Enhanced biological production in the southeastern Arabian Sea during spring intermonsoon

Hydrographic observations in the southeastern Arabian Sea (SEAS) have identified a warm (>30°C) and stratified water mass (stability >5 × 10−5 m−1) along the near shore area between 10°N and 15°N during spring intermonsoon. This water mass was relatively low saline (34.2) and nitrate-rich (0.5 µM), favoring moderate primary production (6.7 mg C m−3 d−1). Since the mixing of the Arabian Sea and the Bay of Bengal waters is an important process during this period, the enhanced primary production in the SEAS is attributed to the entrainment of unconsumed nitrate left over during the previous season from the northern Arabian Sea. The season was further characterized by the presence of a deep chlorophyll a maximum (0.5 mg.m−3) in the outer shelf below (>50 m) the subducted Arabian Sea High Saline Waters, which was photosynthetically less active (<1.5 mg C m−3 d−1) due to light limitation.

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Holocene organic geochemical record from the Western Indus continental shelf (northern Arabian Sea)

The Holocene ◽

10.1177/0959683620902213 ◽

2020 ◽

Vol 30 (6) ◽

pp. 810-819

Author(s):

Sanober Kahkashan ◽

Jianfang Chen ◽

Xinhong Wang ◽

Peter D Clift ◽

Bassem Jalali ◽

...

Keyword(s):

Primary Production ◽

Continental Shelf ◽

Arabian Sea ◽

Warming Trend ◽

Indus River ◽

Geochemical Tracers ◽

Northern Arabian Sea ◽

Show Evidence ◽

Winter Insolation

Primary production on the Western Indus continental shelf has been linked to the large quantities of nutrients delivered to the shelf by the Indus River. Multiple geochemical tracers and biomarker records, including stable isotopes (δ13C and δ15N), total organic carbon (TOC), total nitrogen (TN), molar carbon/nitrogen (C/N) ratio, the branched and isoprenoid tetraether (BIT) index, and glycerol dialkyl glycerol tetraether (GDGT), have been analyzed from the Indus-23AP sediment core recovered from the northern Arabian Sea. Our records show evidence of a mixture of marine and terrestrially derived organic matter (OM) during the last 14,000 years, as indicated by the C/N ratio, δ13C, δ15N, and the BIT index. The three sterol biomarkers (brassicasterol, dinosterol, and cholesterol) show concurrent enrichments during the last 3 millennia reflecting increased phytoplankton abundance because of increased Indus river discharge of nutrients during the summer monsoon. GDGT crenarchaeol enrichment is related to the BIT index. The TEX86-derived sea surface temperature (SST) record is shifted toward the summer season because Crenarchaeota are more abundant and active during periods of high primary production. SSTs indicate a long-term warming trend during the Holocene related to increasing winter insolation in the low latitudes northern Hemisphere.

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The Wintertime Water Mass Formation in the Northern Arabian Sea: A Model Study

Journal of Physical Oceanography ◽

10.1175/1520-0485(2002)032<1028:twwmfi>2.0.co;2 ◽

2002 ◽

Vol 32 (3) ◽

pp. 1028-1040 ◽

Cited By ~ 21

Author(s):

T. G. Prasad ◽

M. Ikeda

Keyword(s):

Arabian Sea ◽

Water Mass ◽

Model Study ◽

Northern Arabian Sea ◽

Water Mass Formation ◽

Mass Formation

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Intra annual Variability of the Arabian Sea high salinity water mass in the South Eastern Arabian Sea during 2016 17

Defence Science Journal ◽

10.14429/dsj.69.14217 ◽

2019 ◽

Vol 69 (2) ◽

pp. 149-155

Author(s):

P. A. Maheswaran ◽

S. Satheesh Kumar ◽

T. Pradeep Kumar

Keyword(s):

Temporal Variability ◽

Arabian Sea ◽

Water Mass ◽

High Salinity ◽

High Salinity Water ◽

South Eastern ◽

Saline Waters ◽

Eastern Arabian Sea ◽

Salinity Water ◽

Spatio Temporal

Intra-annual variability of the Arabian Sea high salinity water mass (ASHSW) in the South Eastern Arabian Sea (SEAS) and Gulf of Mannar (GoM) are addressed in this paper by utilisng the monthly missions carried out onboard INS Sagardhwani during 2016-17. Our observations revealed that the ASHSW was evident along the SEAS irrespective of seasons, whereas in the GoM the presence of ASHSW was observed during winter. The processes such as downwelling/up-welling, coastal currents, intrusion of low saline waters, stratification are clearly affects the spreading of the ASHSW. The characteristics such as core salinity value, depth and thickness of ASHSW exhibited remarkable spatio-temporal variability. Lateral mixing with the low saline waters in the region during winter reduces its core salinity. The intrusion of low saline waters was clearly seen upto 15 ON but the intrusion of low saline waters is not flowing through the GoM. The interface between the ASHSW and the prevailing low saline waters showed strong horizontal gradients of salinity. The presence of the ASHSW makes difference in the SLD and the below layer gradient which is sufficient to complicate or influence sound transmission. The spatio temporal variability of the ASHSW and its acoustic relevance are documented in this paper.

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