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32nd Annual Arctic Workshop Abstracts
March 14-16, 2002
INSTAAR, University of Colorado at Boulder

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WAS THE YOUNGER DRYAS (GS-1) A COLD PERIOD ON THE SOUTHEAST GREENLAND MARGIN?

AUTHORS

JENNINGS, ANNE E.. INSTAAR, Univ. of Colorado.
Hald, Morten . University of Tromsoe.
Weiner, Nancy J.. INSTAAR, Univ. of Colorado.
Kaufman, Kris . INSTAAR, Univ. of Colorado.
Dunhill, Gita . INSTAAR, Univ. of Colorad.
Andrews, John T. INSTAAR, Univ. of Colorad.

The Younger Dryas stadial event is documented in lacustrine and marine proxy climate records in Northwest Europe and the Nordic Seas as a cold period at the end of the last glacial stage. It is well expressed in the GRIP and GISP ice cores at the summit of the Greenland Ice Sheet as a deep annual cooling of 10-20°C. The Younger Dryas cooling has been dated in the GRIP ice core to extend from 12,650 to 11,500 cal. yr BP and has been proposed to be termed Greenland Stadial 1 (GS-1). Several marine cores from the Kangerlussuaq Trough, East Greenland contain sediment records that extend from deglaciation (c. 15-16 cal. ka BP) through the Holocene, and thus contain sediments deposited during GS-1. Two tephras, the Vedde Ash (11,980 ± cal yr BP) which is a marker bed within GS-1, and the Saksunarvatn tephra (10,180 ± cal. yr BP) an early Holocene marker horizon, have been located in these cores. The tephras and calibrated 14C dates on foraminifers and molluscs provide the basis for the age models in the cores. Studies of benthic and planktic foraminiferal assemblages and stable O and C isotopes yielded a surprising result: the Kangerlussuaq Trough cores do not show evidence for cooling in GS-1 until c. 12 cal. ka BP. Strong evidence of inflow of Atlantic Intermediate waters into the Kangerlussuaq Trough beginning c. 15 cal. ka BP continues in GS-1 until c. 12 cal ka BP. This interpretation is based on high percentages of the Atlantic Intermediate Water indicator species, Cassidulina neoteretis. The transition from Greenland Interstadial-1 (Bølling/Allerød) to GS-1 is unmarked by evidence for environmental change. However, a significant light _18-O spike is centered within GS-1 in the middle/inner shelf cores and coincides with a decline in the percentages of C. neoteretis. The light isotope interval is absent or unpronounced on the outer shelf. Because it is most pronounced closer to the coast, this light isotope anomaly is interpreted as a meltwater spike reflecting melting of the ice sheet margin during GS-1. In contrast, a core from a site north of Kangerlussuaq Trough (MD99-2317) shows a large faunal change at the transition to GS-1 as well as lithostratigraphic changes indicating cooling. This core has low percentages of C. neoteretis, even in GI-1. These comparisons and spatial differences suggest that the Atlantic Intermediate Water influx in the Kangerlussuaq Trough in the deglaciation was carried onto the East Greenland shelf in the Irminger Current, as occurs today.

 

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