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The formation of Antarctic Bottom Water-the cold, dense water that occupies the abyssal layer of the global ocean-is a key process in global ocean circulation. This water mass is formed as dense shelf water sinks to depth. Three regions around Antarctica where this process takes place have been previously documented. The presence of another source has been identified in hydrographic and tracer data, although the site of formation is not well constrained. Here we document the formation of dense shelf water in the Cape Darnley polynya (65°-69° E) and its subsequent transformation into bottom water using data from moorings and instrumented elephant seals (Mirounga leonina). Unlike the previously identified sources of Antarctic Bottom Water, which require the presence of an ice shelf or a large storage volume, bottom water production at the Cape Darnley polynya is driven primarily by the flux of salt released by sea-ice formation. We estimate that about 0.3-0.7×106 m3 s−1 of dense shelf water produced by the Cape Darnley polynya is transformed into Antarctic Bottom Water. The transformation of this water mass, which we term Cape Darnley Bottom Water, accounts for 6-13% of the circumpolar total. [ABSTRACT FROM AUTHOR]

Sea ice formation, its transport, and its melting cause the redistribution of heat and salt, which plays an important role in the climate and biogeochemical systems. In the Sea of Okhotsk, a heat and salt flux dataset is created in which such sea ice processes are included, with a spatial resolution of ~12.5 km. The dataset is based on a heat budget analysis using ice concentration, thickness, and drift speed from satellite observations and the ECMWF Interim Re-Analysis (ERA-Interim) data. The salt flux calculation considers both salt supplied to the ocean from sea ice production and freshwater supplied when the ice melts. This dataset will be useful for the validation and boundary conditions of modeling studies. The spatial distribution of the annual fluxes shows a distinct contrast between north and south: significant ocean cooling with salt supply is shown in the northern coastal polynya region, while ocean heating with freshwater supply is shown in the south. This contrast suggests a transport of freshwater and negative heat by ice advection. The annual fluxes also show ocean cooling with freshwater supply in the Kashevarov Bank (KB) region and the central and eastern Sea of Okhotsk, suggesting the effect of warm water advection. In the ice melt season, relatively prominent ice melting is shown in the coastal polynya region, probably due to large solar heating of the upper ocean. This indicates that the polynya works as a 'meltwater factory' in spring, contrasting with its role as an 'ice factory' in winter. In the coastal polynya region, the spatial distribution of phytoplankton bloom roughly corresponds with the ice melt region. [ABSTRACT FROM AUTHOR]

This paper investigates the formation mechanism of broad coastal polynyas beyond 100 km in offshore width. It is known that two regimes for wind-driven polynya opening exist: one is a convergent regime at the polynya edge in which inner frazil ice catches up with outer consolidated ice, whereas the other is a divergent regime in which the consolidated ice drifts offshore faster than the frazil ice at the edge. In this study, the authors focus on the latter, divergent polynya-edge regime. Because in the divergent regime the polynya possibly evolves without bound, they consider a thermal growth for inner frazil ice to find a finite solution of offshore width. Then, the authors investigate responses of the polynya opening for various wind angles ϕ from the offshore direction from the viewpoint of the polynya-edge regimes. At first, the authors estimate the deviation angle and wind factor for the frazil and consolidated ice based on each momentum balance, because sea ice motion driven by wind varies depending on the ice thickness due to relative effect of the Coriolis force. It was found that, when the surface wind deviates leftward about 10°° or greater from offshore, the divergent regime at the polynya edge generates a great polynya evolution. Otherwise, the convergent regime takes place yielding small offshore extent. These theoretical results were verified for the Okhotsk northwestern polynya using thin-ice-thickness data derived from Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) and the Japanese 25-year Reanalysis (JRA-25) surface wind. The data show that the polynya development distinctively changes at ϕ ∼∼ 0°°, and the largest width is shown in the leftward wind angle of ϕ == 0°°--30°°. This clear relationship between the surface wind angle and the offshore extent of polynya nicely supports the theory. [ABSTRACT FROM AUTHOR]