Elsevier

Progress in Oceanography

Volume 126, August 2014, Pages 1-7
Progress in Oceanography

Preface
Biogeochemical and physical processes in the Sea of Okhotsk and the linkage to the Pacific Ocean

https://doi.org/10.1016/j.pocean.2014.04.027Get rights and content

Introduction

To understand Earth systems, it is important to understand how the land and ocean are linked, and marginal seas are key sites where such linkage occurs. The South China Sea, the East China Sea, the Japan Sea, the Sea of Okhotsk, and the Bering Sea, i.e., marginal seas along the northwest rim of the Pacific Ocean, are all strongly influenced by the land via river discharges, which also reflect human influences. Compared with other oceanic regions, marginal seas have high productivity and biogeochemical cycling activity, which are controlled by separate local processes, such as freshwater discharge, interior current systems, tidal mixing, local upwelling, interactions with the continental shelf, sea ice production and melting, and flow through straits. Further, some marginal seas have been shown to have a strong influence on physical and biogeochemical processes in the open Pacific Ocean. Therefore, it is important to investigate the role that marginal seas play in linking the land with oceanic regions to clarify the whole Pacific Ocean system.

The Sea of Okhotsk is located in the sub-polar region at the northwest rim of the Pacific Ocean (Fig. 1). It has a total area of 1,528,100 km2 and is bounded by Siberia, Sakhalin Island, Hokkaido Island, the Kuril Island chain, and the Kamchatka Peninsula. A broad continental shelf extends along the Kamchatka and Siberian coasts, and a deep basin (Kuril Basin) occupies its southern part. The Sea of Okhotsk is connected to the Japan Sea via the Tatar Strait (sill depth, ∼10 m) and the Soya Strait (∼50 m), and to the Pacific via the Kuril Straits, the two deepest of which are the Bussol’ Strait (sill depth, ∼2300 m) and the Kruzenstern Strait (∼1800 m). The Sea of Okhotsk receives a large amount of freshwater discharge from the Amur River, which at 4444 km long is one of the 10 longest rivers in the world (Simonov and Dahmer, 2008). The Amur River basin covers 2,129,700 km2 (Simonov and Dahmer, 2008). The water discharge of the Amur River, whose mean transport is 11,000 m3/s (Ogi et al., 2001), is the major source of freshwater to the Sea of Okhotsk. Every winter, the cold winter winds that blow from East Siberia cause large amounts of sea ice to form along the Siberian coast on the northwestern continental shelf of the Sea of Okhotsk, which is recognized as the lowest latitude seasonal sea-ice area in the world (Alfultis and Martin, 1987, Kimura and Wakatsuchi, 2000). The formation of sea ice produces a large volume of cold brine, which subsequently causes vigorous mixing to the bottom of the shelf and forms Dense Shelf Water (DSW: 26.8–27.0σθ) (Kitani, 1973, Martin et al., 1998, Gladyshev et al., 2000). Previous studies have suggested that the Sea of Okhotsk is important as a source of North Pacific Intermediate Water (NPIW) (Talley, 1991, Warner et al., 1996, Watanabe and Wakatsuchi, 1998, Wong et al., 1998, Yasuda, 1997, Nakamura and Awaji, 2004).

The first comprehensive observations were carried out in the Sea of Okhotsk from 1998 to 2001 (hereafter, the “first era”) by a joint Japanese-Russian-U.S. study. The main findings of their studies were summarized in a special issue of the Journal of Geophysical Research by Ohshima and Martin (2004), which mainly concerned processes related to sea-ice formation and ventilation in the Sea of Okhotsk. In their studies, the generation of DSW by brine rejection was directly observed on the northwestern Okhotsk shelf (Shcherbina et al., 2003, Shcherbina et al., 2004a, Shcherbina et al., 2004b); and the East Sakhalin Current (ESC), which is the western Okhotsk boundary current (Ohshima et al., 2002, Mizuta et al., 2003) as well as the DSW pathway to the southern Okhotsk (Okhotsk Sea Intermediate Water, OSIW; Itoh et al., 2003, Fukamachi et al., 2004, Ohshima et al., 2004), was discovered. In addition, it was clearly shown that the Bussol’ Strait is the main gateway through which water is exchanged between the Sea of Okhotsk and the Pacific (Katsumata et al., 2004, Katsumata and Yasuda, 2010, Ohshima et al., 2010), and that strong tidal currents in and around the Kuril Straits are associated with diapycnal mixing (Ono et al., 2007, Ono et al., 2013). They also produced several biogeochemical studies. Nakatsuka et al., 2002, Nakatsuka et al., 2004 reported that sedimentary materials are transported in DSW and OSIW from the northwestern continental shelf to the open sea. These findings are compatible with the findings of other studies conducted in the Pacific Ocean that reported high concentrations of Dissolved Organic Carbon (DOC) in NPIW, and they suggest that the increased DOC in NPIW may be due to injections of organic matter from the Sea of Okhotsk (Hansell et al., 2002, Hernes and Benner, 2002, Yamashita and Tanoue, 2008). Observations of chlorofluorocarbons and dissolved inorganic carbon in the DSW production area have also revealed that DSW actively exchanges gases with the atmosphere during its formation, and these gases are subsequently transported to NPIW (Wong et al., 1998, Yamamoto-Kawai et al., 2004, Wakita et al., 2003).

Although there were comprehensive studies in the Sea of Okhotsk from the first era, data were still limited in the Sea of Okhotsk, and many biogeochemical features of this marginal sea, especially regarding its linkage to the Pacific Ocean, remained unknown.

Section snippets

International joint study: the second era

Although many features of the Sea of Okhotsk were clarified by the joint Japanese–Russian–U.S. study of the first era, to understand the whole the Sea of Okhotsk–Pacific Ocean system (hereafter, the Okhotsk–Pacific system), more detailed information about the Sea of Okhotsk, especially biogeochemical information, was needed. Therefore, a second joint international collaborative study was carried out from 2005 to 2013 (hereafter, the “second era”). The second era collaborators included more than

Concluding remarks

In this special issue, we present key findings regarding physical and biogeochemical processes in the Okhotsk–Pacific system and the mechanisms that determine them (Fig. 2). Our studies clearly reveal that the Amur River discharge influences the distributions of materials (Fe and organic matter in our studies) and that transport of these materials in the surface layer by the ESC influences the biological systems in the Sea of Okhotsk. The Amur River discharge also strongly influences a wide

Acknowledgements

The Guest Editors express our sincere gratitude to the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan, the Canon Foundation, and participating institutes and universities in Japan, Russia, and Hong Kong for the financial support they provided for this international studies. We also would like to thank all of the authors for their patience during the preparation of manuscripts and the scientific reviewers who anonymously donated their time and expertise to

References (78)

  • Y. Fukamachi et al.

    Transport and modification processes of dense shelf water revealed by long-term moorings off Sakhalin in the Sea of Okhotsk

    Journal of Geophysical Research

    (2004)
  • S. Gladyshev et al.

    Dense water production on the northern Okhotsk shelves: comparison of ship-based spring–summer observations for 1996 and 1997 with satellite observations

    Journal of Geophysical Research

    (2000)
  • D.A. Hansell et al.

    Dissolved organic carbon export with North Pacific Intermediate Water formation

    Global Biogeochemical Cycles

    (2002)
  • Harada, N., Katsuki, K., Nakagawa, M., Matsumoto, A., Seki, O., Addison, J.A., Finney, B.F., Sato, M., 2014. Holocene...
  • T. Isada et al.

    Influence of Amur River discharge on phytoplankton photophysiology in the Sea of Okhotsk during late summer

    Journal of Geophysical Research

    (2013)
  • M. Itoh et al.

    Distribution and formation of Okhotsk Sea Intermediate Water. An analysis of isopycnal climatological data

    Journal of Geophysical Research

    (2003)
  • S. Itoh et al.

    Fine- and microstructure observation in the Urup Strait, Kuril Islands, during August 2006

    Journal of Geophysical Research

    (2010)
  • S. Itoh et al.

    Strong vertical mixing in the Urup Strait

    Geophysical Research Letters

    (2011)
  • Itoh, H., Nishioka, J., Tsuda, A., 2014a. Community structure of mesozooplankton in the western part of the Okhotsk Sea...
  • Itoh, S., Tanaka, Y., Osafune, S., Yasuda, I., Yagi, M., Kaneko, H., Konda, S., Nishioka, J., Volkov, N.Y., 2014b....
  • Iwamoto, Y., Uematsu, M., 2014. Spatial variation of biogenic and crustal elements in suspended particulate matter from...
  • H. Jing et al.

    Phylogenetic diversity of marine Synechococcus in the Sea of Okhotsk

    Aquatic Microbial Ecology

    (2009)
  • H. Jing et al.

    Community compositions of Bacteria and Archaea in the Sea of Okhotsk during summer

    Aquatic Microbial Ecology

    (2010)
  • Kanna, N., Toyota, T., Nishioka, J., 2014. Fe and macro-nutrient concentrations in sea ice and their impact on the...
  • Kashiwase, H., Ohshima, K.I., Nihashi, S., 2014. Long-term variation in sea ice production and its relation to the...
  • K. Katsumata et al.

    Estimate of non-tidal exchange transport between the Sea of Okhotsk and the North Pacific

    Journal of Oceanography

    (2010)
  • K. Katsumata et al.

    Water exchange and tidal currents through the Bussol’ Strait revealed by direct current measurements

    Journal of Geophysical Research

    (2004)
  • N. Kimura et al.

    Relationship between sea-ice motion and geostrophic wind in the Northern Hemisphere

    Geophysical Research Letters

    (2000)
  • K. Kitani

    An oceanographic study of the Sea of Okhotsk, particularly in regard to cold waters

    Bulletin of Far Seas Fisheries Research Laboratory

    (1973)
  • S. Martin et al.

    The production of ice and dense shelf water in the Okhotsk Sea polynyas

    Journal of Geophysical Research

    (1998)
  • G. Mizuta et al.

    Structure and seasonal variability of the East Sakhalin Current

    Journal of Physical Oceanography

    (2003)
  • T. Nakamura et al.

    Tidally induced diapycnal mixing in the Kuril Straits and its role in water transformation and transport: a three-dimensional nonhydrostatic model experiment

    Journal of Geophysical Research

    (2004)
  • Nakamura, T., Takeuchi, Y., Uchimoto, K., Mitsudera, H., Wakatsuchi, M., 2014. Effects of temporal variation in...
  • Nakanowatari, T., Ohshima, K.I., 2014. Coherent sea level variability in and around the Sea of Okhotsk. Progress in...
  • T. Nakanowatari et al.

    Warming and oxygen decrease of intermediate water in the northwestern North Pacific, originating from the Sea of Okhotsk 1955–2004

    Geophysical Research Letters

    (2007)
  • T. Nakatsuka et al.

    An extremely turbid intermediate water in the Sea of Okhotsk: implication for the transport of particulate organic matter in a seasonally ice-bound sea

    Geophysical Research Letters

    (2002)
  • T. Nakatsuka et al.

    Dissolved and particulate organic carbon in the Sea of Okhotsk: transport from continental shelf to ocean interior

    Journal of Geophysical Research

    (2004)
  • J. Nishioka et al.

    Iron supply to the western subarctic Pacific: importance of iron export from the Sea of Okhotsk

    Journal of Geophysical Research

    (2007)
  • J. Nishioka et al.

    Oceanic iron supply mechanisms which support the spring diatom bloom in the Oyashio region, western subarctic Pacific

    Journal of Geophysical Research

    (2011)
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