Arctic sea ice simulation in the PlioMIP ensemble

Fergus W Howell,Nan A Rosenbloom,Camille Contoux,Youichi Kamae,Bette L Otto-Bliesner,Ayako Abe-Ouchi,Mark A Chandler,Alan M Haywood,Fran Bragg,Zhongshi Zhang,Christian Stepanek,Wing-Le Chan

doi:10.5194/cp-12-749-2016

Abstract

Abstract. Eight general circulation models have simulated the mid-Pliocene warm period (mid-Pliocene, 3.264 to 3.025 Ma) as part of the Pliocene Modelling Intercomparison Project (PlioMIP). Here, we analyse and compare their simulation of Arctic sea ice for both the pre-industrial period and the mid-Pliocene. Mid-Pliocene sea ice thickness and extent is reduced, and the model spread of extent is more than twice the pre-industrial spread in some summer months. Half of the PlioMIP models simulate ice-free conditions in the mid-Pliocene. This spread amongst the ensemble is in line with the uncertainties amongst proxy reconstructions for mid-Pliocene sea ice extent. Correlations between mid-Pliocene Arctic temperatures and sea ice extents are almost twice as strong as the equivalent correlations for the pre-industrial simulations. The need for more comprehensive sea ice proxy data is highlighted, in order to better compare model performances.

Highlights

The mid-Pliocene warm period, spanning 3.264–3.025 Myr ago (Dowsett et al, 2010), was a period exhibiting episodes of global warmth, with estimates of an increase of 2–3 ◦C in global mean temperatures in comparison to the pre-industrial period (Haywood et al, 2013)
We have presented a detailed analysis of the simulation of Arctic sea ice in the Pliocene Modelling Intercomparison Project (PlioMIP) model ensemble, for both preindustrial control and mid-Pliocene simulations
The simulated mid-Pliocene sea ice extents are strongly negatively correlated with the Arctic temperatures

Summary

Introduction

The mid-Pliocene warm period (mid-Pliocene), spanning 3.264–3.025 Myr ago (Dowsett et al, 2010), was a period exhibiting episodes of global warmth, with estimates of an increase of 2–3 ◦C in global mean temperatures in comparison to the pre-industrial period (Haywood et al, 2013). The mid-Pliocene is the most recent period of earth history that is thought to have atmospheric CO2 concentrations resembling those seen in the 21st century, with concentrations estimated to be between 365 and 415 ppm Pagani et al, 2010; Seki et al, 2010) This time period is a useful interval in which to study the dynamics and characteristics of sea ice in a warmer world. Under RCP 4.5, many models predict seasonally sea-ice-free conditions in the Arctic by the end of the 21st century (e.g. Stroeve et al, 2012; Massonnet et al, 2012), with some projections suggesting an ice-free Arctic by 2030 under RCP 8.5 (Wang and Overland, 2012), whilst other studies (e.g. Boé et al, 2009) suggest a later date for the disappearance of summer Arctic sea ice.

Methods

Results

Discussion

Conclusion