1. Evidence for the Jumping Jet Hypothesis of abrupt climate Change

2. Evidence of Abrupt Climate Change- DO Events from GISP 2
Warmer
TIME
(Stuiver and Grooves, 2000)
(Stuiver and Grooves, 2001)
At least 20 DO (Dansgaard-Oeschger) events recorded in the last 120 Kyears (Rahmstorf, 2003)
Rapid warming followed by slow cooling then rapid cooling

3. Dust In Greenland During Abrupt Climate Change
Warmer
More
Dust
Time
Cold times in Greenland are dustier (order of magnitude)
Courtesy of Stephen Barker

4. High resolution abrupt warming
Temperature
More
Dust
Warm
Dust
Less
Dust
50 years
Time
Cold
Dust changes are more abrupt and precede temperature changes
Fuhrer, 1999

5. Scatter Plot of ice core oxygen isotope and calcium concentration
More
Dust
Stadial (Cold)
Data Points
Interstadial (Warm) Data
Warmer
[Fuhrer,1999]
Temperature (oxygen isotopes) overlap between regimes but calcium does not
CLIMATE REGIME IS BEST CHARACTERIZED BY ATMOSPHERC DUST LOAD – FACTOR OF 10 change

6. Ideas that do NOT explain dust changes
Strength of Deposition- Wet deposition is dominant [Steffenson, 1997]
Change in source area- all dust is from Asia [Svenson, 2000]
Change in size of source area- Greenland change is too quick [Fuhrer, 1999]
Stronger winds- sea salts in core change moderately [Mogenson, 2002]

7. Could the Laurentide Ice Sheet Cause the Jet Stream to Jump?
Jet flows to the south of the
topography- similar to the
Modern day circulation
Jet flows to the north of
the topography

8. Force A General Circulation Model with glacial conditions and two different ice sheets
Courtesy Camille Li

9. How does the atmospheric circulation change- Stationary waves

10. How does the Atlantic Jet And storm track change?
Small Ice
Contours =
Jet speed (m/s)
At 300 hPa
Colors =
Storm activity
(V’T’ at 700 hPa)
Big Ice
K m/s

11. Back Trajectories from Greenland
Small Ice
Back
Trajectories
From
Summit
Big Ice
Origin
(15 days
At 500 hPa)
The Dust
Highway

12. How sensitive is the transition in atmospheric circulation to the ice sheet topography?
Courtesy Joe Barsugli

13. Conclusions
The dust changes in Greenland during abrupt climate change are more rapid and precede the temperature changes
We speculate these changes indicate a change in the atmospheric circulation regime
A general circulation model shows that the Jet Stream may jump during the glacial in a way which may be consistent with the change in dust loading

14. Courtesy Stephen Barker