Dynamics of the carbonate system in the Indonesian Seas Faisal Hamzah (1,2 *) & Minhan Dai (2)
(a) Institute for Information Management of Marine and Fisheries Resources, Ministry of Marine Affairs and Fisheries, Bali, 82251, Indonesia
faisalhamzah[at]kkp.go.id
(b) State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, 361102, China
Abstract
Located between the Pacific and Indian Oceans, the Indonesian Seas (IS) are the gateway where occurs the largest movement of water on the Earth- known as the Indonesian throughflow (ITF). However, the biogeochemistry of the Indonesian Seas and the material exchanges substances (e.g., carbonate system) carried by the ITF remain poorly understood. By using a comprehensive observation-based dataset, we examine the dynamics of the carbonate system in the Indonesian Seas. Western IS is characterized by relatively homogeneous distributions of salinity, dissolved inorganic carbon (DIC), and total alkalinity (TAlk) due to well-mixed waters and river plumes. Physical processes and air-sea gas exchange exerted predominant controls on the carbonate system in the shallow region, while a net DIC removal was observed in the channel between the shallow and deep ocean. Furthermore, along the main route of ITF, surface distributions of DIC and TAlk were low in the main inflow than in the main outflow passage. Salinity-normalized DIC was relatively higher in the mixing regions along the western and eastern routes suggesting on site-regenerations. The ITF carries a net DIC flux with its largest located in the upper 300 m. Using an isopycnal mixing model, we further estimated the contribution from the western Pacific to the net carbon inventory of the western route, suggesting that the net DIC supply to the region is minimal and that local processes such as upwelling and vertical mixing may play an essential role in determining DIC inventory in the Makassar Strait-Lombok Strait. Our findings help disentangle the complex effect of topography settings and physical-biogeochemical interactions on ocean carbon biogeochemistry which have important regional and global implications.
Keywords: Indonesian Seas- Indonesian throughflow- Carbonate System- Physical mixing- Biological Consumption- Transport- Monsoon
