Summary of Abstract Submission

Abstract Submission No. IO50-04-0010PresentationPoster


Zouhair Lachkar*1, Shafer Smith2

1 New York University Abu Dhabi (NYUAD), UAE
2 New York University, USA


The Arabian Sea (AS) hosts one of the world┐s largest oxygen deficient zones driven by a combination of high primary production (PP) and sluggish ocean ventilation. Anaerobic organic matter decomposition through processes such as denitrification depletes the marine nitrogen inventory, and hence potentially affects PP and the biological pump of carbon. Mesoscale eddies have been suggested to play a key role in the O2 budget in the AS. Here we explore the effects of mesoscale and submesoscale eddies on suboxia in the AS, and examine the implications this has for PP and the marine nitrogen inventory. To this end, we conducted a series of coupled physical-biogeochemical simulations of the AS at horizontal resolutions ranging from 1/3o to 1/24o using the ROMS model. Our results show that increased mesoscale eddy activity (1/3o to 1/12o) enhances the ventilation of the upper ocean, thereby reducing the volume of suboxia (O2< 10μmol) and hypoxia (O2< 60μmol) in the top 100m layer while lowering denitrification by up to 15%. Yet, the decreased nitrogen sink enhances PP and amplifies remineralization, thereby increasing O2 biological consumption at depth (+15%). These two opposing processes result in a deepening of suboxia and an expansion of hypoxia at depth (+12%). When the resolution is further refined (1/12o to 1/24o) to resolve submesoscale mixing, eddy-driven ventilation increases further whereas PP and O2 biological removal change little. This leads to a shrinking of the volume of suboxia by 14% and a decline in denitrification by 25%.