1. Abrupt changes in atmospheric circulation from Greenland Ice Cores

2. Greenland Summit Location
NSF Site = Summit Camp = GISP2 core
European Site = True Summit = GRIP core

3. Summit is very FLAT Elevation = 3200 meters
Annual Mean Temperature about -30 C

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

5. Composite of 13 DO events Composite annual mean warming of 12 C
[Stuvier, 2000]
Composite annual mean warming of 12 C
Half point of transition reached in 2 years

6. Spatial Extent of DO Events- Non Atlantic
coincident changes in monsoon strength observed half way around the world
other proxy records indicate coincident climate changes
Santa Barbara- oxygen 18 in n pachyderma
THIS COULD
BE CRAP!
INCREASING
MONSOON
Time
[Peterson, 2000]

7. Other things in the snow
Calcium Dust in air (insoluble suspended solids)
Sodium Sea Salts in air

8. Calcium (Insoluble dust concentration) Record
[Fuhrer, 1999]
Clear- abrupt changes in dust concentration across DO events
-as temperatures warm, atmospheric dust load goes down

9. Scatter Plot of ice core oxygen isotope and calcium concentration
Stadial (Cold)
Data Points
Interstadial (Warm) Data
[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

10. The dust burden could change by
Change in source area
Change in size of source area
Change in atmospheric transport time
Change in atmospheric residence time
Change in magnitude of flux from source to atmosphere- [WINDS OVER SOURCE]
[Svenson, 2000]
[Fuhrer, 1999]

11. Dust Diameter across DO events
Modal
Dust
Diameter
Interstadial (warm)
Staidal (cold)
[Ruth, 2003]
Dust concentration
More Dust = Larger Dust BUT
Changes in dust diameter are not nearly as big [stadials and interstadials overlap]
DIFFERENT PHYSICAL MECHANISMS IN CLIMATE SYSTEM ARE AT PLAY

12. What changes diameter of dust
affects concentration but not size distribution
Winds over source region
Change in residence time
Change in transport time from source to deposition
doesn’t change dry deposition
Suggests transport was 1.5 times faster during cold stadials

13. Sea Salt concentration change
[Mogenson, 2002]
Sea salts were 2x greater during cold stadials

14. What could change sea salts
Storms in the Atlantic
Likely up during cold stadials
Residence time (strength of wet deposition)
Change in sea salt concentration (2X) give upper bound
on the change in residence time between
stadial and interstadial

15. The dust burden could change by
Change in source area
Change in size of source area
Change in atmospheric transport time
Change in atmospheric residence time
Change in magnitude of flux from source to atmosphere- [WINDS OVER SOURCE]
[Svenson, 2000]
[Fuhrer, 1999]
X 1.5 (size)
X 2 (salts)
Must have changed by factor of 3-4 to explain
X10 change in total dust
(30%-40% change in spring time winds over Asia)

16. Conclusions
Ice cores show rapid, concurrent changes in temperature, dust load, dust grain size and sea salts
Dust load changes can only be explained by changes in atmospheric circulation which are hemispheric in extent
Any proposed mechanism should explain the dust data