A Synthesis of Global Coastal Ocean Greenhouse Gas Fluxes

L. Resplandy, A. Hogikyan, J. D. Müller, R. G. Najjar, H. W. Bange, D. Bianchi, T. Weber, W. J. Cai, S. C. Doney, K. Fennel, M. Gehlen, J. Hauck, F. Lacroix, P. Landschützer, C. Le Quéré, A. Roobaert, J. Schwinger, S. Berthet, L. Bopp, T. T.T. ChauM. Dai, N. Gruber, T. Ilyina, A. Kock, M. Manizza, Z. Lachkar, G. G. Laruelle, E. Liao, I. D. Lima, C. Nissen, C. Rödenbeck, R. Séférian, K. Toyama, H. Tsujino, P. Regnier

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

The coastal ocean contributes to regulating atmospheric greenhouse gas concentrations by taking up carbon dioxide (CO2) and releasing nitrous oxide (N2O) and methane (CH4). In this second phase of the Regional Carbon Cycle Assessment and Processes (RECCAP2), we quantify global coastal ocean fluxes of CO2, N2O and CH4 using an ensemble of global gap-filled observation-based products and ocean biogeochemical models. The global coastal ocean is a net sink of CO2 in both observational products and models, but the magnitude of the median net global coastal uptake is ∼60% larger in models (−0.72 vs. −0.44 PgC year−1, 1998–2018, coastal ocean extending to 300 km offshore or 1,000 m isobath with area of 77 million km2). We attribute most of this model-product difference to the seasonality in sea surface CO2 partial pressure at mid- and high-latitudes, where models simulate stronger winter CO2 uptake. The coastal ocean CO2 sink has increased in the past decades but the available time-resolving observation-based products and models show large discrepancies in the magnitude of this increase. The global coastal ocean is a major source of N2O (+0.70 PgCO2-e year−1 in observational product and +0.54 PgCO2-e year−1 in model median) and CH4 (+0.21 PgCO2-e year−1 in observational product), which offsets a substantial proportion of the coastal CO2 uptake in the net radiative balance (30%–60% in CO2-equivalents), highlighting the importance of considering the three greenhouse gases when examining the influence of the coastal ocean on climate.

Original languageEnglish (US)
Article numbere2023GB007803
JournalGlobal Biogeochemical Cycles
Volume38
Issue number1
DOIs
StatePublished - Jan 2024

All Science Journal Classification (ASJC) codes

  • Global and Planetary Change
  • Environmental Chemistry
  • General Environmental Science
  • Atmospheric Science

Keywords

  • carbon
  • coastal ocean
  • methane
  • nitrous oxide
  • RECCAP2

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