This paper describes the use of the Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) satellite data to study the ice cover in the Sea of Okhotsk during the four winters of 1978-1982. The ice concentration estimates obtained from SMMR are used to study two different polynyas: one over the Kashevarova Bank, and the other over the northwest continental shelf. For the Kashevarova polynya this study shows that the polynya, which may be related to the upwelling observed in historic summer cruises, occurs directly over the bank. For the continental shelf, which because of strong offshore winds and cold temperatures is a region of high ice production, the polynya areas are combined with heat flux estimates from weather station data to yield the production rates of ice, salt, and dense shelf water. As a previous study by Kitani (1973) shows, the mixing of this dense shelf water with Pacific water yields a water mass unique to the Okhotsk, which is the layer of cold, low-salinity intermediate water between depths of 150 and 800 m. From our calculations, we estimate that the dense shelf water is produced at an annual rate of about 0.5 Sv, and that the intermediate water is produced at a rate of 1-2 Sv, which yields a renewal time for this layer of 10-40 years. 1. the Kamchatka Peninsula to the east, the Asian continent to the north, and Sakhalin Island to the west (Figure 1). For this study, the most important topographic features of the Okhotsk are the broad northwest continental shelf between Magadan and Shantarskiy Bay, and the topographic rise northeast of Sakhalin Island called the Kashevarova Bank (55ø5øN, 145øE). Although the Okhoisk is geographically located at temperate latitudes, it has many characteristics of a polar ocean' severe winters with cold temperatures and high winds, mild but short summers, large seasonal variations in atmospheric and water temperatures, and a subarctic water column structure. The Okhotsk also has a seasonal ice cover present from December through April with a thickness of the order of 1 m and an areal coverage comparable to that of the Bering Sea [Tabata, 1958' Parkinson et al., 1987]. The Okhotsk is connected to the Sea of Japan by two narrow, shallow straits' the Soya Strait south of Sakhalin, with a sill depth of 40 m, and the Tartar Strait between Sakhalin and the mainland, with a depth of 10 m [Favorite et al., 1976]. These shallow depths greatly restrict the interaction of the Okhotsk with the Sea of Japan. To the south, the Kuril island chain has two deep straits which allow for exchange of the Okhotsk water with the Pacific. These straits are the Bussol' Strait with a maximum depth of 2300 m, and the Kruzenshterna Strait with a 1900-m depth. The basic circulation in the Okhotsk consists of a large cyclonic gyre, which consists of the surface and subsurface northward flow of Pacific water through the Kruzenshterna Strait then along the Kamchatka Peninsula [Moroshkin, 1966' Leonov, 1960]. The flow next circulates around the northern x Now at International Ice Patrol, Av...
Subtropical mode waters (STWMs) are water masses formed in winter by convective mixing on the equatorward side of western boundary currents in the subtropical gyres. After the return of the seasonal stratification in spring, it is found at the stratification minimum between the seasonal and main pycnoclines. By characterizing STMW primarily at the density gradient minimum, previous studies were limited in their ability to describe STMW properties over large temporal and spatial scales. Rather than using a density-based characterization, the North Atlantic STMW layer was identified here by its much smaller temperature gradient relative to the more stratified seasonal and main thermocline, its temperature, and its large thickness. By using this temperaturebased characterization, this study was able to develop a climatology using the large number of XBTs deployed between 1968 and 1988 and contained in the World Ocean Atlas 1994 historical hydrographic database and to use this climatology to examine STMW properties on large spatial and long temporal scales. Three different characterizations were used to assess the degree of convective renewal of the STMW layer during the 1968-88 winters. Two characterizations were based on comparing the winter mixed layer properties to the STMW layer properties in the previous fall, while the third characterization involved comparing the temperature gradient through the STMW layer in the spring to the STMW layer temperature gradient in the previous fall. Based on these characterizations, there was considerable spatial and temporal variability in the renewal of the STMW layer'
The North Atlantic Subtropical Mode Water (STMW) layer was identified based on its temperature, large thickness, and small temperature gradient. Comparisons between this method and identifying the STMW layer using a density-based (i.e., potential vorticity) criteria indicate that this method successfully identifies the STMW layer as the remnant of the previous winter's convective mixing. By using this temperature-based characterization of the STMW layer, this method was able to develop a climatology using the large number of expendable bathythermographs (XBTs) deployed between 1968 and 1988, and contained in the World Ocean Atlas 1994 historical hydrographic database. From this climatology, the STMW layer that is the remnant of the previous winter's convective activity is typically found between 175 and 450 m, has an average temperature near 18ЊC, and has a mean temperature gradient of 0.5ЊC (100 m) Ϫ1. Comparisons of the STMW temperature, thickness, and temperature gradient characteristics in this climatology agree with other observations of the North Atlantic STMW layer.
Subtropical Mode Water (STMW) is a water mass formed in winter by convective mixing on the equatorward side of western boundary currents in the subtropical gyres. After the return of the seasonal stratification:.in spring, it is found at the ~ stratification minimum between the seasonal and main pycnoclines. By characterizing ng STMW primarily at the density gradient minir~um , previous studies were limited in their ability to describe STMW properties over large temporal and spatial scales. Rather than using a density-based characterization, the North Atlantic STMW layer was identified here by its much smaller temperature gradient relative to the more stratified seasonal and main thermoclines. By using a temperaturebased characterization, this study was able to take advantage of the large volume of XBT data collected between 1968 and 1988 to examine STMW properties on large spatial and long temporal scales. There was considerable spatial and ternporal variability in the renewal of the STMW layer's vertical homogeneity from
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.