Rapid removal of terrigenous dissolved organic carbon over the Eurasian shelves of the Arctic Ocean
Rapid removal of terrigenous dissolved organic carbon over the Eurasian shelves of the Arctic Ocean
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DOI：
10.1016/j.marchem.2010.10.002
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发表时间：
2011-01-20
期刊：
影响因子：
3
通讯作者：
Kadko, David
中科院分区：
文献类型：
--
作者：
Letscher, Robert T.;Hansell, Dennis A.;Kadko, David
河流输送到北冰洋的陆源溶解有机碳（tDOC）的命运在空间和时间尺度上仍然受到很大的限制。早期的报告表明，北极tDOC是难降解的，而最近的研究表明，tDOC的去除是一个积极但缓慢的过程。在这里，我们目前的DOC，盐度，三角洲O-18，Ra-228/Ra-226在极地表层（PSL）的观测外东西伯利亚/楚科奇大陆架和邻近的马卡罗夫和欧亚盆地的北冰洋东部。这个现成的系统在大陆架上停留几年后，接收由河流引入的大气降水。在马卡罗夫盆地的低盐度（类似于27）的水中观察到DOC浓度升高（>120 μ M C）。这表明富含tDOC的河水进入了跨极漂移的源头沃茨。DOC对盐度的回归表明，一个明显的tDOC浓度为315 +/- 7 μ M C的河水部分，这是显着低于估计的DOC浓度在河流来源的区域（724 +/- 55 μ M C）。为了获得去除的时间尺度，估计货架期与测量溶解的Ra-228/Ra-226相结合，Ra-228/Ra-226是货架期以来的同位素示踪剂。货架停留时间加上DOC分布表明，一阶tDOC去除率常数，λ = 0.24 +/- 0.07年（-1），为北极东部，2.5-4倍，比以前观察到的速度在北极西部。观察到的去除tDOC在北极东部发生在广阔的大陆架区域，突出了最初的不稳定性的tDOC交付到北冰洋后，并表明，tDOC是由多个舱室定义的反应。如果预计不稳定的tDOC通量增加，则大陆架上tDOC相对快速的矿化可能会减轻北冰洋大气CO2汇的强度。(C)2010 Elsevier B. V.保留所有权利。
The fate of terrigenous dissolved organic carbon (tDOC) delivered to the Arctic Ocean by rivers remains poorly constrained on both spatial and temporal scales. Early reports suggested Arctic tDOC was refractory to degradation, while recent studies have shown tDOC removal to be an active but slow process. Here we present observations of DOC, salinity, delta O-18, and Ra-228/Ra-226 in the Polar Surface Layer (PSL) over the outer East Siberian/Chukchi shelf and the adjacent Makarov and Eurasian basins of the eastern Arctic Ocean. This off-shelf system receives meteoric water, introduced by rivers, after a few years residence on the shelf. Elevated concentrations of DOC (>120 mu M C) were observed in low salinity (similar to 27) water over the Makarov Basin. suggesting inputs of tDOC-enriched river water to the source waters of the Transpolar Drift. The regression of DOC against salinity indicated an apparent tDOC concentration of 315 +/- 7 mu M C in the river water fraction, which is significantly lower than the estimated DOC concentration in the riverine sources to the region (724 +/- 55 mu M C). To obtain the timescale of removal, estimates of shelf residence were coupled with measurements of dissolved Ra-228/Ra-226, an isotopic tracer of time since shelf residence. Shelf residence time coupled with DOC distributions indicates a first order tDOC removal rate constant, lambda = 0.24 +/- 0.07 yr(-1), for the eastern Arctic, 2.5-4 times higher than rates previously observed in the western Arctic. The observed removal of tDOC in the eastern Arctic occurs over the expansive shelf area, highlighting the initial lability of tDOC upon delivery to the Arctic Ocean, and suggests that tDOC is composed of multiple compartments defined by reactivity. The relatively rapid remineralization of tDOC on the shelves may mitigate the strength of the Arctic Ocean atmospheric CO2 sink if a projected increase in labile tDOC flux occurs. (C) 2010 Elsevier B.V. All rights reserved.