Water, heat and freshwater flux out of the northern Indian Ocean in September–October 1995

Shi, Wei; Morrison, John M.; Bryden, Harry L.

doi:10.1016/s0967-0645(01)00154-0

Cited by 15 publications

(9 citation statements)

References 36 publications

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“…Indeed, over the last 26 kyr, enrichments of organic carbon and Ba in sediments appear to reflect strong-southwesterly wind-induced biological productivity, when d 18 O values document low SSS conditions ( Fig.4i-k). At last, this is in line with 240 overall ISM reconstructions documenting cool and dry conditions in the northern Indian Ocean during the strong glaciation period (Cullens, 1981;Duplessy, 1982;Kudrass et al, 2001;Contreras-Rosales et al, 2014;Dutt et al, 2015) due to enhanced snow accumulation and relatively low temperatures in the Tibetan Plateau and Himalaya (Shi Y, 2002;Mark et al, 2005) that cause a weakened meridional thermal land-sea gradient and an equatorward shift of the ITCZ mean position (Kudrass et al, 2001;Overpeck et al, 1996;Sirocko et al, 1996;Cai et al, 2012). 245…”

Section: Last Glacial: 26 To 19 Kyr Bpsupporting

confidence: 76%

See 1 more Smart Citation

Dynamics of primary productivity in the northeastern Bay of Bengal over the last 26 000 years

Zhou¹,

Duchamp‐Alphonse²,

Kageyama³

et al. 2020

Preprint

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At present, variations of primary productivity (PP) in the Bay of Bengal (BoB) are responding to salinityrelated-stratification which is controlled by the Indian Summer Monsoon (ISM). The relationships between PP, ISM, and to a broader scale, North Atlantic climate rapid variability in the past, are not clearly understood. Here, we present a new record of PP based on the examination of coccolithophore assemblages in a 26,000 years 15 sedimentary record, retrieved in the northeastern BoB (core MD77-176). Comparisons with published climate and monsoon records, as well as outputs from the transient climate simulation TraCE-21 and experiments run with the Earth System Model IPSL-CM5A-LR, including marine biogeochemical components, helped us interpret our PP records in the context of ISM and Atlantic Overturning Meridional Circulation (AMOC) changes. We demonstrate that PP is influenced by vertical stratification in the upper water column over the last 26,000 years (26 kyr BP). It 20 is controlled by wind-driven mixing from 26 to 19 kyr BP, i.e., when dry climate conditions and reduced freshwater inputs occurred, and by salinity-related-stratification over the last 19 kyr BP (since the Last Glacial Maximum), i.e., when humid conditions prevailed. During the deglaciation, salinity and stratification are related to monsoon precipitation dynamics, which are chiefly forced by both, insolation and the strength of the AMOC. The collapse (recovery) of the AMOC during Heinrich Stadial 1 (Bølling Allerød) weakened (strengthened) ISM and diminished 25 (increased) stratification, thus enhancing (subduing) productivity. such as the Atlantic meridional overturning circulation (AMOC) and the temperature fluctuations in the North Atlantic (e.g. Braconnot et al., 2007aBraconnot et al., , 2007bKageyama et al., 2013;Marzin et al., 2013;Contreras-Rosales et al., 2014). However, the relationship between PP and monsoon precipitation in the past has been given less attention 60 due to the absence of high time-resolution PP record in the BoB and the ADS (Phillips et al., 2014;Li et al., 2019), which precludes our complete understanding of how monsoon climate changes impact tropical ocean ecology through different mechanisms and at different time-scales. To fill this gap, a reliable paleo-PP record is needed for the BoB/ADS. On the other hand, the PP record can also indicate the variability of Indian Monsoon strength.Coccolithophores are marine calcifying phytoplankton organisms that constitute one of the most important 65 "functional groups", responsible for primary production and export of carbonate particles (i.e. the coccoliths they produce) to the sedimentary reservoir. The coccoliths preserved in marine sediment are good study material for paleoenvironmental reconstructions. Particularly, Florisphaera profunda is a lower photic zone dweller and its relative abundance in marine coccolithophore assemblages obtained from the sediments has been successfully used to reconstruct past changes of the nutricline depth and PP McIntyre, 1990a, 1...

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Section: Last Glacial: 26 To 19 Kyr Bpsupporting

confidence: 76%

“…This discrepancy together with differences in local evaporation result in hydrological and ecological differences between these two areas (e.g. Prasanna Kumar et al, 2002;Vinayachandran et al, 2002;Shenoi et al, 2002;Shi W et al, 2002;Dey and Singh, 2003;Rao and Sivakumar, 2003;Prasad, 2004;Currie et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Dynamics of primary productivity in the northeastern Bay of Bengal over the last 26 000 years

Zhou¹,

Duchamp‐Alphonse²,

Kageyama³

et al. 2020

Preprint

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“…As part of the Bay of Bengal Process Study (BOBPS) 24 stations along two transects were occupied on board ORV Sagar Kanya during the three seasons;-Southwest monsoon (July-August, 2001), fall intermonsoon (September-October, 2002) and spring intermonsoon (April-May, 2003) as shown in figure 1. Fourteen stations were occupied between 7N to 20N in the open ocean transect along 88E and 10 stations were occupied along the western margin from 11N to 20N.…”

Section: Methodsmentioning

confidence: 99%

“…Bay of Bengal is characterised by its seasonal reversal of surface currents under the influence of monsoonal wind reversal (Shetye et al, 1991) and the surface low salinity regions due to immense fresh water inputs through excessive precipitation over evaporation and river discharge (Yu and McCreary, 2004). This large fresh water influx from the rivers which drain into the Bay show considerable seasonal variability (Shi et al, 2002) and brings along with it seasonally varying sediment load and probably contributes in terms of nutrients input to the upper layers. Accordingly, the hydrochemical properties of the Bay of Bengal are expected to respond to these factors on a seasonal scale.…”

Section: Introductionmentioning

confidence: 99%

Influence of environmental forcings on the seasonality of dissolved oxygen and nutrients in the Bay of Bengal

Sardessai¹,

Ramaiah²,

PrasannaKumar³

et al. 2007

j mar res

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Studies on seasonal variability of oxygen and nutrients during three seasons namely SW monsoon, fall intermonsoon and spring intermonsoon indicate influence of physical forcings on the distribution of these hydrochemical properties in the subsurface layer. In the open ocean the Minimum Oxygen Layer (MOL 10mu Mol L -1 ) during the southwest monsoon and fall intermonsoon is mostly confined to the north of 11N due to the penetration of high salinity water in the deeper waters of the central Bay. During spring intermonsoon MOL is mostly confined to the northern region between 14 to 20N with a narrow band of suboxic waters ( 5mu Mol L -1 ) around 19 to 20N. Along the western margin, the MOL occupies a larger area in the intermediate and deeper waters during the SW monsoon and fall intermonsoon with a thick layer of suboxic waters during the SW monsoon which gets reduced and confined to the northern region during fall intermonsoon. The core of suboxic waters seems to disappear during the spring intermonsoon. The displacement of the water mass to shallower depths under the influence of cold core eddies 1 is the major mechanism supplying nutrients to the surface waters whereas stratification due to the immense runoff from major rivers in the north and the associated suspended load addition seems to be inhibiting the biological production through curtailment of light penetration in the northern Bay of Bengal during the southwest monsoon. Pockets of low oxygen contents are not associated with elevation in secondary nitrite levels suggesting that circulation of the water mass under the influence of seasonal currents and gyres and the geochemical processes play a significant role in regenerative processes and regulating the intensity of the MOL in the Bay of Bengal.

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“…With negative P‐E and the weak river runoff characterize the Arabian Sea, the salt storage divergence in the water column is the main factor responsible for the significant salt storage low observed during SW monsoon. The salt storage divergence in the Arabian may be attributed to the two‐cell vertical recirculation pattern [ Shi et al , 2002]. The meridional overturning circulation in the Arabian Sea upwells low‐salinity deep water to the upper layer while high‐salinity surface water is exported out of the Arabian Sea by the horizontal circulation.…”

Section: Discussionmentioning

confidence: 99%

Estimation of heat and salt storage variability in the Indian Ocean from TOPEX/Poseidon altimetry

2003

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[1] Heat and salt storage variability in the upper 1000 m of the Indian Ocean is investigated using a combination of sea level anomalies derived from TOPEX/Poseidon altimetry (1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000), Reynold's sea surface temperature and monthly climatological hydrographic data (World Ocean Atlas 1998) Boyer et al., 1998]. This new technique allows extension of surface information from altimetric observations to study subsurface variability. Hydrographic data collected in the Indian Ocean during the World Ocean Circulation Experiment are used to evaluate and validate this technique. The results show that the Indian Ocean experienced larger changes in heat storage than in salt storage. Significant differences are found between the 8-year mean seasonal heat storage and the climatological seasonal heat storage, which are attributed to interannual variability, while the 8-year mean seasonal salt storage agrees well with the climatological seasonal salt storage. The variabilities of heat and salt storages are not synchronized in either space or time because of different control mechanisms. The first four empirical orthogonal function (EOF) modes explain nearly 60% of total variance of heat storage variability with the Indian Ocean dipole outweighing the other processes. The dominant first EOF mode for salt storage, which is attributed to the seasonal variability, explains 33% of its total variance. The heat (salt) storage dipole index, representing the heat (salt) storage difference between the west and east equatorial Indian Ocean during the 1994-1995 and 1997-1998 dipole periods, is of the same order as that of the seasonal heat (salt) storage variability.

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Water, heat and freshwater flux out of the northern Indian Ocean in September–October 1995

Cited by 15 publications

References 36 publications

Dynamics of primary productivity in the northeastern Bay of Bengal over the last 26 000 years

Dynamics of primary productivity in the northeastern Bay of Bengal over the last 26 000 years

Influence of environmental forcings on the seasonality of dissolved oxygen and nutrients in the Bay of Bengal

Estimation of heat and salt storage variability in the Indian Ocean from TOPEX/Poseidon altimetry

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