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High-resolution Neural Network Demonstrates Strong CO2 Source-Sink Juxtaposition in the Coastal Zone
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  • Patrick J. Duke,
  • Roberta C Hamme,
  • Debby Ianson,
  • Peter Landschützer,
  • Neil C. Swart,
  • Paul Covert
Patrick J. Duke
University of Victoria

Corresponding Author:[email protected]

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Roberta C Hamme
University of Victoria
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Debby Ianson
Institute of Ocean Sciences
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Peter Landschützer
Flanders Marine Institute
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Neil C. Swart
Environment Canada
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Paul Covert
Institute of Ocean Sciences, Fisheries and Oceans Canada
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Abstract

Coastal oceans may play an important role in regulating the concentration of carbon dioxide in the atmosphere. Quantification of carbon fluxes at this highly dynamic land-ocean interface will aid in monitoring, reporting, and verification for marine carbon dioxide removal. Here, we use a two-step neural network approach to generate basin-wide estimates from sparse observational data in the coastal Northeast Pacific Ocean at an unprecedented spatial resolution of 1/12° with coverage in the nearshore (0 - 25 km offshore). We compiled partial pressure of carbon dioxide (pCO2) observations as well as a range of predictor variables including satellite-based and physical oceanographic reanalysis products. With the predictor variables representing processes affecting pCO2, we created non-linear relationships to interpolate observations from 1998-2019. Compared to in situ shipboard and mooring observations, our coastal pCO2 product captures broad spatial patterns and seasonal cycle variability well. A sensitivity analysis identifies that the parameters responsible for the neural network’s ability to capture regional pCO2 variability agrees with mechanistic processes. Using wind speed and atmospheric CO2, we calculated air-sea CO2 fluxes. We report an anticorrelation between net annual air-sea CO2 flux and air-sea CO2 flux seasonal amplitude and suggest the relationship is driven by regional processes. We show the inclusion of nearshore net outgassing fluxes lowers the overall regional net flux. Overall, our results suggest that the region is a net sink (-0.7 mol m-2 yr-1) for atmospheric CO2 with trends indicating increasing oceanic uptake due to strong connectivity to subsurface waters.
21 Mar 2024Submitted to ESS Open Archive
21 Mar 2024Published in ESS Open Archive