The Antarctic Slope Front and the associated Antarctic Slope Current are central in determining the dynamics along and the exchanges across the continental shelf break around Antarctica. Here, we present new, four-year-long (2017-2021) records from two moorings deployed on the upper part of the continental slope (530 m and 738 m depth) just upstream of the Filchner Trough in the southern Weddell Sea. We use the records to describe the mean state and the seasonal variability of the shelf break current and the regional hydrography. We find that (i) the current is bottom enhanced, (ii) the isotherms slope upwards towards the shelfbreak, and more so for warmer isotherms, and (iii) the monthly mean thermocline depth is shallowest in February-March and deepest in May-June while (iv) the current is strongest in April-June. On monthly timescales, we show that (v) positive (warm) temperature anomalies of the de-seasoned records are associated with weaker-than-usual currents. Our results contribute to the understanding of how warm ocean waters propagate southward and potentially affect basal melt rates at the Filchner-Ronne Ice Shelf.

The Barents Sea is one of the main pathways for warm and saline Atlantic Water (AW) entering the Arctic Ocean. It is an important region for water mass transformation and dense-water production that contribute to the Atlantic meridional overturning circulation. Here, we present data from three cruises and nine glider missions conducted between 2019 and 2022 in the western Barents Sea, and compare with historical data collected from 1950 to 2009. We present circulation pathways, hydrography, heat content and volume fluxes of Atlantic- and Arctic-origin waters. Our observations show that 0.9±0.1 Sv (1 Sv = 106 m3 s-1) of Atlantic-origin water reaches the Polar Front (PF) region before splitting into several branches and eventually subducting beneath Polar Water (PW). The observed increased heat content in the AW inflow over the past decades can be traced under the Polar front. The amount of heat stored in the basin north of the PF is determined by the density difference between AW and PW, and reached a maximum in the 90s when PW was particularly fresh. The inflow of Atlantic Water (AW) into the Barents Sea during the period from 2019 to 2022 exhibits a decrease in salinity of up to 0.1 g kg-1 compared to previous decades. Consequently, this leads to a reduction in the production of dense water, an increased temperature gradient across the PF, and a reduced poleward transport of warm water.

In the Arctic Ocean, semidiurnal-band processes including tides and wind-forced inertial oscillations are significant drivers of ice motion, ocean currents and shear contributing to mixing. Two years (2013-2015) of current measurements from seven moorings deployed along °E from the Laptev Sea shelf (~50 m) down the continental slope into the deep Eurasian Basin (~3900 m) are analyzed and compared with models of baroclinic tides and inertial motion to identify the primary components of semidiurnal-band current (SBC) energy in this region. The strongest SBCs, exceeding 30 cm/s, are observed during summer in the upper ~30 m throughout the mooring array. The largest upper-ocean SBC signal consists of wind-forced oscillations during the ice-free summer. Strong barotropic tidal currents are only observed on the shallow shelf. Baroclinic tidal currents, generated along the upper continental slope, can be significant. Their radiation away from source regions is governed by critical latitude effects: the S baroclinic tide (period = 12.000 h) can radiate northwards into deep water but the M (~12.421 h) baroclinic tide is confined to the continental slope. Baroclinic upper-ocean tidal currents are sensitive to varying stratification, mean flows and sea ice cover. This time-dependence of baroclinic tides complicates our ability to separate wind-forced inertial oscillations from tidal currents. Since the shear from both sources contributes to upper-ocean mixing that affects the seasonal cycle of the surface mixed layer properties, a better understanding of both inertial motion and baroclinic tides is needed for projections of mixing and ice-ocean interactions in future Arctic climate states.