南海海水中DO的平面、垂直分布以及海-气交换通量

Horizontal and vertical distributions of DO content and its flux of ocean-atmosphere exchange in the South China Sea

根据1998年7月和1999年1月南海两个航次的综合调查结果,对溶解氧(DO)的平面、垂直分布以及海-气交换通量进行了研究,结果表明:表层海水是DO浓度最高的含氧层,在次表层20～75 m处普遍存在着DO浓度的最大值(440 μmol/dm3),同时该层还出现了pH值的最大值和活性磷酸盐浓度的最小值,其位置在温跃层的下界附近.对夏季表层DO和活性磷酸盐进行相关性分析可知,其相关系数为-0.915(n=288),两者呈显著负相关;同时,DO和pH值垂向变化趋势相一致,相关系数为0.951(n=288),两者呈强烈正相关.通过计算,得到1998年夏季和1999年冬季海面溶解氧的海-气交换通量:夏季释放通量为-0.346～0.226 mol/(m2·d);冬季为-0.234～3.123 mol/(m2·d).由于夏季南海海水生物的初级生产力相对要高于冬季,因此夏季溶解氧向上通量的区域较冬季广,同时,海-气交换的通量随区域的变化也有所不同.

This article studied horizontal and vertical distributions of DO content and the flux of ocean-atmosphere exchange in two integrated investigation cruises respectively in July 1998 and January 1999 in South China Sea. The results indicated that the maximum DO content occurred in surface water. The maximum of DO content in the vertical distribution universally existed in the subsurface water （20～75m）, with a value of 440 μmol/dm^3, and simultaneously, the maximum of pH content and the minimum of nutrient element PO4 content occurred at the same water level, which was located near the lower bound of thermocline. Correlation analyses were used to analyze the relationship between DO and nutrient element PO4 contents in the surface water in summer. The correlation coefficient r was -0.915 （n=288）, presenting a distinct negative correlation. The vertical distribution of DO content was consistent with the vertical change of pH content and the correlation coefficient r was 0.95 （n=288）, presenting an intense positive correlation. The upward DO flux of ocean-atmosphere exchange was -0.346～0.226 mol/（m^2·d） in summer and -0.234～3.123 mol/（m^2·d） in winter according to the date obtained in July 1998 and January 1999. The primary production of ocean creatures in the South China Sea in summer is relatively higher than that in winner, so the up flux areas of dissolved oxygen in summer is wider than that in winner. In the meanwhile, the variations of exchange flux between sea and atmosphere depending on areas are also different.