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The Arctic Paradox Photo by Janes Glen Gerberg Weather and Climate Summit Breckenridge, CO -- 8-13 January 2012 or... Arctic Sea Ice: A Tragic Tale of.

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Presentation on theme: "The Arctic Paradox Photo by Janes Glen Gerberg Weather and Climate Summit Breckenridge, CO -- 8-13 January 2012 or... Arctic Sea Ice: A Tragic Tale of."— Presentation transcript:

1 The Arctic Paradox Photo by Janes Glen Gerberg Weather and Climate Summit Breckenridge, CO -- 8-13 January 2012 or... Arctic Sea Ice: A Tragic Tale of Loss and Revenge Jennifer Francis, Rutgers University

2 In the good old days… The new normal. The difference in ice area is ~1,300,000 miles 2.

3 Thats an area covering about 42% of the lower 48. generated by J. Masters

4 …its how can it not ? So, the question is not whether sea-ice loss is affecting large-scale atmospheric circulation… …but, lets back up a bit. How did we get into this mess?

5 from Bill Chapmans The Cryosphere Today

6 The story goes like this…The fossil fuel era began with the industrial revolution… CO 2 Concentration

7 Rothrock and Kwok, 2009 Ice thickness (m) Increasing GHGs and related feedbacks caused ice to gradually thin. Good ol days 1990s

8 Normal conditions Positive AO Index Ice extent in the good ol days was controlled mainly by wind variations... …but the recent thinner ice was defenseless against the attack of the AO+ during the 90s Arctic Oscillation Index Ice-age Movie From NOAAs ClimateWatch

9 Ice Age is a Big Deal because… by Maslanik and Fowler, NSIDC, Arctic Report Card 2011 its a proxy for ice thickness. And THATs a big deal because a thinner ice cover is more easily melted, more easily moved by the wind, and more likely to follow a trajectory of loss as GHGs continue to increase. Thick ice

10 From Stroeve et al. (2011) Climatic Change

11 The thinner ice cover is more mobile and more vulnerable to anomalous wind patterns, like those generated by a high-amplitude jet stream: T HE A RCTIC D IPOLE (Overland and Wang, 2010) 20072008200920102011 Thick ice of the good ol days was much less affected by these wind patterns (Wang et al, 2009)

12 All that new open water absorbs additional solar radiation during spring and summer… …that heats the sea surface and adds yet more fuel to the Arctic fire… Sea surface temps SST AK

13 Summary so far… GHGs = > gradual thinning GHGs = > gradual thinning Natural variability: period of AO+ flushes thick ice out of Arctic in 90s Natural variability: period of AO+ flushes thick ice out of Arctic in 90s Thinner ice cover more easily pushed by winds and melted by anomalous heat fluxes: it cant recover Thinner ice cover more easily pushed by winds and melted by anomalous heat fluxes: it cant recover Additional open water absorbs more sunlight, heats ocean surface, melts more ice Additional open water absorbs more sunlight, heats ocean surface, melts more ice Whats up with all that heat?? Whats up with all that heat?? Ice extent anomaly 1960 1970 1980 1990 2000

14 During autumn and winter, energy - lots more than normal – is being transferred to the atmosphere as sensible heat, water vapor, and infrared radiation.

15 …its how can it not ? Which brings us back to the question: Its not whether sea-ice loss is affecting large- scale atmospheric circulation… And what are the mechanisms ? Budikova, Global Planet. Change, 2009 Honda et al, GRL, 2009 Bhatt et al, Geophys. Mono., 2008Overland and Wang, Tellus, 2010 Deser et al, J. Climate, 2007, 2010 Petoukhov and Semenov, JGR, 2010 Francis et al, GRL, 2009Seierstad and Bader, Clim. Dyn., 2009 Higgins and Cassano, JGR, 2009Sokolova et al, GRL, 2007

16 This study focuses on the connections between Arctic Amplification and extreme weather in northern hemisphere mid-latitudes Extreme weather = high-amplitude, slow-moving upper-level patterns that cause persistent weather conditions Coldest days in Tampa 500 hPa Hottest days in Atlanta 500 hPa Wettest days in Chicago 500 hPa

17 OND Data obtained from NCEP/NCAR Reanalysis, Kalnay et al. (1996), NOAA/ESRL Physical Sciences Division, Boulder CO from their web site at http://www.esrl.noaa.gov/psd 700 Temperature anomaly at 700 mb during fall 2000 to 2010 1000-500 hPa thickness anomaly during fall 2000 to 2010 … and winter 850 Temperature anomaly at 850 mb during fall 2000 to 2010 Near-surface temperature anomaly during fall 2000 to 2010 Poleward 1000-500 hPa thickness gradient North Atlantic High ice Low ice 9 10 11 12 1 2 3 month North Pacific High ice Low ice 9 10 11 12 1 2 3 month from Francis et al, GRL, 2009

18 Connecting the dots (focus on fall and winter): Thickness increases are larger in high latitudes than in mid-latitudes => expect 2 main effects: mid-latitudes => expect 2 main effects: First effect: Weaker poleward temperature gradient => weaker zonal wind speeds. Do we see that? => weaker zonal wind speeds. Do we see that? Yep. 1000-500 hPa thickness difference between 80-60 o N and 50-30 o N N. America and N. Atlantic OND JFM OND JAS AMJ Zonal mean wind at 500 hPa, 40-60 o N 14 12 10 8 ~ 20% less

19 Weaker zonal wind speeds favor slower moving Rossby waves, which leads to more persistent stuck weather patterns. Sound familiar?

20 Second effect: Larger warming at high latitudes causes peaks of ridges to elongate Wave amplitude increases Higher-amplitude waves progress more slowly More persistent weather patterns 500 hPa isopleth

21 Is this really happening? Lets dig deeper: Focus on 500 hPa heights – integrates effects of heating in lower troposphere. Focus on 500 hPa heights – integrates effects of heating in lower troposphere. Select narrow height range that captures trajectory Select narrow height range that captures trajectory Analyze temporal and spatial behavior Analyze temporal and spatial behavior All data for this work are from the NCEP/NCAR Reanalysis, Kalnay et al. (1996), obtained from the NOAA/ESRL Physical Sciences Division, Boulder CO at http://www.esrl.noaa.gov/psd

22 Is wave amplitude really increasing? Wave amplitude measured as seasonal- mean difference in latitude between ridges and troughs at each longitude Amplitude is increasing almost everywhere Trends (OND)

23 How has the spatial and temporal distribution of 500 hPa heights changed during autumn? Increased ridging north of 50 o N Decreased troughs Has wave amplitude increased or has whole pattern shifted northward?

24 Maximum latitude of ridges increasing Bottoms of troughs steady since ~1980 Amplitude increasing steadily since ~1980 High correln with ice

25 Where are northward elongations occurring? Ridge peaks located mainly over western N. America and eastern N. Atlantic Ridge peaks located mainly over western N. America and eastern N. Atlantic Number of ridge points north of 50 o N increasing west of Greenland Number of ridge points north of 50 o N increasing west of Greenland Autumn (OND) 300 340 260 Trends (OND)

26 Could this be contributing to increasing max and min fall temperatures in U.S. since mid-1990s?? 1920 1940 1960 1980 2000 T- MIN T- MAX 1920 1940 1960 1980 2000 from NCDC/NOAA Climate Extremes Index

27 Now lets take a look at winter: Increased ridging north of 40 o N Decreased troughs Decreased troughs Increased wave amplitude ? Increased wave amplitude ?

28 Maximum latitude of ridges increasing Bottoms of troughs shifting northward Bottoms of troughs shifting northward Amplitude increasing steadily since late 1980s Amplitude increasing steadily since late 1980s Weak correln with AO Weak correln with AO Winter (JFM) AO Index r = 0.3 r = 0.7 r = 0.1

29 Sunspots from NOAA/CPC

30 300 340 260 Winter (JFM) Ridge peaks located mainly over western N. America and eastern N. Atlantic Ridge peaks located mainly over western N. America and eastern N. Atlantic Number of ridge points north of 40 o N increasing, especially over N. America Number of ridge points north of 40 o N increasing, especially over N. America Trends (JFM)

31 300 340 260 Winter (JFM) troughs Troughs consolidating along US east coast Troughs consolidating along US east coast Fewer (weaker) troughs over west/central US and eastern N. Atlantic Fewer (weaker) troughs over west/central US and eastern N. Atlantic Trends (JFM)

32 What about summer? from Rutgers Snow Lab Snow is melting earlier over high- latitude land Soil is exposed to sunlight earlier, so it dries and warms earlier Soil is exposed to sunlight earlier, so it dries and warms earlier Further Arctic amplification Further Arctic amplification Summersurface T anoms

33 Summer (JAS) Ridge peaks and troughs shifting northward Ridge peaks and troughs shifting northward Amplitude increasing Amplitude increasing High correlations with May snow area High correlations with May snow area May snow area r = -0.9 r = -0.7

34 300 340 260 Summer (JAS) Preferential ridging over western N. America Preferential ridging over western N. America Ridging increasing generally, especially in recent years and in western N. Atlantic (=> Greenland?) Ridging increasing generally, especially in recent years and in western N. Atlantic (=> Greenland?) Trends (JAS)

35 Could this be contributing to increasing max and min summer temperatures in U.S.? 1920 1940 1960 1980 2000 T- MIN T- MAX 1920 1940 1960 1980 2000 from NCDC/NOAA Climate Extremes Index

36 Summary Arctic Amplification High latitudes warming more than mid-latitudes, especially in fall and winter, but also in summer over land => Poleward thickness gradient weakening Weaker upper-level, zonal-mean flow, reduced phase speed Peaks of upper-level ridges elongate northward, wave amplitude increases Rossby waves progress more slowly Rossby waves progress more slowly Weather conditions more persistent Weather conditions more persistent Increased probability of extremes: cold spells, heat waves, flooding, prolonged snowfall, and drought Increased probability of extremes: cold spells, heat waves, flooding, prolonged snowfall, and drought J.A. Francis – Rutgers Univ. Weather and Climate Summit, 2012

37 Northern Hemisphere, OND

38 Northern Hemisphere, JFM (5400)


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