Abstract
Abstract. Almost all global climate models and Earth system models that participated in the Coupled Model Intercomparison Project 5 (CMIP5) show strong declines in Arctic sea ice extent and volume under the highest forcing scenario of the representative concentration pathways (RCPs) through 2100, including a transition from perennial to seasonal ice cover. Extended RCP simulations through 2300 were completed for a~subset of models, and here we examine the time evolution of Arctic sea ice in these simulations. In RCP2.6, the summer Arctic sea ice extent increases compared to its minimum following the peak radiative forcing in 2044 in all nine models. RCP4.5 demonstrates continued summer Arctic sea ice decline after the forcing stabilizes due to continued warming on longer timescales. Based on the analysis of these two scenarios, we suggest that Arctic summer sea ice extent could begin to recover if and when radiative forcing from greenhouse gas concentrations were to decrease. In RCP8.5 the Arctic Ocean reaches annually ice-free conditions in seven of nine models. The ensemble of simulations completed under the extended RCPs provide insight into the global temperature increase at which sea ice disappears in the Arctic and the reversibility of declines in seasonal sea ice extent.
Highlights
The modeled decline in summer Arctic sea ice through 2100 is well documented (e.g., Stroeve et al, 2012; Massonnet et al, 2012) for the representative concentration pathways (RCPs) in the Coupled Model Intercomparison Project 5 (CMIP5) (Taylor et al, 2012)
We have shown here the evolution of Arctic sea ice extent and volume in the extended RCP2.6, RCP4.5, and RCP8.5
RCP2.6 demonstrates an increase in September ice extent in all nine models as the radiative forcing in that scenario decreases after 2044 through 2300
Summary
The modeled decline in summer Arctic sea ice through 2100 is well documented (e.g., Stroeve et al, 2012; Massonnet et al, 2012) for the representative concentration pathways (RCPs) in the Coupled Model Intercomparison Project 5 (CMIP5) (Taylor et al, 2012). 4 of this paper we show that the CMIP5 models predict a global temperature increase at which the summer sea ice disappears consistent with Mahlstein and Knutti (2012), regardless of the model biases in sea ice extent, volume, and trends, and regardless of the forcing scenario.
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