Increased particle flux to the deep ocean related to monsoons

Abstract

MONSOONS cause seasonal reversals in the surface circulation of the northern Indian Ocean¹. In the Arabian Sea this results in the upwelling of nutrient-rich water along the coasts^2–4, making it one of the highly productive regions of the world's oceans. To assess the impact of monsoon-driven processes on the downward particle flux variations in the open ocean we deployed three moored arrays consisting of six time-series sediment traps at selected locations in the western, central and eastern parts of the deep northern Arabian Sea. Strong seasonality was recorded in particle flux at all three sites with peaks during the south-west and northeast monsoons. High primary productivity during the monsoons resulting from wind-induced mixed-layer deepening and the associated nutrient injection to the euphotic zone appeared to be the main factor controlling the observed particle flux pattern. These findings may shed light on CO₂ uptake during glaciation when wind speeds were higher.