Did a Chukchi sea-ice decline cause hemispheric extreme cold winter in 2017-18?
Abstract
In East Asia and North America, extreme cold weather characterized the winter of 2017-18. The Arctic Oscillation, which is a good measure for hemispheric cold weather, was persistently in its negative phase from mid-November through mid-February. The seasonal mean temperature in western Japan was the lowest recorded since 1985-86. La Niña is known as a cause of extreme cold weather. One other possible explanation for the cold winter is sea ice decline in the Barents and Kara Sea, located the northern coast of Norway. However, both of factors were not abnormal anomaly in the 2017-18 winter compared with last decade. Here we hypothesized that a new candidate is sea ice decline in the Chukchi Sea, located the Arctic Ocean Pacific sector, which experienced the lowest sea ice coverage of recent decades. We considered the influence of a Chukchi sea-ice decline on the hemispheric cold winter. Eurasian pattern (EU) and Pacific-North American pattern (PNA) indices, which are good measure for cold winter on East Asia and North America respectively, were both abnormal high values in 2017-18. The winter of 2017-18 was the only case that all the three indices (EU, PNA and a Chukchi sea-ice indices) were abnormal high value. Regressed large-scale atmospheric fields with these indices were similar to observed atmospheric fields appeared in 2017-18 winter (see Figure). In order to verify whether the Chukchi sea-ice decline drives those atmospheric fields, we applied a simple numerical experiment using a linear baroclinic model. Atmospheric response patterns to given heating anomalies to the surface layer over the Chukchi Sea were similar to the regressed atmospheric fields with the Chukchi sea-ice index. These results signify that abnormal Chukchi sea-ice decline affect large-scale atmospheric circulations leading to abnormal cold winter in 2017-18.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A41O2797O
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 3319 General circulation;
- ATMOSPHERIC PROCESSES;
- 3349 Polar meteorology;
- ATMOSPHERIC PROCESSES;
- 1621 Cryospheric change;
- GLOBAL CHANGE