Research press release


Nature Geoscience

Hot Arctic drives North American freeze



Jong-Seong Kugたちは、ベーリング海の海面温度指標を解析して、北極の温度が高い年はアラスカ上空の大気循環の変化がそれに対応する変化を西部の循環に及ぼし、北米の大部分において顕著な寒冷化と大陸南部の乾燥をもたらすことを見いだした。彼らは、このように温度が低く降雨が少ない年は、穀物収穫高が平均1-4%減少すること、そして北アメリカ生態系のCO2吸収量がおよそ14%減少することを発見した。


同時掲載のNews & Views記事でAna Bastosは、「今回見つかった関連性が今後数十年に北アメリカ生態系が吸収できる炭素量の減少を暗示しているかどうかは明らかではない」と述べている。

Warmer-than-average years in the Arctic cause colder winters and springs in North America, according to a study published online in Nature Geoscience. The study finds that these cooler winters and springs result in decreased vegetation growth in North American ecosystems, and hence reduced capacity for those ecosystems to uptake CO2.

Although it has long been known that interannual variability in ocean temperatures can affect climate and productivity (as during El Nino), Arctic temperatures have not been previously linked to North American plant productivity.

Jong-Seong Kug and colleagues analyse an index of sea-surface temperatures from the Bering Sea and find that in years with higher Arctic temperatures, changes in atmospheric circulation over Alaska create corresponding changes in circulation to the west, resulting in substantial cooling over most of North America and drying in the southern part of the continent. In years with these lower temperatures and precipitation, they find that the capacity of North American ecosystems to take up CO2 declined by about 14%, including reductions in crop yields of 1 to 4% on average.

The authors’ examination of the effect of warmer-than-average years focused on the effects of climate variability, rather than climate change. However, they suggest that a strengthening of interannual variability in the Arctic over the past thirty years - related to the rapid decline in Arctic sea-ice - could have resulted in a decline in terrestrial productivity in North America.

In an accompanying News & Views, Ana Bastos writes: “Whether the relationship found implies a decreasing carbon sink capacity of North American ecosystems in the coming decades is unclear.”

doi: 10.1038/ngeo2986


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