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Article Dans Une Revue Global Biogeochemical Cycles Année : 2024

A Synthesis of Global Coastal Ocean Greenhouse Gas Fluxes

L. Resplandy
A. Hogikyan
R G Najjar
  • Fonction : Auteur
H W Bange
D. Bianchi
T. Weber
S C Doney
K. Fennel
F. Lacroix
P. Landschützer
J. Schwinger
S. Berthet
T. Ilyina
M. Manizza
Z. Lachkar
G G Laruelle
E. Liao
  • Fonction : Auteur
I D Lima
C. Rödenbeck
K. Toyama
H. Tsujino

Résumé

The coastal ocean contributes to regulating atmospheric greenhouse gas concentrations by taking up carbon dioxide (CO 2) and releasing nitrous oxide (N 2 O) and methane (CH 4). In this second phase of the Regional Carbon Cycle Assessment and Processes (RECCAP2), we quantify global coastal ocean fluxes of CO 2 , N 2 O and CH 4 using an ensemble of global gap-filled observation-based products and ocean biogeochemical models. The global coastal ocean is a net sink of CO 2 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 km 2). We attribute most of this model-product difference to the seasonality in sea surface CO 2 partial pressure at mid-and high-latitudes, where models simulate stronger winter CO 2 uptake. The coastal ocean CO 2 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 N 2 O (+0.70 PgCO 2-e year-1 in observational product and +0.54 PgCO 2-e year-1 in model median) and CH 4 (+0.21 PgCO 2-e year-1 in observational product), which offsets a substantial proportion of the coastal CO 2 uptake in the net radiative balance (30%-60% in CO 2-equivalents), highlighting the importance of considering the three greenhouse gases when examining the influence of the coastal ocean on climate.
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Dates et versions

hal-04426298 , version 1 (30-01-2024)

Identifiants

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L. Resplandy, A. Hogikyan, J D Müller, R G Najjar, H W Bange, et al.. A Synthesis of Global Coastal Ocean Greenhouse Gas Fluxes. Global Biogeochemical Cycles, 2024, 38 (1), pp.e2023GB007803. ⟨10.1029/2023gb007803⟩. ⟨hal-04426298⟩
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