Seasonal and Interannual Variability of the Tropical Maritime Continent
Upper-Ocean Carbon Cycle Over the Last Decade: Results from a Newly
Developed Regional Scale Model
Abstract
A three-dimensional physical-biogeochemical ocean numerical model with
eddy-permitting horizontal resolution was applied to simulate
upper-ocean carbon cycle variabilities in the Tropical Maritime
Continent (TMC) over the last decade (2010–2019). Forced by atmospheric
and oceanic reanalysis products with high temporal resolution, the model
showed robust consistency with the observed seasonality of pCO2 and
atmospheric CO2 sink/source characteristics across the modeling domain.
Within the TMC, the model results indicated strong CO2 degassing along
the west of Sumatra-south of Java associated with the seasonal cycle of
the upwelling system in the area. While acting as a full-year
atmospheric CO2 source, the TMC exhibited pronounced interannual
modulation in both pCO2 and sea-air CO2 flux over the last decade.
Large-scale anomalous strong CO2 degassing from 2015 to 2016 in response
to the evolution of the 2015/2016 El Niño was observed from the
simulation results. Modulations related to the Indian Ocean Dipole
(IOD), on the other hand, were confined along the west of Sumatra-south
of Java with a higher magnitude compared with anomalies related to El
Niño/La Niña. Simulation results also captured the asymmetric response
of the upper-ocean carbon cycle to the IOD over the last decade, where
anomalies during negative IOD (nIOD) were notably strong despite being
indicated as weak nIOD events by the Dipole Mode Index.