Sensitivity of interglacial Greenland temperature and delta 18 O: ice core data, orbital and increased CO2 climate simulations.

• Published in: Climate of the Past
• Main Authors: Masson-Delmotte, V., Braconnot, P., Hoffman, G., Jouzel, J., Kageyama, M., Landais, A., Lejeune, Q., Risi, C., Sime, Louise, Sjolte, J., Swingedouw, D., Vinther, B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus 2011
• Subjects: Arctic; Greenland; Greenland ice cores; ice core; Ice Sheet
• Online Access: http://nora.nerc.ac.uk/id/eprint/15654/; https://nora.nerc.ac.uk/id/eprint/15654/1/cp-7-1041-2011.pdf; http://www.clim-past.net

The sensitivity of interglacial Greenland temperature to orbital and CO2 forcing is investigated using the NorthGRIP ice core data and coupled ocean-atmosphere IPSL-CM4 model simulations. These simulations were conducted in response to different interglacial orbital configurations, and to increased CO2 concentrations. These different forcings cause very distinct simulated seasonal and latitudinal temperature and water cycle changes, limiting the analogies between the last interglacial and future climate. However, the IPSL-CM4 model shows similar magnitudes of Arctic summer warming and climate feedbacks in response to 2 × CO2 and orbital forcing of the last interglacial period (126 000 years ago). The IPSL-CM4 model produces a remarkably linear relationship between TOA incoming summer solar radiation and simulated changes in summer and annual mean central Greenland temperature. This contrasts with the stable isotope record from the Greenland ice cores, showing a multi-millennial lagged response to summer insolation. During the early part of interglacials, the observed lags may be explained by ice sheet-ocean feedbacks linked with changes in ice sheet elevation and the impact of meltwater on ocean circulation, as investigated with sensitivity studies. A quantitative comparison between ice core data and climate simulations requires stability of the stable isotope – temperature relationship to be explored. Atmospheric simulations including water stable isotopes have been conducted with the LMDZiso model under different boundary conditions. This set of simulations allows calculation of a temporal Greenland isotope-temperature slope (0.3–0.4‰ per °C) during warmer-than-present Arctic climates, in response to increased CO2, increased ocean temperature and orbital forcing. This temporal slope appears half as large as the modern spatial gradient and is consistent with other ice core estimates. It may, however, be model-dependent, as indicated by preliminary comparison with other models. This suggests that further ...