A study suggests a connection between Arctic sea ice melting and altered Pacific El Niño activity. The first decades of the 21st century have witnessed notable global climatic shifts relative to the last decades of the 20th century, including increased summer melting of Arctic sea ice, strengthened Central Pacific trade winds, and increased frequency of Central Pacific El Niño events. Charles Kennel and Elena Yulaeva applied a conceptual model, originally proposed to connect changes in Arctic sea ice to changes in mid-latitude extreme weather events, to explain the observed changes in trade winds and El Niño behavior in the tropics. According to this model, sea ice melt leads to Arctic Ocean warming, which in turn drives vertical convection. Consistent with this hypothesis, static stability calculations revealed recurring periods of atmospheric instability in the Arctic during September-October, lasting approximately 40-45 days. The convection generates planetary waves in the atmosphere that carry heat and momentum southward to the Intertropical Convergence Zone (ITCZ), leading to long-range connections between the Arctic and the ITCZ. The connections manifest as correlations between upper atmospheric circulation data and Arctic sea ice area. Interaction between atmospheric waves and the ITCZ air column creates westerly anomalies in the trade winds in December, and may contribute to Central Pacific El Niño events, according to the authors.
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Article #17-17707: "Influence of Arctic sea-ice variability on Pacific trade winds," by Charles F. Kennel and Elena Yulaeva.
MEDIA CONTACT: Charles F. Kennel, University of California, San Diego, CA; tel: 858-488-0230, 858-232-0219; e-mail: < ckennel@ucsd.edu >
Proceedings of the National Academy of Sciences