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

深海中的溶解有机物（DOM）含有与全球生物量或大气CO2相同的碳含量。DOM的来源和保存机制仍然是全球元素循环模型中缺失的一环。我们假设威德尔海是深层海洋DOM的主要来源，因为来自表层沃茨的海冰DOM可以有效地对流到海洋底部。海冰中DOM的分子特征还很不清楚，也不清楚海冰DOM是否具有足够的持久性，能够在向下的运输中存活下来。根据初步数据，我们粗略估计，约50-75 Tg的溶解有机碳（DOC）可能每年输出到深威德尔海。该项目的主要目标是调查持久性DOM的形成，对该DOM进行化学表征并量化其向威德尔海深处的迁移。在我们的项目的第三年，分析结果将使用多元统计方法进行评估，并与海洋学模型的结果在威德尔海的底层水的形成和持久性氯氟烃（CFC）标记的分布。由于第一批结果支持“DOM泵”的地球化学过程，我们的目标是对该CO²汇进行首次定量估计，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.