Using causal effect networks to analyze different Arctic drivers of mid-latitude winter circulation
File(s)
Published version
Author(s)
Kretschmer, M
Coumou, D
Donges, JF
Runge, J
Type
Journal Article
Abstract
In the past years, the northern hemisphere mid-latitudes have suffered from severe winters like the extreme 2012/2013 winter in Eastern USA. These cold spells were linked to a meandering upper tropospheric jet stream pattern and a negative Arctic Oscillation Index (AO). However, the nature of the drivers behind these circulation patterns remains controversial. Various studies have proposed different mechanisms related to changes in the Arctic, most of them related to a reduction in sea ice concentrations or increasing Eurasian snow cover. Here, a novel type of time series analysis, called Causal Effect Networks (CEN) based on graphical models is introduced to assess causal relationships and their time-delays between different processes. The effect of different Arctic actors on winter circulation on weekly to monthly time-scales is studied and robust network patterns are found. Barents and Kara sea ice concentrations are detected to be important external drivers of the mid-latitude circulation, influencing winter AO via tropospheric mechanisms and through processes involving the Stratosphere. Eurasia snow cover is also detected to have a causal effect on sea level pressure in Asia, but its exact role on AO remains unclear. The CEN approach presented in this study overcomes some difficulties in interpreting correlation analyses, complements model experiments for testing hypotheses involving teleconnections, and can be used to assess their validity. Our findings confirm that sea ice concentrations in autumn in the Barents and Kara Seas are an important driver of winter circulation in the mid-latitudes.
Date Issued
2016-05-20
Date Acceptance
2016-01-22
Citation
Journal of Climate, 2016, 29, pp.4069-4081
ISSN
0894-8755
Publisher
American Meteorological Society
Start Page
4069
End Page
4081
Journal / Book Title
Journal of Climate
Volume
29
Copyright Statement
© 2016 American Meteorological Society.
Subjects
Meteorology & Atmospheric Sciences
0401 Atmospheric Sciences
0405 Oceanography
Publication Status
Published