Climate of the Past www.clim-past.net 1814-9324 1814-9332 4 4 2008 10.5194/cp-4-295-2008 http://www.clim-past.net/4/295/2008/ http://www.clim-past.net/4/295/2008/cp-4-295-2008.html http://www.clim-past.net/4/295/2008/cp-4-295-2008.pdf 295 302 2008-11-24 Revisiting the absolute calibration of the Greenland ice-core age-scales* L. C. Skinner luke00@esc.cam.ac.uk Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK Invited contribution by L. Skinner, one of the EGU Outstanding Young Scientist Award winners 2006. Recently, an absolute "calibration" was proposed for the GRIP and GISP2 Greenland ice-core time scales (Shackleton et al., 2004). This calibration attempted to reconcile the stratigraphic integration of ice-core, marine and speleothem archives with the absolute age constraints that marine and speleothem records incorporate. Here we revisit this calibration in light of the new layer-counted chronology of the NGRIP ice-core (GICC05). The GICC05 age-scale differs from the proposed absolute calibration by up to 1200 years late in the last glaciation, with implications both for radiocarbon cycling and the inferred timing of North Atlantic climate events relative to radiometrically dated archives (e.g. relative sea-level). By aligning the stratigraphy of Iberian Margin marine cores with that of the Greenland ice-cores, it can be shown that either: 1) the radiocarbon content of mid-latitude Atlantic surface-waters was extremely depleted (resulting in average surface reservoir ages up to 1700 years prior to ~22 ka BP); or 2) the GICC05 age-scale includes too few years (is up to 1200 years too young). It is shown here that both of these possibilities are probably correct to some degree. 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