Evidence for a three-phase sequence during Heinrich Stadial 4 using a multiproxy approach based on Greenland ice core records

• Published in: Climate of the Past
• Main Authors: Guillevic, M., Bazin, L., Landais, A., Stowasser, C., Masson-Delmotte, V., Blunier, T., Eynaud, F., Falourd, S., Michel, E., Minster, B., Popp, T., Prié, F., Vinther, B. M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Gesellschaft Mbh 2018
• Subjects: envir; geo; Greenland; Dansgaard-Oeschger events; Greenland ice core; Greenland ice cores; ice core; Ice Sheet; North Atlantic
• Online Access: https://doi.org/10.5194/cp-10-2115-2014; https://cp.copernicus.org/articles/10/2115/2014/

Glacial climate was characterised by two types of abrupt events. Greenland ice cores record Dansgaard–Oeschger events, marked by abrupt warming in-between cold, stadial phases. Six of these stadials appear related to major Heinrich events (HEs), identified from ice-rafted debris (IRD) and large excursions in carbon- and oxygen-stable isotopic ratios in North Atlantic deep sea sediments, documenting major ice sheet collapse events. This finding has led to the paradigm that glacial cold events are induced by the response of the Atlantic Meridional Overturning Circulation to such massive freshwater inputs, supported by sensitivity studies conducted with climate models of various complexities. These models also simulate synchronous Greenland temperature and lower-latitude hydrological changes. To investigate the sequence of events between climate changes at low latitudes and in Greenland, we provide here the first 17O-excess record from a Greenland ice core during Dansgaard–Oeschger events 7 to 13, encompassing H4 and H5. Combined with other ice core proxy records, our new 17O-excess data set demonstrates that stadials are generally characterised by low 17O-excess levels compared to interstadials. This can be interpreted as synchronous change of high-latitude temperature and lower-latitude hydrological cycle (relative humidity at the oceanic source of evaporation or change in the water mass trajectory/recharge) and/or an influence of local temperature on 17O-excess through kinetic effect at snow formation. As an exception from this general pattern, stadial 9 consists of three phases, characterised first by Greenland cooling during 550 ± 60 years (as shown by markers of Greenland temperature δ18O and δ15N), followed by a specific lower-latitude fingerprint as identified from several proxy records (abrupt decrease in 17O-excess, increase in CO2 and methane mixing ratio, heavier δD-CH4 and δ18Oatm), lasting 740 ± 60 years, itself ending approximately 390 ± 50 years prior to abrupt Greenland warming. We hypothesise that ...