1. The Younger Dryas and Rapid Climate Change Bruno Tremblay McGill University bruno.tremblay@mcgill.ca

3. DyasOctopetala Last seen in the pollen record of Northern Europe between 11,600 and 12,800 BP

4. Central Greenland Climate Temperature (C) Accumulation (cm/year) Age (Kyr BP) Abrupt change

5. Proxy Evidence NH

6. Global THC

7. Evidence 10-15 C cooling at Greenland Summit. Other ocean sediment proxi confirms this with several degrees of ocean cooling in the N. Atl. 10-15 C cooling at Greenland Summit. Other ocean sediment proxi confirms this with several degrees of ocean cooling in the N. Atl. Cooling observed off the coast of Portugal and as far south as the Cariaco Basin off the coast of Venezuela, off the coast of Santa Barbara CA, and in cave records from China. Cooling observed off the coast of Portugal and as far south as the Cariaco Basin off the coast of Venezuela, off the coast of Santa Barbara CA, and in cave records from China. Slow down of the thermohaline circulation, and perhaps even a complete shut off. Slow down of the thermohaline circulation, and perhaps even a complete shut off.

8. Sea Level Rise Time Series

9. Parenthesis Carbon Dating

10. But how Global is this signal?

11. Problematic Signal is Global - Synchroneous! Dating of Antarctica ice core is not very good. Northern Hemisphere signal and Antarctic cooling could be one and the same. Dating of Antarctica ice core is not very good. Northern Hemisphere signal and Antarctic cooling could be one and the same. New Zealand ice advance was dated at around the same time as the YD. New Zealand ice advance was dated at around the same time as the YD. Global signal – Our previous mechanism no longer match the data. Global signal – Our previous mechanism no longer match the data.

12. New Technique to synchronize Greenland - Antarctica Ice Core Use methane data in both cores. Use methane data in both cores.

13. Ice Core Locations Antarctica

14. GISP2 and Dome C Ice Core data Bipolar Sea- Saw in the Ocean

15. Recent Findings Barrow et al, Nature, 2007. New Dating of the New Zealand glacial advance is much more recent than the YD. New Dating of the New Zealand glacial advance is much more recent than the YD. Confirmed by nearby ocean sediment that show continued warming during the YD Confirmed by nearby ocean sediment that show continued warming during the YD So now we have data from both Northern and Southern Hemisphere in line with the model So now we have data from both Northern and Southern Hemisphere in line with the model

16. Do we have a complete understanding of the event? Not quite! Not quite! We still don’t know what triggered the event We still don’t know what triggered the event A shift in the drainage pathways of lake Agasiz A shift in the drainage pathways of lake Agasiz A solar trigger or a Pacific trigger (Clement et al, 2001) A solar trigger or a Pacific trigger (Clement et al, 2001) A cometary impact? A cometary impact?

17. Drainage Pathways Lake Agassiz

18. Lake Agassiz Shoreline

19. Evidence Digital Elevation Model – Southern Outlet

20. Evidence – Comet Impact 12,900 BP Glass like carbon Carbon Spherule Magnetic grain rich in Ir

21. More... http://www.realclimate.org/index.php/archives /2007/10/younger-dry-as-dust/ http://www.realclimate.org/index.php/archives /2007/10/younger-dry-as-dust/

22. Sea Level Rise Story Difficulty in measuring sea level Difficulty in measuring sea level Ice flow on glacier Ice flow on glacier Region of uplift-downlift. See Ruddiman discussion. Region of uplift-downlift. See Ruddiman discussion. GRACE GRACE Antarctica without ice! Antarctica without ice!