CC BY
9
RUSSIAN JOURNAL OF EARTH SCIENCES, VOL. 19, ES5002, doi:10.2205/2019ES000674, 2019
Modeling spring hydrodynamic regime of surface waters in Kamchatka Strait
Galina Vlasova1, Svetlana Marchenko1, and Natalia Rudykh1 Received 2 April 2019; accepted 24 June 2019; published 12 September 2019.
On the basis of numerical modeling, an analysis of the average multiyear pattern of the spring circulation of surface waters in the Kamchatka Strait is performed. It was revealed that in the spring period the winter regime of water circulation continues here, however, the transition to the summer circulation mode begins and the influx of warm Pacific water masses to the Bering Sea is intensifying. The results obtained are somewhat different from the generally accepted ones. KEYWORDS: Aleutian Island Arc; Kamchatka Strait; Kamchatka Current; winter and summer monsoons; water circulation.
Citation: Vlasova, Galina, Svetlana Marchenko, and Natalia Rudykh (2019), Modeling spring hydrodynamic regime of surface waters in Kamchatka Strait, Russ. J. Earth. Sci, 19, ES5002, doi:10.2205/2019ES000674.
Introduction
The straits of the Aleutian island arc are important for the formation of many natural processes in the Bering Sea and the North-Western Pacific, providing water exchange between them.
The Aleutian Islands are located in the zone of temperate latitudes, which creates the basic features of its climate (Figure 1).
This region is under the constant influence of the Polar and Hawaiian atmospheric maxima and seasonal large-scale baric formations (Aleutian Low, Siberian High, and Asian Depression). The winds of the north, north-west and north-east directions prevail in winter, and the winds of the south, southwest and south-east directions dominate in summer. Cyclonic eddies forming between the Polar and Hawaiian atmospheric maxima largely create the climate and weather of the Aleutian Islands. 50-60 cyclones reach the Barents Sea during the year, a significant number of which passes over the western islands of the Aleutian Arc (Figure 2).
1V. I. Il'ichev Pacific Oceanological Institute, Far Eastern Branch RAS, Vladivostok, Russia
Copyright 2019 by the Geophysical Center RAS. http://rjes.wdcb.ru/doi/2019ES000674-res.html
The Aleutian Island arc is separated from the Kamchatka Peninsula by the Kamchatka Strait. It is the deepest strait of this region (see Figure 1). The Kamchatka Current carries cold, slightly saline waters of the Bering Sea through this strait into the Pacific Ocean.
It is known that the general circulation of the Bering Sea is formed by the cyclonic gyre, which is a continuation of the large-scale stationary subarctic gyre in the Pacific between 40°-60°N. [Ar-senyev, 1967; Cokelet et al., 1996; Khen, 1989; Khen and Basyuk, 2005; Khen et al., 2013; Reed, 1995; Solomon and Ahlnas, 1978; Stabeno and Reed, 1994; Stabeno et al., 1999; Takenouti and Ohtani, 1974]. The Kamchatka current is the western link of the indicated cyclonic circulation. This current is characterized by active spatial-temporal variability, in connection with which large-scale variability of water exchange with the Pacific Ocean also occurs. The results of the analysis of these processes are described in [Khen and Zaochniy, 2009].
The harsh climate, large-scale baric formations, unstable hydrodynamics, a large number of cyclones, and rugged bottom relief complicate the study of water circulation in the Kamchatka Strait. In this connection, only some aspects of the summer spatial-temporal hydrological characteristics and water exchange in the Kamchatka Strait have
ES5002
1 of 7
Bering Sea
Commander Island
ir - mm m &
1 6 Ax -f * • • V °
u t i an
Pacific Ocean
Google earth
t»a SD. HOAA US. fto/y, HGA GQCO rage Landsa / Ctpeméus rage BCAÛ
Figure 1. Map of the Aleutian Archipelago. The dotted line shows the research area.
been studied at present [Khen and Zavolokin, 2015; Khen and Zaochniy, 2009; Luchin, 2008; Overland et al., 1994; Prants et al., 2014; Rogachev and Shlyk, 2008, 2010; Solomon and Ahlnas, 1978; Zhabin et al., 2010]. Spring transitional period
(April-July) is practically not been studied. This determined the purpose and objectives of our research.
The purpose of our research is to study the average multiyear pattern of the spatial and tempo-
Figure 2. Cyclones trajectories in the Pacific (Polyakova A. M., 2010, Calendar of synoptic situations over North Pacific, http://pacificinfo.ru/en/climate/calendar/).
ES5002
ral variability of surface water circulation in the Kamchatka Strait in the spring season using hydro-dynamic model and software "Ocean Data View" (ODV).
The cell size of the grid was chosen taking into account the bottom relief of the study area, which includes not only the shelf, where the Rossby baro-clinic radius is 2 km, but also depths over 4000 m.
The study area is limited to coordinates 54°-57°N and 162°30' - -166°30' E (see Figure 1).
Data and Methods
To solve these problems, a known quasi-geostrophic model of water circulation was used [Felsenbaum, 1956, 1970; Shapiro, 1965; Vasiliev, 2001, et al.]. This model has been repeatedly described in monographs and articles [Polyakova et al., 2002; Vlasova et al., 2008, 2016a, 2016b, et al.], so here we are limited to its main characteristics.
This model allows to calculate the integral circulation of water in the form of a field of total flows (Sx = -d^/dx, Sy = -d^/dy) by the tangential wind stress (T) and the density of water (p°) on the sea surface. The calculation of the currents structure and the density of water masses for given parameters T and p° leads to the solution of the equation for the integral current function ^(x, y) using the minimal discrepancy method. The function ^ applied on solid boundaries of the water area (coastline), and its normal derivative applied on the liquid boundary.
The model takes into account the vertical distribution of water density, bottom relief, coast orography and the state of the atmosphere over the studied area. Water consumption was determined on the basis of the calculation of the total flows normal to the liquid boundaries of the studied area.
For processing and graphical display of used oceanographic data [Schlitzer, 2002, Schlitzer R., Ocean Data View, 2016, https://odv.awi.de], this model has been adapted to the software "Ocean Data View".
Within the framework of this model, the integral functions of the current in the surface layer were calculated. As a result of calculations, the values of surface temperature, salinity, vertical component of current velocity, as well as tangential stress and wind speed, drift and gradient components of cur-
ES5002
rent velocity, depth of the homogeneous layer, and other oceanographic and meteorological values in a given period of time were obtained.
The following information was used as the initial information:
• monthly mean values of atmospheric pressure at sea level for May and June from the data set NCEP Reanalysis (http://www.esrl.noaa. gov/psd/data/gridded/data.ncep.reanalysis. derived.html);
• depth values from the GEBCO30 dataset;
• calculated monthly mean values of surface temperature and salinity based on ODV algorithms (DIVA-gridding) at 5-minute grid nodes according to WOD2013 data for the period 1950-2017.
For the calculations, the spring hydrological period (May, June) was used as an example of the transition from the winter subarctic regime of waters to moderate summer.
Results and Discussion
As noted above, works devoted to oceanographic research directly to the Kamchatka Strait is very few. Nevertheless, the results of these works show that in the Kamchatka Strait there is not only onesided movement of the Bering Sea waters into the Pacific Ocean, but in different years and seasons there is also two-way water exchange between these basins [Dobrovolsky and Arsenyev, 1961; Wang et al., 2009].
In our case, the spring period (May, June) is considered as a transition from winter to summer, when the process of breaking ice begins. Off the southern coast of the Kamchatka Peninsula, the destruction of ice begins in the second decade of May [Polyakova et al., 2002]. In the winter season, the flow of freshened waters is considerably weakened. In May, the ice edge slowly recedes to the north, starting from the eastern coast of the Kamchatka Peninsula. In June, the process of ice destruction accelerates (Figure 3).
Our calculations have shown that in the period under consideration (May-June) a complex hydro-dynamic situation is simulated in the studied area.
VLASOVA ET AL.: MODELING SPRING HYDRODYNAMIC REGIME
Temperature [degrees_C] @ Depth [m]=first Temperature [degrees_C] @ Depth [m]=first
163°E 164°E 165°E 166°E 163°E 164°E 165°E 166°E
a b
Figure 3. The average monthly surface temperature values calculated on the basis of ODV (DIVA-gridding) algorithms at the 5-minute grid nodes according to WOD2013 data for the period 1950-2017 in May (a) and June (b).
Against the background of a general cyclonic motion, the Kamchatka current does not constitute a single unbroken flow of water masses in the model area. Instead, several hydrodynamic gyres of a different sign are formed here (Figure 4).
Consider this in more detail. First of all, mixed structures form here in surface waters in May and in June. However, the picture of their location and configuration during this period changes.
For example, in May (see Figure 4a) a powerful
Figure 4. Scheme of surface water circulation in the Kamchatka Strait in May (a) and June (b) according to the simulation results (current functions, 1 x 106 cm3/s).
Figure 5. Buoy drift (green lines) at a depth of 200 m in May (a) and June (b), plotted on the water circulation map in the 200th layer.
and extensive anticyclonic gyre forms in the western part of the strait and extends along the coast of Kamchatka between ~ 55° — 57° N. Accordingly, the warm waters of the Pacific Ocean move into the Bering Sea along the shores of Kamchatka; on the contrary, in the eastern part of the strait, the waters of the Bering Sea move into the Pacific Ocean. The formation of this anticyclonic gyre, as well as the pattern of movement of the water masses within it, can be explained by the beginning of the reorganization of the synoptic processes, passing into the regime close to the summer one.
In the eastern part of the strait, near Bering Island, small anticyclonic eddies are modeled with a predominant moving of cold Bering Sea waters into the Pacific Ocean. Thus, in the eastern part of the strait, the winter mode of waters should prevail.
In the center of the strait there are two small whirlwinds of different signs. This provides both a weak runoff of the Bering Sea waters and a weak inflow from the Pacific Ocean.
In June (see Figure 4b), the hydrodynamic pattern changes somewhat, which can be attributed to increased solar activity, accelerated ice destruction and the continuation of surface layer formation processes [Khen and Zaochniy, 2009].
In the western part of the strait, the presence of the May anticyclonic gyre remains, however this structure is significantly deformed: it is divided
into separate, equally powerful submesoscale gyres. At the same time, the current pattern remains the same; near the Kamchatka Peninsula, it corresponds to the summer mode of waters, and within the eastern branch of the anticyclone - to the winter mode.
In the eastern part of the strait, near Bering Island, the May anticyclonic vortex is preserved and, consequently, the winter mode is preserved.
In the central part, the May anticyclonic eddy is destroyed, which should initiate the preferential runoff of Bering Sea waters into the Pacific Ocean (winter mode).
Despite the diversity of hydrodynamic structures, in the Kamchatka Strait are prevailing anticyclonic activity.
Similar anticyclonic circulation around all the Commander Islands, which includes Bering Island, was noted earlier in the works [Dobrovolsky and Arsenyev, 1961; Zhabin et al., 2010; Prants et al., 2014]. In the middle of the last century, an explanation of this phenomenon was given: it is associated with the existence and convergence of the Alaskan and Aleutian currents, the waters of which flow in opposite directions. Transverse irregularity (vorticity) of the wind also affects this phenomenon [Shtokman, 1954]. According to other studies [Ti-monov, 1960], this circulation is also supported by tidal phenomena due to the uneven spatial distri-
bution of tidal flow velocities since the study area is located in the zone of active tidal processes [Zhabin et al., 2017].
During the indicated spring period, the atmospheric situation is extremely unstable; therefore, the runoff of desalinated Bering Sea waters does not appear clearly on the circulation maps of surface waters. This can be explained by drift buoys at a depth of 200 m. Thus, Figure 5 shows that buoys practically do not cross the strait (one section in June), but rotate near it or move across.
Conclusion
The results of numerical modeling of spring water circulation in the Kamchatka Strait led us to the following conclusions:
• The modeled structure and dynamics of water circulation in the Kamchatka Strait is somewhat different from the generally accepted one. So, for example, the Kamchatka Current, at least during this season, does not constitute a uniform, unbroken flow of water masses, but is an active vortex zone;
• In the study period, the current system is transformed towards the summer mode. In this regard, the influence of warm Pacific waters is increasing. This is explained by increased solar radiation, the start of ice destruction and the continuation of the formation of the surface layer;
• Despite the diversity of hydrodynamic structures, in the Kamchatka Strait are prevailing anticyclonic activity;
• The differences in the May and June flow patterns are shown.
References
Arsenyev, V. S. (1967), Flows and Water Masses of the Bering Sea, 135 pp. Science, Moscow. (in Russian)
Cokelet, E. D., M. L. Schall, D. M. Dougherty (1996), ADCP-referenced geostrophic circulation in the Bering Sea Basin, Physical Oceanography, 26, 11131128, Crossref
Dobrovolsky, A. D., V. S. Arsenyev (1961), The Hydrological Characteristic of the Bering Sea, Trudy IO AS USSR, 38, 64-96. (in Russian) Felsenbaum, A. I. (1956), The method of total flows in the classical theory of sea currents, Trudy IO AS USSR, 19, 57-82. (in Russian) Felsenbaum, A. I. (1970), Dynamics of sea currents , Results of Science. Hydromechanics p. 97-338, VINITI, Moscow. (in Russian, http://www.esrl. noaa.gov/psd/data/gridded/data.ncep.reanalysis.deri ved.html)
Khen, G. V. (1989), Oceanographic conditions and Bering Sea biological productivity, Proceedings of the International Symposium: On the Biology and Management of Walleye Pollock p. 31-52, University of Alaska Sea Grant. AK-SG-89-01, Fairbanks. Khen, G. V., E. O. Basyuk (2005), Oceanographic Conditions of the Bering Sea in BASIS, NPAFC Technological Report, No. 6, 21-23. Khen, G. V., E.O. Basyuk, VI. Matveev, N.S.Vanin (2013), Hydrography and biological resources in the western Bering Sea, Deep Sea Resource II, 94, 106-120, Crossref Khen, G. V., A. V. Zavolokin (2015), Change in water circulation and its importance in the distribution and abundance of salmon in the western part of the Bering Sea at the beginning of the 21st century, Izves-tia of TINRO, 181, 95-114, (in Russian)Crossref Khen, G. V., A. N. Zaochniy (2009), The variability of the flow of the Kamchatka current and oceanolog-ical parameters in the Kamchatka Strait, Izvestia of TINRO, 158, 247-260. (in Russian) Luchin, V. A. (2008), Thermal regime of the waters of the Far Eastern seas (Japan, The sea of Okhotsk, Bering), The dissertation of the Dr. Geogr. Sciences, p. 319, Il'ichev Pacific Oceanological Institute, FEBRAS, Vladivostok. (in Russian) Overland, J. E., M. C. Spillane, H. E. Hurlburt, A. J. Wallcraft (1994), A numerical study of the circulation of the Bering Sea basin and exchange with the North Pacific Ocean, Physical Oceanography, 24, 736-758, Crossref Polyakova, A. M., G. A. Vlasova, A. S. Vasilyev (2002), The Influence of the Atmosphere on
the Underlying Surface and Hydrodynamic Processes of the Bering Sea, 202 pp. Dal'nauka, Vladivostok. (in Russian) Prants, S. V., A. G. Andreev, M. Y. Uleysky, M. V. Budyansky (2014), Lagrangian study
of temporal changes of a surface flow through the Kamchatka Strait, Ocean Dynamics, 64, 771-780, Crossref
Reed, R. K. (1995), On geostrophic reference levels in the Bering Sea Basin, Physical Oceanography, 51, 489-498, Crossref Rogachev, K. A., N. V. Shlyk (2008), Disintegration of the Alaskan Current into Aleutian vortices and Temperature Rise in the Western Sub-Arctic of the Pacific Ocean, Bulletin of the Far East Branch RAS, No. 6, 99-102. (in Russian)
ES5002
Rogachev, K. A., N. V. Shlyk (2010), Increase in the radius of Aleutian vortices and their long-term evolution, Meteorology and Hydrology, No. 3, 6873, (in Russian)Crossref Schlitzer, R. (2002), Interactive analysis and visualization of geoscience data with Ocean Data View, Computers & Geosciences, 28, 1211-1218, Cross-ref
Shapiro, N. B. (1965), Analytical study of the relationship between wind and current in the equatorial ocean zone, Doklady AS USSR, 164, No. 2, 319322. (in Russian) Solomon, H., K. Ahlnas (1978), Eddies in the Kamchatka Current, Deep Sea Resource, 25, 403410, Crossref Stabeno, P. J., R. K. Reed (1994), Circulation in the Bering Sea basin by satellite tracked drifters, Physical Oceanography, 24, 848-854, Crossref Stabeno, P. J., J. D. Schumacher, R. Ohtani (1999), The physical oceanography of the Bering Sea, Proceedings of the International Symposium: Dynamics of the Bering Sea p. 1-28, University of Alaska Sea Grant College Programm, Fairbanks. Shtokman, V. B. (1954), About the cause of circular currents near the islands and opposite currents near the coast of the straits, Izvestiya AS USSR. Ser. Ge-ogr., No. 4, 29-37. (in Russian) Takenouti, A. Y., R. Ohtani (1974), Currents and water masses in the Bering Sea: A review of Japanese work, Oceanography of the Bering Sea: with emphasis on renewable resources p. 39-57, Institute of Marine Science University of Alaska, Fairbanks. Timonov, V. V. (1960), Resulting and secondary currents in the seas with tides, Trudy of the Oceano-graphic Commission AS USSR, 10, No. 1, 43-50. (in Russian)
Vasiliev, A. S. (2001), Adaptive Learning System of Forecasting Classes of Natural Processes. Part 1, 136 pp. Gidrometeoizdat, St. Petersburg. (in Russian)
ES5002
Vlasova, G. A., A. S. Vasiliev, G. V. Shevchenko (2008), Spatio-Temporal Variability of the Structure and Dynamics of the Waters of the Sea of Okhotsk, 359 pp. Nauka, Moscow. (in Russian) Vlasova, G. A., M. N. Demenok, Ba Xuan Nguyen, Hong Long Buy (2016a), The role of atmospheric circulation in the spatial-temporal variability of the structure of currents in the western part of the South China Sea, Izvestiya RAN. FAO, 52, No. 3, 361372, (in Russian) Crossref Vlasova, G. A., Ba Xuan Nguyen, M. N. Demenok (2016b), Water Circulation of the South China Sea in the Vietnamese Current Zone under the Conditions of the Southern Tropical Cyclone in the Spring of 1999: Results of Numerical Simulation, Fundamen-tal'naya i Prikladnaya Gidrofizika, 9, No. 4, 25-34. (in Russian)
Wang, J., H. S. Hu, K. Mizobata, S. Saitoh (2009), Seasonal variations of sea ice and ocean circulation in the Bering Sea: A model-data fusion study, Geophysical. Resource, 114, C02011, Crossref Zhabin, I. A., V. B. Lobanov, S. Watanabe, M. Vakita, S. N. Taranova (2010), Water exchange between the Bering Sea and the Pacific Ocean through the Kamchatka Strait, Meteorology and Hydrology, No. 3, 84-92, (in Russian)Crossref Zhabin, I. A., E. V. Dmitrieva, N. S. Vanin (2017), Impact of wind and ice conditions on upwelling off the west coast of the Kamchatka Peninsula (Sea of Okhotsk) according to satellite observations, Izvestiya, - Atmospheric and Oceanic Physics, No. 3, 22-29. (in Russian)
Corresponding author:
Galina Vlasova, Il'ichev Pacific Oceanological Institute, Far Eastern Branch, Russian Academy of Sciences, Baltiiskaya 43, Vladivostok, 690041 Russia. (gavlasova@mail.ru)
VLASOVA ET AL.: MODELING SPRING HYDRODYNAMIC REGIME
