Orca Basin MD02-2550 Deglacial Paired Mg/Ca, d18O, and d18Osw Williams, C.; Flower, B.P.; Hastings, D.W. Williams, C. Flower, B.P. Hastings, D.W. earth science/paleoclimate/paleoceanography (age,null,null,calendar kiloyear before present,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleoceanography (magnesium/calcium,Globigerinoides ruber white,null,millimole per mole,null,paleoceanography,null,null,N,null) earth science/paleoclimate/climate reconstructions|paleoceanography (sea surface temperature,magnesium/calcium,null,degree Celsius,null,climate reconstructions|paleoceanography,null,null,N,using G. ruber white correction) earth science/paleoclimate/paleoceanography (magnesium/calcium,Globigerinoides ruber pink,null,millimole per mole,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleoceanography (delta 18O,Globigerinoides ruber white,null,per mil VPDB,null,paleoceanography,null,null,N,null) earth science/paleoclimate/climate reconstructions|paleoceanography (delta 18O,delta 18O|magnesium/calcium|sea water,null,per mil VSMOW,null,climate reconstructions|paleoceanography,null,null,N,G. ruber white) earth science/paleoclimate/climate reconstructions|paleoceanography (delta 18O,delta 18O|magnesium/calcium|sea water,null,per mil VSMOW,null,climate reconstructions|paleoceanography,corrected,null,N,ice-volume corrected; G. ruber white) earth science/paleoclimate/climate reconstructions|paleoceanography (delta 18O,delta 18O|magnesium/calcium|sea water,null,per mil VSMOW,null,climate reconstructions|paleoceanography,null,null,N,G. ruber pink) earth science/paleoclimate/climate reconstructions|paleoceanography (sea surface temperature,magnesium/calcium,null,degree Celsius,null,climate reconstructions|paleoceanography,null,null,N,using G. ruber pink correction) earth science/paleoclimate/paleoceanography (delta 18O,Globigerinoides ruber pink,null,per mil VPDB,null,paleoceanography,null,null,N,null) earth science/paleoclimate/climate reconstructions|paleoceanography (delta 18O,delta 18O|magnesium/calcium|sea water,null,per mil VSMOW,null,climate reconstructions|paleoceanography,corrected,null,N,ice-volume corrected; G. ruber pink) earth science/paleoclimate/paleoceanography (depth,null,null,centimeter,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean (MD02-2550>LATITUDE 26.9463>LONGITUDE -91.3458) The last deglaciation in the Northern Hemisphere was interrupted by two major stadials, the so-called "Mystery Interval" (17.5-14.5 ka) and the Younger Dryas (12.9-11.7 ka). During these events, the North Atlantic region was marked by cold surface conditions, yet simultaneous glacier and snowline retreat. Rerouting of Laurentide Ice Sheet meltwater from the Gulf of Mexico to an eastern or northern spillway may have reduced meridional overturning circulation at the onset of the Younger Dryas. However, this hypothesis has not been tested for the Mystery Interval. Paired Mg/Ca and 18O measurements on foraminifera from laminated Orca Basin sediments in the Gulf of Mexico, constrained by 35 14C dates, document the timing of meltwater input with subcentennial resolution. Isolating the 18O of seawater (termed 18OGOM) reveals three major melting episodes from ca. 17.5 ka until 12.9 ka, followed by a rapid cessation, consistent with meltwater rerouting at the onset of the Younger Dryas. Conversely, inferred meltwater flow to the Gulf of Mexico during the Mystery Interval does not support a simple routing event, but is consistent with glacier and snowline retreat. We suggest that summer melting of Northern Hemisphere ice sheets during this stadial may have been an important mechanism for enhanced winter sea-ice formation, hypercold winter conditions, and enhanced seasonality in the North Atlantic region. STUDY NOTES: High resolution foraminiferal (Globigerinoides ruber) d18OGOM (ice-volume corrected d18Osw) data from the Orca Basin, in the northern Gulf of Mexico, are used to reconstruct Laurentide Ice Sheet meltwater input during the last deglaciation. Core MD02-2550, Orca Basin, northern Gulf of Mexico: 26°56.78'N, 91°20.75'W, water depth 2248m NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Williams, C. Investigator : Flower, B.P. Investigator : Hastings, D.W. 2012-08-14 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/13214 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/williams2012/williams2012.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/williams2012/williams2012.xls https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/williams2012/williams2012.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/williams2012/williams2012.xls English https://www.ncdc.noaa.gov/paleo/study/13214 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/williams2012/williams2012.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/williams2012/williams2012.xls Williams, C., B.P. Flower, and D.W. Hastings. 2012. Seasonal Laurentide Ice Sheet melting during the "Mystery Interval" (17.5-14.5 ka). Geology, First published on August 9, 2012. doi:10.1130/G33279.1 START YEAR: 18378 cal yr BP * END YEAR: 10731 cal yr BP -91.3458 26.9463 -91.3458 26.9463