European Geosciences Union, Climate of the Past, 2(10), p. 887-902, 2014
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In order to reconstruct the temperature of the North Greenland Ice Core Project (NGRIP) site, new measurements of �d15N have been performed covering the time period from the beginning of the Holocene to Dansgaard– Oeschger (DO) event 8. Together with previously measured and mostly published �d15N data, we present for the first time a NGRIP temperature reconstruction for the whole last glacial period from 10 to 120 kyr b2k (thousand years before 2000 AD) including every DO event based on �d15N isotope measurements combined with a firn densification and heat diffusion model. The detected temperature rises at the onset of DO events range from 5 �°C (DO 25) up to 16.5 °�C (DO 11) with an uncertainty of ±3 °�C. To bring measured and modelled data into agreement, we had to reduce the accumulation rate given by the NGRIP ss09sea06bm timescale in some periods by 30 to 35 %, especially during the last glacial maximum. A comparison between reconstructed temperature and d�18Oice data confirms that the isotopic composition of the stadial was strongly influenced by seasonality. We evidence an anticorrelation between the variations of the �d18Oice sensitivity to temperature (referred to as alpha) and obliquity in agreement with a simple Rayleigh distillation model. Finally, we suggest that alpha might be influenced by the Northern Hemisphere ice sheet volume.