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100th meridian : East-west divide between moist and arid parts of U.S. may be shifting. Warming climate may push western aridity to the east

ScienceDaily (April 11, 2018)

Titre : 100th meridian : East-west divide between moist and arid parts of U.S. may be shifting . Warming climate may push western aridity to the east

ScienceDaily (April 11, 2018)

Résumé
Nearly a century and a half after explorer John Wesley Powell zeroed in on the 100th meridian west as the dividing line between the humid east and arid west of the United States, researchers say he was right — but that climate change is now moving the line eastward, into the traditionally fertile Midwest. The effects on U.S. farming and other pursuits could be huge.

Présentation
In the United States, the effects show up in obvious ways. To the west, population density drops sharply. There are fewer homes, commercial facilities and roads. Farms are fewer, but bigger, reflecting the economics of less water and thus lower productivity. To the east, 70 percent of the crop is moisture-loving corn ; to the west, aridity-resistant wheat is dominant. Now, the researchers say, warming climate appears to be pushing the divide east. In the northern plains, rainfall has not changed much, but temperatures are going up, increasing evaporation from the soil. Further south, concurrent shifts in wind patterns are in fact causing less rain to fall. Either way, this tends to push western aridity eastward. Data collected since about 1980 suggests that the statistical divide between humid and arid has now shifted closer to the 98th meridian, some 140 miles east. (In Texas, this would move it roughly from Abilene to Fort Worth.) Seager says year-to-year weather variations may blur the data, and in any case the changes are still too small and gradual to yet affect land use over wide areas. But he is confident that aridity will perceptibly move eastward during the 21st century, and eventually effect large-scale changes.

Story Source  : Lamont-Doherty Earth Observatory, Columbia University

Annonce (ScienceDaily)

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