[A-CG46] Science in the Arctic Region

[ACG46-P03] Regional Carbon Cycle Assessment and Processes phase 2 (RECCAP2): CO₂ uptake in the Arctic Ocean from 1985 to 2018

*Sayaka Yasunaka^1,2, Manfredi Manizza³, Jens Terhaar^4,5, Are Olsen⁶, Ryohei Yamaguchi², Peter Landschützer^7,8, EIJI WATANABE², Dustin Carroll⁹, Hanani Adiwira¹, Jens Daniel Müller¹⁰, Judith Hauck¹¹ (1.Tohoku University, 2.JAMSTEC, 3.Scripps Institution of Oceanography, 4.Woods Hole Oceanographic Institution, 5.University of Bern, 6.University of Bergen and Bjerknes Centre for Climate Research, 7.Flanders Marine Institute, 8.Max Planck Institute for Meteorology, 9.San José State University, 10.ETH Zurich, 11.Alfred Wegener Institute for Polar and Marine Research)

Keywords:Sea-air CO2 flux, pCO2, Sea ice

As a contribution to the Regional Carbon Cycle Assessment and Processes phase 2 (RECCAP2) project, we present synthesized estimates of the Arctic Ocean CO₂ uptake and their uncertainties from state-of-the-art 8 surface ocean pCO₂-observation products, 18 global and regional ocean biogeochemical models and 6 atmospheric inversions. For the period of 1985−2018, the Arctic Ocean represents a net sink of CO₂ of 103 ± 19 TgC yr⁻¹ in the pCO₂ products and 92 ± 30 TgC yr⁻¹ in the ocean biogeochemical models. The CO₂ uptake peaks in late summer and early autumn, and is low in winter because the sea ice cover inhibits sea-air fluxes. While the CO₂ uptake in the Arctic Ocean is primarily caused by steady-state fluxes of natural carbon, it is enhanced by the atmospheric CO₂ increase (28 ± 7 %) and climate change (16 ± 26 %). The annual mean of CO₂ uptake increased with the decreasing sea ice concentration both in the pCO₂ products and the ocean biogeochemical models (29 ±11 TgC yr⁻¹dec^-1 and 10 ± 4 TgC yr⁻¹dec^-1, respectively), and the climate effect in the Arctic Ocean has become more important in recent years. Both, the mean CO₂ uptake and the trend, is substantially weaker in the atmospheric inversions. Uncertainty across all estimates is large especially in the estimated surface ocean pCO₂ values in the East Siberian Sea and the Laptev Sea, due to scarcity of observations and missing processes in models, such as land-sea fluxes and sediment dynamics.