in the deep Gulf, positive‐ and negative‐sea surface height (SSH) regimes are associated with opposing subsurface temperature changes. Together, these results indicate that a common, seasonally modulated atmospheric warming tendency acts on a pre‐existing, spatially structured ocean: antecedent SSTA provides horizontal thermal memory, whereas stratification, bathymetry, and near‐onset SSH state modulate the vertical realization of warming.