Challenges in Quantifying Air‐Water Carbon Dioxide Flux Using Estuarine Water Quality Data: Case Study for Chesapeake Bay

Authors

Maria Herrmann, The Pennsylvania State University
Raymond G. Najjar, The Pennsylvania State University
Fei Da, College of William & Mary
Jaclyn R. Friedman, College of William & Mary
Marjorie A. M. Friedrichs, College of William & Mary
Sreece Goldberger, The Pennsylvania State University
Alana Menendez, CUNY City CollegeFollow
Elizabeth H. Shadwick, CSIRO Oceans and Atmosphere
Edward G. Stets, U.S. Geological Survey
Pierre St-Laurent, College of William & Mary

Document Type

Article

Publication Date

5-27-2020

Abstract

Estuaries play an uncertain but potentially important role in the global carbon cycle via CO₂ outgassing. The uncertainty mainly stems from the paucity of studies that document the full spatial and temporal variability of estuarine surface water partial pressure of carbon dioxide ( pCO₂). Here, we explore the potential of utilizing the abundance of pH data from historical water quality monitoring programs to fill the data void via a case study of the mainstem Chesapeake Bay (eastern United States). We calculate pCO₂ and the air-water CO₂ flux at monthly resolution from 1998 to 2018 from tidal fresh to polyhaline waters, paying special attention to the error estimation. The biggest error is due to the pH measurement error, and errors due to the gas transfer velocity, temporal sampling, the alkalinity mixing model, and the organic alkalinity estimation are 72%, 27%, 15%, and 5%, respectively, of the error due to pH. Seasonal, interannual, and spatial variability in the air-water flux and surface pCO₂ is high, and a correlation analysis with oxygen reveals that this variability is driven largely by biological processes. Averaged over 1998–2018, the mainstem bay is a weak net source of CO₂ to the atmosphere of 1.2 (1.1, 1.4) mol m⁻² yr⁻¹ (best estimate and 95% confidence interval). Our findings suggest that the abundance of historical pH measurements in estuaries around the globe should be mined in order to constrain the large spatial and temporal variability of the CO₂ exchange between estuaries and the atmosphere.

Comments

This work was originally published in the Journal of Geophysical Research: Oceans, available at https://doi.org/10.1029/2019JC015610.

This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.