アンデス山脈における現在および氷期の雪線高度の分布からみた氷期の気候

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It is the purpose of this paper to infer the atomospheric circulation pattern in the Andes Mountains during the last glacial period, Wisconsin, from the former snow line, on the basis of relationship of the present snow line to the present circulation pattern. The former snow line was reconstructed from the altitude of lowest cirque bottoms. Data were obtained from my own field observations, map interpretations and literatures of some authors. Hights of snow line are shown as distribution map in Fig. 1 and as generalized meridional section in Fig. 2.The curve of present snow line (PSL) takes a maximum value in the center of the subtropical high pressure belt. No difference is apparent in the position of the maximum point between PSL and Wisconsin snow line (WSL). PSL drops abruptly from the maximum point to lat. 40°S, and gently from there to the south pole. This break point in the snow line gradient coincides with the northern limit of the rainy zone where we have much precipitation by westerlies throughout the year. It did not move either. And WSL appears to be somewhat in parallel with PSL for the most part of the Andes Mountains.From the facts described above, it can be concluded that the atomospheric circulation pattern during the Wisconsin glacial period was much the same as the present pattern, and that the Wisconsin snow line depression in the Andean sector was not caused by increasing of precipitation, which would be resulted from climatic zone shift, but mostly by cooling of atomosphere. It. may be considered that the distinctive shift of climatic zones in the Northern Hemisphere was a secondary phenomena caused by enormous expansion of continental ice sheets in the glacial period.
日本第四紀学会の論文

著者

野上道男
東京都立大学

アンデス山脈における現在および氷期の雪線高度の分布からみた氷期の気候

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