Planktonic Foraminiferal and Alkenone Records of the Last Deglaciation from the Eastern Arabian Sea

1999 ◽  
Vol 52 (3) ◽  
pp. 337-342 ◽  
Author(s):  
Olivia Cayre ◽  
Edouard Bard
Keyword(s):  
Arabian Sea ◽  
Transfer Functions ◽  
Sea Water ◽  
Planktonic Foraminifera ◽  
Detailed Comparison ◽  
Last Deglaciation ◽  
Transient Event ◽  
Oxygen Isotope Record ◽  
Eastern Arabian Sea ◽  
Isotope Record

The oxygen isotope record of planktonic foraminifera from tropical core MD77194 (Eastern Arabian Sea) exhibits a clear two-step deglaciation with a brief δ18O transient event. In the tropics, this δ18O maximum could correspond to a cooling or to a change in the δ18O content of sea water. In this study, past sea-surface temperature (SST) and primary production (PP) are reconstructed from foraminiferal transfer functions and compared to values estimated from alkenone measurements. SST and PP records from both proxies indicate a 1.5–2.5°C deglacial warming, coupled with a PP decrease, and a 0.5–1°C cooling during the Younger Dryas (YD). A detailed comparison between independent micropaleontological and geochemical proxies helps us identify potential biases and thus strengthen the paleo-reconstructions.

Direct dating of the oxygen-isotope record of the last deglaciation by 14C accelerator mass spectrometry

Nature ◽  
1986 ◽  
Vol 320 (6060) ◽  
pp. 350-352 ◽  
Author(s):  
Jean-Claude Duplessy ◽  
Maurice Arnold ◽  
Pierre Maurice ◽  
Edouard Bard ◽  
Josette Duprat ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Oxygen Isotope ◽  
Accelerator Mass Spectrometry ◽  
Last Deglaciation ◽  
Oxygen Isotope Record ◽  
Isotope Record ◽  
The Last Deglaciation

Response of shallow-sea benthic foraminifera to environmental changes off the coast of Goa, eastern Arabian Sea, during the last ∼6100 cal yr BP

2019 ◽  
Vol 157 (3) ◽  
pp. 497-505 ◽  
Author(s):  
Ponnusamy Saravanan ◽  
Anil K. Gupta ◽  
Hongbo Zheng ◽  
Mruganka K. Panigrahi ◽  
Sameer K. Tiwari ◽  
...  
Keyword(s):  
Benthic Foraminifera ◽  
Arabian Sea ◽  
Environmental Changes ◽  
Indian Subcontinent ◽  
Planktonic Foraminifera ◽  
Ice Age ◽  
Shallow Sea ◽  
Foraminiferal Assemblage ◽  
Eastern Arabian Sea ◽  
Benthic Foraminiferal Assemblage

AbstractWe have analysed a 6100-year record of benthic and planktonic foraminifera from inner neritic sediments from Core SK291/GC13, off the Goa coast, eastern Arabian Sea, to understand the response of benthic foraminifera to shallow-marine processes. The benthic foraminiferal assemblage is dominated by Nonion cf. asterizans, Ammonia beccarii, A. gaimardii and Virgulinella fragilis, which have been selected on the basis of a population of 10% or more in any three samples analysed. The planktonic foraminiferal population is sporadic and rare, with Globigerinoides ruber as the predominant species showing a variable trend. The foraminiferal proxies combined with total organic carbon (wt%) and δ13C and δ18O values of Ammonia gaimardii suggest distinct variations, indicating changes in productivity and salinity in the shallow eastern Arabian Sea. The coastal waters off Goa were relatively warmer and less saline between 6100 and 4600, or perhaps to 4200, calibrated years before the present (cal yr BP), corresponding to a stronger monsoon in South and East Asia. The shallow sea was cooler from ~4200 to 2600 cal yr BP in the study area, coinciding with a lower sea surface temperature in the northeastern Arabian Sea and an arid phase in the Indian subcontinent. From 2900 to 2600 cal yr BP the study core exhibits the impacts of short-term cold events, which have earlier been observed in the northeastern Arabian Sea, off Pakistan. During the Little Ice Age, the shallow sea off Goa was less productive.

An alternative astronomical calibration of the lower Pleistocene timescale based on ODP Site 677

1990 ◽  
Vol 81 (4) ◽  
pp. 251-261 ◽  
Author(s):  
N. J. Shackleton ◽  
A. Berger ◽  
W. R. Peltier
Keyword(s):  
High Resolution ◽  
Planktonic Foraminifera ◽  
Isotope Analysis ◽  
Ocean Drilling Program ◽  
Ocean Drilling ◽  
Oxygen Isotope Record ◽  
Lower Pleistocene ◽  
Isotope Record ◽  
Proposed Modification ◽  
Precession Signal

ABSTRACTOcean Drilling Program (ODP) Site 677 provided excellent material for high resolution stable isotope analysis of both benthonic and planktonic foraminifera through the entire Pleistocene and upper Pliocene. The oxygen isotope record is readily correlated with the SPECMAP stack (Imbrie et al. 1984) and with the record from DSDP 607 (Ruddiman et al. 1986) but a significantly better match with orbital models is obtained by departing from the timescale proposed by these authors below Stage 16 (620 000 years). It is the stronger contribution from the precession signal in the record from ODP Site 677 that provides the basis for the revised timescale. Our proposed modification to the timescale would imply that the currently adopted radiometric dates for the Matuyama–Brunhes boundary, the Jaramillo and Olduvai Subchrons and the Gauss–Matuyama boundary underestimate their true astronomical ages by between 5 and 7%.

Inconsistent change in surface hydrography of the eastern Arabian Sea during the last four glacial–interglacial intervals

2019 ◽  
Vol 157 (6) ◽  
pp. 989-1000 ◽  
Author(s):  
Rajeev Saraswat ◽  
S. R. Kurtarkar ◽  
R. Yadav ◽  
A. Mackensen ◽  
D. P. Singh ◽  
...  
Keyword(s):  
Arabian Sea ◽  
Isotopic Ratio ◽  
Planktonic Foraminifera ◽  
Foraminiferal Assemblage ◽  
Upwelled Water ◽  
Winter Convection ◽  
Eastern Arabian Sea ◽  
Neogloboquadrina Dutertrei ◽  
Stable Isotopic Ratio ◽  
International Ocean Discovery Program

AbstractThe eastern Arabian Sea is influenced by both the advection of upwelled water from the western Arabian Sea and winter convective mixing. Therefore, sediments collected from the eastern Arabian Sea can help to understand the long-term seasonal hydrographic changes. We used the planktonic foraminifera census and stable isotopic ratio (δ18O) from sediments drilled during the International Ocean Discovery Program Expedition 355 to reconstruct surface hydrographic changes in the eastern Arabian Sea during the last 350 kyr. The increased abundance of Globigerina bulloides suggests enhanced advection of upwelled water during the latter half of MIS7 and the beginning of MIS6, as a result of a strengthened summer monsoon. A large drop in upwelling and/or advection of upwelled water from the western Arabian Sea is inferred during the subsequent interval of MIS6, based on the rare presence of G. bulloides. The comparable relative abundance of Neogloboquadrina dutertrei, G. bulloides and Globigerinoides ruber suggests that during the early part of MIS5, hydrographic conditions were similar to today. The upwelling decreased and winter convection increased with the progress of the glacial interval. A good coherence between planktonic foraminiferal assemblage-based monsoon stacks from both the eastern and western Arabian Sea suggests a coeval response of the entire northern Arabian Sea to the glacial–interglacial changes. The glacial–interglacial difference in δ18Osw-ivc was at a maximum with 4–5 psu change in salinity during Termination 2 and 3, and a minimum during Termination 4. The significantly reduced regional contribution to the glacial–interglacial change in δ18Osw-ivc during Termination 4 suggests a lesser change in the monsoon.

scholarly journals Causes of uncertainties in the representation of the Arabian Sea oxygen minimum zone in CMIP5 models

2021 ◽  
Author(s):  
Henrike Schmidt ◽  
Julia Getzlaff ◽  
Ulrike Löptien ◽  
Andreas Oschlies
Keyword(s):  
Southern Ocean ◽  
Arabian Sea ◽  
Climate Models ◽  
Water Mass ◽  
Sea Water ◽  
Coupled Model ◽  
Detailed Comparison ◽  
Cmip5 Models ◽  
Marine Habitats ◽  
Oxygen Minimum

Abstract. Open ocean oxygen minimum zones (OMZs) occur in regions with high biological productivity and weak ventilation. They restrict marine habitats and alter biogeochemical cycles. Global models show generally a large model-data misfit with regard to oxygen. Reliable statements about their future development and the quantification of their interaction with climate change are currently not possible. One of the most intense OMZs is located in the Arabian Sea (AS). We give an overview of the main model deficiencies with a detailed comparison of the historical state of ten climate models from the 5th coupled model intercomparison project (CMIP5) that present our present-day understanding of physical and biogeochemical processes. Considering a threshold of 60 μmol l−1, we find a general underestimation of the OMZ volume in the AS compared to observations, that is caused by a too shallow layer of oxygen-poor water in the models. The deviation of oxygen values in the deep AS is the result of subduction of higher oxygenated waters in the Southern Ocean in the models compared to observations. In addition, model deficiencies related to the coarse resolution of the abyssal ocean, are identified in the deep water mass transport from the Southern Ocean northward into the AS. Differences in simulated water mass properties and ventilation rates of Red Sea Water and Persian Gulf Water cause different mixing in the AS and thus influence the intensity of the OMZ. These differences also point towards variations in the parametrisations of the overflow from the marginal seas among the models. The results of this study are intended to foster future model improvements regarding the OMZ in the AS.

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