Surface distributions of carbon chemistry parameters in the East China Sea in summer 2007

Abstract

[1] Comprehensive carbon chemistry data including total alkalinity (TA), dissolved inorganic carbon (DIC), pH, fugacity of CO 2 , and other pertinent data (i.e., temperature, salinity, and levels of nitrate and chlorophyll a) were measured in surface waters of the East China Sea (ECS) shelf in July 2007. The results show that spatial variations in these parameters closely correspond to the distributions of various water types. The Changjiang Diluted Water (CDW) and Yellow Sea Water (YSW) areas are the two major sinks of atmospheric CO 2 ; the Coastal Upwelling Water (CUW) area is the most important CO 2 source, whereas the Kuroshio Water and Taiwan Current Warm Water areas are weak sources. The entire ECS acted as a sink for atmospheric CO 2 , with a flux of À2.4 to À4.3 mmol C m À2 d À1 during the study period. Identification of the CUW source area suggests that previous studies might have overestimated CO 2 uptake by the ECS in summer. Our results further suggest that high biological production might be responsible for the strong sink in the CDW area but that high input of TA from the Huanghe River, which led to an elevated TA/DIC ratio, could have resulted in formation of a significant CO 2 sink in the YSW area. The present data set represents the most comprehensive CO 2 survey in the ECS to date and can thus be used as a baseline for monitoring future changes in the CO 2 system arising from the construction of the Three Gorges Dam in the middle stretch of the Changjiang River.

Carbonate mineral saturation states in the East China Sea: present conditions and future scenarios

“…7c), lending support to the hypothesis that biologically induced DIC drawdown may be the driving force that accounts for the observed high a in the CDW. In fact, this result agrees well with previous findings that due to the favorable conditions (i.e., high availability of light and nutrients and warm temperature), the CDW area generally features very high Chl a concentrations Hung et al, 2009) and acts as a strong sink of atmospheric CO 2 in late spring and summer (Zhai and Dai, 2009;Chou et al, 2009a).…”

“…Previous studies have shown that the ECS shelf acts as an important sink of atmospheric CO 2 all year round (Tsunogai et al, 1999;Peng et al, 1999;Wang et al, 2000;Shim et al, 2007;Zhai and Dai, 2009;Chou et al, 2009a and. Consequently, in surface water would be continuously decreasing in response to anthropogenic CO 2 absorption.…”

“…Similar to the distribution pattern of TA, relatively lower DIC values occurred in the nearshore area in spring but shifted to the northern part of the study area in summer, corresponding well to the seasonal dispersion of the Changjiang diluted water (CDW). The highest DIC values were present along the coast of mainland China beyond the influence of the CDW during the summertime, which was associated with the seasonal coastal upwelling induced by the summer monsoon parallel to shore (Chou et al, 2009a). pH 25 varied from 7.98 to 8.34 in spring, and from 7.86 to 8.45 in summer.…”

Carbon dioxide dynamics and fluxes in coastal waters influenced by river plumes

“…Seasonal variations of pCO 2 were also found to be low in the Amazon River plume (Fig. 7.6), in great contrast with those found in river plumes at subtropical and temperate latitudes, where seasonal oscillations from CO 2 over-saturation (typically in winter or fall) to under-saturation (typically in spring or summer) are observed (Borges and Frankignoulle 2002;Lohrenz and Cai 2006;Chou et al 2009a;Chou et al 2009b;Guo et al 2009;Zhai and Dai 2009;Vandemark et al 2011;Bozec et al 2012). Another great contrast between the Amazon plume and some of the other large river plumes is in the DIC (or TAlk) to salinity relationship, which does not show a substantial removal in the Amazon plume (Fig.…”

“…Time and again, the East China Sea (ECS) has been found to be a sink of CO 2 (Chen and Wang 1999;Tsunogai et al 1999;Chou et al 2009a;Zhai and Dai 2009;Tseng et al 2011). This is in part because the Changjiang River not only exports a significant amount of nutrients to the ECS but also a large quantity of freshwater, which also helps to induce an estuarine type flow.…”