1、Introduction to special section:Oceanography of the Okhotsk SeaKay I. OhshimaInstitute of Low Temperature Science, Hokkaido University, Sapporo, JapanSeelye MartinSchool of Oceanography, University of Washington, Seattle, Washington, USAReceived 19 July 2004; accepted 29 July 2004; published 28 Sept
2、ember 2004.INDEX TERMS: 4243 Oceanography: General: Marginal and semienclosed seas; 4540 Oceanography:Physical: Ice mechanics and air/sea/ice exchange processes; 4283 Oceanography: General: Watermasses; 4805 Oceanography: Biological and Chemical: Biogeochemical cycles (1615); 4223 Oceanography:Gener
3、al: Descriptive and regional oceanography; KEYWORDS: Sea of Okhotsk, dense shelf water, coastalpolynyaCitation: Ohshima, K. I., and S. Martin (2004), Introduction to special section: Oceanography of the Okhotsk Sea, J. Geophys. Res.,109, C09S01, doi:10.1029/2004JC002604.1 The Okhotsk Sea is a 1.5 C2
4、 106km2marginal seaadjacent to the Pacific Ocean in the Northern Hemi-sphere. Its defining boundaries are Hokkaido, Japan,Sakhalin Island, the Russian mainland, the KamchatkaPeninsula, and the Kuril Islands. In the Northern Hemi-sphere the Okhotsk is the southernmost sea with a sizableseasonal ice c
5、over, which experiences large interannualvariations in extent. Because of the coupling of this icecover with the Okhotsk oceanography, the ice can beconsidered as a sensitive indicator of climate change.Despite the recent realization of the importance of theOkhotsk Sea, because of severe weather con
6、ditions andthe presence of sea ice, in situ observations have beenlimited, especially in winter.2 Part of the importance of the Okhotsk is that theNorth Pacific Intermediate Water (NPIW) is believed tobe ventilated in and around it, both from hydrographicdata Talley, 1991 and chlorofluorocarbons (CF
7、Cs) obser-vations Warner et al., 1996. Specifically, the Okhotsk isregarded as the only site where the atmosphere candirectly exchange the heat and material (including CO2)with the NPIW. Ventilation of this water is an importantcomponent of the global overturning circulation. Thereare two ventilatio
8、n sites for the intermediate water in theOkhotsk Sea. The first is the northwest shelf, which haslarge active coastal polynyas that are regarded as theprimary area of dense shelf water (DSW) formationKitani, 1973; Wong et al., 1998; Martin et al., 1998;Gladyshev et al., 2000. The second is the area
9、in andaround the straits in the Kuril Islands, where strong tidalcurrents generate diapycnal mixing Talley, 1991.3 As part of a joint Japanese-Russian-U.S. study of theOkhotsk, four international joint cruises were carried outin the Okhotsk during 19982001 on the R/V ProfessorKhromov. These were sup
10、ported by U.S. National ScienceFoundation and the Core Research for Evolutional Scienceand Technology of Japan Science and Technology Corpo-ration. The participants consisted of representatives fromthe Russian Far Eastern Regional HydrometeorologicalResearch Institute, the U.S. Scripps Institution o
11、f Ocean-ography and the University of Washington, and the Japa-nese Hokkaido University and Japan Agency for Marine-Earth Science and Technology (JAMSTEC, previouslyJapan Marine Science and Technology Center). The mainfocus of the study was the ventilation of the NPIW by theOkhotsk Sea. This divides
12、 into three parts: the northwestOkhotsk shelf, where brine rejection generates the DSW;the East Sakhalin Current, which is the western Okhotskboundary current and DSW pathway to the southernOkhotsk Mizuta et al., 2003; and the Bussol Strait,which is the main exchange between the Okhotsk andthe Pacif
13、ic and a site of diapycnal mixing.4 As the accompanying papers show, the project wasan interdisciplinary one, consisting of studies of physicaloceanography, sea ice, biogeochemistry, paleo-oceanogra-phy, and atmospheric sciences. The field methods con-sisted of hydrographical and chemical observatio
14、ns,moorings, bottom lander observations, Lagrangian floatmeasurements, lowered acoustic Doppler current profiler(ADCP) measurements, and sediment corings. At theOcean Sciences Meeting at Honolulu in 2002 a meetingof the Okhotsk participants showed that there weresufficient potential papers and new r
15、esults to justify aJournal of Geophysical special section. In this specialsection, eight papers of the thirteen papers are based onthe field results; others are based on numerical andsatellite studies.5 As the papers derived from these field experimentsdescribe, direct measurements on the northwest
16、shelf ofbrine rejection and formation of DSW were carried outfor the first time using bottom landers Shcherbina et al.,2003, 2004a. These landers directly observed the venti-lation of the intermediate water and also suggest thatbaroclinic instabilities occur on the density front at theJOURNAL OF GEO
17、PHYSICAL RESEARCH, VOL. 109, C09S01, doi:10.1029/2004JC002604, 2004Copyright 2004 by the American Geophysical Union.0148-0227/04/2004JC002604$09.00C09S01 1of3polynya edge. The transport of the DSW south and itsmodification were observed by moorings in the EastSakhalin Current Fukamachi et al., 2004,
18、 which alsoobserved offshore eddy transport of the cold water,suggesting baroclinic instabilities.6 Within the DSW outflow a large amount of dis-solved and particulate organic carbon is transported fromthe shelf into the intermediate layer, characterizing thebiogeochemical cycle in the Okhotsk Sea N
19、akatsuka etal., 2004a. The outflow of cold and turbid DSWintensified the lithogenic particle fluxes into the deepbasin, where these fluxes regulate the Okhotsk sedimen-tation process Nakatsuka et al., 2004b. These areimportant to the understanding of material cycling inthe Okhotsk Sea and past ocean
20、ographic conditions fromthe sediment cores. Relatively high-density observationsof CFCs Yamamoto-Kawai et al., 2004 and methaneYoshida et al., 2004 were carried out over the OkhotskSea. The behavior of the DSW can also be traced byCFCs and methane distributions, suggesting that DSW istransported int
21、o the Kuril Basin through the cyclonic gyreOhshima et al., 2004.7 The NPIW is also ventilated by the diapycnalmixing associated with the strong tidal currents in andaround the Kuril Straits, where the water exchange alsooccurs with the Pacific. Because of the strong tides,conventional geostrophic ca
22、lculations cannot be used toestimate the current structure Riser, 1996. Under theproject, direct current measurements were performed atthe Bussol Strait, the largest and deepest strait, withmoorings Riser, 2001 and with repeated lowered ADCPmeasurements Katsumata et al., 2004. Both observa-tions rev
23、ealed extremely strong diurnal tidal currents inthe strait. The measurements by Katsumata et al. 2004provide the first direct estimation of the mean inflow andoutflow in the Kuril Straits. In a related topic, Nakamuraand Awaji 2004 use a three-dimensional nonhydrostaticnumerical model to examine the
24、 tide-induced diapycnalmixing in the Kuril Straits and its role in water transfor-mation and transport. Their results of tidal residual flowstructure are consistent with the Katsumata et al. 2004direct observations. CFCs observations Yamamoto-Kawaiet al., 2004 also suggest the importance of the vent
25、ilat-ing process in and around Bussol Strait.8 The formation of the DSW is closely related to seaice production. For the northwest shelf, Shcherbina et al.2004b estimate the formation rate of DSW from acombination of the direct measurements and satelliteobservations. Kimura and Wakatsuchi 2004 also
26、exam-ine the sea ice production in the coastal polynyas throughthe analyses of ice drift data derived from the satelliteimages. The Kashevarov Bank polynya is the prominentopen ocean polynya in this sea. Martin et al. 2004 usea combination of satellite observations and a coupled ice-ocean numerical
27、model to show that the polynya areadepends on the fortnightly and diurnal tides. For theentire Okhotsk, Watanabe et al. 2004 use a coupledice-ocean numerical model to examine the role of sea icein the heat and salt balance.9 At longer timescales, Minobe and Nakamura 2004examine for the first time th
28、e interannual-to-decadal var-iability of the upper layer temperature of the Okhotsk Sea.They show that the anomalies of the Okhotsk exhibit aprominent quasi-decadal variability that is closely relatedto the wintertime sea surface temperature anomalies overthe North Pacific subarctic front and to the
29、 changes instrength of the Asian winter monsoon.10 Acknowledgments. As guest editors, we acknowledge and thankthe JGR-Oceans editor, John Klinck, for his assistance and forbearance, thenumerous reviewers for their greatly appreciated assistance, and the authorsfor their patience. S. M. also acknowle
30、dges the support of the NationalScience Foundation under OCE9811097 and of NASA under grant NAG5-11067.ReferencesFukamachi, Y., G. Mizuta, K. I. Ohshima, L. D. Talley, S. C. Riser, andM. Wakatsuchi (2004), Transport and modification processes of denseshelf water revealed by long-term moorings off Sa
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47、 the Sea of Okhotsk: Ventilation of theintermediate water, J. Geophys. Res., C09S11, doi:10.1029/2003JC001919.Yoshida, O., H. Y. Inoue, S. Watanabe, S. Noriki, and M. Wakatsuchi(2004), Methane in the western part of the Sea of Okhotsk in 19982000, J. Geophys. Res., 109, C09S12, doi:10.1029/2003JC001
48、910.C0C0C0C0C0C0C0C0C0C0C0C0C0C0C0C0C0C0C0C0C0C0S. Martin, School of Oceanography, University of Washington, Seattle,WA 98195, USA. (seelyeocean.washington.edu)K. I. Ohshima, Institute of Low Temperature Science, HokkaidoUniversity, Sapporo 060-0819, Japan. (ohshimalowtem.hokudai.ac.jp)C09S01 OHSHIMA AND MARTIN: INTRODUCTION3of3C09S01
