A seventy-two-year record of diminishing deep-water oxygen in the St. Lawrence estuary: The northwest Atlantic connection
A seventy-two-year record of diminishing deep-water oxygen in the St. Lawrence estuary: The northwest Atlantic connection
复制标题
DOI：
10.4319/lo.2005.50.5.1654
复制
发表时间：
2005-09-01
影响因子：
4.5
通讯作者：
Tremblay, GH
中科院分区：
文献类型：
--
作者：
Gilbert, D;Sundby, B;Tremblay, GH
下圣劳伦斯河口（LSLE）底部沃茨的氧浓度从1930年代的125 μ mol L-1（37.7%饱和度）下降到1984-2003年期间的平均65 μ mol L-1（20.7%饱和度）。从20世纪30年代到80年代，底层水同时升温1.65摄氏度，这表明进入劳伦海峡的水体中冷、新鲜、富氧的拉布拉多海流水（LCW）和温暖、咸、贫氧的北大西洋中央水（NACW）的相对比例的变化可能在氧气消耗中发挥了作用。我们估计，大约一半到三分之二的氧气损失的底部沃茨的LSLE可以归因于LCW的比例减少。这之间的三分之一和一半的氧气减少的原因解释的变化以外的水质量组成。在过去的几十年中，沿通道的氧气梯度从卡伯特海峡的LSLE，结合沉积物岩心的数据，增加沉积物的需氧量可能是部分负责其余的氧气下降。2003年7月，LSLE约1，300 km（2）的海底浸泡在低氧水（< 62.5 μ mol L-1）中。
Oxygen concentrations in the bottom waters of the Lower St. Lawrence estuary (LSLE) decreased from 125 mu mol L-1 (37.7% saturation) in the 1930s to an average of 65 mu mol L-1 (20.7% saturation) for the 1984-2003 period. A concurrent 1.65 degrees C warming of the bottom water from the 1930s to the 1980s suggests that changes in the relative proportions of cold, fresh, oxygen-rich Labrador Current Water (LCW) and warm, salty, oxygen-poor North Atlantic Central Water (NACW) in the water mass entering the Laurentian Channel probably played a role in the oxygen depletion. We estimate that about one half to two thirds of the oxygen loss in the bottom waters of the LSLE can be attributed to a decreased proportion of LCW This leaves between one third and one half of the oxygen decrease to be explained by causes other than changes in water mass composition. An increase in the along-channel oxygen gradient from Cabot Strait to the LSLE over the past decades, combined with data from sediment cores, suggests that increased sediment oxygen demand may be partly responsible for the remainder of the oxygen decline. In July 2003, approximately 1,300 km(2) of seafloor in the LSLE was bathed in hypoxic water (< 62.5 mu mol L-1).