Clim. Past Discuss., 6, 1209-1227, 2010
www.clim-past-discuss.net/6/1209/2010/
doi:10.5194/cpd-6-1209-2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Climate of the Past (CP). Please refer to the corresponding final paper in CP.
Objective identification of climate states from Greenland ice cores for the last glacial period
D. J. Peavoy1 and C. Franzke2
1Complexity Science Centre, University of Warwick, Coventry, UK
2British Antarctic Survey, Cambridge, UK

Abstract. We present statistical methods to systematically determine climate regimes for the last glacial period using three temperature proxy records from Greenland: measurements of δ18O from the Greenland Ice Sheet Project 2 (GISP2), the Greenland Ice Core Project (GRIP) and the North Greenland Ice Core Project (NGRIP). By using Bayesian model comparison methods we find that, in two out of three data sets, a model with 3 states is very strongly supported. We interpret these states as corresponding to: a gradual cooling regime due to iceberg influx in the North Atlantic, sudden temperature decrease due to increased freshwater influx following ice sheet collapse and to the Dansgaard-Oeschger events associated with sudden rebound temperature increase after the thermohaline circulation recovers its full flux. We find that these models are far superior to those that differentiate between states based on absolute temperature differences only, which questions the appropriateness of defining stadial and interstadial climate states. We investigate the recurrence properties of these climate regimes and find that the only significant periodicity is within the Greenland Ice Sheet Project 2 data at 1450 years in agreement with previous studies.

Citation: Peavoy, D. J. and Franzke, C.: Objective identification of climate states from Greenland ice cores for the last glacial period, Clim. Past Discuss., 6, 1209-1227, doi:10.5194/cpd-6-1209-2010, 2010.
 
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