Atmospheric impacts of sea ice decline in CO2 induced global warming

Ivana Cvijanovic,Ken Caldeira

doi:10.1007/s00382-015-2489-1

Ivana Cvijanovic, Ken Caldeira

Open Access

https://doi.org/10.1007/s00382-015-2489-1

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Abstract

Changes in sea ice cover have important consequences for both Earth’s energy budget and atmospheric dynamics. Sea ice acts as a positive feedback in the climate system, amplifying effects of radiative forcing while also affecting the meridional and interhemispheric temperature gradients that can impact mid- and low latitude atmospheric circulation. In this study, we partition and evaluate the effects of changing sea ice cover on global warming using a set of simulations with active and suppressed sea ice response. Two aspects of CO2-induced sea ice changes are investigated: (1) the effect of changing sea ice cover on global and local temperature changes; and (2) the impact of sea ice loss on atmospheric circulation and extreme weather events. We find that in the absence of sea ice decline, global temperature response decreases by 21–37 %, depending on the sea ice treatment and the CO2 forcing applied. Weakened global warming in the absence of changes in sea ice cover is not only due to a decreased high latitude warming but is also a consequence of a weaker tropical warming. In the northern midlatitudes, sea ice decline affects the magnitude and sign of zonal wind response to global warming in the winter and autumn seasons. Presence or absence of sea ice cover impacts the intensity and frequency of winter extreme precipitation and temperature events (temperature minima, number of heavy precipitation days and number of ice days). For some of the analyzed extreme weather indices, the difference between the responses with and without sea ice decline is eliminated when taking into account the amplifying effect of sea ice loss on hemispheric warming. However, in other cases, we find the influence of higher order factors, exerting weaker but opposing effects than those expected from the global temperature increase.

Highlights

In recent decades, temperatures in the high northern latitudes have increased more than in any other area in the world, with the Arctic temperature increase being nearly double the global average change (Solomon 2006; Serreze and Francis 2006; IPCC 2007)
We investigate the effects of CO2 induced sea ice loss on global and local temperature changes, climate sensitivity, atmospheric circulation responses and atmospheric heat transport (AHT) partitioning as well as on the occurrence of extreme weather events
We focus on the impacts of sea ice decline on global temperature increase, midlatitude atmospheric circulation changes and extreme weather events

Summary

Introduction

Temperatures in the high northern latitudes have increased more than in any other area in the world, with the Arctic temperature increase being nearly double the global average change (Solomon 2006; Serreze and Francis 2006; IPCC 2007). The amplification is a consequence of a combination of several factors, with retreating sea ice cover playing a central role (Chapman and Walsh 2007; Serreze et al 2009; Screen and Simmonds 2010). Other important factors contributing to amplification of high latitude warming include changes in atmospheric sensible and latent heat transport (Alexeev et al 2005; Langen and Alexeev 2007; Graversen et al 2008; Graversen and Wang 2009; Alexeev and Jackson 2012), I. Caldeira cloud and water vapor radiative forcing (Vavrus and Harrison 2003; Graversen and Wang 2009; Kapsch et al 2013) and changes in ocean heat transport (Polyakov 2005; Mahlstein and Knutti 2011; Stroeve et al 2011)

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