Incursion of the Pacific Ocean Water into the Indian Ocean

Sharma, G S; Gouveia, A.D.; Satyendranath, Shubha

doi:10.1007/bf02839383

Cited by 4 publications

(4 citation statements)

References 6 publications

(4 reference statements)

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“…The main water sources at 200–1000 m originate both from the northwest (the highly saline Red Seawater (RSW) and the Persian Gulf Water (PGW)) and from the south (the Indian Central Water (ICW)) [ Wyrtki , 1973; Swallow , 1984; You , 1998] (Figure 3). The latter is a mixture of aged Antarctic Intermediate Water (AAIW) and Banda Seawater (BSW) coming from the Indonesian throughflow [ Sharma , 1972; Sharma et al , 1978; You , 1998], and enters the AS across the southwestern boundary during the summer monsoon with the Somali current [ You , 1998]. Oxygen concentrations in the northern and southern water masses are equally low but the volume transported across the equator with the southern waters is 1 order of magnitude larger than that contained in the northern source inflow [ Swallow , 1984].…”

Section: Nutrient and Oxygen Inventories In The Modern Asmentioning

confidence: 99%

Evidence of ventilation changes in the Arabian Sea during the late Quaternary: Implication for denitrification and nitrous oxide emission

Pichevin¹,

Bard

Martinez

et al. 2007

Global Biogeochemical Cycles

108

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Modern seawater profiles of oxygen, nitrate deficit, and nitrogen isotopes reveal the spatial decoupling of summer monsoon‐related productivity and denitrification maxima in the Arabian Sea (AS) and raise the possibility that winter monsoon and/or ventilation play a crucial role in modulating denitrification in the northeastern AS, both today and through the past. A new high‐resolution 50‐ka record of δ15N from the Pakistan margin is compared to five other denitrification records distributed across the AS. This regional comparison unveils the persistence of east‐west heterogeneities in denitrification intensity across millennial‐scale climate shifts and throughout the Holocene. The oxygen minimum zone (OMZ) experienced east‐west swings across Termination I and throughout the Holocene. Probable causes are (1) changes in ventilation due to millennial‐scale variations in Antarctic Intermediate Water formation and (2) postglacial reorganization of intermediate circulation in the northeastern AS following sea level rise. Whereas denitrification in the world's OMZs, including the western AS, gradually declined following the deglacial maximum (10−9 ka BP), the northeastern AS record clearly witnesses increasing denitrification from about 8 ka BP. This would have impacted the global Holocene climate through sustained N2O production and marine nitrogen loss.

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Section: Nutrient and Oxygen Inventories In The Modern Asmentioning

confidence: 99%

Evidence of ventilation changes in the Arabian Sea during the late Quaternary: Implication for denitrification and nitrous oxide emission

Pichevin¹,

Bard

Martinez

et al. 2007

Global Biogeochemical Cycles

108

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“…Although the SICC has only recently been recognized as a permanent feature of the SIO circulation, Sharma [] and Sharma et al . [] described a shallow eastward current between 22°S and 26°S associated with a thermal front. He named that current the South Indian Tropical Countercurrent, pointing out that it was evident in all surface geopotential charts from the Indian Ocean Atlas produced by Wyrtki in 1971 and also on the surface currents maps from the Royal Netherlands Meteorological Institute in 1952.…”

Section: Introductionmentioning

confidence: 99%

South Indian Countercurrent and associated fronts

et al. 2014

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A striking feature of the South Indian Ocean circulation is the presence of the eastward South Indian Countercurrent (SICC) that flows in a direction opposite to that predicted by the classical theories of wind-driven circulation. Several authors suggest that the SICC resembles the subtropical countercurrents (STCCs) observed in other oceans, which are defined as narrow eastward jets on the equatorward side of subtropical gyres, where the depth-integrated flow is westward. These jets are associated with subsurface thermal fronts at thermocline depths by the thermal wind relation. However, the subsurface thermal front associated with the SICC has not been described to date. Other studies conjecture an important role for salinity in controlling the SICC. In the present work, we analyze three Argo-based atlases and data from six hydrographic cruises to investigate whether the SICC is accompanied by permanent thermal and density fronts including salinity effects. The seasonal cycle of these fronts in relation to the SICC strength is also investigated. We find that the SICC is better described as composed of three distinct jets, which we name the northern, central, and southern SICC. We find that the southern SICC around 26 S has an associated thermal front at subsurface depths around 100-200 m with salinity being of secondary importance. The southern branch strength is related to mode waters poleward of the front, similar to a STCC-like current. However, the SICC multiple jet structure seems to be better described as resulting from PV staircases.

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“…In the central-eastern South Indian Ocean between 20°S and 30°S, the surface geostrophic flow is generally eastward, opposite to the prediction both of the Ekman and Sverdrup theories (Sharma 1976;Sharma et al, 1978;Godfrey and Ridgway, 1985;Schott et al, 2009). This flow is driven by the large-scale, poleward drop in the dynamic height (steric height) near the surface (Godfrey and Ridgway, 1985;Schott et al, 2009) related to the meridional transition from the very fresh and warm SEC waters to the increasingly cooler, saltier and denser waters to the south.…”

Section: Circulationmentioning

confidence: 82%

Progress in understanding of Indian Ocean circulation, variability, air-sea exchange and impacts on biogeochemistry

Phillips

Tandon

Furue

et al. 2021

Preprint

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Abstract. Over the past decade, our understanding of the Indian Ocean has advanced through concerted efforts toward measuring the ocean circulation and its water properties, detecting changes in water masses, and linking physical processes to ecologically important variables. New circulation pathways and mechanisms have been discovered, which control atmospheric and oceanic mean state and variability. This review brings together new understanding of the ocean-atmosphere system in the Indian Ocean since the last comprehensive review, describing the Indian Ocean circulation patterns, air-sea interactions and climate variability. The second International Indian Ocean Expedition (IIOE-2) and related efforts have motivated the application of new technologies to deliver higher-resolution observations and models of Indian Ocean processes. As a result we are discovering the importance of small scale processes in setting the large-scale gradients and circulation, interactions between physical and biogeochemical processes, interactions between boundary currents and the interior, and between the surface and the deep ocean. In the last decade we have seen rapid warming of the Indian Ocean overlaid with extremes in the form of marine heatwaves. These events have motivated studies that have delivered new insight into the variability in ocean heat content and exchanges in the Indian Ocean, and climate variability on interannual to decadal timescales.This synthesis paper reviews the advances in these areas in the last decade.

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Incursion of the Pacific Ocean Water into the Indian Ocean

Abstract: @ printed in India.

Cited by 4 publications

References 6 publications

Evidence of ventilation changes in the Arabian Sea during the late Quaternary: Implication for denitrification and nitrous oxide emission

Evidence of ventilation changes in the Arabian Sea during the late Quaternary: Implication for denitrification and nitrous oxide emission

South Indian Countercurrent and associated fronts

Progress in understanding of Indian Ocean circulation, variability, air-sea exchange and impacts on biogeochemistry

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