A new data set of temperature and salinity fields reconstructed from satellite altimetry data between January 1993 and April 2014 is combined with satellite observations of mesoscale eddies in the subpolar North Atlantic between 40°N–55°N and 43°W–20.5°W. The data set is used to calculate the meridional heat and freshwater transports related to the propagation of eddies crossing 47°N, a latitude close to the boundary between the subpolar and the subtropical gyres. The largest heat and freshwater transports by eddies are observed in the western part of the Newfoundland Basin. Around 35–45% of the heat and freshwater transports by eddies across 47°N stem from individual isolated eddies with large thermohaline signatures. Northward moving cold and fresh cyclonic eddies carrying subpolar water from the Western Boundary Current make a considerable contribution to the overall heat and freshwater transport by eddies crossing 47°N. While the transport by individual eddies is negligible compared to the transport by the mean flow in this region, it can have a notable influence on the temporal variability. The analysis is repeated for a model simulation with 1/12° horizontal resolution for the period 2002–2013. The observed results are well reproduced in the model simulation; in particular, the modeled number of eddies crossing 47°N, the spatial distribution, and the associated heat and freshwater transports across this latitude are consistent with the observations.

Observations of sea surface salinity (SSS) from NASA’s Soil Moisture Active-Passive (SMAP) and ESA’s Soil Moisture and Ocean Salinity (SMOS) satellite missions are used to characterize and quantify the contribution of mesoscale eddies to the ocean transport of salt. Given large errors in satellite retrievals and, consequently, SSS maps, we evaluate two products from the two missions and also use two different methods to assess the eddy transport of salt. Comparing the two missions, we find that the estimates of the eddy transport of salt agree very well, particularly in the tropics and subtropics. The transport is divergent in the subtropical gyres (eddies pump salt out of the gyres) and convergent in the tropics. The estimates from the two satellites start to differ regionally at higher latitudes, particularly in the Southern Ocean and along the Antarctic Circumpolar Current (ACC), resulting, presumably, from a considerable increase in the level of noise in satellite retrievals (because of poor sensitivity of the satellite radiometer to SSS in cold water), or they can be due to insufficient spatial resolution. Overall, our study demonstrates that the possibility of characterizing and quantifying the eddy transport of salt in the ocean surface mixed layer can rely on the use of satellite observations of SSS. Yet, new technologies are required to improve the resolution capabilities of future satellite missions in order to observe mesoscale and sub-mesoscale variability, improve the signal-to-noise ratio, and extend these capabilities to the polar oceans.

Despite the importance of the Arctic Ocean for the large‐scale circulation and climate, there is still a knowledge gap in our understanding of the spatial characteristics of the Arctic Ocean circulation, especially for the mesoscale. This paper investigates the spatial characteristics of the Arctic Ocean circulation using a simulation with 1 km horizontal resolution. We revealed that there are two peaks in the kinetic energy (KE) spectral density at the 400 m depth, one at the gyre scale of the Arctic Circumpolar Boundary Current (centered at 1,700–2,000 km), and the other associated with the mesoscale (at about 60 km). However, at the 70 m depth, the boundary currents tend to mask the spectrum peak associated with the mesoscale. The KE spectrum exhibits a power‐law scaling typical for ocean eddies. We found that about 80% (50%) of the KE is on scales smaller than 100 km (30 km). The maximum KE content is in the 10–20 km scale band in most of the eddy‐rich regions of the abyssal ocean. The seasonality of the KE spectrum and KE content inside the Arctic Ocean follow the seasonality of eddy activity and baroclinicity, with low values in spring and maxima in late summer to autumn, and the seasonal variation is stronger at the 70 m depth than the 400 m depth. The strong concentration of KE on the very small spatial scales warrants future studies on energy transfer between scales in the Arctic Ocean.

Mesoscale eddies play an important role in driving the dynamics of the Arctic Ocean. Understanding their behavior is crucial for comprehending the ongoing changes in the region. In this study, by using a novel decade‐long simulation at 1 km resolution with the unstructured‐mesh Finite volumE Sea ice‐Ocean Model, we evaluate the spatial and temporal variability of eddy kinetic energy in the Eurasian Basin. We find that monthly, annual, and interannual variability of EKE near the surface is predominantly influenced by changes in sea ice cover, while the eddy activity at deeper depth, being shielded from the surface by ocean stratification, is more strongly influenced by local baroclinic energy conversion. Moreover, our research demonstrates that eddies in the Eurasian Basin can transport ocean heat from the Atlantic Water layer toward sea ice and cause local basal melting in the order of about 20 cm per month even in wintertime. Our study suggests that eddy activity in the Arctic Ocean will strengthen along with future sea ice decline, and that the impact of ocean heat of the Atlantic Water layer on sea ice retreat may become prominent.

We analyze the interannual variability and trends of the eddy heat transport (EHT) in the surface mixed layer of the Atlantic Ocean from covariances of sea surface temperature (SST) and geostrophic velocities from satellite observations between 1993 and 2018. The EHT is largest along the path of the Gulf Stream in the Northern Hemisphere and the vicinity of the Agulhas Retroflection and Argentine basin in the Southern Hemisphere. On average, meridional EHT in the mixed layer leads to a divergence of heat away from the subtropics in both hemispheres toward the equator and higher latitudes. Depending on latitude, the divergence of the EHT accounts for around 1%–5% of the atmospheric net surface heat flux, but reaches as much as 20% for certain regions. The EHT can be linked to eddy kinetic energy (EKE) and meridional SST gradients using mixing length hypothesis, but the variability of EKE and SST gradients are not enough to capture local EHT variability. For different latitudes, the EHT shows different behavior over time, with a strong increase in northward EHT in the Gulf Stream region, and a decadal oscillation of poleward EHT in the tropical and subtropical regions. This oscillation on larger scales is highly correlated with spatially averaged EKE and the large‐scale SST gradients. A comparison with climate indices indicates a relation to Atlantic climate variability, especially the meridional modes of the Tropical Atlantic Variability and the North Atlantic Oscillation (NAO).