Revisiting the absolute calibration of the Greenland ice-core age-scales

Skinner, L. (2008) Revisiting the absolute calibration of the Greenland ice-core age-scales. Climate of the past, 4 (3). pp. 791-807. ISSN 1814-9340

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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. Based on the assumed accuracy of coral and speleothem U-Th ages, Northeast Atlantic surface reservoir ages should be revised upward by 350 years, while the NGRIP age-scale appears to be “missing” time. These findings illustrate the utility of integrated stratigraphy as a test for our chronologies, which are rarely truly “absolute”. This is an important point, since probably the worst error that we can make is to entrench and generalise a precise stratigraphical relationship on the basis of erroneous absolute age assignations.

Item Type: Article
Uncontrolled Keywords: 08AREP IA57 2008 P
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title: Climate of the past
Volume: 4
Page Range: pp. 791-807
Depositing User: Sarah Humbert
Date Deposited: 16 Feb 2009 13:03
Last Modified: 23 Jul 2013 10:08

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