TY - JOUR
T1 - Weakened potential vorticity barrier linked to recent winter Arctic Sea ice loss and midlatitude cold extremes
AU - Luo, Dehai
AU - Chen, Xiaodan
AU - Overland, James
AU - Simmonds, Ian
AU - Wu, Yutian
AU - Zhang, Pengfei
N1 - Funding Information:
Acknowledgments. Luo and Chen acknowledge the support from the National Key Research and Development Program of China (2016YFA0601802), the National Natural Science Foundation of China (Grants 41430533 and 41790473) and the Chinese Academy of Science Strategic Priority Research Program (Grant XDA 19070403). Overland was supported by the Arctic Research Program of the NOAA Climate Prediction Office (PMEL Contribution 4765). Simmonds was supported by the Australian Research Council (DP16010997). Authors YW and PZ are supported by the U.S. National Science Foundation under AGS-1815128. The authors thank Prof. Aiguo Dai for his constructive suggestions on an early draft of the paper.
Funding Information:
Luo and Chen acknowledge the support from the National Key Research and Development Program of China (2016YFA0601802), the National Natural Science Foundation of China (Grants 41430533 and 41790473) and the Chinese Academy of Science Strategic Priority Research Program (Grant XDA 19070403). Overland was supported by the Arctic Research Program of the NOAA Climate Prediction Office (PMEL Contribution 4765). Simmonds was supported by theAustralianResearch Council (DP16010997).Authors YW and PZ are supported by the U.S. National Science Foundation under AGS-1815128. The authors thank Prof. Aiguo Dai for his constructive suggestions on an early draft of the paper.
Publisher Copyright:
© 2019 American Meteorological Society.
PY - 2019
Y1 - 2019
N2 - A winter Eurasian cooling trend and a large decline of winter sea ice concentration (SIC) in the Barents- Kara Seas (BKS) are striking features of recent climate changes. The question arises as to what extent these phenomena are related. A mechanism is presented that establishes a link between recent winter SIC decline and midlatitude cold extremes. Such potential weather linkages are mediated by whether there is a weak north-south gradient of background tropospheric potential vorticity (PV).Astrong background PV gradient, which usually occurs in North Atlantic and Pacific Ocean midlatitudes, acts as a barrier that inhibits atmospheric blocking and southward cold air intrusion. Conversely, atmospheric blocking is more persistent in weakened PV gradient regions over Eurasia, Greenland, and northwestern North America because of weakened energy dispersion and intensified nonlinearity. The small climatological PV gradients over mid- to high-latitude Eurasia have become weaker in recent decades as BKS air temperatures show positive trends due to SIC loss, and this has led to more persistent high-latitude Ural-region blocking. These factors contribute to increased cold winter trend in East Asia. It is found, however, that in years when the winter PV gradient is small the East Asian cold extremes can even occur in the absence of large negative SIC anomalies. Thus, the magnitude of background PV gradient is an important controller of Arctic-midlatitude weather linkages, but it plays no role if Ural blocking is not present. Thus, the ''PV barrier'' concept presents a critical insight into the mechanism producing cold Eurasian extremes and is hypothesized to set up such Arctic- midlatitude linkages in other locations.
AB - A winter Eurasian cooling trend and a large decline of winter sea ice concentration (SIC) in the Barents- Kara Seas (BKS) are striking features of recent climate changes. The question arises as to what extent these phenomena are related. A mechanism is presented that establishes a link between recent winter SIC decline and midlatitude cold extremes. Such potential weather linkages are mediated by whether there is a weak north-south gradient of background tropospheric potential vorticity (PV).Astrong background PV gradient, which usually occurs in North Atlantic and Pacific Ocean midlatitudes, acts as a barrier that inhibits atmospheric blocking and southward cold air intrusion. Conversely, atmospheric blocking is more persistent in weakened PV gradient regions over Eurasia, Greenland, and northwestern North America because of weakened energy dispersion and intensified nonlinearity. The small climatological PV gradients over mid- to high-latitude Eurasia have become weaker in recent decades as BKS air temperatures show positive trends due to SIC loss, and this has led to more persistent high-latitude Ural-region blocking. These factors contribute to increased cold winter trend in East Asia. It is found, however, that in years when the winter PV gradient is small the East Asian cold extremes can even occur in the absence of large negative SIC anomalies. Thus, the magnitude of background PV gradient is an important controller of Arctic-midlatitude weather linkages, but it plays no role if Ural blocking is not present. Thus, the ''PV barrier'' concept presents a critical insight into the mechanism producing cold Eurasian extremes and is hypothesized to set up such Arctic- midlatitude linkages in other locations.
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U2 - 10.1175/JCLI-D-18-0449.1
DO - 10.1175/JCLI-D-18-0449.1
M3 - Article
AN - SCOPUS:85065815776
VL - 32
SP - 4235
EP - 4261
JO - Journal of Climate
JF - Journal of Climate
SN - 0894-8755
IS - 14
ER -