@article {saravanan_reconstructing_2024,
	title = {Reconstructing hypoxia on the eastern Arabian sea continental shelf during the past \~{}7400 years: A multi-proxy approach},
	journal = {Quaternary International},
	year = {2024},
	abstract = {Shallow-sea environmental variations in the eastern Arabian Sea (EAS) have been related to monsoon variability, poorly ventilated intermediate water, and primary productivity changes. To understand these conditions, benthic foraminiferal assemblages, oxygen isotope ratios, and total organic carbon content have been examined in sediment Core SK291/GC13 from the EAS. We aim to retrieve decadal to centennial time-scale changes in past oxygenation and paleoproductivity during the last 7400 calibrated years before the present (cal yr BP). Our proxy data suggest that the oxic benthic foraminifera species were dominant during \~{}7400{\textendash}6000~cal~yr BP. The change from oxic to dysoxic occurred during ca. 6000{\textendash}3500~cal~yr BP, and transition from dysoxic to suboxic environmental conditions happened at ca. \~{}3500~cal~yr BP. These changes are contemporaneous with weakening of the Indian summer monsoon beginning at \~{}5500~cal~yr BP which culminated into a major arid phase so-called ca 4.2 ka event in the Indian subcontinent. The EAS experienced low productivity during the early phase of our studied interval (\~{}7400{\textendash}6000~cal~yr BP) and higher productivity in the middle Holocene (6000{\textendash}3000~cal~yr BP), as revealed by the total organic carbon and benthic assemblages. Furthermore, productivity increased in the warm period and decreased in the Little Ice Age on a decadal scale. The spectral analysis of total organic content and suboxic species indicates a 23-year Hale (solar) cycle during the last millennium, indicating a close relationship between solar activity and monsoon variability. The strengthening of the El Nino-Southern Oscillation perhaps amplified due to increased solar activity in the last millennium, which influenced the climate of the EAS. The study highlights paleo-oxygenation shifts based on benthic foraminiferal assemblages, which are crucial for understanding changes in the oxygen minimum zones (OMZs) and their potential impacts on marine ecosystems.},
	keywords = {Benthic assemblages, Goa coast, Hale cycle, Little ice age, Oxygen minimum zone, Suboxic environment},
	issn = {1040-6182},
	doi = {10.1016/j.quaint.2024.05.007},
	url = {https://www.sciencedirect.com/science/article/pii/S1040618224001630},
	author = {Saravanan, Ponnusamy and Gupta, Anil K. and Li, Xiangzhong and Zheng, Hongbo and Panigrahi, Mruganka K.}
}
@article {2963,
	title = {Indian monsoon variability during the past \~{}8.5~cal~kyr as recorded in the sediments of the northeastern Arabian Sea},
	journal = {Quaternary International},
	year = {2022},
	month = {Jan-04-2022},
	abstract = {We analyzed benthic and planktic foraminifera, total organic carbon and stable isotopes ratios of carbon and oxygen from 100 samples of marine sediment Core ABP, 25/03, off Gujarat in the northeastern Arabian Sea. Factor and cluster analyses of thirty highest-ranked benthic foraminifer species enabled to identify seven biofacies in the study sequence characterizing major changes in deep-sea environments during the past \~{}8.5 cal kyr. The benthic foraminiferal data has been combined with population abundances of upwelling indicator planktic foraminifer Globigerina bulloides and mixed layer species from Core ABP, 25/03 and compared with that from ODP Hole 723A and Core ABP, 25/02, western and eastern Arabian Sea, respectively. A major change in benthic foraminifera occurs during \~{}8.5 to 6 cal kyr BP, when the summer monsoon was stronger whereas during 6 to 2 cal kyr BP, the data suggest a weak summer monsoon. Planktic foraminifer Globigerina bulloides does not show any significant trend in the study core, but deep thermocline species Neogloboquadrina dutertrei and mixed layer species show significant trend with an inverse correlation with the TOC. This core records high TOC from \~{}6.5 to 4 cal kyr BP and during the last 2 cal kyr and low TOC during \~{}8.5 to 6.5 cal kyr BP and 4 to 2 cal kyr BP. It is interesting to note intervals of high mixed layer species coincide with high Neogloboquadrina dutertrei percentages and low TOC values at Core ABP, 25/03 during 8.5 to 6.5 cal kyr BP.The faunal data is supported by carbon and oxygen isotope ratios (δ13C and δ18O) of shells of benthic foraminifer Cibicides spp. to strengthen our understanding of changes in the eastern Arabian Sea since \~{}8.5 cal kyr BP.},
	issn = {10406182},
	doi = {10.1016/j.quaint.2022.03.016},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S104061822200115X},
	author = {Ravichandran, M. and Gupta, Anil K. and Mohan, K. and Tiwari, Sameer K. and Lakshumanan, C. and Panigrahi, M.K.}
}
@article {2893,
	title = {Response of shallow-sea benthic foraminifera to environmental changes off the coast of Goa, eastern Arabian Sea, during the last \~{}6100 cal yr BPAbstract},
	journal = {Geological Magazine},
	volume = {157},
	year = {2020},
	month = {Jan-03-2020},
	pages = {497 - 505},
	abstract = {We 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.},
	keywords = {arabian sea, benthic foraminifera, Indian monsoon, Stable isotopes, western continental margin of India},
	issn = {0016-7568},
	doi = {10.1017/S0016756819000979},
	url = {https://www.cambridge.org/core/product/identifier/S0016756819000979/type/journal_article},
	author = {Saravanan, Ponnusamy and Gupta, Anil K. and Zheng, Hongbo and Panigrahi, Mruganka K. and Tiwari, Sameer K. and Rai, Santosh K. and Prakasam, Muthusamy}
}
@article {2892,
	title = {Late Holocene long arid phase in the Indian subcontinent as seen in shallow sediments of the eastern Arabian Sea},
	journal = {Journal of Asian Earth Sciences},
	volume = {181},
	year = {2019},
	month = {Jan-09-2019},
	pages = {103915},
	abstract = {Multi-proxy record of benthic and planktic foraminifera, total organic carbon and carbon and oxygen isotope ratios from Core SK291/GC15, off the coast of Goa, eastern Arabian Sea reveals significant paleoceanographic and paleoclimatic turnovers during ~6000 to 1700 calibrated years before the Present (cal yr BP). Benthic foraminiferal census data was analyzed with multivariate techniques including factor and cluster analyses of highest ranked species from the studied core that enabled to identify seven biofacies. The record suggests centennial to millennial-scale changes in the surface conditions driven by monsoon-linked upwelling in the eastern Arabian Sea during the studied interval. Various benthic biofacies combined with isotope and planktic foraminiferal data suggest that depletion of dissolved oxygen and increase in organic productivity in the study area was caused by intense monsoonal upwelling since the middle Holocene. The results suggest that during 5400{\textendash}4700 and 3000{\textendash}2500 cal yr BP the southwest (SW) monsoon was strong leading to intense upwelling in the study area as reflected by increased Globigerina bulloides percentages. These were generally warmer intervals in the northern hemisphere. The SW monsoon significantly weakened (abrupt decrease in G. bulloides population) during 4700{\textendash}3400 cal yr BP roughly coinciding with a long arid phase in the Indian subcontinent and a cold interval in Europe. Our record suggests an abrupt increase in SW monsoon intensity during ~3000 to 2500 cal yr BP, when a pronounced change in benthic biofacies is also noted that suggests a major shift in the sub-surface conditions. Our data document a prolong weak SW monsoon phase beginning at ~4600 cal yr BP, little earlier than 4.2 ka event, in the eastern Arabian Sea.},
	issn = {13679120},
	doi = {10.1016/j.jseaes.2019.103915},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S1367912019302676},
	author = {Saravanan, Ponnusamy and Gupta, Anil K. and Zheng, Hongbo and Panigrahi, Mruganka K. and Prakasam, Muthusamy}
}
@article {17,
	title = {Multiproxy record of monsoon variability from the Ganga Plain during 400{\textendash}1200 A.D},
	journal = {Updated Quaternary Climatic Research in parts of the Third Pole Selected papers from the HOPE-2013 conference, Nainital, India},
	volume = {371},
	year = {2015},
	pages = {157-163},
	abstract = {Understanding on the Indian Summer Monsoon (ISM) variability is chiefly based upon the marine proxies and a few continental records. The Ganga Plain, one of the most densely populated regions of the world marked by intensive cultivation of monsoon dependent crops and a rich cultural history, is not yet well understood in the context of monsoon variability. We present here a 400{\textendash}1200 A.D. AMS radiocarbon dated record of Ropan Chhapra tal in the Central Ganga Plain using sedimentology, environmental magnetism, and stable isotope of oxygen for ISM variability. The environmental magnetic parameters (χlf, χARM, SIRM/χlf, S-Ratio, B(0)CR and HIRM) inferred antiferromagnetic mineralogy (hematite and/or goethite) independent of grain size variation during 400{\textendash}900 A.D., depicting climate variability within warm humid to warm arid conditions favouring stronger ISM seasonality. Prevalence of ferrimagnetic mineralogy under less oxygenated conditions intermittently demonstrates an altered catchment regime or possibly in response to stronger winter monsoon. The higher δ18O values around 500, 580 and 740 A.D. indicate warm and arid conditions under weak ISM. The lower δ18O values around 480, 540 and 700 A.D. and from 900 to 1200 A.D. occur during warm and humid conditions indicating maximum intensity of the ISM. Increased silt content from 800 A.D. onwards is due to increased surface runoff in response to enhanced precipitation, and the higher clay percentage around 500, 580 and 740 indicates low-energy (ponding) conditions under weak ISM. The well sorted nature of sediment indicates consistency of the lacustrine environments under fairly uniform energy and constant bottom water conditions, under varied monsoonal intensity. Combinations of sediment textures and stable isotope indicate intense ISM at \~{}480 and \~{}540 A.D. with flooding around \~{}700 A.D. and a weak monsoon at 580 and 740 A.D., with drought at 500 A.D. During \~{}900{\textendash}1200 A.D. the multiproxy record suggests strong summer monsoon synchronous with Medieval Warm Period (MWP), whereas after 1200 A.D. the weak monsoon phase coincides with the onset of the Little Ice Age (LIA).},
	issn = {1040-6182},
	doi = {10.1016/j.quaint.2015.02.040},
	url = {http://www.sciencedirect.com/science/article/pii/S1040618215001470},
	author = {Singh, Dhruv Sen and Gupta, Anil K. and Sangode, S. J. and Clemens, Steven C. and Prakasam, M. and Srivastava, Priyeshu and Prajapati, Shailendra K.}
}
@article {208,
	title = {East{\textendash}West similarities and differences in the surface and deep northern Arabian Sea records during the past 21 Kyr},
	journal = {Palaeogeography, Palaeoclimatology, Palaeoecology},
	volume = {301},
	year = {2011},
	note = {id: 2100},
	pages = {75-85},
	abstract = {This study analyses monsoon proxy Globigerina bulloides from Ocean Drilling Program (ODP) Hole 723A (western Arabian Sea) and Hole ABP-25, 02 (northeastern Arabian Sea) as well as dominant benthic foraminifera, pteropods, total organic carbon (TOC), Inorganic Carbon (IC) and stable isotope values of benthic foraminifera from Hole ABP-25, 02 to understand summer monsoon-driven changes in the western and eastern Arabian Sea and their impacts on deep-sea ventilation during the past 21 Kyr. We have also combined published TOC data from ODP Hole 724B to understand if deep-sea conditions in the Arabian Sea were same throughout the region during the studied interval. The summer monsoon was generally weaker during cold intervals including the Last Glacial Maximum, the Younger Dryas and the Bond events of the Holocene. From 20 to 10 Kyr, the deep northeastern Arabian Sea was better oxygenated with less organic carbon supply except during 14{\textendash}12.5 Kyr when TOC values increased, indicating a weaker summer monsoon and a weak oxygen minimum zone (OMZ). The TOC values and the abundance of the eutrophic benthic foraminiferal species Bulimina aculeata, Melonis barleeanum and Uvigerina peregrina increased during the late Holocene whereas well-oxygenated, low organic carbon benthic species Sphaeroidina bulloides as well as pteropods decreased, indicating an intense OMZ and an increased supply of refractory organic material to the Arabian Sea. It is important to note that although the surface response to monsoon variability was more or less similar in the western and northeastern Arabian Sea, the deep-sea conditions show a marked contrast in the two regions during the past 21 Kyr.},
	issn = {0031-0182},
	doi = {10.1016/j.palaeo.2010.12.027},
	url = {http://www.sciencedirect.com/science/article/pii/S0031018211000022},
	author = {Gupta, Anil K. and Mohan, K. and Sarkar, Sudipta and Clemens, Steven C. and Ravindra, Rasik and Uttam, Rajesh K.}
}
@article {446,
	title = {Deep-sea faunal provinces and their inferred environments in the Indian Ocean based on distribution of Recent benthic foraminifera},
	journal = {Palaeogeography Palaeoclimatology Palaeoecology},
	volume = {291},
	year = {2010},
	note = {id: 1967; PT: J; UT: WOS:000278782400021},
	pages = {429-442},
	abstract = {Multivariate analysis was performed on percentages of 46 species of unstained deep-sea benthic foraminifera from 131 core-top to near-core-top samples (322-5013 m) from across the Indian Ocean. Faunal data are combined with GEOSECS geochemical data to investigate any relationship between benthic foraminifera (assemblages and species) and deep-sea properties. In general, benthic foraminifera show a good correlation to surface productivity, organic carbon flux to the sea floor, deep-sea oxygenation and, to a lesser extent, to bottom temperature, without correlation with the water depths. The foraminiferal census data combined with geochemical data has enabled the division of the Indian Ocean into two faunal provinces. Province A occupies the northwestern Indian Ocean (Arabian Sea region) where surface primary production has a major maximum during the summer monsoon season and a secondary maximum during winter monsoon season that leads to high organic flux to the seafloor, making the deep-sea one of the most oxygen-deficient regions in the world ocean, with a pronounced oxygen minimum zone (OMZ). This province is dominated by benthic foraminifera characteristic of low oxygen and high organic food flux including Uvigerina peregrina, Robulus nicobarensis, Bolivinita pseudopunctata, Bolivinita sp., Bulimina aculeata, Bulimina alazanensis, Ehrenbergina carinata and Cassidulina carinata. Province B covers southern, southeastern and eastern parts of the Indian Ocean and is dominated by Nuttallides umbonifera, Epistominella exigua, Globocassidulina subglobosa, Uvigerina proboscidea, Cibicides wuellerstorfi, Cassidulina laevigata, Pullenia bulloides, Pullenia osloensis, Pyrgo murrhina, Oridorsalis umbonatus, Gyroidinoides (=Gyroidina) soldanii and Gyroidinoides cf. gemma suggesting well-oxygenated, cold deep water with low (oligotrophic) and pulsed food supply. (C) 2010 Elsevier B.V. All rights reserved.},
	issn = {0031-0182},
	doi = {10.1016/j.palaeo.2010.03.012},
	author = {De, Soma and Gupta, Anil K.}
}
@article {381,
	title = {Mid-Brunhes strengthening of the Indian Ocean Dipole caused increased equatorial East African and decreased Australasian rainfall},
	journal = {Geophysical Research Letters},
	volume = {37},
	year = {2010},
	note = {id: 1966; PT: J; UT: WOS:000276025100002},
	pages = {L06706-L06706},
	abstract = {The tropical Indian Ocean is an important component of the largest warm pool, marked by changes in sea surface temperatures and depths of thermocline and mixed layer in its western and eastern extremities leading to the development of a dipole mode - the Indian Ocean Dipole (IOD). A narrow band of westerlies (7 degrees N to 7 degrees S) sweep the equatorial Indian Ocean during the April - May and October - November transitions between the summer - and winter-monsoon seasons. These Indian Ocean equatorial westerlies (IEW) are closely related to the IOD, intensifying the upper ocean Eastward Equatorial current also known as Wyrtki jets. The strength of the IOD/IEW determines the moisture content in East Africa. A major decrease in the strength of the IEW (strengthening or positive mode of the IOD) during the mid-Brunhes epoch (similar to 300-250 Kyr BP) coincides with a wetter equatorial East Africa, a drier Australasia and a stronger Indian summer monsoon, indicating that the IOD/IEW play a significant role in driving climate change in East Africa, Australasia and South Asia. Citation: Gupta, A. K., S. Sarkar, S. De, S. C. Clemens, and A. Velu (2010), Mid-Brunhes strengthening of the Indian Ocean Dipole caused increased equatorial East African and decreased Australasian rainfall, Geophys. Res. Lett., 37, L06706, doi: 10.1029/2009GL042225.},
	issn = {0094-8276},
	doi = {10.1029/2009GL042225},
	author = {Gupta, Anil K. and Sarkar, Sudipta and De, Soma and Clemens, Steven C. and Velu, Angamuthu}
}
@article {387,
	title = {Benthic foraminiferal faunal and isotopic changes as recorded in Holocene sediments of the northwest Indian Ocean},
	journal = {Paleoceanography},
	volume = {23},
	year = {2008},
	note = {id: 1964; PT: J; UT: WOS:000256362400001},
	pages = {PA2214-PA2214},
	abstract = {Historically, the Holocene has been considered an interval of relatively stable climate. However, recent studies from the northern Arabian Sea (Netherlands Indian Ocean Program 905) suggested high-amplitude climate shifts in the early and middle Holocene based on faunal and benthic isotopic proxy records. We examined benthic foraminiferal faunal and stable isotopic data from Ocean Drilling Program (ODP) Site 723 and total organic carbon data from ODP Site 724, Oman Margin (808 and 593 m water depths, respectively). At Site 723 the mid-Holocene shift in delta(18)O values of infaunal benthic species Uvigerina peregrina (1.4 parts per thousand) is 3 times larger than that of epifaunal benthic species Cibicides kullenbergi recorded at Site NIOP 905 off Somalia. However, none of the five other benthic species we measured at Hole 723A exhibits such a shift in delta(18)O. We speculate that the late Holocene delta(18)O decrease in U. peregrina represents species-specific changes in ecological habitat or food preference in response to changes in surface and deep ocean circulation. While the stable isotopic data do not appear to indicate a middle Holocene climatic shift, our total organic carbon and benthic faunal assemblage data do indicate that the early Holocene deep Arabian Sea was influenced by increased ventilation perhaps by North Atlantic Deep Water and/or Circumpolar Deep Water incursions into the Indian Ocean, leading to remineralization of organic matter and a relatively weak early Holocene oxygen minimum zone in the northwest Arabian Sea in spite of strong summer monsoon circulation.},
	issn = {0883-8305},
	doi = {10.1029/2007PA001546},
	author = {Gupta, Anil K. and Das, Moumita and Clemens, Steven C. and Mukherjee, Baidehi}
}
@article {1994,
	title = {Solar influence on the Indian summer monssoon during the Holocene},
	journal = {Geophysical Research Letters},
	volume = {32},
	year = {2005},
	note = {id: 535},
	month = {2005},
	pages = {1-4},
	author = {Gupta, Anil K. and Das, Moumita and Anderson, David M.}
}
