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Sensitivity of interglacial Greenland temperature and δ 18O : Ice core data, orbital and increased CO 2 climate simulations

Masson-Delmotte, V. ; Braconnot, P. ; Hoffmann, G. LU ; Jouzel, J. ; Kageyama, M. ; Landais, A. ; Lejeune, Q. ; Risi, C. ; Sime, L. and Sjolte, J. LU orcid , et al. (2011) In Climate of the Past 7(3). p.1041-1059
Abstract

The sensitivity of interglacial Greenland temperature to orbital and CO 2 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 CO 2 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 × CO 2 and orbital forcing of the last interglacial period (126 000 years ago). The... (More)

The sensitivity of interglacial Greenland temperature to orbital and CO 2 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 CO 2 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 × CO 2 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 CO 2, 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 simulations and detailed inter-model comparisons are also likely to be of benefit. Comparisons with Greenland ice core stable isotope data reveals that IPSL-CM4/LMDZiso simulations strongly underestimate the amplitude of the ice core signal during the last interglacial, which could reach +8-10 °C at fixed-elevation. While the model-data mismatch may result from missing positive feedbacks (e.g. vegetation), it could also be explained by a reduced elevation of the central Greenland ice sheet surface by 300-400 m.

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publication status
published
subject
in
Climate of the Past
volume
7
issue
3
pages
19 pages
publisher
Copernicus Gesellschaft mbH
external identifiers
  • scopus:80053427416
ISSN
1814-9324
DOI
10.5194/cp-7-1041-2011
language
English
LU publication?
yes
id
44745624-7891-456c-9a0c-d6594d0d6cda
date added to LUP
2019-06-19 10:34:00
date last changed
2021-03-09 04:14:28
@article{44745624-7891-456c-9a0c-d6594d0d6cda,
  abstract     = {<p>The sensitivity of interglacial Greenland temperature to orbital and CO <sub>2</sub> 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 CO <sub>2</sub> 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 × CO <sub>2</sub> 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 CO <sub>2</sub>, 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 simulations and detailed inter-model comparisons are also likely to be of benefit. Comparisons with Greenland ice core stable isotope data reveals that IPSL-CM4/LMDZiso simulations strongly underestimate the amplitude of the ice core signal during the last interglacial, which could reach +8-10 °C at fixed-elevation. While the model-data mismatch may result from missing positive feedbacks (e.g. vegetation), it could also be explained by a reduced elevation of the central Greenland ice sheet surface by 300-400 m.</p>},
  author       = {Masson-Delmotte, V. and Braconnot, P. and Hoffmann, G. and Jouzel, J. and Kageyama, M. and Landais, A. and Lejeune, Q. and Risi, C. and Sime, L. and Sjolte, J. and Swingedouw, D. and Vinther, B.},
  issn         = {1814-9324},
  language     = {eng},
  month        = {10},
  number       = {3},
  pages        = {1041--1059},
  publisher    = {Copernicus Gesellschaft mbH},
  series       = {Climate of the Past},
  title        = {Sensitivity of interglacial Greenland temperature and δ <sup>18</sup>O : Ice core data, orbital and increased CO <sub>2</sub> climate simulations},
  url          = {http://dx.doi.org/10.5194/cp-7-1041-2011},
  doi          = {10.5194/cp-7-1041-2011},
  volume       = {7},
  year         = {2011},
}