First evidence of denitrification vis-à-vis monsoon in the Arabian Sea since Late Miocene

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  • IODP Expedition 355 Scientists

Colleges, School and Institutes

External organisations

  • National Centre for Antarctic and Ocean Research (NCAOR)
  • Pusan National University
  • Louisiana State University
  • Texas A and M University
  • University of Milano-Bicocca
  • Macquarie University
  • University of Texas at Arlington
  • Manipal University
  • University of Bremen
  • Kochi University
  • Wadia Institute of Himalayan Geology
  • National Institute of Ocean Technology
  • University of Southern California
  • Nanjing University
  • Oregon State University
  • National Centre for Earth Science Studies
  • University College London
  • ONGC
  • Universidade Estadual Paulista
  • Kumaun University India
  • Banaras Hindu University
  • Department of Chemistry, College of Chemistry and Chemical Engineering, and MOE Key Laboratory of Analytical Sciences, Xiamen University, Xiamen 361005, China.
  • Hokkaido University
  • Scripps Institution of Oceanography
  • Chinese Academy of Sciences
  • Universite Paris Sud


In the Arabian Sea, South Asian monsoon (SAM)-induced high surface water productivity coupled with poor ventilation of intermediate water results in strong denitrification within the oxygen minimum zone (OMZ). Despite the significance of denitrification in the Arabian Sea, we have no long-term record of its evolution spanning the past several million years. Here, we present the first record of denitrification evolution since Late Miocene (∼10.2 Ma) in the Eastern Arabian Sea, where the SAM generates moderate surface water productivity, based on the samples retrieved during the International Ocean Discovery Program (IODP) Expedition 355. We find that (i) the SAM was persistently weaker from ∼10.2 to 3.1 Ma; it did not intensify at ∼8 Ma in contrast to a few previous studies, (ii) on tectonic timescale, both the SAM and the East Asian Monsoon (EAM) varied synchronously, (iii) the first evidence of denitrification and productivity/SAM intensification was at ∼3.2-2.8 Ma that coincided with Mid-Pliocene Warm Period (MPWP), and (iv) the modern strength of the OMZ where denitrification is a permanent feature was attained at ∼1.0 Ma.


Original languageEnglish
Article number43056
Number of pages7
JournalScientific Reports
Publication statusPublished - 21 Feb 2017

ASJC Scopus subject areas