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Although observational efforts have been made to detect submesoscale currents (submesoscales) in regions with deep mixed layers and/or strong mesoscale kinetic energy (KE), there have been no long-term submesoscale observations in subtropical gyres, which are characterized by moderate values of both mixed layer depths and mesoscale KE. To explore submesoscale dynamics in this oceanic regime, two nested mesoscale- and submesoscale-resolving mooring arrays were deployed in the northwestern Pacific subtropical countercurrent region during 2017–19. Based on the 2 years of data, submesoscales featuring order one Rossby numbers, large vertical velocities (with magnitude of 10–50 m day −1 ) and vertical heat flux, and strong ageostrophic KE are revealed in the upper 150 m. Although most of the submesoscales are surface intensified, they are found to penetrate far beneath the mixed layer. They are most energetic during strong mesoscale strain periods in the winter–spring season but are generally weak in the summer–autumn season. Energetics analysis suggests that the submesoscales receive KE from potential energy release but lose a portion of it through inverse cascade. Because this KE sink is smaller than the source term, a forward cascade must occur to balance the submesoscale KE budget, for which symmetric instability may be a candidate mechanism. By synthesizing observations and theories, we argue that the submesoscales are generated through a combination of baroclinic instability in the upper mixed and transitional layers and mesoscale strain-induced frontogenesis, among which the former should play a more dominant role in their final generation stage.

Submesoscale processes (submesoscales) play a crucial role in vertical tracer transport, which are typically stronger in winter than summer. However, recent studies revealed enhanced submesoscale activities following tropical cyclones (TCs) during summer months, though their characteristics, mechanisms, and dynamical impacts remain obscure. Through combining high‐resolution satellite and simulation data, we demonstrate that energetic submesoscales are present within TC‐induced cold wakes across the northwestern Pacific, which can produce strong upward vertical heat flux (VHF) in the upper ocean. Further analysis reveals that submesoscales are more active in stronger cold wakes induced by slower‐moving and stronger TCs and they may be generated through a combination of baroclinic instability and strain‐induced frontogenesis. Crucially, submesoscale VHF can accelerate the post‐TC temperature recovery of cold wakes which may influence the sequential TC intensification. Our results improve the understanding of TC‐ocean feedback and underscore the necessity of resolving or parameterizing submesoscales in TC prediction models. Plain Language Summary Oceanic submesoscale processes with horizontal scales of O(0.1–10) km are key drivers of vertical tracer transport such as heat and nutrients. While these processes are typically more energetic in winter, recent observations show that they can also intensify during summer following tropical cyclones (TCs). Using high‐resolution satellite data and simulations, we found that strong submesoscale processes occurred within cold wakes left behind by TCs in the northwestern Pacific. These submesoscale processes generate intense upward heat transport and are particularly pronounced in strong cold wakes caused by powerful and slow‐moving TCs. They are likely generated by a combination of baroclinic instability and frontogenesis in the cold wakes. Importantly, the upward heat transport caused by submesoscale processes helps warm the cold wakes faster after a TC passes, potentially affecting how rapidly later TCs intensify over the same area. Our findings advance the understanding of how TCs interact with submesoscale processes and highlight the need to include submesoscale dynamics in TC prediction models to improve forecast accuracy. Key Points Submesoscales are ubiquitously observed within tropical cyclone (TC)‐induced cold wakes TC‐triggered submesoscales generate intense vertical heat fluxes (VHFs) in the upper ocean Submesoscale VHFs accelerate the temperature recovery of cold wakes

Ocean microstructure measurements collected during three austral summers (2023–2025) along the Antarctic continental slope off Dronning Maud Land show enhanced subsurface mixing. Mean turbulent dissipation between 100 and 800 m depth is an order of magnitude higher than in the open ocean, with an extreme event reaching 3×10−6$3\\times 1{0}^{-6}$W kg−1${\\text{kg}}^{-1}$at mid‐depth. Elevated dissipation coincides with peaks in vertical velocity shear during periods of strong tidal acceleration associated with spring‐tide flow reversals. Enhanced continental slope mixing drives a mean upward heat flux of 3 W m−2${\\mathrm{m}}^{-2}$into the base of cold surface waters, in agreement with independent estimates from an internal tide model. Combined with reanalysis data, the model suggests tidal mixing along the Antarctic continental slope could produce a circumpolar mean vertical heat flux of 9 W m−2${\\mathrm{m}}^{-2}$ . This upward heat transport may warm the upper ocean and limit sea ice formation around Antarctica.

Oceanic motions across meso‐, submeso‐, and turbulent scales play distinct roles in vertical heat transport (VHT) between the ocean's surface and its interior. While it is commonly understood that during summertime the enhanced stratification due to increased solar radiation typically results in an reduced upper‐ocean vertical exchange, our study reveals a significant upward VHT associated with submesoscale fronts (<30 km) through high‐resolution observations in the eddy‐active South China Sea. The observation‐based VHT reaches ∼100 W m−2 and extends to ∼150 m deep at the fronts between eddies. Combined with microstructure observations, this study demonstrates that mixing process can only partly offset the strong upward VHT by inducing a downward heat flux of 0.5–10 W m−2. Thus, the submesoscale‐associated VHT is effectively heating the subsurface layer. These findings offer a quantitative perspective on the scale‐dependent nature of VHT, with crucial implications for the climate system. Plain Language Summary Understanding the upper‐ocean heat budget is of great importance for gaining insight into how oceanic processes modulate the climate system, yet vertical heat transport (VHT) by submesoscale processes remains rarely studied using observations. Recently, scientists have identified the potential importance of submesoscale instabilities to enhance upward VHT within the mixed layer. However, the vertical pathways of heat from the ocean interior to the surface and the underlying mechanisms remain unclear, largely due to the limitations in observing such small, fast scales. To elucidate these questions, we conducted high‐resolution (a horizontal resolution of ∼0.6 km), synoptic in‐situ observations targeted at submesoscale phenomena near mesoscale eddies. Our study reveals substantial contributions of submesoscale processes to upward VHT in the stratified subsurface layer. This causes a notable imbalance in VHT by mesoscale, submesoscale, and mixing processes. These findings provide valuable insights for enhancing our understanding of heat uptake in the ocean. Key Points Quasi‐synoptic submesoscale‐resolving observations reveal strong upward vertical heat transport (VHT) in the ocean interior (over nearly 10x the mixed layer depth (MLD)) Submesoscale fronts (<30 km) between eddies act as the primary driver for enhanced vertical heat transport >100 W m−2 There is a significant imbalance in VHT associated with oceanic mesoscale, submesoscale, and mixing processes

High‐resolution simulations reveal that summer monsoon‐induced upwelling in the western Arabian Sea triggers vigorous submesoscale vertical heat flux (SVHF), challenging the conventional view of winter‐dominant submesoscale activity in open‐ocean settings. This intense SVHF, arising from monsoon‐amplified frontal gradients and submesoscale instabilities, transports heat upward more efficiently than mesoscale eddies and substantially strengthens a mesoscale positive feedback loop linking upwelling, isopycnal tilting, baroclinic eddy growth, and mesoscale vertical heat transport. The submesoscale reinforcement not only boosts vertical heat exchange but also prolongs the persistence and intensity of the feedback loop under strong monsoonal forcing and a forward cascade of kinetic energy. These findings unveil a previously unrecognized multiscale mechanism likely occurring in coastal upwelling systems and underscore the critical role of submesoscale‐mesoscale coupling in shaping vertical heat redistribution.

Submesoscale eddies (those smaller than 50 km) are ubiquitous throughout the ocean, as revealed by satellite infrared images. Diagnosing their impact on ocean energetics from observations remains a challenge. This study analyzes a turbulent field of submesoscale eddies using airborne observations of surface currents and sea surface temperature, with high spatial resolution, collected during the S‐MODE experiment in October 2022. Assuming surface current divergence and temperature are homogeneous down to 30 m depth, we show that more than 80% of the upward vertical heat fluxes, reaching ∼${\\sim} $ 227 W m−2${\\mathrm{m}}^{-2}$ , is explained by the smallest resolved eddies, with a size smaller than 15 km. This result emphasizes the contribution of small‐scale eddies, poorly represented in numerical models, to the ocean heat budget and, therefore, to the climate system. Plain Language Summary Vertical heat transport is a key mechanism that regulates ocean heat storage and, therefore, the Earth's climate. Using airborne observations with very high spatial resolution, the present study shows that the upward vertical heat fluxes explained by ocean submesoscales smaller than 15 km are greater than those due to larger eddies. This highlights the contribution of small oceanic scales, poorly resolved in previous studies, to the Earth's climate system. Key Points Airborne observations reveal the contribution of coherent submesoscale eddies to ocean turbulence Phase relationship between SST and divergence at submesoscale leads to upward vertical heat fluxes A large part of the upward vertical heat fluxes is principally explained by eddies with a size smaller than 15 km

The interior flux of a giant planet impacts atmospheric motion, and the atmosphere dictates the interior’s cooling. Here we use a non-hydrostatic general circulation model (Simulating Non-hydrostatic Atmospheres on Planets) coupled with a multi-stream multi-scattering radiative module (High-performance Atmospheric Radiation Package) to simulate the weather impacts on the heat flow of hot Jupiters. We found that the vertical heat flux is primarily transported by convection in the lower atmosphere and regulated by dynamics and radiation in the overlying radiation-circulation zone. The temperature inversion occurs on the dayside and reduces the upward radiative flux. The atmospheric dynamics relay the vertical heat transport until the radiation becomes efficient in the upper atmosphere. The cooling flux increases with atmospheric drag due to increased day–night contrast and spatial inhomogeneity. The temperature dependence of the infrared opacity greatly amplifies the opacity inhomogeneity. Although atmospheric circulation could transport heat downward in a narrow region above the radiative-convective boundary, the opacity inhomogeneity effect overcomes the dynamical effect and leads to a larger overall interior cooling than the local simulations with the same interior entropy and stellar flux. The enhancement depends critically on the equilibrium temperature, drag, and atmospheric opacity. In a strong-drag atmosphere hotter than 1600 K, a significant inhomogeneity effect in three-dimensional (3D) models can boost interior cooling several-fold compared to the 1D radiative-convective equilibrium models. This study confirms the analytical argument of the inhomogeneity effect in the companion papers by Zhang. It highlights the importance of using 3D atmospheric models in understanding the inflation mechanisms of hot Jupiters and giant planet evolution in general.

The occurrence of a period of slowdown in surface air temperature increase from 1998 to 2013 despite continued greenhouse gas emissions (the warming hiatus) has suggested that ocean heat uptake (OHU) is susceptible to decadal variability. Here, we identify mechanisms that lead to decadal changes in OHU to revisit the origin of the warming hiatus. Sensitivities of the vertical heat flux were calculated with the adjoint of the MITgcm ocean model to describe atmospheric forcing patterns that most effectively modulate OHU. By projecting historical atmospheric anomalies onto these sensitivity patterns, we quantified the contributions by different forcing, regions, and time‐periods. The impact of various climate modes on changes in OHU through multiple linear regression analysis revealed that the excessive OHU during the hiatus period is primarily governed by in‐phase uptake modulation by the El Niño Southern Oscillation and Atlantic Multidecadal Oscillation variability.

Experimental closure of the surface energy balance during convective periods is a long-standing problem. With experimental data from the Idealized horizontal Planar Array experiment for Quantifying Surface heterogeneity, the terms of the temperature-tendency equation are computed, with an emphasis on the total derivative. The experiment occurred at the Surface Layer Turbulence and Environmental Science Test facility at the U.S. Army Dugway Proving Ground during the summer of 2019. The experimental layout contained an array of 21 flux stations over a 1 km2 grid. Sensible heat fluxes show high spatial variability, with maximum variability occurring during convective periods. Maximum variability in the vertical heat flux is 50–80 W m-2 (median variability of 40%), while in the horizontal flux, it is 200–500 W m-2 (median variability of 48% for the streamwise and 40% for the spanwise fluxes). Ensemble averages computed during convective afternoon periods show large magnitudes of horizontal advection (48 W m-3 or 172 K h-1) and vertical flux divergence (13 W m-3 or 47 K h-1). Probability density functions of the total derivative from convective cases show mean volumetric heating rates of 43 W m-3 (154 K h-1) compared to 13 W m-3 (47 K h-1) on non-convective days. A conceptual model based on persistent mean flow structures from local-surface-temperature heterogeneities may explain the observed advection. The model describes the difference between locally-driven advection and advection driven by larger-scale forcings. Of the cases examined, 83% with streamwise and 81% with spanwise advection during unstable periods are classified as locally driven by nearby surface thermal heterogeneities.

We present the first lidar-based characterization of seasonal variations in gravity–wave induced vertical heat flux, sodium flux, and associated parameters – sodium density and temperature – between 80 and 100 km over Hainan, China (19° N, 109° E). Observations were carried out using a narrow band sodium lidar equipped with a laser frequency-locking and real-time monitoring module, achieving a root-mean-square (RMS) frequency stability of 0.5 MHz. Since February 2024, the system has provided continuous measurements of mesospheric sodium density, temperature, and vertical wind. The lidar results are generally consistent with coincident satellite measurements and model simulations at the near geographic location. Observations indicate that the highest temperatures below 95 km occur in May and November, with seasonal patterns closely matching from the SABER satellite data. The annual mean vertical heat flux shows two peak descent rates, −1.21 K m s−1 at 89 km and −1.38 K m s−1 at 92 km, corresponding to a cooling rate of approximately 95 K d−1 between 82 and 97 km. The sodium flux reveals pronounced maxima exceeding −65 m s−1 cm−3 at 92, with the resulting dynamical transport producing a maximum net sodium loss of 75 cm−3 h−1 near 93 km.