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- Title
Trends of Anthropogenic Dissolved Inorganic Carbon in the Northwest Atlantic Ocean Estimated Using a State Space Model.
- Authors
Boteler, Claire; Dowd, Michael; Oliver, Eric C. J.; Krainski, Elias T.; Wallace, Douglas W. R.
- Abstract
The northwest Atlantic Ocean is an important sink for carbon dioxide produced by anthropogenic activities. However the strong seasonal variability in the surface waters paired with the sparse and summer biased observations of ocean carbon makes it difficult to capture a full picture of its temporal variations throughout the water column. We aim to improve the estimation of temporal trends of dissolved inorganic carbon (DIC) due to anthropogenic sources using a new statistical approach: a time series generalization of the extended multiple linear regression (eMLR) method. Anthropogenic increase of northwest Atlantic DIC in the surface waters is hard to quantify due to the strong, natural seasonal variations of DIC. We address this by separating DIC into its seasonal, natural and anthropogenic components. Ocean carbon data is often collected in the summer, creating a summer bias, however using monthly averaged data made our results less susceptible to the strong summer bias in the available data. Variations in waters below 1000m have usually been analyzed on decadal time scales, but our monthly analysis showed the anthropogenic carbon component had a sudden change in 2000 from stationary to an increasing trend at the same rate as the waters above. All depths layers had similar rates of anthropogenic increase of ∼0.57µmol kg−1 year−1, and our uncertainty levels are smaller than with eMLR results. Integration throughout the water column (0–3,500 m) gives an anthropogenic carbon storage rate of 1.37 ± 0.57 mol m−2 year−1, which is consistent with other published estimates. Plain Language Summary: We need to measure the ocean sink for the CO2 emitted by industrialized societies, and it is particularly important for the northwest Atlantic Ocean. The rate of carbon increase is often overshadowed by natural and seasonal variability. We introduce new statistical approaches to better estimate the rate of anthropogenic carbon that has accumulated due to human activities. Ocean carbon data is often collected in the summer, creating a summer bias, however using monthly averaged data made our results less susceptible to the strong summer bias in the available data. From 1993 to 2015 in the northwest Atlantic Ocean, anthropogenic carbon increased at ∼0.57 μmol kg−1 year−1 within all depth‐layers. Integration of results throughout the water column (0–3,500 m) gives an anthropogenic carbon storage rate of 1.37 ± 0.57 mol m−2 year−1. Key Points: A time series generalization of the extended multiple linear regression (eMLR) method is developed to produce monthly estimates with uncertainties of anthropogenic ocean carbonThe rate of anthropogenic carbon increase in northwest Atlantic is roughly the same for all depth layers, at 0.57 µmol/kg/yearOur method produces estimates of anthropogenic carbon increase that are comparable to those from eMLR, but with smaller uncertainties
- Subjects
CARBON dioxide sinks; OCEAN; CARBON; WATER hardness; HUMAN activity recognition
- Publication
Journal of Geophysical Research. Oceans, 2023, Vol 128, Issue 7, p1
- ISSN
2169-9275
- Publication type
Article
- DOI
10.1029/2022JC019483