Quantifying the influence of CO2 seasonality on future aragonite undersaturation onset

[摘要] Ocean acidification is a predictable consequence of rising atmosphericcarbon dioxide (CO₂), and is highly likely to impact the entire marineecosystem – from plankton at the base of the food chain to fish at the top.Factors which are expected to be impacted include reproductive health,organism growth and species composition and distribution. Predicting whencritical threshold values will be reached is crucial for projecting thefuture health of marine ecosystems and for marine resources planning andmanagement. The impacts of ocean acidification will be first felt at theseasonal scale, however our understanding how seasonal variability willinfluence rates of future ocean acidification remains poorly constrained dueto current model and data limitations. To address this issue, we firstquantified the seasonal cycle of aragonite saturation state utilizing newdata-based estimates of global ocean-surface dissolved inorganic carbon andalkalinity. This seasonality was then combined with earth system modelprojections under different emissions scenarios (representative concentration pathways; RCPs 2.6, 4.5 and 8.5) toprovide new insights into future aragonite undersaturation onset. Under ahigh emissions scenario (RCP 8.5), our results suggest accounting forseasonality will bring forward the initial onset of month-longundersaturation by 17 ± 10 years compared to annual-mean estimates,with differences extending up to 35 ± 16 years in the North Pacific dueto strong regional seasonality. This earlier onset will result inlarge-scale undersaturation once atmospheric CO₂ reaches 496 ppm in theNorth Pacific and 511 ppm in the Southern Ocean, independent of emissionscenario. This work suggests accounting for seasonality is critical toprojecting the future impacts of ocean acidification on the marineenvironment.

[学科分类] 地球化学与岩石