Decadal ventilation and mixing of Indian Ocean waters
Decadal ventilation and mixing of Indian Ocean waters
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DOI：
10.1016/j.dsr.2007.10.002
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发表时间：
2008-01-01
影响因子：
2.4
通讯作者：
Weiss, Ray F.
中科院分区：
文献类型：
--
作者：
Fine, Rana A., Jr.;Smethie, William M.;Weiss, Ray F.
世界海洋环流实验（WOCE）印度洋考察的氯氟烃（CFC）和水文数据被用来评估水团的十年通风的贡献。在给定的密度下，从南到北，CFC衍生的年龄增加，浓度降低，孟加拉湾的浓度最低，年龄最大。温跃层水的平均年龄为0-40年，中层水的平均年龄为10年至40年以上。与边缘海或贯穿流相比，12 ° N以南印度洋CFC的最重要来源是南半球。一个简单的计算表明，即使在中间水平的情况下，由于气体溶解度的差异和混合的南极中层水和红海Water. The底层水在澳大利亚-南极海盆是较高的CFC浓度比西部的恩德比海盆，由于较短的距离，这个水的阿德利陆地海岸和罗斯海的来源。然而，到南纬40度时，源自威德尔海的克罗泽盆地底层水中的氟氯化碳浓度与南澳盆地相似。独立的观测结果表明，底层水在澳大利亚-南极海盆之间以及在进入亚热带之前经历了高度混合，这与东南印度洋海脊从南到北的高氟氯化碳稀释（3-14倍）和浓度大幅下降（5倍）是一致的。含CFC的底层沃茨年龄为30年或更长时间，通过三个西部边界流被输送到亚热带南印度洋，在最西部的边界流中观察到最高浓度。在WOCE期间，含CFC的底层水在珀斯盆地达到约30度，在马斯克林盆地达到20度。将亚热带底层水-CFC浓度与南太平洋和大西洋的底层水-CFC浓度相比较，在可比较的纬度上，印度洋底层水-CFC浓度较低，这与其他地方显示的潮汐混合和海流波动的高消散率相一致。因此，印度洋底层水中的稀释度普遍较高，氟氯化碳浓度较低，这是由于与水团源区的距离和混合的相对有效性。虽然在温跃层、中层和底层，十年时间尺度上的重要通风源都来自南方并不奇怪，但CFC显示了海洋内的本地源和混合如何影响通风。(c)2007爱思唯尔有限公司版权所有。
Chlorofluorocarbon (CFC) and hydrographic data from the World Ocean Circulation Experiment (WOCE) Indian Ocean expedition are used to evaluate contributions to decadal ventilation of water masses. At a given density, CFC-derived ages increase and concentrations decrease from the south to north, with lowest concentrations and oldest ages in Bay of Bengal. Average ages for thermocline water are 0-40 years, and for intermediate water they are less than 10 years to more than 40 years. As compared with the marginal seas or throughflow, the most significant source of CFCs for the Indian Ocean south of 12 degrees N is the Southern Hemisphere. A simple calculation is used to show this is the case even at intermediate levels due to differences in gas solubilities and mixing of Antarctic Intermediate Water and Red Sea Water.Bottom water in the Australia-Antarctic Basin is higher in CFC concentrations than that to the west in the Enderby Basin, due to the shorter distance of this water to the Adelie Land coast and Ross Sea sources. However, by 40 degrees S, CFC concentrations in the bottom water of the Crozet Basin originating from the Weddell Sea are similar to those in the South Australia Basin. Independent observations, which show that bottom water undergoes elevated mixing between the Australia-Antarctic Basin and before entering the subtropics, are consistent with high CFC dilutions (3-14-fold) and a substantial concentration decrease (factor of 5) south to north of the Southeast Indian Ridge. CFC-bearing bottom waters with ages 30 years or more are transported into the subtropical South Indian Ocean by three western boundary currents, and highest concentrations are observed in the westernmost current. During WOCE, CFC-bearing bottom water reaches to about 30 degrees S in the Perth Basin, and to 20 degrees S in the Mascarene Basin. Comparing subtropical bottom water-CFC concentrations with those of the South Pacific and Atlantic oceans, at comparable latitudes, Indian Ocean bottom water-CFC concentrations are lower, consistent with its high dissipation rates from tidal mixing and current fluctuations as shown elsewhere. Thus, the generally high dilutions and low CFC concentrations in bottom water of the Indian Ocean are due to distance to the water mass source regions and the relative effectiveness of mixing. While it is not surprising that at thermocline, intermediate, and bottom levels, the significant ventilation sources on decadal time scales are all from the south, the CFCs show how local sources and mixing within the ocean affect the ventilation. (c) 2007 Elsevier Ltd. All rights reserved.