St. Lawrence Estuary Younger Dryas Geochemical Data Carlson, A.E.; Clark, P.U.; Haley, B.A.; Klinkhammer, G.P.; Simmons, K.R.; Brook, E.J.; Meissner, K.J. Carlson, A.E. Clark, P.U. Haley, B.A. Klinkhammer, G.P. Simmons, K.R. Brook, E.J. Meissner, K.J. earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean (HU90031-044>LATITUDE 44.657>LONGITUDE -55.619) (HU90031-047>LATITUDE 45.852>LONGITUDE -57.626) The Younger Dryas cold interval represents a time when much of the Northern Hemisphere cooled from ~12.9 to 11.5 kiloyears B.P. The cause of this event, which has long been viewed as the canonical example of abrupt climate change, was initially attributed to the routing of freshwater to the St. Lawrence River with an attendant reduction in Atlantic meridional overturning circulation. However, this mechanism has recently been questioned because current proxies and dating techniques have been unable to confirm that eastward routing with an increase in freshwater flux occurred during the Younger Dryas. Here we use new geochemical proxies (ŋMg/Ca, U/Ca, and 87Sr/86Sr) measured in planktonic foraminifera at the mouth of the St. Lawrence estuary as tracers of freshwater sources to further evaluate this question. Our proxies, combined with planktonic ŋ18Oseawater and ŋ13C, confirm that routing of runoff from western Canada to the St. Lawrence River occurred at the start of the Younger Dryas, with an attendant increase in freshwater flux of 0.06 ą 0.02 Sverdrup (1 Sverdrup = 10^6 m3ˇs-1). This base discharge increase is sufficient to have reduced Atlantic meridional overturning circulation and caused the Younger Dryas cold interval. In addition, our data indicate subsequent fluctuations in the freshwater flux to the St. Lawrence River of ~0.06-0.12 Sverdrup, thus explaining the variability in the overturning circulation and climate during the Younger Dryas. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Carlson, A.E. Investigator : Clark, P.U. Investigator : Haley, B.A. Investigator : Klinkhammer, G.P. Investigator : Simmons, K.R. Investigator : Brook, E.J. Investigator : Meissner, K.J. 2007-01-01 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/8457 https://www1.ncdc.noaa.gov/pub/data/paleo/paleocean/by_contributor/carlson2007 https://www1.ncdc.noaa.gov/pub/data/paleo/paleocean/by_contributor/carlson2007 English https://www.ncdc.noaa.gov/paleo/study/8457 https://www1.ncdc.noaa.gov/pub/data/paleo/paleocean/by_contributor/carlson2007 Carlson, A.E., P.U. Clark, B.A. Haley, G.P. Klinkhammer, Simmons, K., E.J. Brook, and K.J. Meissner. 2007. Geochemical proxies of North American freshwater routing during the Younger Dryas cold event.Proceedings of the National Academy of Sciences, 104(16), 6556-6561. START YEAR: 14872 cal yr BP * END YEAR: 0 cal yr BP -57.626 44.657 -55.619 45.852