The Younger DryasThe Younger Dryasandand
Rapid Climate ChangeRapid Climate Change
Bruno TremblayBruno Tremblay
McGill UniversityMcGill University
DyasOctopetalaDyasOctopetala
Last seen in the pollen record of Northern Europe between 11,600 and 12,800 BP
Central Greenland Central Greenland ClimateClimate
Tem
pera
ture
(C
)
Acc
umul
atio
n (c
m/y
ear)
Age (Kyr BP)
Abrupt change
EvidenceEvidence
10-15 C cooling at Greenland Summit. Other 10-15 C cooling at Greenland Summit. Other ocean sediment proxi confirms this with ocean sediment proxi confirms this with several degrees of ocean cooling in the N. several degrees of ocean cooling in the N. Atl.Atl.
Cooling observed off the coast of Portugal Cooling observed off the coast of Portugal and as far south as the Cariaco Basin off the and as far south as the Cariaco Basin off the coast of Venezuela, off the coast of Santa coast of Venezuela, off the coast of Santa Barbara CA, and in cave records from China.Barbara CA, and in cave records from China.
Slow down of the thermohaline circulation, Slow down of the thermohaline circulation, and perhaps even a complete shut off.and perhaps even a complete shut off.
Problematic Problematic Signal is Global - Signal is Global - Synchroneous!Synchroneous!
Dating of Antarctica ice core is not Dating of Antarctica ice core is not very good. Northern Hemisphere very good. Northern Hemisphere signal and Antarctic cooling could be signal and Antarctic cooling could be one and the same.one and the same.
New Zealand ice advance was dated at New Zealand ice advance was dated at around the same time as the YD.around the same time as the YD.
Global signal – Our previous Global signal – Our previous mechanism no longer match the data.mechanism no longer match the data.
New Technique to New Technique to synchronize synchronize Greenland - Greenland -
Antarctica Ice CoreAntarctica Ice Core
Use Use methane methane data in data in both both cores.cores.
Recent FindingsRecent FindingsBarrow et al, Nature, 2007.Barrow et al, Nature, 2007.
New Dating of the New Zealand glacial New Dating of the New Zealand glacial advance is much more recent than the advance is much more recent than the YD. YD.
Confirmed by nearby ocean sediment that Confirmed by nearby ocean sediment that show continued warming during the YDshow continued warming during the YD
So now we have data from both Northern So now we have data from both Northern and Southern Hemisphere in line with the and Southern Hemisphere in line with the modelmodel
Do we have a complete Do we have a complete understanding of the understanding of the
event?event? Not quite!Not quite! We still don’t know what triggered We still don’t know what triggered
the eventthe event A shift in the drainage pathways of lake A shift in the drainage pathways of lake
AgasizAgasiz A solar trigger or a Pacific trigger (Clement A solar trigger or a Pacific trigger (Clement
et al, 2001)et al, 2001) A cometary impact?A cometary impact?
Evidence – Comet ImpactEvidence – Comet Impact12,900 BP12,900 BP
Glass like carbon
Carbon Spherule
Magnetic grain rich in Ir
More...More...
http://www.realclimate.org/http://www.realclimate.org/index.php/archives/2007/10/index.php/archives/2007/10/younger-dry-as-dust/younger-dry-as-dust/
Sea Level Rise StorySea Level Rise Story
Difficulty in measuring sea levelDifficulty in measuring sea level Ice flow on glacierIce flow on glacier Region of uplift-downlift. See Region of uplift-downlift. See
Ruddiman discussion.Ruddiman discussion. GRACEGRACE Antarctica without ice!Antarctica without ice!