Glacial-interglacial changes in bottom-water oxygen content on the Portuguese margin
Glacial-interglacial changes in bottom-water oxygen content on the Portuguese margin
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DOI：
10.1038/ngeo2317
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发表时间：
2015-01-01
影响因子：
18.3
通讯作者：
Rickaby, Rosalind E. M.
中科院分区：
文献类型：
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作者：
Hoogakker, Babette A. A.;Elderfield, Henry;Rickaby, Rosalind E. M.
在最后一次也是倒数第二次冰川高峰期，大气中的二氧化碳浓度比现在低，部分原因可能是深海中呼吸碳的储存增加(1)。水团中存在的呼吸碳量可以通过表观氧利用根据其含氧量计算出来；氧含量又可以通过沉淀柱内的碳同位素梯度计算(2)。在这里，我们分析了出现在沉积物表面和葡萄牙边缘的氧/缺氧界面上的底栖有孔虫的壳，以重建过去15万年来的碳同位素梯度和底水氧化作用。我们发现，在末次和倒数第二次冰期高峰期，底水氧浓度分别比现在低45和65mU·mol·kg(-1)。我们计算出，在冰川鼎盛时期，再矿化有机碳的浓度至少是今天的两倍。我们将这些变化归因于与海洋环流重组有关的通风减少(3)和全球生物泵的加强(4)。如果整个大西洋冰川深盆地的呼吸碳库具有类似的大小，那么这个汇可以占到最后一次也就是倒数第二次冰川高峰期间冰川P-CO2下降的15%和20%
During the last and penultimate glacial maxima, atmospheric CO2 concentrations were lower than present, possibly in part because of increased storage of respired carbon in the deep oceans(1). The amount of respired carbon present in a water mass can be calculated from its oxygen content through apparent oxygen utilization; the oxygen content can in turn be calculated from the carbon isotope gradient within the sediment column(2). Here we analyse the shells of benthic foraminifera occurring at the sediment surface and the oxic/anoxic interface on the Portuguese Margin to reconstruct the carbon isotope gradient and hence bottom-water oxygenation over the past 150,000 years. We find that bottom-water oxygen concentrations were 45 and 65 mu mol kg(-1) lower than present during the last and penultimate glacial maxima, respectively. We calculate that concentrations of remineralized organic carbon were at least twice as high as today during the glacial maxima. We attribute these changes to decreased ventilation linked to a reorganization of ocean circulation(3) and a strengthened global biological pump(4). If the respired carbon pool was of a similar size throughout the entire glacial deep Atlantic basin, then this sink could account for 15 and 20 per cent of the glacial P-CO2 drawdown during the last and penultimate glacial maxima