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南海的氟氯烃分布、通风过程及人为碳估算研究
Ventilation time and anthropogenic CO2 in the South China Sea based on CFC-11 measurements
发布日期：2016-10-23      浏览次数：1659

    本研究首次将“转移时间分布”的概念首次应用于南海；采用“转移时间分布”方法首次估算出南海2011年的人为来源碳储量；首次基于示踪物数据估算出南海水体的垂直扩散速率。研究表明南海表层水体的平均年龄为0-30年，通风时间较短。500 m的平均年龄约170年，明显大于上层水体。而深度大于1500 m的水体，平均年龄超过500年。年龄分布的证据表明南海存在深层的翻转流系统。估算得出南海500 m以深水体上升速率为13-34 m yr-1。基于该上升速率估算的南海500 m以深水体停留时间约为60-140年。南海500 m以深的垂直扩散率为2-4.6×10-4 m2 s-1。相关文章《Ventilation time and anthropogenic CO2 in the South China Sea based on CFC-11 measurements》于2016年10月发表于海洋学SCI（大类二区）期刊《Deep Sea Research Part I: Oceanographic Research Papers》。

Figure. Profiles of (a) CFC-11 (ppt), (b) mean ages (years) and (c) Cant (μmol kg-1) in the South China Sea in 2011 together with the error bars. The blue dots indicate the stations south of 15°N, the red dots the stations north of 15°N. The solid lines are averaged profiles.

 

 

Abstract:

      The South China Sea (SCS) is the largest semi-enclosed marginal sea in Southeast Asia, and is bounded by the Asian continent, Philippine Archipelago, and Great Sunda Islands. Due to the wide shelves on its northwestern and southern ends as well as the presence of numerous islets, atolls and reefs, the average depth of the SCS is only 1350 m. In this study we used measurements of the transient tracer CFC-11 from the SCS to calculate ventilation time-scales and the concentration of anthropogenic CO2 (Cant) based on the transit time distribution. The CFC-11 concentrations decreased consistently with depth and the deep and bottom water in the SCS had a CFC-11 value close to the detection limit (0.01 pmol kg-1 or 0.5 ppt). The ventilation times (mean ages) for the deep and bottom water column were ~500-600 years, and based on the mean age profiles the southern part of the intermediate SCS water was older than the northern part. The ventilation time distribution was in agreement with the existence of mean annual cyclonic circulation in the SCS. The mean column inventory of Cant in the northern SCS was 28.9 mol C m-2 (error range (ER): 22.8-35.6 mol C m-2), while in the southern SCS it was 28.4 mol m-2 (ER: 21.9-35.2 mol C m-2). The total Cant inventory was estimated to be 1 Pg C (ER: 0.8-1.3 Pg C, referenced to the year 2011), suggesting that the SCS stores less Cant then the adjacent seas. The vertical diffusivity was estimated to be 2-4.6×10-4 m2 s-1 in the SCS based on the “transient steady state”. The upwelling was estimated as 13-34 m yr-1. The high diffusivity was probably due to the strong internal tide, while the strong upwelling was due to the persistent counterclockwise (cyclonic) circulation.