Evolution and dynamics of the denitrification in the Arabian Sea on millennial to million-year timescale

Abstract

Denitrification in the Arabian Sea is a vital process that provides feedback to global warming by releasing nitrous oxide to the atmosphere. Therefore, it is important to understand the evolution and dynamics of denitrification on different timescales. We present here the denitrification variability spanning the past ∼600 thousand years (kyr). It is based on ∼300 new measurements from IODp 355 Expedition. We compared the existing records of denitrification to understand the factors influencing the denitrification on various timescales. On glacial–interglacial timescale, we find stronger denitrification during interglacial and weaker denitrification during glacial periods. During the Holocene, we observe declining denitrification in the Western Arabian Sea in response to the reduced monsoon-induced productivity but find increasing denitrification in the Northeastern Arabian Sea due to reduced ventilation.