Arctic sea ice seasonal-to-decadal variability and long-term change

Abstract

Introduction The large-scale loss of Arctic sea ice in recent decades is one of the most prominent indicators of the ongoing global climate change. This derives from three main reasons. First, climate change is amplified in the Arctic (" Arctic amplification " , e.g. Pithan et al. (2013)), so consequences of changes in the global-mean climate are more readily observed at high latitudes compared to middle and lower latitudes. Second, while many observables change gradually with global mean climate, Arctic sea ice is among those observables that might eventually cross a binary threshold from " existing " to " non-existing " , which amplifies the perception of the underlying gradual trend. And third, as a consequence, changes in " Arctic sea ice coverage " are easier to grasp and communicate to a general public than changes in more abstract metrics such as " global mean temperature " . The observed changes in Arctic sea ice are not only a clear local indicator of large-scale climate change; the ice loss also has a number of sometimes far-reaching worldwide consequences. These include physical phenomena such as the possible impact on mid-latitude weather system or the disruption of the oceanic uptake of CO 2 , but also societal consequences such as the opening of new shipping routes or the necessary changes in the lifelihood of the Arctic indigenous population. The importance of sea ice loss both as an indicator and as an active player in the ongoing climate change has motivated some intense research into understanding the temporal evolution of sea ice on time scales from seasons to decades. In this contribution, I use a combined analysis of the observational record and of climate model simulations to explain and summarize some of these findings.