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The West Antarctic Ice Sheet is experiencing rapid thinning of its floating ice shelves, largely attributed to oceanic basal melt. Numerical models suggest that the Bellingshausen Sea has a key role in setting water properties in the Amundsen Sea and further downstream. Yet, observations confirming these pathways of volume and tracer exchange between coast and shelf break and their impact on inter‐sea exchange remain sparse. Here we analyze the circulation and distribution of glacial meltwater at the boundary between the Bellingshausen Sea and the Amundsen Sea using a combination of glider observations from January 2020 and hydrographic data from instrumented seals. Meltwater distributions over previously unmapped western regions of the continental shelf and slope reveal two distinct meltwater cores with different optical backscatter properties. At Belgica Trough, a subsurface meltwater peak is linked with hydrographic properties from Venable Ice Shelf. West of Belgica Trough, the vertical structure of meltwater concentration changes, with peak values occurring at greater depths and denser isopycnals. Hydrographic analysis suggests that the western (deep) meltwater core is supplied from the eastern part of Abbot Ice Shelf, and is exported to the shelf break via a previously‐overlooked bathymetric trough (here named Seal Trough). Hydrographic sections constructed from seal data reveal that the Antarctic Coastal Current extends west past Belgica Trough, delivering meltwater to the Amundsen Sea. Each of these circulation elements has distinct dynamical implications for the evolution of ice shelves and water masses both locally and downstream, in the Amundsen Sea and beyond. Floating ice shelves in West Antarctica are thinning, which is largely due to melting of the ice shelf base by the ocean. Here, measurements of ocean temperature, salinity, and dissolved oxygen, collected by a remotely‐controlled underwater vehicle (a glider), are used to estimate the amount of ice shelf meltwater released in the Bellingshausen Sea. Distinct cores of meltwater can be distinguished by the amount of suspended material that is present in the water, which we attribute to meltwater following different circulation pathways after entering the ocean. Historical data from seals equipped with temperature and salinity sensors provide additional information about how the meltwater circulates in the region. The seal data show the presence of a narrow coastal current that brings meltwater from the Bellingshausen Sea into the Amundsen Sea. The pathways of meltwater revealed in this study suggest an important influence of the Bellingshausen Sea on ice shelves throughout West Antarctica. Hydrographic observations identify both shelf‐break and coastal meltwater pathways from the western Bellingshausen Sea into the Amundsen SeaDifferences in optical backscatter properties associated with meltwater are related to distinct coast‐to‐shelf break pathwaysThe main pathway to the shelf break is via Seal Trough, identified as the de factowestern boundary of the Bellingshausen Sea Hydrographic observations identify both shelf‐break and coastal meltwater pathways from the western Bellingshausen Sea into the Amundsen Sea Differences in optical backscatter properties associated with meltwater are related to distinct coast‐to‐shelf break pathways The main pathway to the shelf break is via Seal Trough, identified as the de factowestern boundary of the Bellingshausen Sea

Oceanic macroturbulence is efficient at stirring and transporting tracers. The dynamical properties of this stirring can be characterized by statistically quantifying tracer structures. Here, we characterize the macroscale (1–100 km) tracer structures observed by two Seagliders downstream of the Southwest Indian Ridge in the Antarctic Circumpolar Current (ACC). These are some of the first glider observations in an energetic standing meander of the ACC, a region associated with enhanced ventilation. The small‐scale density variance in the mixed layer (ML) was relatively enhanced near the surface and base of the ML, while being muted at mid‐depth in the ML, suggesting the formation mechanism to be associated with ML instabilities and eddies. In addition, ML density fronts were formed by comparable contributions from temperature and salinity gradients. In the interior, along‐isopycnal spectra and structure functions of spice indicated that there is relatively lower variance at smaller scales than would be expected based on non‐local stirring, suggesting that flows smaller than the deformation radius play a role in the cascade of tracers to small scales. These interior spice anomalies spanned across isopycnals, and were found to be about 3–5 times flatter than the aspect ratio that would be expected for O(1) Burger number flows like interior QG dynamics, suggesting the ratio of vertical shear to horizontal strain is greater than N/f. This further supports that small‐scale flows, with high‐mode vertical structures, impact tracer distributions. Ocean eddies and fronts are efficient at stirring and generating tracer structures spanning a wide range of scales. This stirring is important for uptake of tracers, particularly in the Southern Ocean where sloping density surfaces provide a direct pathway from the surface into the interior. While the qualitative nature of stirring seems clear, quantitatively characterizing properties of this stirring is necessary to build accurate parameterizations and understand how the ocean is ventilated. One way to characterize this is by quantifying the distribution of the tracer concentration as a function of scale. Here, we do this characterization by analyzing data collected by two gliders in a region where the mean current of the Southern Ocean meanders as it flows over topography, and is likely to be a hot spot for ventilation. This analysis reveals that relatively small eddies generated by a process known as mixed layer instability are active in the mixed layer and play an important role in setting the near‐surface stratification. Surprisingly, tracer structure below the mixed layer also indicates that flows with small horizontal and vertical scales play a role in stirring. This challenges conventional wisdom, which assumes that only the largest eddies are important for stirring. Glider observations were used to analyze tracer structure at scales ≤100 km in the Antarctic Circumpolar CurrentThe vertical structure of density variance in the mixed layer (ML) is suggestive of ML instabilities and eddiesSmall‐scale flows contribute to stirring in the interior, as indicated by passive tracer structure Glider observations were used to analyze tracer structure at scales ≤100 km in the Antarctic Circumpolar Current The vertical structure of density variance in the mixed layer (ML) is suggestive of ML instabilities and eddies Small‐scale flows contribute to stirring in the interior, as indicated by passive tracer structure

Estimates of the kinetic energy transfer from the wind to the ocean are often limited by the spatial and temporal resolution of surface currents and surface winds. Here we examine the wind work in a pair of global, very high‐resolution (1/48° and 1/24°) MIT general circulation model simulations in Latitude‐Longitude‐polar Cap (LLC) configuration that provide hourly output at spatial resolutions of a few kilometers and include tidal forcing. A cospectrum analysis of wind stress and ocean surface currents shows positive contribution at large scales (>300 km) and near‐inertial frequency and negative contribution from mesoscales, tidal frequencies, and internal gravity waves. Larger surface kinetic energy fluxes are in the Kuroshio in winter at large scales (40 mW/m2) and mesoscales (−30 mW/m2). The Kerguelen region is dominated by large scale (∼20 mW/m2), followed by inertial oscillations in summer (13 mW/m2) and mesoscale in winter (−12 mW/m2). Kinetic energy fluxes from internal gravity waves (−0.1 to −9.9 mW/m2) are generally stronger in summer. Surface kinetic energy fluxes in the LLC simulations are 4.71 TW, which is 25–85% higher than previous global estimates from coarser (1/6–1/10°) general ocean circulation models; this is likely due to improved representation of wind variability (6‐hourly, 0.14°, operational European Center for Medium‐Range Weather Forecasts). However, the low wind power input to the near‐inertial frequency band obtained with LLC (0.16 TW) compared to global slab models suggests that wind variability on time scales less than 6 hr and spatial scales less than 15 km are critical to better representing the wind power input in ocean circulation models. Surface kinetic energy fluxes from LLC simulations lead to 4.71 TW, this is 25–85% higher than previous global estimatesThere is positive contribution to wind power input (WPI) at large scale and near‐inertial (NI) band, and negative WPI at mesoscale, tidal frequencies and IGWsLow WPI at NI band (0.16 TW) suggests that wind variability on scales <6 hr and <15 km are critical to better representing WPI in GCMs

Mesoscale eddies are a dominant source of spatial variability in the surface ocean and play a major role in the biological marine carbon cycle. Satellite altimetry is often used to locate and track eddies, but this approach is rarely validated against in situ observations. Here we compare measurements of a small (under 25 km radius) mode water anticyclonic eddy over the Porcupine Abyssal Plain in the northeastern Atlantic Ocean using CTD and Acoustic Doppler Current Profiler (ADCP) measurements from three ships, two gliders, two profiling floats, and one Lagrangian float with those derived from sea level anomaly (SLA). In situ estimates of the eddy center were estimated from maps of the thickness of its central isopycnal layer, from ADCP velocities at a reference depth, and from the trajectory of the Lagrangian float. These were compared to three methods using altimetric SLA: one based on maximizing geostrophic rotation, one based on a constant SLA contour, and one which maximizes geostrophic velocity speed along the eddy boundary. All algorithms were used to select CTD profiles that were within the eddy. The in‐situ metrics agreed to 97%. The altimetry metrics showed only a small loss of accuracy, giving >90% agreement with the in situ results. This suggests that current satellite altimetry is adequate for understanding the spatial representation of even relatively small mesoscale eddies. Rotating water masses called eddies are ubiquitous features in the ocean and are important because they can transport nutrients and heat and are often associated with enhanced biological activity. Eddies are accompanied by sea level anomalies (SLA), in the same way that atmospheric weather systems are associated with high or low pressure systems, and can therefore be observed and monitored by satellite altimeters. However, observations of SLA from satellite are relatively coarse compared with the spatial scales of eddies, and satellite‐based algorithms are rarely rigorously tested against “ground truth” observations. We use data from a dense network of observations in the vicinity of a relatively small eddy in the northeastern Atlantic Ocean to track this eddy for several weeks from direct ocean measurements and satellite algorithms. We find widespread agreement between the in situ metrics and the satellite altimetry results, suggesting that satellite‐based eddy tracking is sufficient to track even eddies that are relatively small compared with the resolution of SLA products. Ship‐based, autonomous, and remote sensing observations were combined to identify, characterize, and track a coherent anticyclonic eddyEstimates of the eddy center and spatial extent derived from altimetry and in situ observations had similar accuracyConstant or smoothly varying sea level anomaly thresholds better represent eddy spatial extent than other satellite‐based methods Ship‐based, autonomous, and remote sensing observations were combined to identify, characterize, and track a coherent anticyclonic eddy Estimates of the eddy center and spatial extent derived from altimetry and in situ observations had similar accuracy Constant or smoothly varying sea level anomaly thresholds better represent eddy spatial extent than other satellite‐based methods

This study combines sea surface height (SSH) estimates of the ice‐covered Southern Ocean with conventional open‐ocean SSH estimates from CryoSat‐2 to produce monthly composites of dynamic ocean topography (DOT) and sea level anomaly (SLA) on a 50 km grid spanning 2011–2016. This data set reveals the full Southern Ocean SSH seasonal cycle for the first time; there is an antiphase relationship between sea level on the Antarctic continental shelf and the deeper basins, with coastal SSH highest in autumn and lowest in spring. As a result of this pattern of seasonal SSH variability, the barotropic component of the Antarctic Slope Current (ASC) has speeds that are regionally up to twice as fast in the autumn. Month‐to‐month circulation variability of the Ross and Weddell Gyres is strongly influenced by the local wind field, and is correlated with the local wind curl (Ross: −0.58; Weddell: −0.67). SSH variability is linked to both the Southern Oscillation and the Southern Annular Mode, dominant modes of southern hemisphere climate variability. In particular, during the strong 2015–2016 El Niño, a sustained negative coastal SLA of up to −6 cm, implying a weakening of the ASC, was observed in the Pacific sector of the Southern Ocean. The ability to examine sea level variability in the seasonally ice‐covered regions of the Southern Ocean—climatically important regions with an acute sparsity of data—makes this new merged sea level record of particular interest to the Southern Ocean oceanography and glaciology communities. New monthly merged sea level record of the ice‐covered and ice‐free Southern Ocean between 2011 and 2016, from CryoSat‐2 radar altimetryAntarctic coastal sea level peaks in autumn, minimum in spring; Antarctic Slope Current speeds regionally up to twice as fast in autumnSouthern Oscillation and Southern Annular Mode drive significant Antarctic coastal sea level response, modulating the ASC strength

Signatures of ocean eddies, fronts, and filaments are commonly observed within marginal ice zones (MIZs) from satellite images of sea ice concentration, and in situ observations via ice‐tethered profilers or underice gliders. However, localized and intermittent sea ice heating and advection by ocean eddies are currently not accounted for in climate models and may contribute to their biases and errors in sea ice forecasts. Here, we explore mechanical sea ice interactions with underlying submesoscale ocean turbulence. We demonstrate that the release of potential energy stored in meltwater fronts can lead to energetic submesoscale motions along MIZs with spatial scales O(10 km) and Rossby numbers O(1). In low‐wind conditions, cyclonic eddies and filaments efficiently trap the sea ice and advect it over warmer surface ocean waters where it can effectively melt. The horizontal eddy diffusivity of sea ice mass and heat across the MIZ can reach O(200 m2s−1). Submesoscale ocean variability also induces large vertical velocities (order 10 m d−1) that can bring relatively warm subsurface waters into the mixed layer. The ocean‐sea ice heat fluxes are localized over cyclonic eddies and filaments reaching about 100 W m−2. We speculate that these submesoscale‐driven intermittent fluxes of heat and sea ice can contribute to the seasonal evolution of MIZs. With the continuing global warming and sea ice thickness reduction in the Arctic Ocean, submesoscale sea ice‐ocean processes are expected to become increasingly prominent. Energetic submesoscale ocean variability forms at marginal ice zones due to mixed‐layer instabilities of ice‐edge meltwater frontsMechanical sea ice‐ocean interactions trap sea ice in cyclonic eddies and filaments—regions with dramatically enhanced ocean heat fluxesThe strength of submesoscale sea ice‐ocean coupling is expected to increase with thinning of Arctic sea ice and marginal ice zone expansion

We investigate statistical properties of surface currents as well as coherent mesoscale eddies in the seasonally ice‐covered Southern Ocean. Based on a recent regional Sea Level Anomaly satellite altimetry data set, we compute Eddy Kinetic Energy (EKE) and detect mesoscale eddies. EKE is about one order of magnitude higher in the northern sector of the subpolar basin and over the continental slope, as compared to the middle of the subpolar gyres. An eddy detection methodology reveals that eddies are distributed evenly in the subpolar Southern Ocean, and their amplitude follows the spatial pattern of EKE. In addition to regional circulation variations, sea ice concentration arises as an important driver of eddy properties. Eddies have low amplitude and density in the pack ice, in particular in the middle of the gyres where the background circulation is unfavorable for instabilities. In contrast, the northern part of the Marginal Ice Zone is favorable for mesoscale eddies, especially cyclonic. There, eddies are stronger and their density is higher than in any other region of the ice‐covered or ice‐free subpolar Southern Ocean. This region is expected to be a site of frontogenesis due to sea ice melt and upwelling generated from interactions between the wind and the sea ice. While many mesoscale eddies will fall below detection level due to the small Rossby radius at high latitudes, these results contribute to understanding the interactions between mesoscale eddies, sea ice, and the background circulation in the subpolar region. Ocean eddies are spatially coherent vortices, ubiquitous in the global oceans, and are central structures contributing to shaping the global ocean circulation. In the Southern Ocean, they have been shown to play a potentially important role in the cross‐front transport of heat and nutrients at mid and high latitudes. Recent improvements in satellite altimetry capabilities in the ice‐covered regions allow for a first description of mesoscale eddies in the ice‐covered Southern Ocean, and the investigation of their interactions with sea ice. The location of the detected eddies is consistent with the main large‐scale circulation features. In addition to the background circulation, the sea ice cover has a strong impact on the size of eddies. While weaker eddies are found in the highly concentrated sea ice areas, the marginal ice zone seems to be a region with enhanced eddy activity, with more and stronger eddies detected. A new satellite altimetry data set allows the detection of mesoscale eddies in the ice‐covered Southern OceanEddy generation and strength are primarily impacted by sea ice concentration and the background circulationWhile the eddy strength is damped under high sea‐ice concentration, the northern edge of the sea‐ice region is a hotspot of large eddies A new satellite altimetry data set allows the detection of mesoscale eddies in the ice‐covered Southern Ocean Eddy generation and strength are primarily impacted by sea ice concentration and the background circulation While the eddy strength is damped under high sea‐ice concentration, the northern edge of the sea‐ice region is a hotspot of large eddies

A high‐resolution satellite image that reveals a train of coherent, submesoscale (6 km) vortices along the edge of an ocean front is examined in concert with hydrographic measurements in an effort to understand formation mechanisms of the submesoscale eddies. The infrared satellite image consists of ocean surface temperatures at ∼390m resolution over the midlatitude North Atlantic (48.69°N, 16.19°W). Concomitant altimetric observations coupled with regular spacing of the eddies suggest the eddies result from mesoscale stirring, filamentation, and subsequent frontal instability. While horizontal shear or barotropic instability (BTI) is one mechanism for generating such eddies (Munk's hypothesis), we conclude from linear theory coupled with the in situ data that mixed layer or submesoscale baroclinic instability (BCI) is a more plausible explanation for the observed submesoscale vortices. Here we assume that the frontal disturbance remains in its linear growth stage and is accurately described by linear dynamics. This result likely has greater applicability to the open ocean, i.e., regions where the gradient Rossby number is reduced relative to its value along coasts and within strong current systems. Given that such waters comprise an appreciable percentage of the ocean surface and that energy and buoyancy fluxes differ under BTI and BCI, this result has wider implications for open‐ocean energy/buoyancy budgets and parameterizations within ocean general circulation models. In summary, this work provides rare observational evidence of submesoscale eddy generation by BCI in the open ocean. Here, we test Munk's theory for small‐scale eddy generation using a unique set of satellite‐ and ship‐based observations. We find that for one particular set of observations in the North Atlantic, the mechanism for eddy generation is not pure horizontal shear, as proposed by Munk et al. ([Munk, W., 2000]) and Munk ([Munk, W., 2001]), but is instead vertical shear, or baroclinic instability. While by itself, this is not a globally important result, taken in the context of mesoscale eddies which are ubiquitous in the World Ocean, this suggests energy exchanges in the more ambient, open ocean are the result of the latter mechanism. In conclusion, submesoscale eddy generation is poorly understood in the ocean and we need to better constrain our geographical and temporal understanding of these processes for representation in coarse‐resolution models. A high‐resolution satellite image reveals an ocean front populated by submesoscale vorticesLinear theory applied to coincident hydrography suggests vortices result not from barotropic but baroclinic instabilityThis study documents rare observational evidence of submesoscale baroclinic instability in the open ocean

The Bellingshausen Sea hosts heat transport onto the continental shelf, potentially enhancing ice shelf basal melt. Here, we use the GLORYS12V1 1993–2018 reanalysis to identify physical processes that set seasonal and interannual variability of water mass properties in the Eltanin and Latady Bays on the southern Bellingshausen Sea continental shelf. Annual means of potential temperature from 300 m to the seabed reveal interannual variability and allow separation into warm and cold regimes. The Amundsen Sea Low (ASL) is more intense and extends further east during the warm regime than the cold regime. In the warm regime, a wind‐induced reduction of sea ice concentration near the coast increases surface heat loss, convection, and formation of cold dense water in winter, associated with a decrease in heat content of the southern Bellingshausen Sea over time and a net northward heat transport. In contrast, in the cold regime, increased sea ice concentration reduces surface heat loss and thus formation of cold, dense water. Combined with an increase in heat content over time and a net southward heat transport, this results in a warming of the southern Bellingshausen Sea. This suggests that variability in the deep water temperature in the southern Bellingshausen Sea is primarily due to local surface heat fluxes above the shelf. The variability of surface heat fluxes is related to the variability of the ASL and its influence on sea ice extent and local formation of cold, dense water in winter. The stability of the West Antarctic Ice Sheet is a key factor in uncertainty in global sea level predictions on decadal to centennial time scales. Today, melt of West Antarctic ice shelves is dominated by relatively warm (above freezing) ocean waters, and the warmest waters around Antarctica are found in the Bellingshausen Sea. There is a lack of long‐term observations in this inaccessible region so we use a model product to investigate variability of deep water temperatures, identifying warm and cold years. We find a link between sea ice concentration, heat loss to the atmosphere and cold water formation and the wind fields associated with a weather system, the Amundsen Sea Low (ASL). Winds in the southern Bellingshausen Sea are stronger in warm years than in cold years and blow the ice away from the coast more rapidly, allowing more heat loss to the atmosphere, cooling the ocean in winter. Conversely, in cold years increased sea ice cover reduces heat loss to the atmosphere, less cold water is formed, and there is increased southward transport of warm water. We highlight the importance of the ASL's location and intensity for cold water formation and its impacts on temperature. Intensity and location of Amundsen Sea Low (ASL) affect ocean properties of southern Bellingshausen Sea continental shelf in 26‐year reanalysisThe ASL modifies the surface heat flux, warming Bellingshausen Sea shelf when it shifts westward and weakens, and vice versaThe southern Bellingshausen Sea temperature depends more on surface heat fluxes above the continental shelf than southward heat transport Intensity and location of Amundsen Sea Low (ASL) affect ocean properties of southern Bellingshausen Sea continental shelf in 26‐year reanalysis The ASL modifies the surface heat flux, warming Bellingshausen Sea shelf when it shifts westward and weakens, and vice versa The southern Bellingshausen Sea temperature depends more on surface heat fluxes above the continental shelf than southward heat transport

The spatial and temporal variability of upwelling into the mixed layer in the Southern Ocean is studied using a 1/10 °ocean general circulation model. Virtual drifters are released in a regularly spaced pattern across the Southern Ocean at depths of 250, 500, and 1000 m during both summer and winter months. The drifters are advected along isopycnals for a period of 4 years, unless they outcrop into the mixed layer, where lateral advection and a parameterization of vertical mixing are applied. The focus of this study is on the discrete exchange between the model mixed layer and the interior. Localization of interior‐mixed layer exchange occurs downstream of major topographic features across the Indian and Pacific basins, creating “hotspots” of outcropping. Minimal outcropping occurs in the Atlantic basin, while 59% of drifters outcrop in the Pacific sector and in Drake Passage (the region from 140 °W to 40 °W), a disproportionately large amount even when considering the relative basin sizes. Due to spatial and temporal variations in mixed layer depth, the Lagrangian trajectories provide a statistical measure of mixed layer residence times. For each exchange into the mixed layer, the residence time has a Rayleigh distribution with a mean of 30 days; the cumulative residence time of the drifters is 261 ± 194 days, over a period of 4 years. These results suggest that certain oceanic gas concentrations, such as CO2and 14C, will likely not reach equilibrium with the atmosphere before being resubducted. Spatial and temporal variability of Southern Ocean upwelling is studied using virtual driftersUpwelling locations are highly constrained by topographic featuresMean mixed layer residence times are found to be on the order of one month

This study presents the characterization of variability in temperature, salinity and oxygen concentration, including the vertical structure of the variability, in the upper 1000 m of the ocean over a full year in the northeast Atlantic. Continuously profiling ocean gliders with vertical resolution between 0.5 and 1 m provide more information on temporal variability throughout the water column than time series from moorings with sensors at a limited number of fixed depths. The heat, salt and dissolved oxygen content are quantified at each depth. While the near surface heat content is consistent with the net surface heat flux, heat content of the deeper layers is driven by gyre‐scale water mass changes. Below ∼150m, heat and salt content display intraseasonal variability which has not been resolved by previous studies. A mode‐1 baroclinic internal tide is detected as a peak in the power spectra of water mass properties. The depth of minimum variability is at ∼415m for both temperature and salinity, but this is a depth of high variability for oxygen concentration. The deep variability is dominated by the intermittent appearance of Mediterranean Water, which shows evidence of filamentation. Susceptibility to salt fingering occurs throughout much of the water column for much of the year. Between about 700–900 m, the water column is susceptible to diffusive layering, particularly when Mediterranean Water is present. This unique ability to resolve both high vertical and temporal variability highlights the importance of intraseasonal variability in upper ocean heat and salt content, variations that may be aliased by traditional observing techniques. Intraseasonal variability in upper ocean temperature and salinity, not previously reportedMode‐1 baroclinic internal tide detectedDeep variability dominated by intermittent patches of Mediterranean Water, which show evidence of filamentation

Marginal ice zones are composed of discrete sea‐ice floes, whose dynamics are not well captured by the continuum representation of sea ice in most climate models. This study makes use of an ocean large eddy simulation (LES) model, coupled to cylindrical sea‐ice floes, to investigate thermal and mechanical interactions between melt‐induced submesoscale features and sea‐ice floes, during summer conditions. We explore the sensitivity of sea‐ice melt rates and upper‐ocean turbulence properties to floe size, ice‐ocean drag, and surface winds. Under low wind conditions, upper ocean turbulence transports warm cyclonic filaments from the open ocean toward the center of the floes and enhances their basal melt. This heat transport is partially suppressed by trapping of ice within cold anticyclonic features. When winds are stronger, melt rates are enhanced by the decoupling of floes from the cold, melt‐induced lens underneath sea ice. Distinct dynamical regimes emerge in which the influence of warm filaments on sea‐ice melt is mitigated by the strength of ice‐ocean coupling and eddy size relative to floe size. Simple scaling laws, which may help parameterize these processes in coarse continuum‐based sea‐ice models, successfully capture floe melt rates under these limiting regimes. At high latitudes, the ocean is often covered by a thin layer of sea ice, which forms in the winter due to the freezing of seawater. Sea ice is typically characterized by a collection of distinct pieces, known as ice floes, which range in size between several meters to tens of kilometers. In the summer, floes melt due to a warm atmosphere above, as well as a warm ocean below. The melting of sea‐ice floes often generates small‐scale (1–10 km) ocean currents at the surface, which in turn affect sea‐ice motion and melt. Here, we study these ice‐ocean interactions, using an idealized sea‐ice model coupled to a regional ocean model that resolves these fine‐scale dynamics. We find that small‐scale oceanic currents and surface winds accelerate the sea‐ice melt rate by allowing warm waters to move into colder regions under the ice floes. Simple relationships, or scalings, involving the floe size, wind speed, and ice‐ocean friction, are able to explain these varying ice floe melt rates across a range of environmental conditions. These scalings, when included in global climate models, may help to improve future predictions of sea‐ice changes by accounting for the impact of small‐scale ocean currents. The relative size of sea‐ice floes and submesoscale eddies controls lateral heat transport to sea iceMechanical coupling shields floes from warm filaments but winds disrupt this coupling and advect ice into warm watersScaling laws capture sea‐ice melt rate dependence on floe size, ice‐ocean drag and wind speed The relative size of sea‐ice floes and submesoscale eddies controls lateral heat transport to sea ice Mechanical coupling shields floes from warm filaments but winds disrupt this coupling and advect ice into warm waters Scaling laws capture sea‐ice melt rate dependence on floe size, ice‐ocean drag and wind speed

Standing meanders are a key component of the Antarctic Circumpolar Current (ACC) circulation system, and numerical studies have shown that these features may locally enhance subduction, upwelling, as well as lateral and vertical tracer transport. Yet, observational data from these regions remain sparse. Here, we present results based on measurements made by a group of autonomous platforms sampling an ACC standing meander formed due to the interaction of the Polar Front with the Southwest Indian Ridge. Two Seagliders were deployed alongside a Biogeochemical‐Argo float that was advected through the standing meander. In the high eddy kinetic energy region of the standing meander, the glider observations reveal enhanced submesoscale frontal gradients as well as heightened tracer variability at depth, as compared to the more quiescent region further downstream. Vertical gradients in spice and apparent oxygen utilization are reduced in the standing meander despite similarities in the large‐scale vertical stratification, suggesting greater ventilation of the surface ocean. These observations are consistent with numerical studies that highlight standing meanders as hotspots for ventilation and subduction due to enhanced mesoscale stirring and submesoscale vertical velocities. Our results emphasize the need to account for spatial heterogeneity in processes influencing air‐sea exchange, carbon export, and biogeochemical cycling in the Southern Ocean. The Southern Ocean plays a vital role in taking up carbon dioxide and heat from the Earth's atmosphere. Yet, historically, this region has suffered from a lack of direct observations, making it difficult to quantify rates of exchange. In regions where the strongest currents of the Southern Ocean interact with underwater topography turbulence and mixing may be locally enhanced. Data collected from two different types of robotic vehicles, including steerable ocean gliders, were used to study one of these mixing “hotspots.” The instrumented platforms provided expanded data as compared to typical Southern Ocean observational techniques. The results show that these turbulent regions allow water properties, such as temperature and oxygen, to mix vigorously. In particular, at these hotspots the exchange of waters between the ocean surface and interior increases. It is important to document the magnitude and regional patterns of this exchange because only surface waters interact with the atmosphere to take up or release carbon and heat, while interior waters store these properties for centuries or longer. Numerical models of the ocean have indicated that these turbulent regions of the Southern Ocean are particularly influential, and we provide some of the first observational evidence confirming these hotspots' importance. Observations with high spatial and temporal resolution were collected from two ocean gliders following a Biogeochemical‐Argo floatPhysical and biogeochemical tracer variance is enhanced within a standing meander of the Antarctic Circumpolar CurrentThe standing meander shows evidence of heightened exchange of water properties between the ocean surface boundary layer and the interior Observations with high spatial and temporal resolution were collected from two ocean gliders following a Biogeochemical‐Argo float Physical and biogeochemical tracer variance is enhanced within a standing meander of the Antarctic Circumpolar Current The standing meander shows evidence of heightened exchange of water properties between the ocean surface boundary layer and the interior

Hydrographic data are analyzed for the broad continental shelf of the Bellingshausen Sea, which is host to a number of rapidly thinning ice shelves. The flow of warm Circumpolar Deep Water (CDW) onto the continental shelf is observed in the two major glacially carved troughs, the Belgica and Latady troughs. Using ship‐based measurements of potential temperature, salinity, and dissolved oxygen, collected across several coast‐to‐coast transects over the Bellingshausen shelf in 2007, the velocity and circulation patterns are inferred based on geostrophic balance and further constrained by the tracer and mass budgets. Meltwater was observed at the surface and at intermediate depth toward the western side of the continental shelf, collocated with inferred outflows. The maximum conversion rate from the dense CDW to lighter water masses by mixing with glacial meltwater is estimated to be 0.37 ± 0.1 Sv in both depth and potential density spaces. This diapycnal overturning is comparable to previous estimates made in the neighboring Amundsen Sea, highlighting the overlooked importance of water mass modification and meltwater production associated with glacial melting in the Bellingshausen Sea. The Bellingshausen Sea is sandwiched between the Amundsen Sea and the West Antarctic Peninsula continental shelf sea and where warm offshore waters around Antarctica can flow onto the continental shelf and directly melt the floating ice‐shelves. However, in situ observations are historically very sparse in this region due to the heavy sea‐ice cover throughout most of the year. In this study, we present the distribution of temperature, salinity, dissolved oxygen, and the diagnosed meltwater concentration over the broad continental shelf of the Bellingshausen Sea from one of the most comprehensive hydrographic surveys so far. We further infer the velocity and circulation patterns by balancing the input and output rates of tracers (heat, salt, and dissolved oxygen) within selected regions. A clockwise‐flowing boundary current is identified over the shelf, consistent with the meltwater distribution and previous findings. Lastly, we measure the overturning circulation over the Bellingshausen Shelf, which consists of warm water inflow in the lower water column and meltwater outflow near the surface. We conclude that the magnitude of this circulation is comparable to previous estimates made in the neighboring Amundsen Sea where the ice‐shelf melting has drawn much attention recently. Tracer distribution over the Bellingshausen shelf is presented with data from a comprehensive hydrographic surveyMeltwater is present from mid‐depth to surface and is accumulated toward the western shelf, consistent with a cyclonic gyre circulationThe inferred overturning circulation driven by ice‐shelf melting is comparable to previous estimates made in the neighboring Amundsen Sea Tracer distribution over the Bellingshausen shelf is presented with data from a comprehensive hydrographic survey Meltwater is present from mid‐depth to surface and is accumulated toward the western shelf, consistent with a cyclonic gyre circulation The inferred overturning circulation driven by ice‐shelf melting is comparable to previous estimates made in the neighboring Amundsen Sea

The rate of ocean heat uptake depends on the mechanisms that transport heat between the surface and the ocean interior. A recent study found that the vertical heat transport driven by motions with scales smaller than 0.5° (submesoscales) and frequencies smaller than 1 day−1is upward. This transport competes with the other major components of the global heat transport, namely, the downward heat transport explained by the large‐scale wind‐driven vertical circulation and vertical diffusion at small scales and the upward heat transport associated with mesoscale eddies (50‐ to 300‐km size). The contribution from motions with small spatial scales (<0.5°) and frequencies larger than 1 day−1, including internal gravity waves, has never been explicitly estimated. This study investigates this high‐frequency (subdaily) submesoscale contribution to the global heat transport. The major result of this study, based on the analysis of a high‐resolution ocean model, is that including this high‐frequency contribution surprisingly doubles the upward heat transport due to submesoscales in winter in the global ocean. This contribution typically concerns depths down to 200–500 m and can have a magnitude of up to 500 W m−2in terms of wintertime heat fluxes at 40‐m depth, which causes a significant upward heat transport of ~7 PW when integrated over the global ocean. Thus, such submesoscale heat transport, which is not resolved by climate models, impacts the heat uptake in the global ocean. The mechanisms involved in these results still need to be understood, which should be the scope of future work. Ocean heat flux is large at high frequencySuch high‐frequency flux is generated at submesoscaleSuch heat flux is a key component of global heat budget