The orbital-scale transition from the last interglacial to glacial climate corresponds to the progressive organization of global millennial-scale climate variability. Here, we investigate the structure and the global fingerprint of the first warming event occurring during the last glacial inception, the Greenland InterStadial 25 (GIS 25). Using centennial to decadal-resolution measurements ofδ18O and δD in the ice together with δ15N, δ18O2 and CH4in the trapped air, we show that GIS 25 does not coincide with large environmental changes at lower latitudes. Such an equivocal fingerprint questions whether GIS 25 is simply a smaller amplitude version of later rapid events or whether it reflects a more regional northern hemisphere origin for the initiation of the millennial-scale climatic variability. After this ambiguous first rapid event, the onset of the global millennial-scale variability -characteristic of the last glacial period- occurs as a short (300 years) event ending GIS 25.
EPIC Alfred Wegener Institut