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Reducing Spread in Climate Model Projections of a September Ice-Free ArcticThis paper addresses the specter of a September ice-free Arctic in the 21st century using newly available simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5). We find that large spread in the projected timing of the September ice-free Arctic in 30 CMIP5 models is associated at least as much with different atmospheric model components as with initial conditions. Here we reduce the spread in the timing of an ice-free state using two different approaches for the 30 CMIP5 models: (i) model selection based on the ability to reproduce the observed sea ice climatology and variability since 1979 and (ii) constrained estimation based on the strong and persistent relationship between present and future sea ice conditions. Results from the two approaches show good agreement. Under a high-emission scenario both approaches project that September ice extent will drop to approx. 1.7 million sq km in the mid 2040s and reach the ice-free state (defined as 1 million sq km) in 2054-2058. Under a medium-mitigation scenario, both approaches project a decrease to approx.1.7 million sq km in the early 2060s, followed by a leveling off in the ice extent.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Liu, Jiping (State Univ. of New York Albany, NY, United States)
Song, Mirong (Academia Sinica Beijing, China)
Horton, Radley M. (Columbia Univ. New York, NY, United States)
Hu, Yongyun (Peking Univ. Beijing, China)
Date Acquired
December 2, 2014
Publication Date
July 30, 2013
Publication Information
Publication: PNAS
Volume: 110
Issue: 31
Subject Category
Meteorology and Climatology
Earth Resources and Remote Sensing
Report/Patent Number
Funding Number(s)
Distribution Limits
Public Use Permitted.
Arctic regions

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