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A 15-yr duration record of mooring observations from the eastern (>70°E) Eurasian Basin (EB) of the Arctic Ocean is used to show and quantify the recently increased oceanic heat flux from intermediate-depth (~150–900 m) warm Atlantic Water (AW) to the surface mixed layer and sea ice. The upward release of AW heat is regulated by the stability of the overlying halocline, which we show has weakened substantially in recent years. Shoaling of the AW has also contributed, with observations in winter 2017–18 showing AW at only 80 m depth, just below the wintertime surface mixed layer, the shallowest in our mooring records. The weakening of the halocline for several months at this time implies that AW heat was linked to winter convection associated with brine rejection during sea ice formation. This resulted in a substantial increase of upward oceanic heat flux during the winter season, from an average of 3–4 W m−2 in 2007–08 to >10 W m−2 in 2016–18. This seasonal AW heat loss in the eastern EB is equivalent to a more than a twofold reduction of winter ice growth. These changes imply a positive feedback as reduced sea ice cover permits increased mixing, augmenting the summer-dominated ice-albedo feedback. [ABSTRACT FROM AUTHOR]

A 15‐year (2004–2018) record of mooring observations from the upper 50 m ocean in the eastern Eurasian Basin reveals increased current speeds and shear, associated with an increasing coupling between wind, ice, and oceanic currents and their vertical shear over 2004–2018, particularly in summer. Substantial increases in both current speeds and shears in the upper 50 m are dominated by a two times amplification of currents in the semidiurnal band, which includes tides and wind‐forced near‐inertial oscillations. For the first time the strengthened upper ocean currents and shear are observed to coincide with weakening stratification. This coupling links the Atlantic Water heat to the sea ice, a consequence of which would be reducing regional sea ice volume. These results point to a new positive feedback mechanism in which reduced sea ice extent facilitates more energetic inertial oscillations and associated upper‐ocean shear, thus leading in enhanced ventilation of the Atlantic water. Plain Language Summary: Previous studies demonstrated that in recent years density gradients above the warm and salty intermediate (~150–900 m) water of Atlantic origin in the eastern Arctic Ocean have weakened, allowing stronger upward transport heat to the bottom of the sea ice. Using mooring observations, we show that this weakening of stratification has been accompanied by stronger upper‐ocean currents and their vertical shear and by increasing coupling between the wind and sea ice with upper ocean currents and shear. Most of this enhanced energy and shear is in the semidiurnal band, which includes baroclinic tides and wind‐driven inertial oscillations. The increased shear together with the weakening stratification indicate a greater potential for shear‐driven turbulent mixing. We propose a new process, the ice/ocean‐heat positive feedback, that can accelerate current sea ice loss and impede the rate of recovery of eastern Arctic sea ice even if large‐scale climate warming conditions relax. Key Points: Currents and associated shear in the upper 50 m in the eastern Eurasian Basin are increased in the 2010sIncreased currents and shear are dominated by accelerating currents in the semidiurnal (inertial and tidal) bandThere was an increasing coupling between wind, ice, and oceanic currents in the eastern Eurasian Basin over 2004–2018 [ABSTRACT FROM AUTHOR]

The interior shelves of the Arctic Mediterranean are the shelves of the Kara Sea, Laptev Sea, East Siberian Sea and Beaufort Sea. They comprise approximately 40% of the total arctic shelf area (∼2.5 × 10 6 km 2 ) and are distinguished from inflow and outflow shelves by their principal forcing dynamics. Along their southern (continental) boundary the interior shelves are dominated by the major arctic rivers, receiving over 80% of the total freshwater input to the Arctic Ocean. In the mid-shelf region wind and ice motion surface stresses dominate mixing and circulation, resulting in high variability. Along, their northern (seaward) boundary they are forced by upwelling- and downwelling-favourable surface stresses which drive shelf-basin exchanges with Atlantic- and Pacific-origin cyclonic boundary currents over the upper slope. Shelf-basin exchange is further modified by shelf-break morphometry (e.g. canyons, valleys, headlands and bottom slope). Here we review the physical oceanographic settings and forcing of the interior shelves and then focus on shelfbreak exchange and supply of nutrients for new primary production due to upwelling across the shelfbreak. As a proxy for this nutrient supply, we show seasonal and annual time series of along-shelfbreak surface-stress due to wind and ice motion from 1979 to 2011. We apply this analysis to the shallow shelves from the Kara Sea to the Beaufort Sea and comment on recent increases due to atmospheric changes and sea-ice retreat. [ABSTRACT FROM AUTHOR]

The foremost flooding event of the past century happened in 2013 on the Amur River, which flows into the Sea of Okhotsk. Concurrently, the winter of 2012–2013 was a year of heavy sea ice and delayed onset of melting in this region. To examine the joint effects of these major, regional-scale hydrological freshening events on oceanographic processes, we compared physical (CTD, tides and currents) and biological (zooplankton) data measured in 2004 and 2013 in Academy Bay, Sea of Okhotsk. Our results indicate that the difference in sea water temperature between the two years played a primary role in shaping zooplankton variability. Data collected in 2013 showed that water temperature was colder and that the upper layer was substantially fresher (∼4–5 psμ) than in 2004. This decrease in water temperature and salinity reduction was accompanied by a significant decrease in the abundance of some key zooplankton species including Calanus glacialis, Pseudocalanus spp. and Sagitta elegans and a corresponding increase in the abundance of Limacina helicina. Delayed melting of sea ice in 2013 potentially triggered a mismatch in pelagic production that may have impacted the recruitment of calanoid copepods. Variation in tidal and subtidal advection of cold and highly saline Okhotsk Sea shelf water appears to be an important process influencing regional variation in zooplankton abundance. The occurrence of such hydrological events has the potential to trigger cascading effects through the food web. [ABSTRACT FROM AUTHOR]

The North Water is a large recurring polynya in northern Baffin Bay. Over 400 hydrographic CTD profiles taken over a grid of stations between April and July 1998 were analysed to understand the water-column structures underlying the polynya during spring transition. In the North Water, imported and dissimilar water masses converge over a complex bathymetry: Northern assembly (NA) waters are derived from inflows through Nares Strait and Jones Sound; Southern assembly (SA) waters are derived from a northern-moving branch of the West Greenland Current (WGC). NA and SA waters mix primarily over the north-south Smith Sound Canyon, between 76.5°N and 77°N latitude, to form a distinct, relatively thick halocline layer (termed 'North Water assembly', NWA), characterised by densitycompensating thermohaline intrusions. In the southern portion of the North Water, a sharp front between NWA waters and SA waters roughly aligns with the 500-m isobath. Flow patterns, deduced from potential temperature vs. salinity (θ -S) diagrams and from minima in stability frequency (N) profiles, indicate that this front results from the convergence of NWA waters and a branch of the WGC that is cyclonically re-directed as it approaches Smith Sound Canyon. Not all SA waters are immediately re-directed south towards the front, as a second branch follows the Greenland coast toward Smith Sound. While θ -S signatures show some evidence of upwelling along the Greenland coast (e.g. outcropping of isopycnal surfaces), no surfacing of warm Atlantic-derived water was observed during the sampling period (1998), suggesting that mechanical removal of ice by winds and currents is the primary mechanism by which the North Water forms. Some sensible heat exchange associated with brine rejection and penetrative convection may occur, but only during periods of active ice formation. [ABSTRACT FROM AUTHOR]

The article discusses the prospective effect of global warming on phytoplankton in ocean water affected by sea ice meltwater and river runoff. The authors predict that the smallest phytoplankton cells in the Arctic Ocean will thrive while larger ones will not. It notes ocean stratification conditions and chemistry that will change with global warming. The authors compare and contrast upper-ocean bacterio-plankton, picophytoplankton, and larger nanoplankton and their responses to ocean temperature changes. Biomass in the forms of chlorophyll and fucoxanthin is discussed.