Magnitude, Trends, and Variability of the Global Ocean Carbon Sink From 1985 to 2018

Tim DeVries, Kana Yamamoto, Rik Wanninkhof, Nicolas Gruber, Judith Hauck, Jens Daniel Müller, Laurent Bopp, Dustin Carroll, Brendan Carter, Thi Tuyet Trang Chau, Scott C. Doney, Marion Gehlen, Lucas Gloege, Luke Gregor, Stephanie Henson, Ji Hyun Kim, Yosuke Iida, Tatiana Ilyina, Peter Landschützer, Corinne Le QuéréDavid Munro, Cara Nissen, Lavinia Patara, Fiz F. Pérez, Laure Resplandy, Keith B. Rodgers, Jörg Schwinger, Roland Séférian, Valentina Sicardi, Jens Terhaar, Joaquin Triñanes, Hiroyuki Tsujino, Andrew Watson, Sayaka Yasunaka, Jiye Zeng

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

This contribution to the RECCAP2 (REgional Carbon Cycle Assessment and Processes) assessment analyzes the processes that determine the global ocean carbon sink, and its trends and variability over the period 1985–2018, using a combination of models and observation-based products. The mean sea-air CO2 flux from 1985 to 2018 is −1.6 ± 0.2 PgC yr−1 based on an ensemble of reconstructions of the history of sea surface pCO2 (pCO2 products). Models indicate that the dominant component of this flux is the net oceanic uptake of anthropogenic CO2, which is estimated at −2.1 ± 0.3 PgC yr−1 by an ensemble of ocean biogeochemical models, and −2.4 ± 0.1 PgC yr−1 by two ocean circulation inverse models. The ocean also degasses about 0.65 ± 0.3 PgC yr−1 of terrestrially derived CO2, but this process is not fully resolved by any of the models used here. From 2001 to 2018, the pCO2 products reconstruct a trend in the ocean carbon sink of −0.61 ± 0.12 PgC yr−1 decade−1, while biogeochemical models and inverse models diagnose an anthropogenic CO2-driven trend of −0.34 ± 0.06 and −0.41 ± 0.03 PgC yr−1 decade−1, respectively. This implies a climate-forced acceleration of the ocean carbon sink in recent decades, but there are still large uncertainties on the magnitude and cause of this trend. The interannual to decadal variability of the global carbon sink is mainly driven by climate variability, with the climate-driven variability exceeding the CO2-forced variability by 2–3 times. These results suggest that anthropogenic CO2 dominates the ocean CO2 sink, while climate-driven variability is potentially large but highly uncertain and not consistently captured across different methods.

Original languageEnglish (US)
Article numbere2023GB007780
JournalGlobal Biogeochemical Cycles
Volume37
Issue number10
DOIs
StatePublished - Oct 2023

All Science Journal Classification (ASJC) codes

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

Keywords

  • anthropogenic carbon
  • carbon cycle
  • climate change
  • ocean
  • RECCAP2

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