North Atlantic RAPiD Deglacial Paired Mg/Ca-d18O and d18Osw-SST Reconstructions Thornalley, D.J.R.; McCave, I.N.; Elderfield, H. Thornalley, D.J.R. McCave, I.N. Elderfield, H. Sea Surface Temperature Reconstruction abrupt climate change earth science/paleoclimate/climate reconstructions|paleoceanography (depth at sample start,null,null,centimeter,null,climate reconstructions|paleoceanography,null,null,N,null) earth science/paleoclimate/climate reconstructions|paleoceanography (depth at sample end,null,null,centimeter,null,climate reconstructions|paleoceanography,null,null,N,null) earth science/paleoclimate/climate reconstructions|paleoceanography (age,null,null,calendar kiloyear before present,null,climate reconstructions|paleoceanography,null,null,N,present defined as 2000 CE) earth science/paleoclimate/paleoceanography (delta 18O,Globigerina bulloides,null,per mil VPDB,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleoceanography (delta 18O,Globigerina bulloides,null,per mil VPDB,null,paleoceanography,corrected,null,N,0.6 per mil subtracted) earth science/paleoclimate/paleoceanography (magnesium/calcium,Globigerina bulloides,null,millimole per mole,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleoceanography (delta 18O,Globorotalia inflata,null,per mil VPDB,null,paleoceanography,null,null,N,corrected for ice volume) earth science/paleoclimate/paleoceanography (Neogloboquadrina pachyderma sinistral,null,null,percent,null,paleoceanography,null,null,N,150-250 microns) earth science/paleoclimate/paleoceanography (delta 18O,Globigerina bulloides,null,per mil VPDB,null,paleoceanography,null,null,N,corrected for ice volume) earth science/paleoclimate/climate reconstructions|paleoceanography (depth,null,null,centimeter,null,climate reconstructions|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,based on G. bulloides) earth science/paleoclimate/paleoceanography (ice rafted debris,null,null,count per gram,null,paleoceanography,null,null,N,excluding volcanics; 150-250 microns; count per gram of dry sediment + 1) earth science/paleoclimate/climate reconstructions|paleoceanography (sea water temperature,magnesium/calcium,null,degree Celsius,null,climate reconstructions|paleoceanography,null,null,N,based on G. inflata) earth science/paleoclimate/paleoceanography (delta 18O,Globorotalia inflata,null,per mil VPDB,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleoceanography (magnesium/calcium,Globorotalia inflata,null,millimole per mole,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean earth science/paleoclimate/paleocean (RAPiD-12-1K>LATITUDE 62.08>LONGITUDE -17.82) (RAPiD-15-4P>LATITUDE 62.2994>LONGITUDE -17.1344) Greenland ice core records indicate that the last deglaciation (~7-21 ka) was punctuated by numerous abrupt climate reversals involving temperature changes of up to 5°C-10°C within decades. However, the cause behind many of these events is uncertain. A likely candidate may have been the input of deglacial meltwater, from the Laurentide ice sheet (LIS), to the high-latitude North Atlantic, which disrupted ocean circulation and triggered cooling. Yet the direct evidence of meltwater input for many of these events has so far remained undetected. In this study, we use the geochemistry (paired Mg/Ca-d18O) of planktonic foraminifera from a sediment core south of Iceland to reconstruct the input of freshwater to the northern North Atlantic during abrupt deglacial climate change. Our record can be placed on the same timescale as ice cores and therefore provides a direct comparison between the timing of freshwater input and climate variability. Meltwater events coincide with the onset of numerous cold intervals, including the Older Dryas (14.0 ka), two events during the Allerød (at ~13.1 and 13.6 ka), the Younger Dryas (12.9 ka), and the 8.2 ka event, supporting a causal link between these abrupt climate changes and meltwater input. During the Bølling-Allerød warm interval, we find that periods of warming are associated with an increased meltwater flux to the northern North Atlantic, which in turn induces abrupt cooling, a cessation in meltwater input, and eventual climate recovery. This implies that feedback between climate and meltwater input produced a highly variable climate. A comparison to published data sets suggests that this feedback likely included fluctuations in the southern margin of the LIS causing rerouting of LIS meltwater between southern and eastern drainage outlets, as proposed by Clark et al. (2001). STUDY NOTES: Paired Mg/Ca and d18O measurements from foraminifera plus reconstructed d18Oseawater and SST from RAPiD cores collected in the North Atlantic south of Iceland. Data collected by David J.R. Thornalley (Univ. of Cambridge) Principal Investigator: I. Nick McCave (Univ. of Cambridge) Cruise CD-159, funded by UK RAPID program Stable isotope values relative to VPDB standard, run in Godwin Laboratory, Univ. of Cambridge Temperature calculated using Mg/Ca = B exp (0.1 × T) B = 0.794 and 0.675 for G. bulloides and G. inflata, respectively d18Osw calculated using Kim and O'Neil (1997), including a 0.6‰ offset for G. bulloides, and VPDB to SMOW conversion of 0.27‰ "Ice-volume corrected" for whole ocean changes using Fairbanks (1989) sea-level curve, assuming a LGM to late Holocene shift of 1 ‰ NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Thornalley, D.J.R. Investigator : McCave, I.N. Investigator : Elderfield, H. 2010-01-18 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/10488 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/thornalley2010/thornalley2010.xls https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/thornalley2010/thornalley2010.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/thornalley2010/thornalley2010.xls https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/thornalley2010/thornalley2010.txt English https://www.ncdc.noaa.gov/paleo/study/10488 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/thornalley2010/thornalley2010.xls https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/thornalley2010/thornalley2010.txt Thornalley, D.J.R., I.N. McCave, and H. Elderfield. 2010. Freshwater input and abrupt deglacial climate change in the North Atlantic. Paleoceanography, 25, PA1201, doi:10.1029/2009PA001772. START YEAR: 21292 cal yr BP * END YEAR: 7004 cal yr BP -17.82 62.08 -17.1344 62.2994