Chemical oceanography of the Arabian Gulf

Al-Yamani, Faiza; Naqvi, S.W.A.

doi:10.1016/j.dsr2.2018.10.003

Cited by 50 publications

(36 citation statements)

References 41 publications

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“…However, further away from the coast in the center of the Kuwait Bay, monthly sampling at a fixed station (K6, latitude 29.45 • N, longitude 47.967 • E, depth 12 m) being carried out since 2004 revealed that bottom water oxygen content has almost always been above 4 mg l −1 (2.8 ml l −1 , 125 µM), the nominal threshold for mild hypoxia (Dr. Faiza Al-Yamani, personal communication). However, eutrophication has led to a marked increase in the frequency of algal blooms, including harmful blooms, in Kuwait's waters in recent years (Al-Yamani et al, 2012;Al-Yamani and Naqvi, 2019). There have been instances of fish mortality in Kuwait waters associated with hypoxia as described by Al-Yamani et al (2020).…”

Section: Andaman Seamentioning

confidence: 99%

“…Of the three marginal seas of the Indian Ocean, two (the Red Sea and Persian Gulf) are connected to the NWIO, while the third (the Andaman Sea) forms a part of the NEIO (Figure 1). The Mediterranean-type marginal seas of the NWIO have been fairly well investigated (Morcos, 1970;Grasshoff, 1975Grasshoff, , 1976Brewer and Dyrssen, 1985;Yao et al, 2014a,b;Al-Yamani and Naqvi, 2019). In comparison, oceanographic processes of the Andaman Sea are not so well known (Sen Gupta et al, 1981;Sarma and Narvekar, 2001;Jithin and Francis, 2020).…”

Section: Introductionmentioning

confidence: 99%

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Deoxygenation in Marginal Seas of the Indian Ocean

Naqvi

2021

Front. Mar. Sci.

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This article describes oxygen distributions and recent deoxygenation trends in three marginal seas – Persian Gulf and Red Sea in the Northwestern Indian Ocean (NWIO) and Andaman Sea in the Northeastern Indian Ocean (NEIO). Vertically mixed water column in the shallow Persian Gulf is generally well-oxygenated, especially in winter. Biogeochemistry and ecosystems of Persian Gulf are being subjected to enormous anthropogenic stresses including large loading of nutrients and organic matter, enhancing oxygen demand and causing hypoxia (oxygen < 1.4 ml l–1) in central and southern Gulf in summer. The larger and deeper Red Sea is relatively less affected by human activities. Despite its deep water having remarkably uniform thermohaline characteristics, the central and southern Red Sea has a well-developed perennial oxygen minimum at mid-depths. The available data point to ongoing deoxygenation in the northern Red Sea. Model simulations show that an amplified warming in the marginal seas of the NWIO may cause an intensification of the Arabian Sea oxygen minimum zone (OMZ). Increases in particulate organic carbon and decreases in oxygen contents of the outflows may also have a similar effect. In the Andaman Sea, waters above the sill depth (∼1.4 km) have characteristics similar to those in the Bay of Bengal, including an intense OMZ. As in the case of the Bay of Bengal, oxygen concentrations within the Andaman Sea OMZ appear to have declined slightly but significantly between early 1960s and 1995. The exceedingly isothermal and isohaline water that fills the deep Andaman Basin is also remarkably homogenous in terms of its oxygen content. A very slight but statistically significant decrease in oxygen content of this water also seems to have occurred over three decades preceding 1995. New information is badly needed to assess the extent of further change that may have occurred over the past 25 years. There have been some reports of coastal “dead zones” having developed in the Indian Ocean marginal seas, but they are probably under-reported and the effects of hypoxia on the rich and diverse tropical ecosystems – coral reefs, seagrasses, and mangroves – in these seas remain to be investigated.

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Section: Andaman Seamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Deoxygenation in Marginal Seas of the Indian Ocean

Naqvi

2021

Front. Mar. Sci.

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“…More recently, using sea glider data and historical observations, Queste et al (2018) showed an intensification of the suboxic conditions at depth in the Gulf of Oman over the last three decades. Although there has been little work done on documenting potential deoxygenation in the Arabian marginal seas (i.e., the Red Sea and the Gulf), preliminary observations suggest ongoing deoxygenation in the Gulf with recent emergence of summertime hypoxia documented there (Al-Ansari et al, 2015;Al-Yamani and Naqvi, 2019).…”

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confidence: 99%

Fast local warming of sea-surface is the main factor of recent deoxygenation in the Arabian Sea

Lachkar¹,

Mehari²,

Azhar³

et al. 2020

Preprint

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Abstract. The Arabian Sea (AS) hosts one of the most intense oxygen minimum zones (OMZs) in the world. Observations show a decline of O2 in the northern AS over the recent decades accompanied by an intensification of the suboxic conditions there. Over the same period, the local sea-surface temperature has risen significantly, particularly over the Arabian Gulf (also known as Persian Gulf, hereafter the Gulf), while summer monsoon winds have intensified. Here, we reconstruct the evolution of dissolved oxygen in the AS from 1982 through 2010 and explore its controlling factors, with a focus on changing atmospheric conditions. To this end, we use a set of eddy-resolving hindcast simulations forced with observation-based winds and heat and freshwater fluxes. We find a significant deoxygenation in the northern AS with O2 inventories north of 20° N dropping by over 2 % decade-1 and 7 % decade-1 in the top 200 m and the 200–1000 m layer, respectively. These changes cause an increase in the volume of suboxia and the rate of denitrification by 10 % decade-1 and 13 % decade-1, respectively. Using a set of sensitivity simulations we demonstrate that deoxygenation in the northern AS is essentially caused by a reduced ventilation induced by the recent fast warming of the sea surface, in particular in the Gulf. Concomitant summer monsoon wind intensification contributes to deoxygenation at depth and in the upper ocean north of 20° N but enhances oxygenation of the upper ocean elsewhere. This is because surface warming enhances vertical stratification, thus limiting ventilation of the intermediate ocean, while summer monsoon wind intensification causes the thermocline depth to rise in the northern AS and deepen elsewhere, thus contributing to lowering O2 levels in the upper 200 m in the northern AS and increasing it in the rest of the AS. Our findings confirm that the AS OMZ is strongly sensitive to upper-ocean warming and concurrent changes in the Indian monsoon winds. Finally, our results also demonstrate that changes in the local climatic forcing play a key role in regional dissolved oxygen changes and hence need to be properly represented in global models to reduce uncertainties in future projections of deoxygenation.

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“…The north-westerly winds and south-eastward coastal currents cause the upwelling along the eastern Iranian coasts and downwelling along the western Arabian coasts [18]. The recent study of Al-Yamani and Naqvi [39] showed that the salinity has increased in the northern area of the Gulf because of the reduction of river runoff. The Gulf is one of the main sources of aeolian dust deposits in the world [40].…”

Section: Study Area 21arabian Gulfmentioning

confidence: 99%

“…However, a significant increase in nutrients has been identified, caused chiefly by the sewage discharge from the urban coastal areas along the coasts of the Gulf. Recently, the anthropogenic stresses have been cited as one of the biggest challenges facing the marine ecological environment of the Arabian Gulf [39]. Nezlin et al [21] has divided the Gulf into regional sub-basins according to their properties, and a more recent study by Polikarpov et al [27] sought to modify this partition (Fig.…”

Section: Study Area 21arabian Gulfmentioning

confidence: 99%

Seasonal Spatial and Temporal Distribution of Chlorophyll-<em>a</em> Concentration over Kuwait and the Arabian Gulf using Satellite and In-Situ Data

Ja¹

2021

Preprint

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The concentration of chlorophyll-a (chlor-a) is an important indicator of marine water quality, as it is considered an indicator of the phytoplankton density in a specific area. Remote sensing techniques have been developed to measure the near-surface concentration of chlor-a in water across the correlation between spectral bands and in situ data. This algorithm applies to sensors of varying spatial, temporal and spectral resolutions. However, in this study, chlor-a level 2 and 3 products of SNPP – VIIRS spectrometer (Equation OC3) of NASA OceanColor suite was relied upon to study the spatial and temporal distribution of chlor-a concentration in the Arabian Gulf (also known as the Persian Gulf) and the State of Kuwait’s water (located to the north-eastern part of the Arabian Gulf) from 2012 to 2019. Ground truthing points (n = 192) matched to the level 2 products have been used to build an empirical model and cross-validate it. The correlation was positive where was 0.79 and the validation RMSE was = ± 0.64 mg/m-3. The derived algorithm was then applied to chlor-a level 3 seasonal products. Additionally, the chlor-a concentration values of Kuwaiti waters have been enhanced using the IDW algorithm to increase the spatial resolution, as it is considered as a small area compared to the spatial resolution of level 3 chlor-a products. The model derived from IDW was tested using the Mann Whitney test (Sig = 0.948 p > 0.01). However, the result showed that the chlor-a concentration is higher in Kuwait Bay compared to Kuwaiti water, and it is higher in Kuwaiti water compared to the Arabian Gulf. The coasts have higher concentrations too, when compared to the open water. Generally, the chlor-a increases in winter and makes a semi-regular cycle during the years of study; this cycle is more regular in the Gulf’s waters than in Kuwait’s.

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Chemical oceanography of the Arabian Gulf

Cited by 50 publications

References 41 publications

Deoxygenation in Marginal Seas of the Indian Ocean

Deoxygenation in Marginal Seas of the Indian Ocean

Fast local warming of sea-surface is the main factor of recent deoxygenation in the Arabian Sea

Seasonal Spatial and Temporal Distribution of Chlorophyll-<em>a</em> Concentration over Kuwait and the Arabian Gulf using Satellite and In-Situ Data

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