CGD Seminar - Meehl

Antarctic sea ice should be melting but it's not:
Connections to global temperature trends and
decadal variability in the tropical Pacific

Gerald Meehl, NCAR/CGD

Antarctic sea ice extent has been slowly increasing in the satellite record since it began in 1979.   Since the late 1990s, the increase has accelerated, but the average of all climate models shows a retreat of Antarctic sea ice as could intuitively be expected in a warming climate.  Meanwhile, the Interdecadal Pacific Oscillation, an internally-generated mode of climate variability, transitioned from positive to negative about the time Antarctic sea ice retreat accelerated, with 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.  Here 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.  These are conducive to expanding Antarctic sea ice extent, particularly in the Ross Sea region in all seasons, involving a deepening of the Amundsen Sea Low.   These atmospheric circulation changes, and thus the expansion of Antarctic sea ice, are shown mainly to be driven by internally-generated IPO-related precipitation and convective heating anomalies in the equatorial eastern Pacific, with additional contributions from convective heating anomalies in the South Pacific Convergence Zone and tropical Atlantic regions.

Tuesday, 25 April 2017
11:00 AM, refreshments at 10:45
Mesa Lab, Main Seminar Room

Live webcast:
For more information, contact Gaylynn Potemkin,, 303.497.1618


Room Number: 
Main Seminar Room

Type of event:

Will this event be webcast to the public by NCAR|UCAR?: 
Yes - ML-Main Seminar Room -
Announcement Timing: 
April 24, 2017 to April 26, 2017
Calendar Timing: 
Tuesday, April 25, 2017 - 11:00am to 12:00pm