Global estimates of net carbon production in the nitrate‐depleted tropical and subtropical oceans
Global estimates of net carbon production in the nitrate‐depleted tropical and subtropical oceans
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对硝酸盐耗尽的热带和亚热带海洋净碳产量的全球估计
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发表时间：
2002
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通讯作者：
Jia
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作者：
Kitack Lee;D. Karl;R. Wanninkhof;Jia
硝酸盐的可用性通常被认为是海洋新产量的限制因素，这一概念在我们的观测和模拟工作中是中心的。然而，最近在百慕大和夏威夷海域的时间序列观测表明，在没有可测量硝酸盐的情况下，总溶解无机碳（CT）的去除效果显著。在这里，我们估算了温度高于20°C的硝酸盐枯竭的热带和亚热带水域的净碳产量，这是根据表层混合层中盐度归一化CT库存的减少来估算的。这种方法产生的全球碳值为每年0.8±0.3 g (Pg C yr - 1, Pg = 1015 g)，相当于最近估计的热带和亚热带海洋总新产量（2.0-4.2 Pg C yr - 1）的很大一部分（20-40%）[Emerson等人，1997；李，2001]。其余部分可能是由营养物质通过涡流扩散和湍流混合过程或横向交换向上流入光区所支持的。我们的计算在没有可测量的硝酸盐的情况下提供了第一个全球尺度的净碳产量估计。我们假设这是由于固氮微生物，它们可以利用取之不尽的溶解的N2池，从而绕过硝酸盐的限制。
Nitrate availability is generally considered to be the limiting factor for oceanic new production and this concept is central in our observational and modeling efforts. However, recent time‐series observations off Bermuda and Hawaii indicate a significant removal of total dissolved inorganic carbon (CT) in the absence of measurable nitrate. Here we estimate net carbon production in nitrate‐depleted tropical and subtropical waters with temperatures higher than 20°C from the decrease in the salinity normalized CT inventory within the surface mixed layer. This method yields a global value of 0.8 ± 0.3 petagrams of carbon per year (Pg C yr−1, Pg = 1015 grams), which equates to a significant fraction (20–40%) of the recent estimates (2.0–4.2 Pg C yr−1) of total new production in the tropical and subtropical oceans [ Emerson et al., 1997 ; Lee, 2001 ]. The remainder is presumably supported by upward flux of nutrients into the euphotic zone via eddy diffusion and turbulent mixing processes or lateral exchange. Our calculation provides the first global‐scale estimate of net carbon production in the absence of measurable nitrate. We hypothesize that it is attributable to dinitrogen (N2) fixing microorganisms, which can utilize the inexhaustible dissolved N2 pool and thereby bypass nitrate limitation.