Consistent Changes in the Sea Ice Seasonal Cycle in Response to Global Warming
The Northern Hemisphere sea ice cover has diminished rapidly in recent years and is projected to continue to diminish in the future. The year-to-year retreat of Northern Hemisphere sea ice extent is faster in summer than winter, which has been identified as one of the most striking features of satellite observations as well as of state-of-the-art climate model projections. This is typically understood to imply that the sea ice cover is most sensitive to climate forcing in summertime, and previous studies have explained this by calling on factors such as the surface albedo feedback. In the Southern Hemisphere, however, it is the wintertime sea ice extent that retreats fastest in climate model projections. Here, it is shown that the interhemispheric differences in the model projections can be attributed to differences in coastline geometry, which constrain where sea ice can occur. After accounting for coastline geometry, it is found that the sea ice changes simulated in both hemispheres in most climate models are consistent with sea ice retreat being fastest in winter in the absence of landmasses. These results demonstrate that, despite the widely differing rates of ice retreat among climate model projections, the seasonal structure of the sea ice retreat is robust among the models and is uniform in both hemispheres.
© 2011 American Meteorological Society. Received: September 3, 2010; Accepted: March 16, 2011 This work was supported by a TPF Postdoctoral Fellowship through the Caltech Division of Geological and Planetary Sciences, a NOAA Climate and Global Change Postdoctoral Fellowship administered by the University Corporation for Atmospheric Research, a David and Lucile Packard Fellowship, and the Davidow Discovery Fund. We thank the modeling groups and the Program for Climate Model Diagnosis and Intercomparison for making available the CMIP3 multimodel dataset.
Published - Eisenman2011p16294J_Climate.pdf