The adjustment mechanism of the surface salinity in the Indian Ocean by oceanic advection
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摘要: 本文利用Argo表层盐度、OSCAR海流等数据，基于盐度收支方程的平流输送项来阐述海洋平流输送对热带印度洋表层盐度的调整作用；利用淡水输运量计算公式揭示6条关键断面海洋平流输送对表层盐度空间结构的调整机制。结果表明，海洋平流将赤道西印度洋和阿拉伯海的高盐水输送到低盐海域的赤道东印度洋和孟加拉湾、安达曼海；将赤道东印度洋和孟加拉湾、安达曼海的低盐水输送到高盐海域的赤道西印度洋、阿拉伯海以及赤道南印度洋海域，起到了调整印度洋盐度基本平衡的作用。断面淡水输运量的分析结果表明，导致苏门答腊岛西部海域的强降水中心与低盐中心不重合，澳大利亚西部海域的强蒸发中心与高盐中心不重合的主要原因是水平环流所致；夏季，来自赤道西印度洋和阿拉伯海的高盐水在西南季风环流的驱动下，入侵孟加拉湾，是导致孟加拉湾夏季表层盐度较高的主要原因。Abstract: In this study, Argo surface salinity, OSCAR current and other data are used to explore the influence of oceanic advection transport on the surface salinity in the Tropical Indian Ocean based on the advection term of the salinity budget equation. The adjustment mechanism of the spatial structure of surface salinity by oceanic advection is revealed by freshwater transport calculation along 6 key sections. The results show that the oceanic advection which transports the high-salinity water in the Equatorial Western Indian Ocean (EWIO) and the Arabian Sea (AS) to the Equatorial Eastern Indian Ocean (EEIO), the Bay of Bengal (BOB) and the Andaman Sea, and also transports the low-salinity water in the EEIO, the BOB and the Andaman Sea to the EWIO, the AS and the Equatorial Southern Indian Ocean, plays a role in adjusting the basic balance of salinity in the Indian Ocean. The analysis of freshwater transport along sections shows that the inconsistency between the center of high precipitation and low salinity in the western sea area of Sumatra, and the inconsistency between the center of high evaporation and high salinity in the western sea area of Australia, are both caused by oceanic advection. In summer, the high-salinity water in the EWIO and the AS transported by the southwest monsoon forced circulation into the BOB, is the main reason for the high surface salinity in the BOB.
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Key words:
- freshwater transport /
- advection /
- adjustment mechanism /
- surface salinity /
- Indian Ocean
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图 1 多年平均1月、4月、7月、10月Argo表层盐度和OSCAR表层流速矢量的平面分布
Fig. 1 The plane distribution of annual average Argo surface salinity and OSCAR surface current vector in January, April, July and October
图 2 多年平均1月、4月、7月、10月平流输送项的平面分布和淡水输运量的计算断面
Fig. 2 The plane distribution of annual average advection term in January, April, July and October and positions of the sections for freshwater transport calculation
图 3 赤道南印度洋矩形海域平均表层盐度、纬向流速时间序列（a）和超前滞后相关系数（b）
Fig. 3 The time series of mean surface salinity and zonal velocity in the rectangular region of the Equatorial Southern Indian Ocean (a) and the results of lag correlation analysis (b)
图 4 A、B、C断面的流速U、盐度差（S0−S）和淡水输运量的纬度−时间分布
Fig. 4 The latitude-time distribution of velocity U, difference of salinity (S0−S) and freshwater transport for sections A, B and C
图 5 A、B、C断面的年平均淡水输运量、纬向流速随纬度的变化
Fig. 5 The latitudinal variation of annual average freshwater transport and zonal velocity for sections A, B and C
图 6 A、B、C断面淡水输运量正值和负值的年平均值
Fig. 6 Annual average value of the positive and negative freshwater transport for sections A, B and C
图 7 多年平均表层盐度、年净淡水通量的平面分布和淡水输运量的计算断面
Fig. 7 The distribution of annual average surface salinity and net freshwater flux and positions of the sections for freshwater transport calculation
图 8 D断面淡水输运量的经度−时间分布（a）和年平均淡水输运量、经向流速随经度的变化（b）
Fig. 8 Longitude-time distribution of freshwater transport (a) and the longitudinal variation of annual average freshwater transport and meridional velocity for Section D (b)
图 9 E断面淡水输运量的经度−时间分布（a）和年平均淡水输运量、经向流速随经度的变化（b）
Fig. 9 Longitude-time distribution of freshwater transport (a) and the longitudinal variation of annual average freshwater transport and meridional velocity (b) for Section E
图 10 F断面淡水输运量的经度−时间分布（a）和年平均淡水输运量、经向流速随经度的变化（b）
Fig. 10 Longitude-time distribution of freshwater transport (a) and the longitudinal variation of annual average freshwater transport and meridional velocity (b) for Section F
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