Last Glacial Paleoclimate Reconstructed from Glacial and Periglacial Landforns in Japan

ONO Yugo

doi:10.4157/grj1984b.57.87

Paleoclimate during the Last Glacial age was reconstructed from glacial and periglacial landforms in Japan. Both the summer air temperature and the winter precipitation were the major controlling factors for the glaciation in the Japanese high mountains. Because of the change of paleogeography of the Japan Sea, which was caused by the sea-level changes, the fluctuation of the amount of snowfall must have been large. Mountain glaciation attained to its maximum between about 60, 000 and 40, 000 y. B. P., when the warm current still entered into the Japan Sea. The glacial extension was much more limited between 30, 000 and 10, 000 y. B. P., when the Japan Sea had been almost isolated from the outer ocean. Distributions of the glacial landforms, both horizontal and vertical, indicate that the winter monsoon had basically the westerly direction during the Last Glacial age. That is also verified by the distribution of fossil periglacial phenomena. The latter was used for the reconstruction of winter and annual mean air temperatures. Decrease of the summer monsoon precipitation was evidenced by tracing of the valley filling with debris which indicates a considerable diminution of river discharge during the Last Glacial age. Location of the polar front during the Last Glacial age was inferred together with the southern limit of sea ice and the distribution of permafrost. Decrease of the summer air temperature and the effect of snowfall on the glaciation were discussed by comparing the altitude of the present and Last Glacial snowlines.

Last Glacial Paleoclimate Reconstructed from Glacial and Periglacial Landforns in Japan

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