C15 Cryosphere, Atmosphere and Climate: Evaluation of the Cryosphere in CMIP5 Models

IACS (Cryosphere)



23-Jun-2015, 15:00 - 16:30


 
Abstract content:

Anthropogenic influence on recent Antarctic sea-ice changes: Why do models and observations disagree?

Observations reveal an increase of Antarctic sea ice over the past three decades, yet global climate models tend to simulate a sea-ice decrease for that period. Here we combine observations with model experiments (MPI-ESM) to investigate causes for this discrepancy and for the observed sea ice increase. Based on observations and atmospheric reanalysis, we show that on multidecadal time scales Antarctic sea-ice changes are linked to intensified meridional winds that are caused by a zonally asymmetric lowering of the high-latitude surface pressure. In our simulations, this surface pressure lowering is a response to a combination of anthropogenic stratospheric ozone depletion and greenhouse gas increase. Combining these two lines of argument, we infer a possible anthropogenic influence on the observed sea-ice changes. However, similar to other models, MPI-ESM simulates a surface-pressure response that is rather zonally symmetric and has a too unstable Southern Ocean stratification, which explains why the simulated sea-ice response differs from observations.

 
Author(s):
A. Haumann1,2,3, D. Notz1, H. Schmidt2.
1Max Planck Institute for Meteorology, Sea Ice in the Earth System, Hamburg, Germany.
2Max Planck Institute for Meteorology, The Atmosphere in the Earth System, Hamburg, Germany.

 

Keywords:
Antarctic     sea ice     climate change     anthropogenic     model     observations     atmospheric circulation