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Abstract <p>The structure and characteristics of watermass along the eastern Arabian Sea (EAS) have been re-evaluated using ship-based monthly repeat measurements along the 2000 m isobath in 2018. Overall, the EAS is identified by various watermasses, <i>viz</i>., Bay of Bengal Water (BBW) and Arabian Sea High Saline Water (ASHSW) in the surface layers (0–150 m) associated with poleward/equatorward West India Coastal Currents, Persian Gulf Water (PGW) in the 200–500 m, Red Sea Waters (RSW) in intermediate depth (500–800 m), Arabian Sea Bottom Water (ASBW) in the bottom layers (1000–2000 m). A salinity minimum was observed along the EAS at a depth of 100–200 m, termed Modified Arabian Sea Waters (MASW). The MASW is formed by mixing different watermasses, <i>viz</i>., BBW, Indian Central Water (ICW), and Indian Ocean Equatorial Water (IOEW) in the south (6–15°N), whereas in the north (15–22°N), it is formed due to the mixing of ASHSW (0–100 m) and PGW (200–500 m). The reanalysis of the current dataset revealed the advection of IOEW (100–200 m) and ICW (200–800 m) associated with poleward undercurrent up to 15°N, restricting the southward penetration of PGW. The region between 12 and 17°N is found to be a mixing zone of these low and high-saline water masses of EAS.</p> Highlights <p><UnorderedList Mark="Bullet"> <ItemContent> <p>Watermass structure and characteristics were reassessed using <i>in-situ</i> repeated measurements along the eastern Arabian Sea (EAS).</p> </ItemContent> <ItemContent> <p>A salinity minimum was observed between 100 and 200 m depth along the EAS, termed Modified Arabian Sea Waters (MASW).</p> </ItemContent> <ItemContent> <p>Undercurrents played a significant role in structuring watermass along the intermediate depths.</p> </ItemContent> <ItemContent> <p>This movement of intermediate watermasses created a seasonal oscillation in the 200–600 m water column in the central Eastern Arabian Sea (CEAS).</p> </ItemContent> </UnorderedList></p>

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Reassessing the structure and characteristics of watermass using ship-based repeat observations along the eastern Arabian Sea

  • 期刊论文

  • 发表日期：

    2025年2月6日

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  • S Vishnu Narayanan Nampoothiri,
  • Nanda Kishore,
  • K Rasheed,
  • V Sudheesh,
  • Ch Venkata Ramu,
  • G V M Gupta

摘要

Abstract

The structure and characteristics of watermass along the eastern Arabian Sea (EAS) have been re-evaluated using ship-based monthly repeat measurements along the 2000 m isobath in 2018. Overall, the EAS is identified by various watermasses, viz., Bay of Bengal Water (BBW) and Arabian Sea High Saline Water (ASHSW) in the surface layers (0–150 m) associated with poleward/equatorward West India Coastal Currents, Persian Gulf Water (PGW) in the 200–500 m, Red Sea Waters (RSW) in intermediate depth (500–800 m), Arabian Sea Bottom Water (ASBW) in the bottom layers (1000–2000 m). A salinity minimum was observed along the EAS at a depth of 100–200 m, termed Modified Arabian Sea Waters (MASW). The MASW is formed by mixing different watermasses, viz., BBW, Indian Central Water (ICW), and Indian Ocean Equatorial Water (IOEW) in the south (6–15°N), whereas in the north (15–22°N), it is formed due to the mixing of ASHSW (0–100 m) and PGW (200–500 m). The reanalysis of the current dataset revealed the advection of IOEW (100–200 m) and ICW (200–800 m) associated with poleward undercurrent up to 15°N, restricting the southward penetration of PGW. The region between 12 and 17°N is found to be a mixing zone of these low and high-saline water masses of EAS.

Highlights

Watermass structure and characteristics were reassessed using in-situ repeated measurements along the eastern Arabian Sea (EAS).

A salinity minimum was observed between 100 and 200 m depth along the EAS, termed Modified Arabian Sea Waters (MASW).

Undercurrents played a significant role in structuring watermass along the intermediate depths.

This movement of intermediate watermasses created a seasonal oscillation in the 200–600 m water column in the central Eastern Arabian Sea (CEAS).