The climate of the Indian Ocean is dominated by monsoon reversals, influencing hydrography and biogeochemistry of the Indian Ocean as well as land vegetation through changes in precipitation. During summer or southwest monsoon season, intense upwelling zones driven by Ekman spiral appear in the western and eastern parts of the Arabian Sea that enhance surface primary production and thus proliferation of distinct fauna and flora. During the winter season, northeast monsoon winds cause deep convective over turning (mixing) that injects nutrients to the surface ocean and increases surface production. As a result, the primary production in the Arabian Sea has bimodal annual distribution.