Research press release


Nature Geoscience

Climate science: Iberian Peninsula drying out by Azores High expansion

アゾレス高気圧(大西洋に現れる高気圧)の拡大が、過去数千年の間でイベリア半島に最も乾燥した条件をもたらしていることを示したモデル化研究が、Nature Geoscience に掲載される。


Caroline Ummenhoferたちは今回、アゾレス高気圧のサイズと空間的広がりが過去1200年間にわたり、どのように変化したかをモデル化した。著者たちは、アゾレス高気圧が、約200年前の人類起源の温室効果ガス放出が大きく増加し始めた時に、平均としてより大きな領域に広がり始め、この空間的な拡大は20世紀により顕著になったことを明らかにしている。彼らのモデルを、西暦紀元850年までさかのぼるポルトガルの石筍内に保存された過去の降水量に対する地球化学的指標と比較することで、アゾレス高気圧の拡大が地中海西部の乾燥した冬の始まりと関連があることが示唆された。


The expansion of a high pressure system over the Atlantic — the Azores High — is leading to the driest conditions on the Iberian Peninsula in the last thousand years, according to a modelling study published in Nature Geoscience.

Weather and longer-term climate patterns in Western Europe are strongly impacted by atmospheric circulation associated with a persistent, clockwise-rotating area of high pressure known as the Azores High. Dry air descending towards the surface within the system is a leading cause of hot, arid summers in much of Portugal and Spain, as well as the western Mediterranean more broadly. During the characteristically wetter winter months, shifts in the position of the Azores High are responsible for westerly winds along its’ southern edge, moving moisture towards the Iberian Peninsula. This wintertime precipitation has, however, been decreasing in recent decades.

Caroline Ummenhofer and colleagues modelled how the size and spatial extent of the Azores High has changed over the last 1,200 years. The authors reveal that the Azores High began to, on average, cover a greater area starting around 200 years ago when human greenhouse gas emissions began to substantially increase, with this spatial expansion becoming more pronounced in the twentieth century. Comparison of their models with geochemical indicators of past precipitation levels preserved in Portuguese stalagmites extending back to 850 CE, suggests that the expansion of the Azores High is linked to the onset of drier winters in the western Mediterranean.

The authors conclude that the Azores High will continue to expand in to the twenty-first century as greenhouse gas levels continue to rise, leading to elevated risk of drought on the Iberian Peninsula.

doi: 10.1038/s41561-022-00971-w


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