Articles | Volume 9, issue 4
The Cryosphere, 9, 1481–1504, 2015
The Cryosphere, 9, 1481–1504, 2015

Research article 06 Aug 2015

Research article | 06 Aug 2015

Recent changes in north-west Greenland climate documented by NEEM shallow ice core data and simulations, and implications for past-temperature reconstructions

V. Masson-Delmotte1,*, H. C. Steen-Larsen1,*, P. Ortega1,a, D. Swingedouw2, T. Popp3, B. M. Vinther3, H. Oerter4, A. E. Sveinbjornsdottir5, H. Gudlaugsdottir5, J. E. Box6, S. Falourd1, X. Fettweis7, H. Gallée8, E. Garnier9, V. Gkinis3, J. Jouzel1, A. Landais1, B. Minster1, N. Paradis1, A. Orsi1, C. Risi10, M. Werner4, and J. W. C. White11 V. Masson-Delmotte et al.
  • 1LSCE (UMR CEA-CNRS-UVSQ 8212/IPSL), Gif-sur-Yvette, France
  • 2UMR CNRS 5805 EPOC, OASU, Université Bordeaux 1, 33615 Pessac, France
  • 3Centre for Ice and Climate, University of Copenhagen, Copenhagen, Denmark
  • 4AWI, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
  • 5Institute of Earth Sciences, University of Iceland, Reykjavik, Iceland
  • 6GEUS, Copenhagen, Denmark
  • 7University of Liège, Liège, Belgium
  • 8LGGE (UMR 5183 CNRS-UJF), 54 rue Molière, Domaine Universitaire, BP96, 38 402 St Martin d'Hères cédex, France
  • 9UMR CNRS LIENSs, Université de La Rochelle, La Rochelle, France
  • 10LMD, Paris, France
  • 11INSTAAR, Boulder, Colorado, USA
  • anow at: LOCEAN, Paris, France
  • *These authors contributed equally to this work.

Abstract. Combined records of snow accumulation rate, δ18O and deuterium excess were produced from several shallow ice cores and snow pits at NEEM (North Greenland Eemian Ice Drilling), covering the period from 1724 to 2007. They are used to investigate recent climate variability and characterise the isotope–temperature relationship. We find that NEEM records are only weakly affected by inter-annual changes in the North Atlantic Oscillation. Decadal δ18O and accumulation variability is related to North Atlantic sea surface temperature and is enhanced at the beginning of the 19th century. No long-term trend is observed in the accumulation record. By contrast, NEEM δ18O shows multidecadal increasing trends in the late 19th century and since the 1980s. The strongest annual positive δ18O values are recorded at NEEM in 1928 and 2010, while maximum accumulation occurs in 1933. The last decade is the most enriched in δ18O (warmest), while the 11-year periods with the strongest depletion (coldest) are depicted at NEEM in 1815–1825 and 1836–1846, which are also the driest 11-year periods. The NEEM accumulation and δ18O records are strongly correlated with outputs from atmospheric models, nudged to atmospheric reanalyses. Best performance is observed for ERA reanalyses. Gridded temperature reconstructions, instrumental data and model outputs at NEEM are used to estimate the multidecadal accumulation–temperature and δ18O–temperature relationships for the strong warming period in 1979–2007. The accumulation sensitivity to temperature is estimated at 11 ± 2 % °C−1 and the δ18O–temperature slope at 1.1 ± 0.2 ‰ °C−1, about twice as large as previously used to estimate last interglacial temperature change from the bottom part of the NEEM deep ice core.

Short summary
The deep NEEM ice core provides the oldest Greenland ice core record, enabling improved understanding of the response of ice core records to local climate. Here, we focus on shallow ice cores providing a stack record of accumulation and water-stable isotopes spanning the past centuries. For the first time, we document the ongoing warming in a Greenland ice core. By combining our data with other Greenland ice cores and model results, we characterise the spatio-temporal patterns of variability.