The influence of natural variability on future California Current upwelling

Transcript

1. The Influence of Natural Variability on Future California Current Upwelling

   Evaluating human impacts in the presence of internal climate variability Riley X. Brady University of South Carolina Acknowledgements: NOAA Hollings Scholarship Program Ryan Rykaczewski (U. South Carolina) Michael Alexander (NOAA ESRL) Jamie Scott (NOAA ESRL) Giuliana Turi (NOAA ESRL)

2. Ÿ Upwelling Ÿ Uncertainty Ÿ Large Ensemble Ÿ Historical Upwelling

   Ÿ Natural Variability Ÿ SNR Ÿ Summary Ÿ A mechanism exists whereby global greenhouse warming could . . . lead to acceleration of coastal upwelling. (Bakun, 1990) Source: Rykaczewski & Checkley 2008

3. Ÿ Upwelling Ÿ Uncertainty Ÿ Large Ensemble Ÿ Historical Upwelling

   Ÿ Natural Variability Ÿ SNR Ÿ Summary Ÿ Emissions Scenario: How will we emit greenhouse gases in the future? Model Response: How does each model simulate change in response to an identical scenario? Internal (Natural) Variability: How does the climate behave void of human intervention? Source: Hawkins & Sutton 2010 Could this be an underappreciated source of uncertainty?

4. Ÿ Upwelling Ÿ Uncertainty Ÿ Large Ensemble Ÿ Historical Upwelling

   Ÿ Natural Variability Ÿ SNR Ÿ Summary Ÿ By holding the model and emissions scenario constant, we can attribute disparities entirely to internally-generated climate variability. Modified from Kay et al. 2015 1850 Control Member 1 Observations Members 2-35 Generated ensemble with 10-14K air temperature differences Forced with RCP8.5 emissions scenario

5. Ÿ Upwelling Ÿ Uncertainty Ÿ Large Ensemble Ÿ Historical Upwelling

   Ÿ Natural Variability Ÿ SNR Ÿ Summary Ÿ J F M A M J J A S O N D Vertical Velocity (cm/s x 10-4) General spatial and temporal characteristics of upwelling are well-represented in the model. Northern Region Central Region Southern Region J F M A M J J A S O N D Month 15 10 5 0 -5 -10 -15 1941-2000 Mean Vertical Velocity Northern Central Southern 1941-2000 Mean Vertical Velocity by Region

6. Ÿ Upwelling Ÿ Uncertainty Ÿ Large Ensemble Ÿ Historical Upwelling

   Ÿ Natural Variability Ÿ SNR Ÿ Summary Ÿ J F M A M J J A S O N D Vertical Velocity (cm/s x 10-4) General spatial and temporal characteristics of upwelling are well-represented in the model. Northern Region Central Region Southern Region J F M A M J J A S O N D Month 15 10 5 0 -5 -10 -15 1941-2000 Mean Vertical Velocity Northern Central Southern 1941-2000 Mean Vertical Velocity by Region

7. Ÿ Upwelling Ÿ Uncertainty Ÿ Large Ensemble Ÿ Historical Upwelling

   Ÿ Natural Variability Ÿ SNR Ÿ Summary Ÿ Change in Vertical Velocity (cm/s x 10-4) June Total Change in Upwelling (2041-2100) – (1941-2000) June Natural Change in Upwelling (2041-2100) – (1941-2000) Forced Natural Total Change in Vertical Velocity (cm/s x 10-4)

8. Ÿ Upwelling Ÿ Uncertainty Ÿ Large Ensemble Ÿ Historical Upwelling

   Ÿ Natural Variability Ÿ SNR Ÿ Summary Ÿ Coastal Grid-Cell A Signal-to-Noise Ratio quantifies the relative strength of anthropogenic climate change. Signal (S) = ∆ Noise (N) = ∆ N = 35 1∘ 1∘ ∆$ %∆& ≡ ( ) > is considered a significant emergence of the signal. (There is a 95% chance that the change in upwelling will be detectable in the presence of natural variability)

9. Ÿ Upwelling Ÿ Uncertainty Ÿ Large Ensemble Ÿ Historical Upwelling

   Ÿ Natural Variability Ÿ SNR Ÿ Summary Ÿ Changes in upwelling vary by season and location. 46N 42N 38N 34N 30N Historical (1941-2000) 15 10 5 0 -5 -10 -15 Future (2041-2100) 4 0 -4 2 -2 Future (2041-2100) – Historical (1941-2000) J M M J S N J M M J S N J M M J S N SNR >2 Vertical Velocity (cm/s x 10-4) Change in Vertical Velocity (cm/s x 10-4)

10. Summary Probabilistic forecasts accommodate for uncertainty intrinsic to the climate

    system. Ÿ Upwelling Ÿ Uncertainty Ÿ Large Ensemble Ÿ Historical Upwelling Ÿ Natural Variability Ÿ SNR Ÿ Summary Ÿ The sign of change in upwelling may vary meridionally and seasonally. Natural variability can largely impact the magnitude of change in California Current Upwelling.

11. Future Direction What changes to the position, intensity, and areal

    coverage of the North Pacific High produce the forced and individual responses? Ÿ Upwelling Ÿ Uncertainty Ÿ Large Ensemble Ÿ Historical Upwelling Ÿ Natural Variability Ÿ SNR Ÿ Summary Ÿ