Preprints
https://doi.org/10.5194/tc-2019-332
https://doi.org/10.5194/tc-2019-332

  10 Feb 2020

10 Feb 2020

Review status: this preprint has been withdrawn by the authors.

Brief communication: CMIP6 does not suggest any circulation change over Greenland in summer by 2100

Alison Delhasse1, Edward Hanna2, Christoph Kittel1, and Xavier Fettweis1 Alison Delhasse et al.
  • 1Laboratory of Climatology, Department of Geography, SPHERES, University of Liège, Liège, Belgium
  • 2School of Geography and Lincoln Centre for Water and Planetary Health, University of Lincoln, Lincoln, UK

Abstract. The Greenland blocking index (GBI), an indicator of the synoptic-scale circulation over Greenland, has been anomalously positive during summers since the late 1990s. Such changes in atmospheric circulation have led to an increase in Greenland summer temperatures, a decrease in cloud cover and greater surface melt. The GBI is therefore a key indicator of melting and surface mass balance variability over the Greenland ice sheet. However, the fifth phase of the Coupled Model Intercomparison Project (CMIP5) models do not represent any increase in GBI as suggested by observations. Until 2100, no significant long-term trend in the GBI, and therefore no circulation changes, are projected. In this study the new generation of CMIP6 Earth-system models is evaluated in order to analyze the evolution of the future GBI. All CMIP5 and CMIP6 projections reveal the same trend towards a decrease of the GBI until 2100 and no model reproduces the strong increase in GBI observed over the last few decades. Significant melting events related to a highly positive GBI, as observed this summer 2019, are still not considered by CMIP6 models and therefore the projected surface melt increase of the ice sheet is likely to be underestimated if such circulation changes persist in the next decades.

This preprint has been withdrawn.

Alison Delhasse et al.

Interactive discussion

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Interactive discussion

Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Alison Delhasse et al.

Alison Delhasse et al.

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This preprint has been withdrawn.

Short summary
Significant melting events over Greenland ice sheet related to unusual atmospheric pattern in summer, as observed this summer 2019, are still not considered by the new generation of Earth-system models (CMIP6) and therefore the projected surface melt increase of the ice sheet is likely to be underestimated if such changes persist in the next decades.