Production and sequestration of dissolved organic carbon in the Weddel Sea: Tracing deep-water formation with molecular methods

深海中溶解的有机物（DOM）所含的碳与全球生物量或大气中二氧化碳的含量大致相同。DOM的来源和保存机制在全球元素循环模型中仍然是一个缺失的环节。我们假设威德尔海是深海DOM的主要来源，因为来自地表水的海冰产生的DOM可以有效地对流到海底。海冰中DOM的分子特征尚不清楚，也不清楚海冰衍生的DOM是否足够持久，能够在向下运输中存活下来。根据初步数据，我们粗略估计每年约有50-75 Tg的溶解有机碳（DOC）可能出口到威德尔海深处。该项目的主要目标是研究持久性DOM的形成，对这种DOM进行化学表征，并量化其向威德尔海深处的运输。在我们项目的第三年，将使用多元统计方法评估分析结果，并将其与威德尔海底水形成的海洋学模型和持久性氟氯烃（CFC）标记物分布的结果联系起来。由于最初的结果支持“dom泵”的生物地球化学过程，我们的目标是对这个二氧化碳汇进行第一次定量估计，作为该项目第三年的中心目标。

Dissolved organic matter (DOM) in the deep oceans contains about the same amount of carbon as the global biomass or atmospheric CO2. Sources and preservation mechanisms of DOM remain a missing link in models of global elemental cycles. We hypothesize that the Weddell Sea is a primary source of DOM in the deep ocean because sea-ice derived DOM from surface waters can efficiently convect down to the oceans’ bottom. The molecular characteristics of DOM in sea ice are widely unknown, and it is not clear whether sea-icederived DOM is persistent enough to survive downward transport. Based on preliminary data we roughly estimate that ~50-75 Tg of dissolved organic carbon (DOC) may be exported annually into the deep Weddell Sea. The main objective of this project is to investigate the formation of persistent DOM, to chemically characterize this DOM and to quantify its transport to the deep Weddell Sea. In the third year of our project the analytical results will be evaluated using multivariate statistical methods and related to results from oceanographic models for bottom-water formation in the Weddell Sea and from the distribution of persistent chlorofuorocarbon (CFC) markers. Since the first results support the biogeochemical process of a “DOM-pump” we aim at a first quantitative estimate of this CO² sink as a central aim of the third year of this project.