Implications of all season Arctic sea-ice anomalies on the stratosphere

Abstract

In this study the impact of a substantially reduced Arctic sea-ice cover on the lower and middle stratosphere is investigated. For this purpose two simulations with fixed boundary conditions (the so-called time-slice mode) were performed with a Chemistry-Climate Model. A reference time-slice with boundary conditions representing the year 2000 is compared to a second sensitivity simulation in which the boundary conditions are identical apart from the polar sea-ice cover, which is set to represent the years 2089–2099. <br></br> Three features of Arctic air temperature response have been identified which are worth to be discussed in detail. Firstly, tropospheric mean polar temperatures increase up to 7 K during winter. This warming is primarily driven by changes in outgoing long-wave radiation. Secondly, temperatures decrease significantly in the summer stratosphere caused by a decline in outgoing short-wave radiation, accompanied by a characteristic increase of ozone mixing ratios. Thirdly, there are short periods of statistical significant temperature anomalies in the winter stratosphere probably driven by modified planetary wave activity. <br></br> Both the internal as well as the inter-annual variability of Arctic sea-ice content is related to Arctic climatic fields like surface air temperature, sea level pressure or precipitation, which are analogue with the variability of the Arctic Oscillation (AO)-index. In this study significant changes in the AO-index are detected in the course of winter. Neutral phases of AO appear more often. As expected, the dominating dynamical response of the stratosphere during winter turned out to be consistent to alterations in the tropospheric AO, although it is not statistically significant most of the time

Mechanisms of Stratospheric and Tropospheric Circulation Response to Projected Arctic Sea Ice Loss*

“…others by the effects from the Pacific ice loss (Cai et al 2012), or without a statistically significant structure [e.g., the future sea ice loss experiment in Peings and Magnusdottir (2014); Screen et al (2013);Sun et al (2014)]. The extent to which the different stratospheric circulation responses affect the tropospheric response remains an open question.…”

“…This has been found to be the case in some modeling and empirical studies (e.g., Peings and Magnusdottir 2014;Kim et al 2014;Feldstein and Lee 2014), in which Arctic sea ice loss induces a weakening of the polar vortex in February and a subsequent negative NAM response over the following weeks. However, other modeling studies instead find a strengthening of the polar vortex either in November (Cai et al 2012) or in March (Scinocca et al 2009;Screen et al 2013;Sun et al 2014) in response to Arctic sea ice loss. These discrepancies highlight the need for further research to understand the impact of Arctic sea ice loss on the stratospheric circulation and the role of the stratosphere in the tropospheric circulation response.…”

“…Some studies highlight the impact of sea ice loss in particular regions, for example, the Barents and Kara Seas (Honda et al 2009;Kim et al 2014;Nakamura et al 2015), while others consider the full geographical pattern of Arctic sea ice loss (Scinocca et al 2009;Deser et al 2010;Cai et al 2012;Screen et al 2013;Peings and ) response in DICE total (solid black curve), DICE autumn (solid green curve), and DICE total_cam4 (dashed red curve). Note the inverted scale for sea ice area.…”

Arctic Sea Ice Loss in Different Regions Leads to Contrasting Northern Hemisphere Impacts

“…However, these mechanisms remain uncertain because it is difficult to disentangle the complex web of potential processes involved (Overland et al, ), there are high levels of natural atmospheric variability (McCusker et al, ; Screen et al, ), and model results are contrasting—for example, some studies find a positive AO/NAO response (Orsolini et al, ; Screen et al, ), no significant AO/NAO response (Boland et al, ; Screen et al, ; Singarayer et al, ), or a stronger polar vortex (Cai et al, ; Scinocca et al, ; Screen et al, ; Sun et al, ). Here we make understanding these mechanisms more tractable by conducting idealized modeling experiments.…”

The stratospheric pathway for Arctic impacts on midlatitude climate

“…On the other hand, modeling studies have also provided supporting evidence for this dynamical process in the stratosphere and troposphere as responses to changes in both sea ice [ Orsolini et al , ; Kim et al , ; Nakamura et al , ] and snow boundary conditions [ Fletcher et al , ; Peings et al , ]. Other modeling studies have contradicting results on the AO phase as an Arctic sea ice response [ Cai et al , ].…”