30 November 2016

Antarctic Sea Ice Expansion between 2000-2014 Driven by Tropical Pacific Decadal Climate Variability

Science

Increases in Antarctic sea-ice extent accelerated after the late 1990s, but the average of all climate models shows a decline. Meanwhile, the Interdecadal Pacific Oscillation, an internally generated mode of climate variability, transitioned from positive to negative in the late 1990s as the Antarctic sea ice increase accelerated.  At the same time there was an average cooling of tropical Pacific sea surface temperatures, a slowdown of the global warming trend, and a deepening of the Amundsen Sea Low near Antarctica that has contributed to regional circulation changes in the Ross Sea region and expansion of sea ice.

Impact

We show that the negative phase of the Interdecadal Pacific Oscillation in global coupled climate models is characterized by anomalies similar to the observed sea-level pressure and near-surface 850 hPa wind changes near Antarctica since 2000 that are conducive to expanding Antarctic sea-ice extent, particularly in the Ross Sea region.

Summary

in all seasons, involving a deepening of the Amundsen Sea Low. Additional climate model experiments show that these atmospheric circulation changes are mainly driven by precipitation and convective heating anomalies related to the Interdecadal Pacific Oscillation in the equatorial eastern Pacific.  Thus the models are not wrong, and can simulate the processes involved with internally-generated climate variability that can produce increases in Antarctic sea ice even when global temperatures are increasing

Contact
Gerald Meehl
National Center for Atmospheric Research (NCAR)