606 / 2024-09-18 16:08:22
Estimate of biological carbon pump: External versus internal constraints
biological carbon pump,Inverse Model,inter-annual variation,Net primary productivity
Session 28 - Towards a Holistic Understanding of the Ocean's Biological Carbon Pump
Abstract Accepted
The biological carbon pump (BCP), a process that synthesizes CO2 to organic carbon and transports it from the surface ocean to deep waters, is thought to be responsible for the 80-100 ppm atmospheric CO2 changes during the glacial-interglacial transitions. Due to the importance of BCP in regulating atmospheric CO2, multiple methods have been developed to constrain its strength. One means to obtain a global-scale BCP estimate is to use bottom-up methods by converting satellite-based net primary production (NPP) to export efficiency using empirical algorithms (external constraint). Another means is to use top-down methods that infer BCP from the distributions of nutrients and oxygen, whose distributions in the ocean are shaped by BCP (internal constraint). Here, we use an inverse biogeochemical model to demonstrate that climatological mean strength of BCP is strongly constrained by internal constraint regardless of NPP products being used to drive the model. However, due to the relatively short observational record, the climatological mean circulation model combined with hydrographic data cannot fully capture the inter-annual variability of BCP. This variability, however, can potentially be detected by the combining internal and external constraints. We, therefore, recommend extending both hydrographic and satellite observations to ensure that the temporal signals in the ocean become statistically significant, enabling a more accurate representation of the inter-annual variability of BCP.