Summary of Abstract Submission

Abstract Submission No. IO50-07-0019PresentationPoster


Birgit Gaye*1, Tim Rixen2, Anna Böll1, Kay-Christian Emeis1, V. Ramaswamy3

1 Institute of Geology, University of Hamburg, Germany
2 Leibniz Center for Tropical Marine Ecology, Bremen, Germany
3 National Institute of Oceanography, India


The northern Arabian Sea is one of the main oceanic regions with a permanent low oxygen layer at intermediate water depth that results in water column denitrification. While glacial/interglacial variations in the Arabian Sea oxygen minimum zone (OMZ) are relatively well studied, little is known about the spatial and temporal extent of mid-water oxygen throughout the Holocene. We analyzed parameters indicative of mid-water oxygenation together with records of southwest monsoon strength in two sediment cores from the northern Oman Margin to reconstruct the temporal variability of the Arabian Sea OMZ and its relation to changing SW monsoon activity over the Holocene. Comparison of δ15N and Mn/Al records with other reconstructions of denitrification and oxygenation from the northern Arabian Sea reveal a Holocene shift in the location of the core OMZ from the northwestern (early Holocene) to the northeastern Arabian Sea (late Holocene). This shift was caused by the interplay of spatial differences in oxygen demand, caused by varying responses of primary productivity to SW monsoonal upwelling, and changes in mid-water ventilation due to sea level rise. Regional short-term (centennial scale) fluctuations in the oxygen inventory of the northern Arabian Sea were linked to variations in SW monsoon activity over the mid Holocene: Phases of strong wind intensity triggered intense upwelling in the coastal region of northern Oman that induced high rates of primary productivity and invigorated denitrification. Although it is unknown how the Arabian Sea OMZ will change in the future, our data infer that future short-term fluctuations in monsoonal wind strength might induce regional changes in mid-water oxygen.