Contribution of mesoscale processes to nutrient budgets in the Arabian Sea

• Published in: Journal of Geophysical Research: Oceans Vol. 116; no. C11
• Main Authors: Resplandy, L., Lévy, M., Madec, G., Pous, S., Aumont, O., Kumar, D.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-11-2011; Wiley-Blackwell
• Subjects: Advection; Arabian Sea; Biogeochemistry; Biological production; Blooms; Budgets; Coastal upwelling; Coastal zone; Dynamics; Earth Sciences; Filaments; Geophysics; Marine; Mathematical models; mesoscale; Mesoscale phenomena; Mesoscale processes; Monsoon effects; Monsoons; Numerical models; Nutrient cycles; Nutrient dynamics; Nutrients; Ocean circulation; Oceanography; Physical oceanography; Primary production; Regions; Satellite observation; Sciences of the Universe; Seasonal variation; Summer; Upwelling; Vertical advection; Vertical velocities; Vortices; Arabian Sea; ISW, Arabian Sea
• ISSN: 0148-0227; 2169-9275; 2156-2202; 2169-9291
• DOI: 10.1029/2011JC007006

We examine the impact of mesoscale dynamics on the seasonal cycle of primary production in the Arabian Sea with an eddy‐resolving (1/12°) bio‐physical model. Comparison with observations indicates that the numerical model provides a realistic description of climatological physical and biogeochemical fields as well as their mesoscale variability during the Southwest and Northeast Monsoons. We show that mesoscale dynamics favors biological production by modulating the nutrient supplies throughout the year. Different processes are involved depending on the blooming season. During the summer bloom period, we found that the main process is the export of nutrients from coastal upwelling regions into the central Arabian Sea by mesoscale filaments. Our model suggests that lateral advection accounts for 50–70% of the total supply of nutrients to the central AS. A less expected result is the major input of nutrients (up to 60–90%) supplied to upwelling regions during the early stage of the summer bloom period by eddy‐induced vertical advection. During the winter bloom period, our model evidences for the first time how vertical velocities associated with mesoscale structures increase the supply of nutrients to the upper layer by 40–50% in the central Arabian Sea. Finally, the restratification effect of mesoscale structures modulates spatially and temporally the restratification that occurs at large‐scale at the end of the Northeast Monsoon. Although this effect has no significant impact on the large‐scale budget, it could be a source of uncertainty in satellite and in‐situ observations.
Key Points
The impact of mesoscale on biogeochemistry in the Arabian Sea
Eddy‐induced vertical advection enhances upwelling nutrient supply by 60‐90%
Mesoscale structures spatially and temporally modulate spring restratification