Sea surface temperature (SST) in the Indonesian Seas drives atmospheric deep convection, influencing regional and global climate. Yet, the processes controlling SST in this region remain poorly understood. Using a high‐resolution regional model that explicitly resolves internal tides, we show that tidal displacements lift cold thermocline water into the surface ocean, exposing it to vigorous surface mixing and thus enhancing the surface‐interior heat exchange. The heat exchange facilitated by tides shows strong seasonality, intensifying during monsoons in areas where the mixed layer is deep and the thermocline is shallow. This tidal exposure mechanism augments, with comparable impact, the mixing driven by internal tide breaking in the interior. However, it dominates the tidal impacts for the vertical heat exchange in the upper ocean. This novel pathway for vertical heat exchange must be represented in coarse‐resolution climate models to improve simulations of SST and air–sea interactions in the region.
A large share of energy within the global oceans lies within the mesoscale range, (100 km), where very large dynamic and thermodynamic variability has been observed. We address how the marine atmospheric boundary layer (MABL) in a trade‐wind region adapts to fast and spatially varying sea‐surface temperature (SST) structures, with a focus on changes in behaviour as a function of spatial scales. High‐resolution atmospheric simulation data indicate that, at scales smaller than 1000 km, the effects of enhanced entrainment of dry free tropospheric air overcome those of surface evaporation over warm SST anomalies. This is supported by computations from a conceptual bulk model, which confirm two different responses in MABL temperature and specific humidity: an increase in the forcing SST warms the MABL and reduces its humidity content slightly. Locally, this behaviour suppresses the surface sensible heat flux (SHF) and enhances the surface latent heat flux (LHF), as observed recently with in situ, satellite, and numerical modelling data. At larger scales, instead, the MABL is more in equilibrium with the ocean surface and the sensitivity of turbulent fluxes to the underlying SST anomalies is significantly smaller. The scale dependence of the LHF variability is analysed with a linear scale decomposition method. SST is found to be the primary driver of LHF variability when scales smaller than about 1000 km are resolved, whereas atmospheric variability takes the lead for larger scales. Despite the effects on the mean LHF being small, the link between SST and LHF variability potentially has important implications for atmospheric shallow mesoscale circulations, which remain to be explored.
Alessandro Storer, M. Borgnino, C. Pasquero et al.· Quarterly Journal of the Roy...· 0 citations
Marine heatwaves (MHWs) are increasing in frequency and intensity in global boundary current systems such as the Gulf Stream (GS), where ocean circulation regulates upper‐ocean heat and water‐mass properties. We examine temperature–salinity co‐evolution during MHWs in the Northwest (NW) Atlantic using satellite observations and ocean reanalysis for 2012–2023. Applying a consistent threshold‐based framework to sea surface temperature and sea surface salinity (SSS), we identify co‐occurring MHWs and salinity extremes and evaluate their spatial extent and vertical structure. Results reveal a statistically significant high‐salinity imprint during MHWs along the GS North wall and shelf‐break corridor, consistent with advection of warm, saline GS waters preconditioning the upper ocean for vertically extensive warming. Low‐SSS extremes tend to cover greater area on the continental shelf, where surface freshening likely favors shallow, surface‐intensified MHWs. These results underscore SSS as a critical diagnostic for advective water‐mass influence and stratification during MHWs in the NW Atlantic.
Natalie Stamper, Ganesh Gopalakrishnan, B. Subrahmanyam· Geophysical Research Letters· 0 citations
Marine heatwaves (MHWs) are persistent extreme warm events in the ocean that pose substantial threats to marine ecosystems, fisheries, aquaculture, and offshore energy infrastructure. In 2024, the Yellow Sea experienced the most intense MHW on record in terms of cumulative intensity, with sea surface temperature (SST) anomalies exceeding 5 °C and an exceptional duration of 118 days. Using the ERA5 atmospheric reanalysis and GLORYS12V1 ocean reanalysis, this study systematically investigates the characteristics, driving mechanisms, and extremity of this event. Mixed-layer heat budget analysis indicates that enhanced shortwave radiation was the primary contributor to the warming, which is closely linked to the westward-extending and northward-shifting subtropical high. During MHW decay, sea surface cooling is dominated by enhanced latent heat flux, closely linked to typhoon and cold air activities. Further analysis links the positive SST anomalies to the North Atlantic and the Barents Sea warming, which triggered a Eurasian teleconnection wave train. These results highlight the importance of cross-basin climate connectivity in driving regional maritime temperature extremes.
Aimei Wang, Dong Wang, Jingxin Luo et al.· Journal of Marine Science an...· 0 citations
Many coupled climate models exhibit an Intertropical Convergence Zone (ITCZ) south of the Equator in the annual‐mean tropical Pacific that is more pronounced than observed. This bias impacts winds, wind‐driven ocean circulation, including the meridional subtropical cells, and the zonal distribution of waters supplying the equatorial thermocline. To explore the impact of these biases, we compare particle pathways from a double‐ITCZ‐biased coupled climate simulation with those from an ocean simulation forced by atmospheric reanalysis. In the forced ocean simulation, Southern Hemisphere (SH) subducted waters travel directly to the equator in the Central and Eastern Pacific. In the coupled simulation, surface winds associated with the South Pacific Convergence Zone intensify the SH subsurface meridional potential vorticity gradient, blocking and diverting interior flow to western boundary currents. These circulation changes are accompanied by modifications of subducted water potential densities, altering equatorial water mass properties and potentially the simulation of decadal climate variability.
Cassia Cai, Matthew T. Luongo, A. Deppenmeier et al.· Geophysical Research Letters· 0 citations
Abstract. Global shelf seas have experienced unprecedented marine heatwaves (MHWs) in recent decades. Although MHWs have been extensively studied at the global scale, their regional variability and underlying mechanisms remain poorly understood, particularly in shelf seas influenced by multiple climate modes. Here, we examine MHW variability in the Northeastern Atlantic shelf using a correlation-based k-means clustering approach. Two distinct subregions with contrasting seasonal patterns are identified. In winter, the southern North Sea experiences increased MHW frequency, intensity, and duration. This enhancement is linked to a positive East Atlantic Pattern, which intensifies westerly winds and enhances warm Atlantic inflow through both atmospheric and oceanic pathways. In contrast, the northern North Sea shows enhanced MHW frequency and duration in summer, while MHW intensity weakens. This summer response is modulated by Atlantic Multidecadal Variability, with its positive phase strengthening Pacific–Atlantic connections via Rossby wave propagation, altering cloud cover and surface radiative forcing. A shallow mixed layer, enhanced stratification, and circulation-induced upwelling favor frequent and persistent but less intense summer MHWs. This north–south contrast demonstrates that different combinations of atmospheric and oceanic processes shape MHW variability across the shelf, providing a diagnostic and mechanistic framework for understanding regional MHW variability and its potential predictability.
Mesoscale eddies in the Southern Ocean extend from the surface to the deep ocean and contribute to regional and global ocean heat budgets. However, sparse in situ observations have limited estimates of eddy meridional heat transport (EMHT) to the near surface, leaving deep-ocean processes poorly understood. Here we quantify deep eddy kinetic energy (EKE) and EMHT using Argo observations. We find that deep EMHT reaches at least the same order of magnitude as surface transport, despite deep EKE being only one-fifth of surface levels. Float observations and sensitivity experiments reveal that, relative to mean-flow transport alone, deep EMHT extends the meridional movement of subtropical warm waters towards Antarctica by over ten degrees of latitude. About 60% of this deep transport originates from the Indian Ocean sector. These findings provide observational evidence that mesoscale eddies can modulate deep Southern Ocean heat redistribution, with potential implications for Antarctic climate.
Tongya Liu, Xiaoming Zhai, Qingyou He et al.· Nature Communications· 0 citations