Baffin Island 1400 Year Ice Margin Radiocarbon Data Miller, G.H.; Geirsdóttir, A.; Zhong, Y.; Larsen, D.J.; Otto-Bliesner, B.L.; Holland, M.M.; Bailey, D.A.; Refsnider, K.A.; Lehman, S.J.; Southon, J.R.; Anderson, C.; Björnsson, H.; Thordarson, T. Miller, G.H. Geirsdóttir, A. Zhong, Y. Larsen, D.J. Otto-Bliesner, B.L. Holland, M.M. Bailey, D.A. Refsnider, K.A. Lehman, S.J. Southon, J.R. Anderson, C. Björnsson, H. Thordarson, T. Arctic earth science/paleoclimate/others (M09-B107v>LATITUDE 71.04155>LONGITUDE -74.66817) Northern Hemisphere summer temperatures over the past 8000 years have been paced by the slow decrease in summer insolation resulting from the precession of the equinoxes. However, the causes of superposed century-scale cold summer anomalies, of which the Little Ice Age (LIA) is the most extreme, remain debated, largely because the natural forcings are either weak or, in the case of volcanism, short lived. Here we present precisely dated records of ice-cap growth from Arctic Canada and Iceland showing that LIA summer cold and ice growth began abruptly between 1275 and 1300 AD, followed by a substantial intensification 1430-1455 AD. Intervals of sudden ice growth coincide with two of the most volcanically perturbed half centuries of the past millennium. A transient climate model simulation shows that explosive volcanism produces abrupt summer cooling at these times, and that cold summers can be maintained by sea-ice/ocean feedbacks long after volcanic aerosols are removed. Our results suggest that the onset of the LIA can be linked to an unusual 50-year-long episode with four large sulfur-rich explosive eruptions, each with global sulfate loading >60 Tg. The persistence of cold summers is best explained by consequent sea-ice/ocean feedbacks during a hemispheric summer insolation minimum; large changes in solar irradiance are not required. STUDY NOTES: Radiocarbon dates on rooted vegetation revealed by receding ice collected on Baffin Island, Arctic Canada. These data provide a history of snowline lowering dates, which are highly correlated with Arctic summer temperatures. Samples from Baffin Island, Arctic Canada: ~67 - 71ºN, ~74 - 82ºW NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Miller, G.H. Investigator : Geirsdóttir, A. Investigator : Zhong, Y. Investigator : Larsen, D.J. Investigator : Otto-Bliesner, B.L. Investigator : Holland, M.M. Investigator : Bailey, D.A. Investigator : Refsnider, K.A. Investigator : Lehman, S.J. Investigator : Southon, J.R. Investigator : Anderson, C. Investigator : Björnsson, H. Investigator : Thordarson, T. 2012-03-14 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/12881 https://www1.ncdc.noaa.gov/pub/data/paleo/radiocarbon/baffin2012c14.xls https://www1.ncdc.noaa.gov/pub/data/paleo/radiocarbon/baffin2012c14.txt https://www1.ncdc.noaa.gov/pub/data/paleo/radiocarbon/baffin2012c14.xls https://www1.ncdc.noaa.gov/pub/data/paleo/radiocarbon/baffin2012c14.txt English https://www.ncdc.noaa.gov/paleo/study/12881 https://www1.ncdc.noaa.gov/pub/data/paleo/radiocarbon/baffin2012c14.xls https://www1.ncdc.noaa.gov/pub/data/paleo/radiocarbon/baffin2012c14.txt Miller, G.H, Á. Geirsdóttir, Y. Zhong, D.J. Larsen, B.L. Otto-Bliesner, M.M. Holland, D.A. Bailey, K.A. Refsnider, S.J. Lehman, J.R. Southon, C. Anderson, H. Björnsson, and T. Thordarson. 2012. Abrupt onset of the Little Ice Age triggered by volcanism and sustained by sea-ice/ocean feedbacks. Geophys. Res. Lett., 39, L02708, doi:10.1029/2011GL050168 START YEAR: 1724 AD * END YEAR: 1724 AD -74.66817 71.04155 -74.66817 71.04155