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Evidence of ventilation changes in the Arabian Sea during the late Quaternary: Implication for denitrification and nitrous oxide emission
Author(s) -
Pichevin Laetitia,
Bard Edouard,
Martinez Philippe,
Billy Isabelle
Publication year - 2007
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2006gb002852
Subject(s) - denitrification , holocene , oceanography , nitrous oxide , quaternary , environmental science , nitrate , nitrogen cycle , geology , climatology , nitrogen , ecology , chemistry , paleontology , organic chemistry , biology
Modern seawater profiles of oxygen, nitrate deficit, and nitrogen isotopes reveal the spatial decoupling of summer monsoon‐related productivity and denitrification maxima in the Arabian Sea (AS) and raise the possibility that winter monsoon and/or ventilation play a crucial role in modulating denitrification in the northeastern AS, both today and through the past. A new high‐resolution 50‐ka record of δ 15 N from the Pakistan margin is compared to five other denitrification records distributed across the AS. This regional comparison unveils the persistence of east‐west heterogeneities in denitrification intensity across millennial‐scale climate shifts and throughout the Holocene. The oxygen minimum zone (OMZ) experienced east‐west swings across Termination I and throughout the Holocene. Probable causes are (1) changes in ventilation due to millennial‐scale variations in Antarctic Intermediate Water formation and (2) postglacial reorganization of intermediate circulation in the northeastern AS following sea level rise. Whereas denitrification in the world's OMZs, including the western AS, gradually declined following the deglacial maximum (10−9 ka BP), the northeastern AS record clearly witnesses increasing denitrification from about 8 ka BP. This would have impacted the global Holocene climate through sustained N 2 O production and marine nitrogen loss.