Since the SCS is semi-enclosed, the calculation of the decomposition and dissolution rates of particles based on the mass-balance method is straightfor-ward. The approach assumes that the source of the deep SCS water is at 2000 m immediately outside the Bashi Channel. The water in the SCS proper, say at 2000 m, is between 40 and 52 years older than the source water, and the increase in AOU, nitrate, phosphate and silicate are 27 " 2, 2.47 " 0.10, 0.16
" 0.02 and 8 " 2 mmol kgy1, respectively. These increases have OrN and NrP ratios of 10.9 " 2.0
and 15 " 2, respectively, and are in good agreement with the Redfield ratios of 8.6 and 16 Chen et al.,Ž
. Ž y1 y1.
1996b . The rates of increase in mmol kg year
Ž . Ž .
are: 0.59 " 0.12 AOU , 0.054 " 0.016 nitrate ,
Ž . Ž
0.0035 " 0.0010 phosphate and 0.17 " 0.05 sili-cate ..
For waters between about 800 and 3000 m where the urS plot is relatively linear, the one dimensional advection–diffusion model can be performed
follow-Ž .
ing the method of Craig and Weiss 1970 . The resultant JrW for oxygen, nitrate, phosphate and silicate are y5.40 " 1.00, 0.81 " 0.17, 0.09 " 0.04 and 4.70 " 0.11 mmol kgy1 kmy1, respectively, where J is the consumption or production rate, and W is the upwelling rate. These rates represent OrN and NrP ratios of 6.7 " 2.0 and 9 " 4, respectively, both lower than the Redfield ratios.
The upwelling rate of 0.055 km yeary1 was obtained by dividing the distance Župwelling the 3000-m deep water to the 800-m intermediate depth. by the residence time of 40 years for deep water. The oxygen consumption rate from multiplying JrW by the upwelling rate gives 0.30 " 0.06 compared to 0.59 " 0.12 mmol kgy1 yeary1 from the mass-bal-ance method above. The nitrate, phosphate and sili-cate production rates are 0.045 " 0.010, 0.005 "
0.002 and 0.26 " 0.07 mmol kgy1 kmy1, respec-tively. These are in fair agreement with the above estimations based on mass-balance.
These rates are compared with those for the Bering
Ž .
Sea and the Sea of Japan Table 5 . Clearly, the rates for the SCS sit in between, with the highest in the Sea of Japan and the lowest in the Bering Sea. It should be cautioned, however, that these rates have different reference states. The Bering Sea rates are relative to the source waters from the Weddell Sea, rendering the deep Bering Sea waters very old, to the
Ž .
order of 600 years Chen et al., 1996c . For waters of the same local surface production and downward flux of sinking particles, older waters have fewer fine suspended particles left for decomposition or dissolution. Further, these particles are more refrac-tory. In contrast, the Sea of Japan deep waters are very young, to the order of 120 years relative to the
Ž .
source within the Sea Chen et al., 1996c . More particles remain for decomposition and the remain-ing particles are more labile, brremain-ingremain-ing about such high rates. The SCS deep water is only 40 years
Table 5
Ž y1 y1.
Consumption or production rates of oxygen and nutrients in the deep South China Sea Basin mmol kg year
a a
SCS Bering Sea Sea of Japan
Mass balance 1-d model Mass balance Mass balance
Oxygen consumption rate 0.59 " 0.12 0.30 " 0.06 0.2 1.13 " 0.04
NO production rate3 0.054 " 0.016 0.045 " 0.010 0.012 0.12 " 0.008 PO production rate4 0.0035 " 0.0010 0.005 " 0.002 0.0011 0.0091 " 0.0004
SiO production rate2 0.17 " 0.05 0.26 " 0.07 0.17 0.52 " 0.02
aTaken from Chen et al. 1996c .Ž .
older than the source water, which is several hundred
Ž .
years old based on C-14 data Broecker et al., 1986 . As a result, the rates are much lower than those of the Sea of Japan.
10. Conclusions
Recent hydrographic and nutrient data collected in the SCS indicate that salinity, AOU and nutrient extremes are less pronounced than in the West Philippine Sea. This is because of the intensive upwelling and rapid flushing of the SCS. Box model
Ž .
results indicate that in the wet season, 13.9 "1.8 Sv SCS surface water flows out of the Bashi
Chan-Ž .
nel, while 12.8 "1.1 Sv Kuroshio surface water enters it. The nutrient-rich SCSW exports 26.8 Ž"3.5 = 10 mol P, 358 "47 = 10 mol N and. 9 Ž . 9
Ž . 9
1790 "232 = 10 mol Si out of the Bashi
Chan-Ž . 9
nel, while the KSW imports 20.6 "1.9 = 10 mol
Ž . 9 Ž . 9
P, 288 "26 = 10 mol N and 412 "37 = 10 mol Si through the channel. The intermediate water
Ž .
flows out of the SCS at a rate of 1.8 "0.36 Sv,
Ž . 9
carrying with it 48.5 "9.6 = 10 mol P, 668 Ž"134 = 10 mol N and 1742 "157 = 10 mol. 9 Ž . 9 Si. Balancing the N budgets gives a net
denitrifica-Ž . 9
tion rate of 80.4 "91 = 10 mol over 6 months.
In the dry season, the fluxes are significantly
Ž .
reduced. The SCSW exports 1.8 "0.2 Sv seawater,
Ž . 9 Ž . 9
3.4 "0.3 = 10 mol P, 45 "4 = 10 mol N and
Ž . 9
227 "20 = 10 mol Si out of the Bashi Channel,
Ž .
while the KSW imports 4.7 "0.4 Sv seawater, 7.6 Ž"0.7 = 10 mol P, 106 "10 = 10 mol N and. 9 Ž . 9
Ž . 9
151 "14 = 10 mol Si through the channel. The
Ž .
SCS intermediate water exports 2.0 "0.4 Sv
sea-Ž . 9 Ž . 9
water, 54 "11 = 10 mol P, 743 "148 = 10
Ž . 9
mol N and 1940 "175 = 10 mol Si out of the
SCS through the Bashi Channel. The net
denitrifica-Ž . 9
tion rate is 33 "92 = 10 mol over 6 months. The net export of nutrients in the SCSW is mainly
sup-Ž .
ported by deep water inflow. The rate is 1.2 "0.2
Ž . 9
Sv seawater, 52.5 "10.5 = 10 mol P, 716 Ž"143 = 10 mol N and 2710 "542 = 10 mol. 9 Ž . 9 Si in both the wet and dry seasons. The outflowing SCSW is relatively nutrient-rich compared with the KSW, and plays an important role in the ECS. To a certain extent, the intermediate water also upwells onto the ECS shelf, thus providing nutrients to sup-port its high productivity. As a result, the SCS acts as a pump which moves nutrients from the deep water and eventually to the euphotic zone.
Acknowledgements
The authors wish to thank the National Science Council for supporting this research NSC89-2611-Ž M110-001 . The assistance of C.T. Liu, M.H. Huang,. W. Lucas, and the captain and crew of the RrV Ocean Researcher 1 is also greatly appreciated. Two anonymous reviewers and M. Altabet gave construc-tive criticisms, which strengthened the manuscript.
References
Ayers, G., Gillett, R., Hara, H., 1997. Acid deposition in East
Ž .
Asia and Oceanic. In: Whelpdale, D.M., Kaiser, M.S. Eds. , Global Acid Deposition Assessment. World Meteorological Organization Global Atmosphere Watch No. 106, pp. 107–134.
Broecker, W.S., Patzert, W.C., Toggweilar, J.R., Stuiver, M., 1986. Hydrography, chemistry and radioisotopes in the South-east Asian basins. J. Geophys. Res. 91, 14345–14354.
Chao, S.Y., Shaw, P.T., Wu, S.Y., 1996. Deep water ventilation in the South China Sea. Deep-Sea Res. 43, 445–466.
Chen, C.T.A., 1981. Oxygen solubility in seawater. In: Battino, R.
ŽEd. , Solubility Data Series. Oxygen and Ozone, vol. 7,. Pergamon, Oxford, pp. 41–55.
Chen, C.T.A., 1995. Fluxes of seawater and some dissolved chemicals in the Bashi Strait, Chin. J. Oceanol. Limnol. 13, 240–246.
Chen, C.T.A., 1996. The Kuroshio Intermediate Water is the major source of nutrients on the East China Sea continental shelf. Oceanol. Acta 19, 523–527.
Chen, C.T.A., Huang, M.H., 1995. Carbonate chemistry and the anthropogenic CO2 in the South China Sea. Acta Oceanol.
Sin. 14, 47–57.
Chen, C.T.A., Huang, M.H., 1996. A mid-depth front separating the South China Sea water and the West Philippine Sea water.
J. Oceanogr. 52, 17–25.
Chen, C.T.A., Wang, B.J., 1997. Acidification of lakes and reser-voirs in Taiwan. Geochem. J. 31, 345–355.
Chen, C.T.A., Wang, S.L., 1998. Influence of intermediate water in the western Okinawa Trough by the outflow from the South China Sea. J. Geophys. Res. 103, 12683–12688.
Chen, C.T.A., Wang, S.L., 1999. Carbon, alkalinity and nutrient budgets on the East China Sea continental shelf. J. Geophys.
Res. 104, 20675–20686.
Chen, C.T.A., Wang, B.J., Hsu, H.C., Hung, J.J., 1994. Rain and lake waters in Taiwan: composition and acidity. Terr. Atmos.
Oceanic Sci. 5 4 , 573–584.Ž .
Chen, C.T.A., Ruo, R., Pai, S.C., Liu, C.T., Wong, G.T.F., 1995.
Exchange of water masses between the East China Sea and the Kuroshio off northeastern Taiwan. Cont. Shelf Res. 15, 19–39.
Chen, C.T.A., Wang, S.L., Huang, M.H., 1996a. Preliminary data report of ocean researcher 1 cruises 403 and 418 B, Inst. Mar.
Geol. Tech. Rep. No. 25, Nat. Sun Yat-sen Univ., 199 pp.
Chen, C.T.A., Lin, C.M., Huang, B.T., Chang, L.F., 1996b. The stoichiometry of carbon, hydrogen, nitrogen, sulfur and oxy-gen in the particular matter of the western North Pacific marginal seas. Mar. Chem. 54, 179–190.
Chen, C.T.A., Gong, G.C., Wang, S.L., Bychkov, A.S., 1996c.
Redfield ratios and regeneration rates of particulate matter in the Sea of Japan as a model of closed system. Geophys. Res.
Ž .
Lett. 23 14 , 1785–1788.
Chen, C.T.A., Wang, S.L., Wang, B.J., Lin, Y.P., Li, F.C., Shu L.M., Chen, L.C., 1997. Preliminary data report of Ocean Researcher 1 cruises 433, 434 and 462, Inst. Mar. Geol. and Chem. Tech. Rep. No. 32, Nat. Sun Yat-sen Univ., 173 pp.
Chen, C.T.A., Wang, S.L., Wang, B.J., Lin, Y.P., Liu, W.H., Li, F.C., Chen, L.C., 1998. Preliminary data report of Ocean Researcher I cruises 508 and Ocean Researcher III 403, Inst.
Mar. Geol. and Chem. Tech. Rep. No. 33, Nat. Sun Yat-Sen Univ., 137 pp.
Chu, T.Y., 1972. Oceanographic data of the South China Sea Researcher 1 cruises 1 and 2, Inst. Oceanogr. Special Publica-tion: No. 2, Nat. Taiwan Univ., 74 pp.
Codispoti, L.A., 1995. Is the ocean losing nitrate? Nature 376, 724.
Craig, H., Weiss, R.F., 1970. The GEOSECS 1969
intercalibra-tion staintercalibra-tion: introducintercalibra-tion and hydrographic features, and total CO –O relationships. J. Geophys. Res. 75, 7641–7647.2 2 Fanning, K.A., Pilson, M.E.Q., 1973. On the spectrophotometric
determination of dissolved silica in natural waters. Anal. Chem.
45, 136–141.
Frische, A., Quadfasel, D., 1990. Hydrography of the Sulu Sea.
Ž .
In: Rangin, C., Silver, E., Von Breymann, M.T. Eds. , Pro-ceedings of the Ocean Drilling Program, Initial Reports, vol.
124, Texas A&M University, College Station, pp. 101–104.
Fujien Oceanological Institute, 1988. A Comprehensive Oceano-graphic Survey of the Central and Northern Part of the Taiwan
Ž .
Strait. Kexue Pub., Beijing, 423 pp. in Chinese .
Gong, G.C., Liu, K.K., Liu, C.T., Pai, S.C., 1992. The chemical hydrography of the South China Sea west of Luzon and a comparison with the West Philippine Sea. Terr. Atmos.
Oceanic Sci. 3, 587–602.
Han, W.Y., 1995. Marine Chemistry of the Nansha Islands and South China Sea. China Ocean Press, Beijing, 376 pp.
Ž .
Hong, H.S. Ed. , 1994. Marine Biogeochemistry Research Pa-pers. Xiamen Univ. Press, Xiamen, China, 283 pp.
Hong, H.S., Dai, M.H., 1994. Biogeochemical studies of biologi-cally important elements in the Taiwan Strait. In: Zhou, D.
ŽEd. , Oceanology of China Seas, vol. V1, Kluwer Academic. Publishing, Boston, pp. 201–212.
INDOPAC, 1978, Data report, Univ. Calif. Scripps Inst. Oceanogr.
SID 78–21, 424 pp.
Lai, Z.L., Liu, K.K., 1994. The distribution of carbon, nitrogen and sulfur in surfacial sediments on the continental shelf and slope in northern South China Sea. Acta Oceanogr. Taiwan.
32, 30–44.
Liu, C.T., Liu, R.J., 1988. The deep current in the Bashi Channel.
Acta Oceanogr. Taiwan. 20, 107–116.
Liu, Q.Y., Liu, Z.T., Zheng, S.P., Xu, Q.C., Li, W., 1996. The deformation of Kuroshio in the Luzon Strait and its dynamics.
J. Ocean Univ. Qingdao 26, 413–420 in Chinese with EnglishŽ abstract ..
Metzger, E.J., Hurlburt, H.E., 1995. Coupled dynamics of the South China Sea, the Sulu Sea and the Pacific Ocean. J.
Ž .
Geophys. Res. 101 C5 , 12331–12352.
Meybeck, M., 1993. C, N, P and S in rivers: from sources to global inputs. In: Wollast, R., Mackenzie, F.T., Chou, L.
ŽEds. , Interactions of C, N, P, and S Biogeochemical Cycles. and Global Change. Springer, Berlin, pp. 163–193.
Middelburg, J.J., Soetaert, K., Herman, P.M.J., Heip, C.H.R., 1996. Denitrification in marine sediments: a model study.
Global Biogeochem. Cycle 10, 661–673.
Milliman, J.D., Rutkowski, C.M., Meybeck, M., 1995. River
Ž .
Discharge to the Sea, A Global River Index GLORI . LOICZ Core Project Office, Netherlands, 125 pp.
Murphy, J., Riley, J.P., 1962. A modified single solution method for the determination of phosphate in natural waters. Anal.
Chim. Acta 27, 31–36.
NOAA, 1994a. World Ocean Atlas 1994, V.3: Salinity, NOAA Atlas NESDIS 3, 99 pp.
NOAA, 1994b. World Ocean Atlas 1994, V.1: Nutrients, NOAA Atlas NESDIS 1, 150 pp.
Pai, S.-C., Yang, C.-C., Riley, J.P., 1990a. Formation kinetics of
the pink azo dye in the determination of nitrite in natural waters. Anal. Chim. Acta 232, 345–349.
Pai, S.-C., Yang, C.-C., Riley, J.P., 1990b. Effects of acidity and molybdate concentration on the kinetics of the formation of the phosphoantimonylmolybdenum blue complex. Anal. Chim.
Acta 229, 115–120.
Pai, S.-C., Gong, G.-C., Liu, K.-K., 1993. Determination of dissolved oxygen in seawater by direct spectrophotometry of total iodine. Mar. Chem. 41, 343–351.
San Diego-McGlone, M.L., Jacinto, G.S., Dupra, V.C., Narcise, I.S., Padayao, D.O., Velasquez, I.B., 1999. A comparison of nutrient characteristics and primary productivity in the Sulu and South China Sea. Acta Oceanogr. Taiwan. 37, 219–229.
Seitzinger, S.P., Giblin, A.E., 1996. Estimating denitrification in North Atlantic continental shelf sediments. Biogeochemistry 35, 235–260.
Shaw, P.T., Chao, S.Y., Liu, K.K., Pai, S.C., Liu, C.T., 1996.
Winter upwelling off Luzon in the northeastern South China Sea. J. Geophys. Res. 101, 16435–16448.
Strickland, J.D.H., Parsons, T.R., 1972. A Practical Handbook of Seawater Analysis. Fisheries Research Board of Canada, Ot-tawa, Canada, 310 pp.
Su, G.Q., Wang, T.X., 1994. Basic characteristics of modern sedimentation in South China Sea. In: Zhou, D., Liang, Y.B.,
Ž .
Zeng, C.K. Eds. , Oceanology of China Seas, vol. 2, Kluwer Academic Publishing, Boston, pp. 407–418.
Wang, J., 1986. Observation of abyssal flows in the northern South China Sea. Acta Oceanogr. Taiwan. 16, 36–45.
Wang, Y.H., 1991. Marine Atlas of Boshi Sea, Yellow Sea, East China Sea, Chemistry. China Ocean Press, Beijing, 257 pp.
Wang, P.X., 1999. Response of Western Pacific marginal seas to glacial cycles: paleoceanographic and sedimentological fea-tures. Mar. Geol. 156, 5–39.
Wang, J., Chen, C.S., 1992. On the distribution of bottom cold waters in Taiwan Strait during summertime. La mer 30, 213–221.
Wang, H.C., Yuan, Y.C., 1997. Calculation of currents in the Taiwan Strait during summertime. Acta Oceanol. Sin. 19, 10–20.
Wollast, R.J., 1998. Evaluation and comparison of the global carbon cycle in the coastal zone and in the open ocean. In:
Ž .
Brink, K.H., Robinson, A.R. Eds. , The Sea, vol. 10, Wiley, New York, pp. 213–252.
Wyrtki, K., 1961. Physical oceanography of the southeast Asian waters. Scientific results of marine investigations of the South China Sea and the Gulf of Thailand, Scripps Institution of Oceanography, La Jolla, CA, NAGA report, vol. 2, 195 pp.
Zhang, J., 1996. Nutrient elements in large Chinese estuaries.
Cont. Shelf Res. 16, 1023–1045.
Zhang, Y.K., Wang, X.C., Zhang, Q.L., Wang, C.M., 1991.
Bottom current in Taiwan Strait. Oceanol. Limnol. Sin. 22,
Ž .
124–131 in Chinese with English abstract .