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| Titel |
Revisiting the absolute calibration of the Greenland ice-core age-scales* |
| VerfasserIn |
L. C. Skinner |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 4, no. 4 ; Nr. 4, no. 4 (2008-11-24), S.295-302 |
| Datensatznummer |
250001870
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| Publikation (Nr.) |
 copernicus.org/cp-4-295-2008.pdf |
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| Zusammenfassung |
| 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. |
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