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  • 1
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    The role of stratospheric ozone for Arctic-midlatitude linkages (2019)
    Nature Publishing Group
    In:  EPIC3Scientific Reports, Nature Publishing Group, 9(7962), ISSN: 2045-2322
    Details
    Publication Date: 2019-06-11
    Description: Arctic warming was more pronounced than warming in midlatitudes in the last decades making this region a hotspot of climate change. Associated with this, a rapid decline of sea-ice extent and a decrease of its thickness has been observed. Sea-ice retreat allows for an increased transport of heat and momentum from the ocean up to the tropo- and stratosphere by enhanced upward propagation of planetary-scale atmospheric waves. In the upper atmosphere, these waves deposit the momentum transported, disturbing the stratospheric polar vortex, which can lead to a breakdown of this circulation with the potential to also significantly impact the troposphere in mid- to late-winter and early spring. Therefore, an accurate representation of stratospheric processes in climate models is necessary to improve the understanding of the impact of retreating sea ice on the atmospheric circulation. By modeling the atmospheric response to a prescribed decline in Arctic sea ice, we show that including interactive stratospheric ozone chemistry in atmospheric model calculations leads to an improvement in tropo-stratospheric interactions compared to simulations without interactive chemistry. This suggests that stratospheric ozone chemistry is important for the understanding of sea ice related impacts on atmospheric dynamics.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
    Format: application/pdf
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  • 2
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    Improving the representation of linkages between the Arctic and mid-latitudes by implementing fast interactive ozone chemistry (2019)
    In:  EPIC3PAMIP Workshop 2019, Totnes, UK, 2019-06-24-2019-06-27
    Details
    Publication Date: 2019-07-10
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 3
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    Atmospheric mechanisms for�Arctic-midlatitude linkages (2019)
    In:  EPIC3REKLIM Konferenz, Berlin, 2019-09-23-2019-09-26
    Details
    Publication Date: 2020-07-14
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 4
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    Regime behaviour in the Atlantic-Eurasian Arctic related to sea ice and sea surface temperature changes (2020)
    In:  EPIC3EGU General Assembly 2020, Online, 2020-05-04-2020-05-08
    Details
    Publication Date: 2020-07-14
    Description: Climate change in the Arctic is embedded in the global climate system leading to phenomenon like Arctic Amplification and linkages to the mid-latitudes. A major forcing emerges from changed surface conditions like declining sea ice cover (SIC) and rising sea surface temperatures (SST). We performed time-slice model experiments with the global atmosphere-only model ECHAM6 and changed SIC and SST to either high or low states, respectively. These experiments are compared to reanalysis data and analysed aiming at a separation between the influences of SIC and SST, while focusing on linkages between the Arctic and mid-latitudes in winter. We identify five significant regimes in the Atlantic-Eurasian sector with the k-means clustering method. The regimes include different blocking patterns, situation with strong low pressure influence and the North Atlantic Oscillation in its two phases. Their frequency of occurrence is discussed for winter months. In the reanalysis we observe an increase of blocking patterns in early winter of the most recent decades. This is reproduced by our experiments with increased SST, where blocking becomes more dominant overall. In late winter, an increased frequency of occurrence of the North Atlantic Oscillation in its negative phase is observed. This and the overall temporal behaviour of regimes in recent years is best represented if SST and SIC are changed to their more recent state simultaneously. Therefore, our results suggest that increased SSTs and reduced SIC together act on observed linkages between polar regions and mid-latitudes.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 5
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    The linkage between Arctic sea ice changes and mid-latitude atmospheric circulation in reanalysis data and model simulations - The role of tropo-stratospheric coupling (2017)
    In:  EPIC3US CLIVAR Workshop: Arctic Change and Its Influence on Mid-Latitude Climate and Weather, Washington, DC, 2017-02-01-2017-02-03
    Details
    Publication Date: 2017-02-13
    Description: Observed global warming trends have their maximum in Arctic regions, a phenomenon referred to as Arctic Amplification. Consequently, Arctic sea ice shows a strong decreasing trend. These changes imprint modifications on atmospheric flow patterns not only in Arctic regions themselves. Changes of teleconnections and planetary scale motions like Rossby waves affect mid-latitude climate as well. We identified mechanisms that link recent Arctic changes through vertically propagating planetary waves to weakening events of the stratospheric polar vortex. Related anomalies then propagate downward and lead to negative AO-like situations in the troposphere. These results based on ERA-Interim reanalysis data do not allow to entirely dismiss other potential forcing factors leading to observed mid-latitude climate changes. More importantly, properly designed Atmospheric General Circulation Model (AGCM) experiments with AFES and ECHAM6 are able to reproduce observed atmospheric circulation changes if only observed sea ice changes in the Arctic are prescribed. This includes the potential mechanism explaining how Arctic Amplification can lead to a negative AO response via a stratospheric pathway. A further examination of barotropic-baroclinic interactions based on nonlinear kinetic energy and enstrophy interaction will be given by Handorf et al. (abstract submitted).
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 6
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    Linkages between Arctic sea-ice changes and atmospheric circulation patterns in reanalysis data and model simulations (2017)
    In:  EPIC3The International Workshop Polar Climate Change, Nanjing, China, 2017-10-23-2017-10-24
    Details
    Publication Date: 2017-11-20
    Description: Observed global warming trends have their maximum in Arctic regions, a phenomenon referred to as Arctic Amplification. Consequently, Arctic sea ice shows a strong decreasing trend. These changes imprint modifications on atmospheric flow patterns not only in Arctic regions themselves. Changes of teleconnections and planetary scale motions like Rossby waves affect mid-latitude climate as well. The application of a cluster analysis revealed two circulation patterns that occur more frequently for low Arctic sea ice conditions: a Scandinavian blocking in December and January and a negative North Atlantic Oscillation pattern in February and March. The first pattern is related to enhanced upward wave propagation in this region and period. These waves reach the stratosphere and disturb the polar vortex. The downward response is again linked to the higher frequency of negative NAO events in late winter. These results are consistent in reanalysis data and model simulations.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 7
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    Separating the impact of sea ice and sea surface temperature changes onArctic climate and its linkages to mid-latitudes (2019)
    In:  EPIC3EGU General Assembly 2019, Wien, 2019-04-08-2019-04-12
    Details
    Publication Date: 2019-06-11
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 8
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    Atmospheric winter response to Arctic sea ice changes in reanalysis data and model simulations - The role of troposphere-stratosphere coupling (2017)
    In:  EPIC3EGU General Assembly, Wien, Austria, 2017-04-23-2017-04-28
    Details
    Publication Date: 2017-06-08
    Description: In recent years, Arctic regions showcased the most pronounced signals of a changing climate: Sea ice is reduced by more the ten percent per decade. At the same time, global warming trends have their maximum in Arctic latitudes often labled Arctic Amplification. There is strong evidence that amplified Arctic changes feed back into mid-latitudes in winter. We identified mechanisms that link recent Arctic changes through vertically propagating planetary waves to events of a weakened stratospheric polar vortex. Related anomalies propagate downward and lead to negative AO-like situations in the troposphere. European winter climate is sensitive to negative AO situations in terms of cold air outbreaks that are likely to occur more often in that case. These results based on ERAInterim reanalysis data do not allow to dismiss other potential forcing factors leading to observed mid-latitude climate changes. Nevertheless, properly designed Atmospheric General Circulation Model (AGCM) experiments with AFES and ECHAM6 are able to reproduce observed atmospheric circulation changes if only observed sea ice changes in the Arctic are prescribed. This allows to deduce mechanisms that explain how Arctic Amplification can lead to a negative AO response via a stratospheric pathway. Further investigation of these mechanisms may feed into improved prediction systems.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 9
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    Linkages between Arctic and Mid-Latitude Weather and Climate: Unraveling the Impact of Changing Sea Ice and Sea Surface Temperatures (2021)
    In:  EPIC3EMS Annual Meeting 2021, online, 2021-09-05-2021-09-09
    Details
    Publication Date: 2021-09-29
    Description: The study addresses the question, if Arctic sea ice decline is the main driver of observed changes in terms of Arctic-midlatitude linkages during winter. We discuss, if the increase of global sea surface temperatures plays an additional role. A set of four model sensitivity experiments with different sea ice and sea surface temperature boundary conditions is analyzed and compared to observed changes in reanalysis data. A detection of atmospheric circulation regimes is performed. These regimes are evaluated for their cyclone and blocking characteristics and their changes in frequency during winter to reveal tropospheric changes induced by the change of boundary conditions. Furthermore, the impacts on the large-scale circulation up into the stratosphere are investigated. The results show that the impact from sea surface temperature changes is generally stronger than the impact of sea ice concentration changes alone. However, in particular in terms of the startospheric pathway, the combined impact of sea ice and sea surface temperature changes reproduces findings from the reanalysis best. For early winter, the observed increase in atmospheric blocking in the region between Scandinavia and the Ural are primarily induced by the changes in sea surface temperatures. Nevertheless, the impacts on the stratospheric circulation in terms of a weakened polar vortex, are only observed if sea ice is reduced and sea surface temperatures are increased. Late winter impacts are more inconsistent in the model sensitivity study, but slightly improved when both components of forcing are changed. In this context, we further identify a discrepancy in the model to reproduce the weakening of the stratospheric polar vortex through blocking induced upward propagation of planetary waves.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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