What controls the variability of CO2 fluxes in Eastern Boundary Upwelling Systems?

Transcript

1. What controls the variability of CO2 fluxes in Eastern Boundary

   Upwelling Systems? Riley Brady Nicole Lovenduski, Michael Alexander, Michael Jacox, Nicolas Gruber Ocean Sciences Meeting February 15th, 2018 Institute o f Arctic and Alpin e Research INSTAAR

2. Boundary Current Undercurrent CO2 outgassing Eastern Boundary Upwelling Systems have

   complex and variable carbon dynamics, leading to high rates of CO2 exchange with the atmosphere. Adapted from Pennington et al. 2005 CO2 uptake Offshore Ekman Transport High DIC Low DIC * * * * * * * * Biological Activity

3. Absolute Magnitude of Internal Variability Std. Dev. of FCO2 residuals

   [mol/m2/yr] CO2 fluxes in upwelling systems are characterized by significant internal variability that tends to be larger than the seasonal cycle. Brady et al. 2018, in prep

4. What controls this CO2 flux variability?

5. The CESM Large Ensemble provides 34 independent simulations with a

   unique representation of the natural climate system.

6. CESM-LENS captures the general characteristics of CO2 fluxes in EBUS.

   Observations Model Brady et al. 2018, in prep

7. The North Pacific Gyre Oscillation (NPGO) is the primary driver

   of California Current variability. Corr(SSTa, FCO2 ) r value Brady et al. 2018, in prep

8. Corr(SSTa, FCO2 ) El Niño modulates CO2 fluxes in the

   Humboldt Current. r value Brady et al. 2018, in prep

9. Corr(SLPa, FCO2 ) r value AMOC and the NAO control

   the variability of the Canary Current. Brady et al. 2018, in prep

10. What are the mechanisms that control the CO2 flux anomalies?

11. Gas transfer velocity (Wind Speed)2 oceanic pCO2 SST Salinity Total

    Carbon Alkalinity Freshwater CO2 flux is complex and is driven by a myriad of factors, including ocean state, circulation, biology, and chemistry.

12. 1 std. dev. Direct ∆FCO2 The Humboldt Current experiences anomalous

    uptake during El Niño. The large reduction in DIC is the dominating term. Brady et al. 2018, in prep

13. 1 std. dev. Direct ∆FCO2 Anomalous outgassing occurs in the

    California Current during a positive NPGO. SST and smaller positive factors outweigh the reduction in DIC. Brady et al. 2018, in prep

14. 1 std. dev. Direct ∆FCO2 Anomalous outgassing in the Canary

    Current occurs during a positive NAO. Increased winds and the supply of DIC drive this change. Brady et al. 2018, in prep

15. Conclusions EBUS have significant internal variability in FCO2 relative to

    the coastal oceans and much of the global oceans. This internal variability tends to be larger than the seasonal cycle.

16. Conclusions EBUS have significant internal variability in FCO2 relative to

    the coastal oceans and much of the global oceans. This internal variability tends to be larger than the seasonal cycle. Humboldt Current anomalies are modulated by ENSO (R = -0.42). Large reductions in DIC cause anomalous uptake during El Niño.

17. Conclusions EBUS have significant internal variability in FCO2 relative to

    the coastal oceans and much of the global oceans. This internal variability tends to be larger than the seasonal cycle. Humboldt Current anomalies are modulated by ENSO (R = -0.42). Large reductions in DIC cause anomalous uptake during El Niño. California Current FCO2 anomalies are most prominently driven by the NPGO (R = -0.5). Colder SSTs and smaller negative terms outweigh DIC enhancement to promote anomalous uptake during positive events.

18. Conclusions EBUS have significant internal variability in FCO2 relative to

    the coastal oceans and much of the global oceans. This internal variability tends to be larger than the seasonal cycle. Humboldt Current anomalies are modulated by ENSO (R = -0.42). Large reductions in DIC cause anomalous uptake during El Niño. California Current FCO2 anomalies are most prominently driven by the NPGO (R = -0.5). Colder SSTs and smaller negative terms outweigh DIC enhancement to promote anomalous uptake during positive events. Canary Current anomalies are associated with the NAO (R = 0.28). A strong Azores High supplies more DIC to the system and intensifies wind stress, causing anomalous outgassing.