Journal of Marine Sciences ›› 2020, Vol. 38 ›› Issue (4): 26-39.DOI: 10.3969/j.issn.1001-909X.2020.04.003

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Decadal variation of isopycnal layer in the Indian Ocean based on WOA18 dataset

WU Shouchang1,2, HE Hailun*1,2, CHEN Meixiang3, WANG Yuan1,2,4, LIN Feilong1,2   

  1. 1. State Key Laboratory of Satellite Ocean Environment Dynamics, Hangzhou 310012, China;
    2. Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China;
    3. College of Oceanography, Hohai University, Nanjing 210098, China;
    4. Key Laboratory of Submarine Geosciences, Ministry of Natural Resources, Hangzhou 310012, China
  • Received:2020-02-20 Online:2020-12-15 Published:2020-12-15

Abstract: The climatology distribution of isopycnal layer in the Indian Ocean were analyzed based on the WOA18 (World Ocean Atlas 2018) dataset firstly. And then three time periods were defined as 1985-1994, 1995-2004 and 2005-2017 to research the decadal variation. The results show the climatology distributions of 11 isopycnal layers. As far as σ0=26.00kg/m3 (reference pressure as 0 dbar) isopycnal layer was concerned, the layer was outcropping at roughly 40°S. As the potential density increased, the outcrop area of the isopycnal layer gradually moved southward until it disappeared. When the potential density was greater than σ0=26.95 kg/m3 and less than or equal to σ2=37.00kg/m3, the deepest part of the isopycnal layers were located in southern Madagascar, and the depth of the North Indian Ocean was almost the same. Furthermore, present study investigates the decadal variances of depth and salinity of isopycnal layers, where the three layers include σ0=26.00 kg/m3, σ1=31.87 kg/m3 (reference pressure as 1 000 dbar) and σ2=36.805kg/m3 (reference pressure as 2 000 dbar). Studies show that the depth and salinity of the isopycnal layer had significant decadal changes in the three periods from 1985 to 2017. For the isopycnal layer of σ0=26.00kg/m3, the depth decreased first and then increased during the three periods. And the decadal variation of the isopycnal depth was mainly located in 30°S-40°S(the rapid change area of the isopycnal depth). The difference of salinity between 1995-2004 and 1985-1994 was basically opposite to the difference between 2005-2017 and 1995-2004 when the isopycnal layer was σ0=26.00kg/m3. For the isopycnal layer of σ1=31.87kg/m3 and σ2=36.805kg/m3, the decadal variations of the depth were concentrated on 40°S-50°S. Overall, the salinity of σ1=31.87kg/m3 show a decreasing trend but σ2=36.805kg/m3 show an increase trend.

Key words: the Indian Ocean, isopycnal layer, decadal variance

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