Wind induced changes in the ocean carbon sink Neil Swart John Fyfe Oleg Saenko Canadian Centre for Climate Modelling and Analysis, Environment Canada Ocean carbon and heat uptake workshop 14 December 2014
Overview Metrics and uncertainties 1. Observed and simulated changes in the SH westerlies. 2. Ocean carbon uptake in an OBGCM driven by specified winds, with uncertainties due to... model parametrization of mesoscale eddies. poorly constrained winds. Wind induced changes in the ocean carbon sink Neil Swart, Environment Canada 2 / 17
Historical and future changes CMIP5 jet position and strength Position anomaly (deg. latitude) Strength anomaly ( 10-2 Pa) 1 0.5 0-0.5-1 -1.5-2 -2.5 2.5 2 1.5 1 0.5 0-0.5-1 Historical RCP2.6 RCP4.5 Historical / RCPs RCP6.0 RCP8.5 1980 2000 2020 2040 2060 2080 1 N. C. Swart and J. C. Fyfe (Aug. 2012a), Observed and simulated changes in the Southern Hemisphere surface westerly wind-stress, Geophys. Res. Lett., 39. Wind induced changes in the ocean carbon sink Neil Swart, Environment Canada 3 / 17
Historical changes CMIP5 vs 6 reanalyses Position ( S) Umax (m/s) 48.0 49.5 51.0 52.5 54.0 8.8 8.0 7.2 6.4 5.6 1890 1910 1930 1950 Year 1970 1990 2010 R1 R2 20CR ERA CFSR MERRA CMIP5 Wind induced changes in the ocean carbon sink Neil Swart, Environment Canada 4 / 17
Historical trends (1979-2010) CMIP5 vs reanalyses Position trend ( lat./dec) 0.8 0.0 0.8 R1 R2 20CR ERA CFSR MERRA CMIP5 Umax trend (ms 1 /dec) 0.30 0.15 0.00 0.15 0.30 MAM JJA SON DJF ANN Wind induced changes in the ocean carbon sink Neil Swart, Environment Canada 5 / 17
Historical trends (1979-2010) Zonal mean trends in u10m Trend (m s 1 dec. 1 ) 0.24 0.16 0.08 0.00 0.08 CMIP5 R1 R2 20CR ERA-Int CFSR MERRA 0.16 50 0 50 Latitude Wind induced changes in the ocean carbon sink Neil Swart, Environment Canada 6 / 17
forced with 20CR winds 20CR winds UVic ESCM Ocean carbon uptake N. C. Swart et al. (2014), Wind-driven changes in the ocean carbon sink, Biogeosciences, 11., Wind induced changes in the ocean carbon sink Neil Swart, Environment Canada 7 / 17
Net global carbon flux and wind feedback N. C. Swart et al. (2014), Wind-driven changes in the ocean carbon sink, Biogeosciences, 11., Wind induced changes in the ocean carbon sink Neil Swart, Environment Canada 8 / 17
Wind induced flux anomaly N. C. Swart et al. (2014), Wind-driven changes in the ocean carbon sink, Biogeosciences, 11., Wind induced changes in the ocean carbon sink Neil Swart, Environment Canada 9 / 17
a) 6 Carbon uptake4 in an OBGCM Wind stress tre ( 10 3 Pa dec. Introduction Changing westerlies OBGCM uptake CMIP winds Conclusions Wind induced trends in Southern Ocean surface flux 2 Flux trend ( 10 2 Pg yr 1 dec. 1 ) 8 6 4 2 0 2 4 b) constant GM variable GM difference 1880 1900 1920 1940 1960 1980 Trend start year N. C. Swart et al. (2014), Wind-driven changes in the ocean carbon sink, Biogeosciences, 11., Wind induced changes in the ocean carbon sink Neil Swart, Environment Canada 10 / 17
Changes in eddy diffusivity and MOC N. C. Swart et al. (2014), Wind-driven changes in the ocean carbon sink, Biogeosciences, 11., Wind induced changes in the ocean carbon sink Neil Swart, Environment Canada 11 / 17
Uncertainty in reanalysis winds 6 Reanalyzes winds UVic ESCM Ocean carbon uptake Trend (m s 1 dec. 1 ) 0.24 0.16 0.08 0.00 0.08 0.16 50 0 50 Latitude R1 R2 20CR ERA-Int CFSR MERRA N. C. Swart et al. (2014), Wind-driven changes in the ocean carbon sink, Biogeosciences, 11., Wind induced changes in the ocean carbon sink Neil Swart, Environment Canada 12 / 17
Introduction Changing westerlies OBGCM MERRA uptake CMIP winds Conclusions Effect of reanalysis wind uncertainty on carbon uptake trends a) MERRA CFSR ERA 20CR R2 R1 0.4 0.3 0.2 0.1 0.0 0.1 0.2 0.3 0.4 Trend (Pg yr 1 dec. 1 ) b) MERRA 0.18 0.16 CFSR 0.14 0.12 N. C. Swart et al. (2014), Wind-driven changes in the ocean carbon sink, Biogeosciences, 11., ERA 0.10 Wind induced changes in the ocean carbon sink Neil Swart, Environment Canada 13 / 17 1 dec. 1 CFSR ERA 20CR R2 R1 0.4 0.3 0.2 0.1 0.0 0.1 0.2 0.3 0.4 Trend (Pg yr 1 dec. 1 ) b) MERRA CFSR ERA 20CR R2 R1 R1 R2 20CR ERA CFSR MERRA 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00 Pg yr 1 dec. 1
The bias in CMIP3 pre-industrial winds CMIP3 winds Observed winds UVic ESCM Control run ( 1) UVic ESCM CMIP3 experiments ( 18) N. C. Swart and J. C. Fyfe (Jan. 2012b), Ocean carbon uptake and storage influenced by wind bias in global climate models, Nature Clim. Change, 2. Wind induced changes in the ocean carbon sink Neil Swart, Environment Canada 14 / 17
The effect of CMIP3 wind-stress biases on ocean carbon Ocean Atmosphere Year Year N. C. Swart and J. C. Fyfe (Jan. 2012b), Ocean carbon uptake and storage influenced by wind bias in global climate models, Nature Clim. Change, 2. Wind induced changes in the ocean carbon sink Neil Swart, Environment Canada 15 / 17
The effect of CMIP5 wind biases on ocean carbon Wind induced changes in the ocean carbon sink Neil Swart, Environment Canada 16 / 17
Conclusions 1. Intensifying westerlies reduce ocean carbon uptake, but... 2. observed and simulated changes in the westerlies are highly uncertain. OBGCM estimates of ocean carbon uptake depend on choice of forcing. Carbon uptake differences in CMIP ESMs stem partly from wind spread. 3. the wind feedback is sensitive to the eddy parameterization scheme in coarse resolution models. Wind induced changes in the ocean carbon sink Neil Swart, Environment Canada 17 / 17