Evidence Linking Arctic Amplification with Changing Weather Patterns in Mid-Latitudes

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1 Evidence Linking Arctic Amplification with Changing Weather Patterns in Mid-Latitudes Jennifer Francis Institute of Marine and Coastal Sciences Rutgers, the State University of New Jersey Steve Vavrus Center for Climatic Research University of Wisconsin-Madison

2 Chain of Events Linking Arctic Amplification (AA) with Increased Extreme Weather in Mid-Latitudes Arctic Amplification More persistent weather patterns, extremes more likely Poleward temperature gradient weakening Larger waves progress eastward more slowly Upper-level westerly winds decreasing Amplitude of waves increasing, blocking more likely Upper-level flow becoming more wavy

3 Arctic Amplification Winter JFM Spring AMJ Summer JAS Fall OND T 1000mb o N o N OND JAS mb Thickness 2000 to 2012

4 Poleward temperature gradient weakening OND Trends in poleward thickness gradient ( hpa) from 1979 to PDO? % change in 500 mb zonal winds in 4 x CO 2 run of CCSM4 AMO? Zonal winds decreasing where gradient weakens 0 Winter -10 Fall Spring Summer hpa U anom. 30 o N 45 o N 60 o N

5 Upper-level flow becoming more meridional OND CCSM4 4 x CO 2 Change in Meridional Wind o N Trends in meridional component Winter of the +33% 500 Spring hpa wind ( % to 2011) Summer +21% Fall +19% Less wavy More wavy

6 Amplitude of waves increasing, blocking more likely Francis and Vavrus, GRL 2012

7 Amplitude of waves increasing, blocking more likely OND Northern Hemisphere Ridge peaks Blocking More likely? from Barnes (2013) 500mb heights Trough bottoms Trends in Amplitude Amplitude

8 Amplitude of Rossby waves increasing, blocking more likely March 2012 Heatwave Blocking => Extreme Waviness A typical blocking high Unprecedented Spain flooding Record snowfall in Japan Jan Polar Vortex

9 Types of Extreme Waviness Typical blocking Extreme Contour Folding pattern Amplitude Count extreme waves exceeding 40 o latitude

10 Increasing frequency of large waves OND mb Northern Thickness Hemisphere Anomalies U500 High-amplitude waves r = Folding contours High-Amp Waves Folding contours

11 Increasing frequency of large waves CCSM4 HadGEM Do GCMs capture this behavior? => 4 members of CMIP5: OND Northern Hemisphere U500 High-amplitude waves MPI GFDL Folding contours Models seem to capture about the right number, some have increasing trends, some not.

12 Attack of the Polar Vortex Early January 2014 Warm Warm Cold

13 Summary Some links in the chain are solid: AA is emerging in all seasons, strongest in fall and winter Poleward gradients weakening, but seasonally and spatially variable Where gradients weaken, upper-level zonal winds decrease, flow becomes more meridional (wavy) Others not so much: Changing amplitude and propagation speed of large-scale waves, mechanism linking to AA unconfirmed Changing frequency of persistent weather patterns? Interactions among AA and other large-scale influences (ENSO, PDO, NAM, PNA, stratosphere, etc.)? Thank-you!

14 Extras

15 More persistent weather patterns, extremes more likely Winter Summer cold heat extremes waves Fall Summer and loss winter of sea-ice loss and snow associated cover with associated cold extremes, with heat waves, but influence but seaice influence ice is is of winter stronger Tang, Tang, Zhang, Zhang, and Francis, Yang, and Nature Francis, Cl. ERL Ch. (2013)

16 Upper-level flow becoming more meridional OND CCSM4 4 x CO 2 Change in Meridional Trends in meridional Wind component of the N 500 Winter hpa wind ( % to 2011) Spring +21% Summer +21% Fall +19% Less wavy More wavy

17 Large-scale waves progress more slowly eastward From Barnes (2013) We find a robust decrease in wave phase speeds in OND, which is consistent with the u500 reductions.

18 An Artifact of the Methodology? mb height with maximum waviness 500 mb height contour used in FV12 Wave amplitude (deg. latitude) from Barnes (2013)

19 An Artifact of the Methodology? Typical 500 hpa pattern in Nov Wave amplitude (deg. latitude) from Barnes (2013) Contour with max waviness has different shape from FV12 s contour in max gradient

20 An Artifact of the Methodology? Contour with max waviness has is 15 o different farther north, shape not from in max FV12 s wind zone, contour not representative in max gradient of jet stream trajectory.

21 Anomalies in zonal-mean heights and zonal winds for OND