The Pacific and Global Climate: Insights into the role of the world’s largest ocean in abrupt climate change

Date & time

1–2pm 10 May 2018

Location

Jaeger 1 Seminar Room, RSES

Speakers

Maureen Walczak (Oregon State University)

Event series

Much remains unresolved concerning the origin and global implications of the episodes of rapid glacial failure in the North Atlantic known as Heinrich Events. Thought to occur during or at the termination of the coldest of the abrupt stadial climate events known as Dansgaard-Oschger cycles, various trigger mechanisms have been theorized, including external forcing in the form of oceanic or atmospheric warming, internal dynamics of the large Laurentide ice sheet, or the episodic failure of another (presumably European) ice sheet. Heinrich events may also be associated with a decrease in North Atlantic deep-water formation. New results from Gulf of Alaska IODP Expedition 341 reveal events of Cordilleran Ice Sheet retreat (based on ice-rafted detritus and sedimentation rates) synchronous with reorganization of ocean circulation (based on benthic-planktic 14C pairs) spanning the past 45,000 years on an independent high-resolution radiocarbon-based chronology. We document the relationship between these Pacific records and the North Atlantic Heinrich events, and find the data show an early Pacific expression of ice sheet instability in the form of pulses of Cordilleran glacial discharge. The Cordilleran IRD events documented at Site U1419 are synchronous with benthic radiocarbon anomalies in the Northeast Pacific throughout MIS-2, indicating a close coupling of ice-ocean dynamics. These data are hard to reconcile with internal triggering in the North Atlantic or Laurentide ice sheet, requiring us to re-think the mechanisms that generate Heinrich events as well as their far-field impacts. 

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