Enhanced oceanic CO2 uptake along the rapidly changing West Antarctic Peninsula

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Abstract

The global ocean is an important sink for anthropogenic CO2 (ref. 1). Nearly half of the oceanic CO2 uptake occurs in the Southern Ocean2. Although the role of the Southern Ocean CO2 sink in the global carbon cycle is recognized, there are uncertainties regarding its contemporary trend3,4, with a need for improved mechanistic understanding, especially in productive Antarctic coastal regions experiencing substantial changes in temperature and sea ice5. Here, we demonstrate strong coupling between summer upper ocean stability, phytoplankton dynamics and oceanic CO2 uptake along the rapidly changing West Antarctic Peninsula using a 25-year dataset (1993–2017). Greater upper ocean stability drives enhanced biological production and biological dissolved inorganic carbon drawdown, resulting in greater oceanic CO2 uptake. Diatoms achieve higher biomass, oceanic CO2 uptake and uptake efficiency than other phytoplankton. Over the past 25 years, changes in sea ice dynamics have driven an increase in upper ocean stability, phytoplankton biomass and biological dissolved inorganic carbon drawdown, resulting in a nearly fivefold increase in summer oceanic CO2 uptake. We hypothesize that continued warming and declines in sea ice will lead to a decrease in biological dissolved inorganic carbon drawdown, negatively impacting summer oceanic CO2 uptake. These results from the West Antarctic Peninsula provide a framework to understand how oceanic CO2 uptake in other Antarctic coastal regions may be altered due to climate change.

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Fig. 1: Study area.
Fig. 2: Relationship between summer WAP phytoplankton biomass and oceanic CO2 uptake.
Fig. 3: Relationship between summer WAP upper ocean stability, phytoplankton dynamics and oceanic CO2 uptake.
Fig. 4: Trends in summer WAP regional upper ocean stability, phytoplankton biomass and oceanic CO2 uptake.

Data availability

The Palmer LTER dataset, sampling and analysis protocols and Palmer Station atmospheric pressure dataset can be accessed at http://pal.lternet.edu. The DPT \(p_{{\mathrm{CO}}_2}\) dataset can be accessed at https://www.socat.info/. The NOAA ESRL Greenhouse Gas Marine Boundary Layer Reference can be accessed at https://www.esrl.noaa.gov/gmd/ccgg/mbl/data.php. Figs. 24, Supplementary Tables 1 and 2 and Supplementary Figs. 17 present data from the above datasets.

Code availability

The custom MATLAB (R2018a) code written to read and analyse data and generate figures is fully available on request from the corresponding author.

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Acknowledgements

We thank all past and present members of the Palmer LTER for their dedication in the field and laboratory. Additionally, we thank all past and present support crew for their assistance. This paper benefitted from comments provided by R. Sherrell, S. Stammerjohn and T. Takahashi. This research was supported by NSF Office of Polar Programs Integrated Systems Science Program Award No. 1440435 to H.W.D. and O.M.S. for the Palmer LTER, NSF Office of Polar Programs Award No. 1543457 to D.R.M. and C.S. for the DPT and NSF Office of Polar Programs Award No. 1501997 to C.S. for additional support. This is Palmer LTER Contribution No. 622.

Author information

M.S.B. and O.M.S. conceived the study. M.S.B. analysed the data and wrote the manuscript. C.S. and D.R.M. provided the DPT \(p_{{\mathrm{CO}}_2}\) dataset. C.J.F. and D.R.M. provided valuable data interpretation and synthesis. H.W.D. led the Palmer LTER programme. All authors reviewed and edited the manuscript.

Correspondence to Michael S. Brown.

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Peer review information: Nature Climate Change thanks Nicolas Metzl and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Tables 1–2 and Figs. 1–7.

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