Interdisciplinary physical and biological processes of the Sea of Okhotsk and the Japan/East Sea (11,S) (original) (raw)
Related papers
Distribution, formation, and seasonal variability of Okhotsk Sea Mode Water
Journal of Geophysical Research, 2003
1] Russian historical data and recently completed conductivity-temperature-depth surveys are used to examine the formation and spread in the deep Ohkotsk Sea of dense shelf water (DSW) produced in the Okhotsk Sea polynyas. Isopycnal analysis indicates that all of the main polynyas contribute to the ventilation at s q < 26.80, including the Okhotsk Sea Mode Water (OSMW), which has densities s q = 26.7-27.0. At densities greater than 26.9 s q the northwest polynya is the only contributor to OSMW. (Although Shelikhov Bay polynyas produce the densest water with s q > 27.1, vigorous tidal mixing leads to outflow of water with a density of only about 26.7 s q ). In the western Okhotsk Sea the East Sakhalin Current rapidly transports modified dense shelf water along the eastern Sakhalin slope to the Kuril Basin, where it is subject to further mixing because of the large anticyclonic eddies and tides. Most of the dense water flows off the shelves in spring. Their average flux does not exceed 0.2 Sv in summer and fall. The shelf water transport and water exchange with the North Pacific cause large seasonal variations of temperature at densities of 26.7-27.0 s q (depths of 150-500 m) in the Kuril Basin, where the average temperature minimum occurs in April-May, and the average temperature maximum occurs in September, with a range of 0.2°-0.7°C. The average seasonal variations of salinity are quite small and do not exceed 0.05 psu. The Soya Water mixed by winter convection, penetrating to depths greater than 200 m, in the southern Kuril Basin also produces freezing water with density greater than 26.7 s q . Using a simple isopycnal box model and seasonal observations, the OSMW production rate is seen to increase in summer up to 2.2 ± 1.7 Sv, mainly because of increased North Pacific inflow, and drops in winter to 0.2 ± 0.1 Sv. A compensating decrease in temperature in the Kuril Basin implies a DSW volume transport of 1.4 ± 1.1 Sv from February through May. The residence time of the OSMW in the Kuril Basin is 2 ± 1.7 years.
Seasonal variation in the in- and outflow of the Okhotsk Sea with the North Pacific
Deep Sea Research Part II: Topical Studies in Oceanography, 2010
This paper examines the seasonal variation in the in-and outflow of the Okhotsk Sea with the Pacific, mainly based on profiling float and satellite altimeter data. The motions of the floats at depths of 500-750 m show that the waters of the Okhotsk tend to flow out to the Pacific through the southern Kuril Straits, mostly Bussol' Strait, in winter seasons (November-March). Based on data from the floats exiting the Sea, the mean residence time of the intermediate water in the Kuril Basin is estimated as about one year. Isopycnal analysis from the profiling data shows that, in the mid-eastern area of the Okhotsk Sea, potential temperature of the intermediate water with σθ= 26.6-27.2 increases by 0.2-0.5 C in every spring, suggesting the inflow from the Pacific in the preceding season. These suggest that the in-and outflow predominantly occurs during winter, with the inflow at the northern straits and outflow at the southern straits. The surface current field 1 inferred from satellite altimeter data also shows that the inflow to the Sea of Okhotsk through the northern straits is strengthened in winter, linked with strengthening of the East Kamchatka Current (EKC). From yearly anomalies of the altimeter data, the winter inflow to the Okhotsk through the northern straits is significantly correlated with the EKC and Sverdrup transport over the North Pacific. Further, interannual variations in property of Okhotsk Sea Intermediate Water appear to be related with the EKC and wind stress over the North Pacific in winter, possibly through the change in inflowing Pacific water transport. These suggest that the seasonal and interannual variations of the in-and outflow are, to some extent, controlled by the large scale wind stress over the North Pacific, being consistent with Island Rule qualitatively.
Deep Sea Research Part I: Oceanographic Research Papers, 2019
The seasonal variability of the hydrography and anticyclonic circulation in the Kuril Basin of the Sea of Okhotsk, from which the North Pacific ventilation originates, is studied from bimonthly climatologies of temperature, salinity, dynamic height and current velocity. The subsurface hydrography of the Kuril Basin is characterized by the dominant role of fresh and cold waters transported by the East Sakhalin Current during winter and spring, and relatively warm and saline waters flowing with the Soya Warm Current. At the intermediate layer, the influence of dense shelf water is maximum from May to August, and this water mixes with surrounding waters in around half a year to form a well homogenized Okhotsk Sea Intermediate Water, the source of North Pacific ventilation. The anticyclonic circulation typical of the Kuril Basin exhibits a strong seasonality, being absent in winter and showing a maximum amplitude in summer. Its formation is mainly related to the dynamic response of isopycnals to wind forcing. A dynamic height maximum appears along the coastal regions 2 from Sakhalin Island to the southern Kuril Straits in winter, likely migrates towards the Kuril Basin in March-April and forms the anticyclonic system between May and October. The dynamic height and thus flow field is mainly determined by isopycnal displacement in and around the Kuril Basin, whereas advection of water masses has a negligible effect. Surface intensification and decay of the anticyclonic circulation seems to be related to other processes such as heat exchange with the atmosphere.
How does the Amur River discharge flow over thenorthwestern continental shelf in the Sea of Okhotsk?
Progress in Oceanography, 2014
The paths of the Amur River discharge on the continental shelf in the Sea of Okhotsk are still unknown despite their significance in transporting dissolved and particulate iron. In this study, we conduct a coupled ice-ocean simulation for the northern Sea of Okhotsk from June 1998 to September 2000 to answer the question: Does the Amur River discharge deposit materials to the pathway of the dense shelf water? In a series of numerical experiments, we identified two routes (the western and eastern routes) that could transport the river water more than 100 km offshore over the northwestern continental shelf. The two routes share the clockwise gyre in the Sakhalin Gulf and the northeastward flow on the northwestern continental shelf. These features are connected through the westward jet along the slope from the Sakhalin Gulf (the western route) and the northward transport over the shelf break canyon (the eastern route). The river water, the dense shelf water, and the easterly wind are in a fine geophysical balance for those features, and all are required for the formation of the two routes. The model results show that these unique joint effects in the Sea of Okhotsk allow the Amur River discharge to be effectively transported over the northwestern continental shelf, unlike a general river discharge that flows along the coast, and deposit materials into the pathway of the dense shelf water.
2008
The influence of interannual variability of water transport by the East Kamchatka Current, the Oyashio, and the East Sakhalin Current on the dissolved oxygen concentration in the western subarctic Pacific and the Sea of Okhotsk is considered for studying climate change impact on sea water chemical parameters. It is shown that statistically significant relation is observed between the calculated with the Sverdrup equation interannual variations in water transport with the East Kamchatka Current, the Oyashio, and the East Sakhalin Current and changes in mean sea water level at coastal stations in winter. It is found that the main reason of interannual variability of the dissolved oxygen concentration at isopycnic surfaces in the intermediate water layer (100-800 m) of the Sea of Okhotsk and in the western subarctic Pacific is caused by variations in water transport by the East Kamchatka Current, the Oyashio, and the East Sakhalin Current.
Journal of Geophysical Research, 2000
For the northern Okhotsk Sea polynyas, five Russian CTD surveys taken during 1995 to 1997 are used to examine the evolution of the polynya dense water. The surveys show that consistent with other investigations, the largest potential densities are 26.99 •0, and the densest water occurs in Sakhalin and Shelikhov Bays. The surveys also suggest that the Shelikhov water drains directly into the deep Okhotsk, while on the northern shelves, gravity currents transport the dense water west to Sakhalin Bay. For comparison, determination of the polynya sizes and ice production from satellite passive microwave and meteorological observations shows that polynyas occur on the northwest shelf (NWS) between Ayan and Okhotsk City, on the northern shelf between Okhotsk City and Magadan, and in Shelikhov Bay. In contrast, the observations show that Sakhalin Bay is a region of land fast ice with no polynyas, so that the dense water observed here cannot form locally. For all polynyas the satellite observations show that the NWS contributes 60 to 70% of the total ice production, and due to the warmer 1997 air temperatures, the 1996 production is about 1.5 times the 1997 value. An estimate of the ice production from the surveys shows a similar regional distribution and enhancement of the 1996 production, with the satellite and ship estimates in agreement within their error bars. Finally, analysis of the dense water outflow shows that the upper Okhotsk Sea Mode Water has a renewal time of about 4 years; the lower part, about 14 years. the OSMW formation to tidal mixing in the Kuril Straits and to the formation and mixing of dense shelf water. There are two proposed mechanisms for the formation of the OSMW. First, Watanabe and Wakatsuchi [1998], who refer to the OSMW as Kuril Basin Intermediate Water, discuss the role of forerunner Soya Water (FSW) in the OSMW formation and conclude that the OSMW is the product of isopycnal mixing between the FSW, which is that water flowing through the Soya Strait in late spring, and the dense water in the East Sakhalin Current, which originates from the northern Okhotsk. Second, Alfultis and Martin [1987] and Wong et al. [1998] (hereafter W-98) assume that the OSMW, or what W-98 call the upper Sea of Okhotsk Intermediate Water (upper SOIW), forms by isopycnal mixing of North Pacific water with the dense shelf water. From CFC measurements, W-98 also estimate that the OSMW renewal time is 1.4 years and argue that there is insufficient water produced on the shelf for the second mixing mechanism to work alone, so that there must be an additional source for the OSMW. Although the formation of the NPIW and OSMW is generally attributed to ice processes on the northern shelves, little is known about the dy-26,281 Basin Kuril Basin I Penzhinskaya Magadan Bussol' Strait Kruzenshtern Strait Pacific Ocean 140E 145E 150E 155E 160E ß ß ß ß ß ß ß 14(•E -1.5 300 m 145E 5J' ' ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß 15(•E Longitude 155E 160E 140E 32.9 33.1 145E ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ß ßß i 33.0 33.2 2.0-0.0ß ß -2.0 , , 55N ß ß 200 rn ß 0.3 ß ß ß ß ß ß ß ß ß ß 200 ß 60N 55N 50 ß 20(•m ß ß ß ß ß , ß ß ß ß ß ß ß ß ß ß ß ß ß 140E Figure 11. The thickness and brine enrichment of dense water on the northern shelves in (a and b
Roles of the Okhotsk Sea and Gulf of Alaska in forming the North Pacific Intermediate Water
Journal of Geophysical Research, 2000
Recently obtained World Ocean Circulation Experiment (WOCE) sections and pre-WOCE hydrography are used to study the water -mass structure and formation and transformation of North Pacific Intermediate Water (NPIW). Five neutral density surfaces are selected and mapped, encompassing NPIW from 400 to 900 m in the subtropical latitudes with a distance of-100 m between a pair of surfaces. NPIW is defined as a subtropical gyre salinity minimum which is well followed by a neutral density surface ON=26.9. Formation and transformation of NPIW is examined by the mapped Turner angle on neutral density surfaces. Apparent diffusive double diffusion is found in the Alaskan gyre on ON=26.5 neutral surface, in the northwest subpolar gyre and the Okhotsk Sea on ON=26.9 neutral surface, and mainly in the Okhotsk Sea on the two deep neutral surfaces ON=27.2 and ON=27.4. These diffusive regions indicate transformation sources for NPIW. Along with additional information of potential vorticity and stream function, it is found that there are two different NPIW formation sources: one in the Gulf of Alaska characterized by high potential vorticity and the other in the Okhotsk Sea characterized by low potential vorticity. The former lies shallower at ON=26.2-26.5, but its effect deepens to NPIW core density level at ON=26.8 on the basis of potential vorticity distribution. The latter includes the influence of the northwest subpolar gyre and extends much deeper to ON=27.4. We call them Gulf of Alaska Intermediate Water (GAIW) and Okhotsk Intermediate Water (OIW), respectively. GAIW contributes to NPIW in the eastern part of the subtropical gyre east of date line, whilst OIW dominates in the west and entire lower part of NPIW. Seasonal flow stream function mapped on neutral surfaces shows that the contribution of GAIW to NPIW occurs mainly in the wintertime, because in winter a significant northward shift of zero wind stress curl makes the Gulf of Alaska an additional source for NPIW.
Flux of low salinity water from Aniva Bay (Sakhalin Island) to the southern Okhotsk Sea
Estuarine, Coastal and Shelf Science, 2011
In this study, we examined the relationship between the low salinity water in the shelf region of the southern Okhotsk Sea which was seasonally sampled (0-200 m), and fluxes of low salinity water from Aniva Bay. To express the source of freshwater mixing in the surface layer, we applied normalized total alkalinity (NTA) and stable isotopes of seawater as chemical tracers. NTA-S diagrams indicate that NTA of low salinity water in the upper 30 m layer just off the Soya Warm Current is clearly higher than in the far offshore region in summer and autumn. Using NTA-S regression lines, we could deduce that the low salinity and high NTA water in the upper layer originates from Aniva Bay. For convenience, we defined this water as the Aniva Surface Water (ASW) with values S<32, NTA>2450 µmol kg-1. Formation and transport processes of ASW are discussed using historical data. The interaction between the maximum core of high NTA water on the bottom slope of eastern Aniva Bay and an anticyclonic eddy at the mouth of Aniva Bay are concluded to control ASW formation. Upwelling of the Cold Water Belt water at the tip of Cape Krillion is considered to cause ASW outflow from Aniva Bay.
Deep Sea Research Part II: Topical Studies in Oceanography, 2012
Core GC9A, a 6.7 m long gravity core collected from the central region of the Okhotsk Sea during Cruise YK0712 on R/V Yokosuka (JAMSTEC), was used to reconstruct the changes in surface water conditions by measuring biogenic components (biogenic opal, CaCO 3 , total organic carbon and d 15 N of sediment organic matter) of sediment samples. The age of Core GC9A was determined indirectly by graphic correlation comparing the b n (psychometric yellow-blue chromaticness) values with those of well-dated Core MD01-2415, with complement to the tephra layer (K3; 50 ka). The bottom age of Core GC9A was estimated to be about 180 kyr; therefore it provides the history of surface water conditions from MIS 1 to MIS 6. The biogenic opal, CaCO 3 , and TOC contents were high during the interglacial periods as expected, indicating enhanced surface water production under warm climatic conditions. This condition resulted from sufficient nutrient supply to the surface waters by active vertical mixing, which was validated by low d 15 N values of the sediment organic matter. In contrast, surface water productivity was depressed during the colder glacial periods, probably due to the expanded sea-ice distribution and limited nutrient supply. However, the glacial sediments had moderately high d 15 N values, indicating enhanced nitrate utilization resulting from the limited nutrient supply caused by strong stratification of the surface water.