Data-based estimates show that the global oceanic carbon flux has increased rapidly since around 2000 with little decadal variability during 1992-1999 (Rödenbeck et al., 2015). An article published in Geophysical Research Letters (Li and Ilyina, 2017) used large ensemble climate model simulations to show that the observed increase is much faster than simulated by their biogeochemical process model. By analyzing ensemble spread versus forced trend, the study found that on decadal time scales, internal variability (ensemble spread) is as large as the forced temporal variability (ensemble mean), and the largest internal variability is found in major carbon sink regions, that is, the 50-65°S band of the Southern Ocean, the North Pacific, and the North Atlantic.
Li, H., & Ilyina, T. (2018). Current and future decadal trends in the oceanic carbon uptake are dominated by internal variability. Geophysical Research Letters, 45(2), 916-925. https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017GL075370.
Rödenbeck, C., Bakker, D. C., Gruber, N., Iida, Y., Jacobson, A. R., Jones, S., … & Park, G. H. (2015). Data-based estimates of the ocean carbon sink variability–first results of the Surface Ocean pCO2 Mapping intercomparison (SOCOM). Biogeosciences, 12, 7251-7278. https://www.biogeosciences.net/12/7251/2015.