アイテム詳細

要旨

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 multi-decadal 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, which explains why the simulated sea-ice response differs from observations.