On the majestic seasonal upwelling system of the Arafura Sea

Abstract

AbstractA three‐dimensional hydrodynamic model is applied to explore the development of phytoplankton blooms in the Arafura Sea during the southeast monsoon (June–November). Before this season, blooms are restricted to nearshore waters covering a total area of ∼25,000 km2. Satellite data indicate that the bloom area grows substantially to >90,000 km2 during the southeast monsoon covering most of the northwestern Arafura Sea. Findings confirm that the southeast monsoon creates undercurrents via the classical lee effect driving nutrient‐rich Banda Sea slope water into this region. This nutrient‐rich slope water is driven over vast distances (∼300 km) into the northwestern Arafura Sea where it upwells and/or is entrained into the surface mixed layer. The associated overturning circulation is slow but continuous and it takes 1–2 months before nutrient‐rich water appears in surface waters of the region. The predicted pathways of nutrient‐rich inflows across the shelf break both north and south of the Ara Islands agree with observational evidence.