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SUMMARY:Subtropical icebergs\, glacial lakes\, and Heinrich Events: How di
 d meltwater trigger past abrupt climate change? - Dr. Alan Condron\, Unive
 rsity of Massachusetts\, Amherst
DTSTART:20150311T140000Z
DTEND:20150311T150000Z
UID:TALK56642@talks.cam.ac.uk
CONTACT:Dr Alexander Brearley
DESCRIPTION:During the last deglaciation (20\,000 – 6\,000 yrs BP)\, man
 y prominent abrupt climate cooling episodes (e.g. 8.2-kyr-event\, Younger 
 Dryas\, Heinrich Event 1) aligned with times of enormous meltwater and ice
 berg discharge to the North Atlantic. A freshening of the subpolar gyre is
  thought to have weakened the AMOC and initiated a cooling. But exactly ho
 w changes in high latitude runoff impacted the AMOC is unclear. The classi
 c way to model these events has been to look at the response of the AMOC t
 o an instantaneous freshening of the subpolar North Atlantic gyre (50-70N)
 . In this talk I will show that during periods of massive glacial lake dra
 inage\, a large fraction of meltwater would have first been routed to the 
 subtropics. The meltwater would have then been advected northwards to the 
 subpolar gyre\, but mixing with the ambient ocean along the way resulted i
 n the meltwater becoming saltier and less effective at weakening NADW form
 ation. The subtropical pathway simulated by the model is supported by evid
 ence that massive (>300m thick) icebergs drifted along the east coast of N
 orth America to Southern Florida during the last deglaciation. Once the me
 ltwater flood ended\, icebergs were no longer transported to the subtropic
 s\, but became confined to the subpolar gyre (40-50N\; Ruddiman belt). Thi
 s result suggests that iceberg discharge was probably more effective at we
 akening NADW formation and the AMOC than catastrophic glacial outburst flo
 ods due to freshwater being constantly routed closer to sites of NADW form
 ation. I will end the talk by mentioning some of my other research topics\
 , including the development of MITberg (an iceberg model for MITgcm) and p
 lanned Southern Ocean freshwater forcing experiments.
LOCATION:British Antarctic Survey\, Room 307
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