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Update on the Temperature Corrections of Global Air-Sea CO2 Flux Estimates
  • +4
  • Yuanxu Dong,
  • Dorothee C. E. Bakker,
  • Thomas G Bell,
  • Boyin Huang,
  • Peter Landschützer,
  • Peter S. Liss,
  • Mingxi Yang
Yuanxu Dong
University of East Anglia

Corresponding Author:[email protected]

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Dorothee C. E. Bakker
University of East Anglia
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Thomas G Bell
Plymouth Marine Laboratory
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Boyin Huang
NOAA/NCEI
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Peter Landschützer
Max Planck Institute for Meteorology
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Peter S. Liss
University of East Anglia
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Mingxi Yang
Plymouth Marine Laboratory
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Abstract

The oceans are a major carbon sink. Sea surface temperature (SST) is a crucial variable in the calculation of the air-sea carbon dioxide (CO2;) flux from surface observations. Any bias in the SST or any upper ocean vertical temperature gradient (e.g., the cool skin effect) potentially generates a bias in the CO2 flux estimates. A recent study suggested a substantial increase (~50% or ~0.9 Pg C yr-1) in the global ocean CO2 uptake due to this temperature effect. Here, we use a gold standard buoy SST dataset as the reference to assess the accuracy of in-situ SST used for flux calculation. A physical model is then used to estimate the cool skin effect, which varies with latitude. The bias-corrected SST (assessed by buoy SST) coupled with the physics-based cool skin correction increases the average ocean CO2 uptake by ~35% (0.6 Pg C yr-1) for 1982 to 2020, which is significantly smaller than the previous correction. After these temperature considerations, we estimate an average net ocean CO2 uptake of 2.2 +- 0.4 Pg C yr-1 for 1994 to 2007 based on an ensemble of surface observation-based flux estimates, in line with the independent interior ocean carbon storage estimate corrected for the river induced natural outgassing flux (2.1 +- 0.4 Pg C yr-1).