Potential mechanisms responsible for occurrence of core oxygen minimum zone in the north-eastern Arabian Sea

Sarma, V. V. S. S.; Bhaskar, T. V. S. Udaya; Kumar, J. Pavan; Chakraborty, Kunal

doi:10.1016/j.dsr.2020.103393

Cited by 32 publications

(26 citation statements)

References 55 publications

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“…A similar C org but different CaCO 3 in various parts of the eastern Arabian Sea is intriguing. A relatively high CaCO 3 in the Gulf of Mannar is attributed to its better preservation, due to a less intense oxygen-deficient zone as compared to the NE Arabian Sea (Sarma et al 2020). The increased microbial respiration in a C org -rich environment decreases the pH, leading to dissolution of biogenic carbonates (Cai et al 2011).…”

Section: Discussionmentioning

confidence: 99%

Persistent increase in carbon burial in the Gulf of Mannar, during the Meghalayan Age: Influence of primary productivity and better preservation

et al. 2023

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The oceans store a substantial fraction of carbon as calcium carbonate (CaCO3) and organic carbon (Corg) and constitute a significant component of the global carbon cycle. The Corg and CaCO3 flux depends on productivity and is strongly modulated by the Asian monsoon in the tropics. Anthropogenic activities are likely to influence the monsoon and thus it is imperative to understand its implications on carbon burial in the oceans. We have reconstructed multi-decadal CaCO3 and Corg burial changes and associated processes during the last 4.9 ky, including the Meghalayan Age, from the Gulf of Mannar. The influence of monsoon on carbon burial is reconstructed from the absolute abundance of planktic foraminifera and relative abundance of Globigerina bulloides. Both Corg and CaCO3 increased throughout the Meghalayan Age, except between 3.0–3.5 ka and the last millennium. The increase in Corg burial during the Meghalayan Age was observed throughout the eastern Arabian Sea. The concomitant decrease in the Corg to nitrogen ratio suggests increased contribution of marine organic matter. Although the upwelling was intense until 1.5 ka, the lack of a definite increasing trend suggests that the persistent increase in Corg and CaCO3 during the early Meghalayan Age was mainly driven by higher productivity during the winter season coupled with better preservation in the sediments. Both the intervals (3.0–3.5 ka and the last millennium) of nearly constant carbon burial coincide with a steady sea-level. The low carbon burial during the last millennium is attributed to the weaker-upwelling-induced lower productivity.

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Section: Discussionmentioning

confidence: 99%

Persistent increase in carbon burial in the Gulf of Mannar, during the Meghalayan Age: Influence of primary productivity and better preservation

et al. 2023

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“…However, considering that the flow of PGW (~0.1 Sv) and RSW (~0.3 Sv) is much smaller than the Somali coastal current (~10 Sv, Schott et al, 1990;Schott and McCreary, 2001), they are not included in this study for this reason. Moreover, some new mechanisms have also not been considered in this study, for instance, the contribution of poorly ventilated waters to the ASOMZ due to the lack of mesoscale mixing (McCreary et al, 2013;Schmidt et al, 2020) and the effect of oxygen consumption by remineralization of organic matter originating from the eastern Arabian Sea shelf on ASOMZ (Sarma et al, 2020). In addition, increased primary productivity due to the eastward transport of excess upwelled nutrients induced by iron limitation in the western Arabian Sea thus intensifies the OMZ in the central/northern Arabian Sea (Moffett and Landry, 2020).…”

Section: Limitations Of This Studymentioning

confidence: 99%

“…These POMs are small and slow-sinking enough to be transported northward and eastward before being remineralized (Wiggert and Murtugudde, 2007;Hood et al, 2009;McCreary et al, 2013;Acharya and Panigrahi, 2016). Other explanations include the lack of mesoscale mixing in the eastern Arabian Sea, which results in poorly ventilated subsurface waters (McCreary et al, 2013;Schmidt et al, 2020); Persian Gulf water (PGW) and Red Sea Water (RSW) ventilating the upper ASOMZ (e.g., Lachkar et al, 2019); the cross-shelf transport of organic matter from the eastern Arabian Sea shelf, which increases oxygen consumption in the eastern Arabian Sea (Sarma et al, 2020); iron limitation in the western Arabian Sea, which leads to an eastward shift in the utilization of upwelled nutrients and intensifies the OMZ (Moffett and Landry, 2020); and the regulation of westward Rossby waves (Kim et al, 2001;Shenoy et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Role of ocean circulation and settling of particulate organic matter in the decoupling between the oxygen minimum zone and the phytoplankton productive zone in the Arabian Sea: A modeling study

Zhang

Chai

2022

Front. Mar. Sci.

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The oxygen minimum zone has a significant effect on primary production, marine biodiversity, food web structure, and marine biogeochemical cycle. The Arabian Sea oxygen minimum zone (ASOMZ) is one of the largest and most extreme oxygen minimum zones in the world, with a positional decoupling from the region of phytoplankton blooms. The core of the ASOMZ is located to the east of the high primary production region in the western Arabian Sea. In this study, a coupled physical–biogeochemical numerical model was used to quantify the impact of ocean circulation and settling of particulate organic matters (POMs) on the decoupling of the ASOMZ. Model results demonstrate that the increased (decreased) dissolved oxygen replenishment in the western (central) Arabian Sea is responsible for decoupling. The oxygen-rich intermediate water (200–1,000 m) from the southern Arabian Sea enters the Arabian Sea along the west coast and hardly reaches the central Arabian Sea, resulting in a significant oxygen replenishment in the western Arabian Sea high-productivity region (Gulf of Aden) but only a minor contribution in the central Arabian Sea. Besides that, the POMs that are remineralized to consume central Arabian Sea dissolved oxygen comprises not only local productivity in winter bloom but also the transport from the western Arabian Sea high-productivity region (Oman coast) in summer bloom. More dissolved oxygen replenishment in the western Arabian Sea, and higher dissolved oxygen consumption and fewer dissolved oxygen replenishment in the central Arabian Sea could contribute to the decoupling of the ASOMZ and phytoplankton productive zone.

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“…Recently Sarma et al. (2020) noticed that cross‐shelf transport of organic matter seems to be one of the potential mechanisms for existence of intense OMZ and denitrification zone in the northeastern Arabian Sea. On the other hand, Naqvi et al.…”

Section: Introductionmentioning

confidence: 99%

Potential Mechanisms Responsible for Spatial Variability in Intensity and Thickness of Oxygen Minimum Zone in the Bay of Bengal

2021

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Spatial variability in boundaries and thickness of oxygen minimum zone (OMZ) is derived based on measured dissolved oxygen data obtained from sensors on board biogeochemical (BGC) Argo floats between 2013 and 2019 in the Bay of Bengal (BoB). Upper and lower boundaries of the OMZ varied from 60 to 200 m and 100 to 800 m respectively with the thickness of 80–650 m in the BoB. Relatively thicker OMZ is noticed in the northern than southern BoB associated with stratification. The oxygen concentrations in the OMZ in the NW was low (<1.5 μM) than NE BoB (2.5 μM) indicating that thick and intense OMZ occurs in the NW region associating with stratification and high primary production. Significant decrease in particle‐back‐scatter signal was observed toward offshore from shelf indicating organic matter from the shelf sediments may be supporting bacterial carbon demand in the OMZ. The particle backscatter signal peaked in the OMZ region with a higher signal in the north than southern BoB and it is consistent with the low oxygen concentration in the former indicating that organic matter from shelf sediments may be supporting carbon needs in the OMZ. In addition to this, the occurrence of eddies significantly controls the intensity of the OMZ in the BoB through mixing at the upper boundary of OMZ. Therefore, this study suggests that spatial variations in intensity of OMZ in the BoB are governed by stratification, primary and export productions, organic matter decomposition, and eddy‐driven mixing.

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Potential mechanisms responsible for occurrence of core oxygen minimum zone in the north-eastern Arabian Sea

Cited by 32 publications

References 55 publications

Persistent increase in carbon burial in the Gulf of Mannar, during the Meghalayan Age: Influence of primary productivity and better preservation

Persistent increase in carbon burial in the Gulf of Mannar, during the Meghalayan Age: Influence of primary productivity and better preservation

Role of ocean circulation and settling of particulate organic matter in the decoupling between the oxygen minimum zone and the phytoplankton productive zone in the Arabian Sea: A modeling study

Potential Mechanisms Responsible for Spatial Variability in Intensity and Thickness of Oxygen Minimum Zone in the Bay of Bengal

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