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The Sea of Okhotsk is a marginal sea that plays a major role in the ventilation of the North Pacific, being the key location where Dense Shelf Water (DSW) forms at the surface and sinks to the intermediate layer. The Okhotsk Sea Intermediate Water (OSIW) is a key water mass because it includes large amounts of DSW, outflows to the North Pacific, and supplies the ocean with the micronutrient iron. OSIW has been warming over the past few decades, which is attributed to a decreasing trend in DSW production. The acquisition of numerous hydrographic data after 2000 in the Kuril Basin, especially dissolved oxygen from profiling floats, offers an opportunity to better quantify the water mass composition of OSIW, and the changes in OSIW properties and DSW volume. Here, we used all available hydrographic records and a mapping technique specially adapted to polar and sub‐polar regions to revisit the Sea of Okhotsk water properties and document their long‐term changes. Our analysis revealed that the volume of heavier DSW (potential density above 26.9 kg.m−3) has decreased over the past three decades by 3,600 km3, or 15% of the volume present before 1990. This decline is nearly entirely compensated for by an increase in lighter DSW. This shift toward lighter DSW is possibly a sign of the weakening of the intermediate overturning circulation starting in the Okhotsk Sea. Additionally, we found that dense Soya Current Water only accounts for about 1% of OSIW, against the 5% previously estimated. Plain Language Summary: The water of the Sea of Okhotsk is a mix of several water masses which includes the Dense Shelf Water (DSW), a water mass generated in winter via sea ice formation. When sea ice forms, the surface water salinity and density increase, and the cold DSW is generated as the surface water sinks to the bottom of the continental shelf while micronutrients, especially iron, are also incorporated. DSW mixes with other water masses and becomes the Okhotsk Sea Intermediate Water (OSIW) before being exported to the North Pacific where it plays an important role for both the climate and the biological productivity. In this study, we used all the temperature, salinity, and dissolved oxygen data acquired since 1930 to evaluate how global warming may have affected the composition of OSIW. We found that, over the past century, the amount of denser DSW has strongly decreased whereas that of lighter DSW has increased, which is consistent with the decline in sea ice production in the Sea of Okhotsk. This also suggests that the ventilation of the Sea of Okhotsk and the circulation of the intermediate layer of the North Pacific is weakening, which could indirectly affect the ocean's biological productivity. Key Points: The composition of the Okhotsk Sea Intermediate Water (OSIW) is reevaluated using an updated data set and a new mapping techniqueOSIW properties have changed in the long‐term (≥50 years) scale, with a decrease (increase) in the amount of heavy (light) Dense Shelf WaterThis suggests that the North Pacific intermediate overturning is weakening, which could affect the ocean's biological productivity [ABSTRACT FROM AUTHOR]

The Labrador Sea and contiguous Baffin Bay play an important role in the formation of the upper layer of the North Atlantic Deep Water, an essential component of the Atlantic Meridional Ocean Circulation. The hydrography of these two seas is strongly influenced by the melting of sea-ice and glacier-ice, which has likely been affected by long-term climate changes. In this study, we use historical data of ocean temperature and salinity from 1950 to 2022 to estimate the summer freshwater volume (SFV) in Baffin Bay and the Labrador Sea, establish climatologies, and assess the impact of multi-decadal climate change. The SFV climatology (1956 km3)and the summer freshwater budget (2286 km3)estimated from various components are in good agreement. Sea ice and glacial melt account for 37 % and 26 % of the freshwater budget, respectively. SFV climatologies before and after 1995 reveal an increase in Baffin Bay (+226 km3) because of enhanced glacier melting, and a decline (-112 km3) in the Labrador Sea because of recent sea ice volume decreases. The time series of Labrador Sea SFV and total freshwater content are uncorrelated at the multi-decadal scale possibly because the influx of freshwater from the Beaufort Sea dominates the long-term variability. [ABSTRACT FROM AUTHOR]

Polar and subpolar oceans play a particularly important role in the global climate and its temporal changes, yet these regions are less well sampled than the rest of the global ocean. To better understand the physical or biogeochemical properties and their variabilities in these regions, accurate data mapping is crucial. In this paper, we introduce a mapping methodology that includes a water column shrinking and stretching constraint (SSC) based on the principle of conservation of potential vorticity. To demonstrate the mapping scheme efficiency, we map the ocean temperature in the southern Sea of Okhotsk, where the bottom topography comprises a broad and shallow shelf, a sharp continental slope, and a deep oceanic basin. Such topographic features are typical of polar and subpolar marginal seas. Results reveal that the SSC integrated (SSCI) mapping strongly reduces the mapping error in the broad and shallow shelf compared with a recently introduced topographic constraint integrated (TCI) mapping procedure. We also tested our mapping scheme in the Southern Ocean, which has a comparatively slanted shelf, a wider and gentler slope, and a deep and broad oceanic basin. We found that the SSCI and TCI methods are practically equivalent there. The SSCI mapping is thus an effective method to map the ocean's properties in various topographic environments and should be adequate in all polar and subpolar regions. Importantly, we introduced a standardized procedure for determining the decorrelation length scales—a necessary step prior to implementing any mapping scheme—in any topographic conditions. [ABSTRACT FROM AUTHOR]

Like a cake, the ocean is made up of several layers. The heaviest (highest density) layer of water on the bottom of the ocean is called Antarctic Bottom Water (AABW). AABW forms around the coast of Antarctica in areas where lots of sea ice is produced due to freezing temperatures and strong winds. When sea ice is formed, most of the salt from the sea water is left behind, so the water underneath the sea ice becomes very salty and cold, making it heavy and dense. This dense water sinks to the bottom of the ocean to become AABW. AABW acts like a pump, powering the circulation of ocean waters all over the world. With climate change, warming temperatures and melting ice sheets will influence the formation of AABW, which could affect global ocean circulation, climate, and the plants and animals living both in the oceans and on land. [ABSTRACT FROM AUTHOR]

The article presents a study on dominant frazil ice production in the Cape Darnley polynya (CDP) which leads to Antarctic Bottom Water (ABW) formation. It discusses the process of Antarctic Bottom Water (AABW) formation, mapping of sea ice production and active-frazil area in the CDP, change in salinity, and implications of the dominant underwater frazil ice.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2005.11.002 Byline: Jun Ono (a)(b), Kay I. Ohshima (b), Genta Mizuta (a), Yasushi Fukamachi (b), Masaaki Wakatsuchi (b) Abstract: To clarify the characteristics of tidal currents and heights over Kashevarov Bank (KB) in the Sea of Okhotsk, continuous mooring observation with ADCP and CT sensors was carried out near the summit of KB from 20 September 1999 to 20 June 2000. The velocity, sea-surface height, and bottom-water temperature were dominated by the diurnal signal with fortnightly modulation. The velocity amplitude reached [approximately equal to]1.4ms.sup.-1 during the spring tide. The K.sub.1 and O.sub.1 tidal current ellipses are clockwise with a nearly circular shape and nearly barotropic. To interpret the physical mechanism of the amplified diurnal currents over KB, a seamount-trapped wave (SMTW) model was applied to KB. The frequency of SMTW approximated to KB is close to the diurnal tidal frequencies for the first-gravest mode of first azimuthal wavenumber. The structure and properties of the SMTW mode are consistent with the observations. It is proposed that the amplified diurnal currents over KB are caused by the resonance with SMTW. The observed fortnightly variability in tidal currents and bottom- and surface-temperatures suggests that both the cold spot in summer and the low sea-ice concentration in winter over KB are due to the horizontal and vertical mixing with the surrounding subsurface water, caused by strong tidal currents. Author Affiliation: (a) Graduate School of Environmental Earth Science, Hokkaido University, Sapporo, Japan (b) Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan Article History: Received 13 December 2004; Revised 20 September 2005; Accepted 14 November 2005