7.
Despite growing evidence for environmental oscillations during the last glacial–interglacial transition from high latitude, terrestrial sites of the North Pacific rim, oxygen-isotopic records of these oscillations remain sparse. The lack of data is due partially to the paucity of lakes that contain carbonate sediment suitable for oxygen-isotopic analysis. We report here the first record of oxygen-isotopic composition in diatom silica (δ
18O
Si) from a lake in that region. δ
18O
Si increases gradually from 19.0 to 23.5‰ between 12,340 and 11,000
14C yr B.P., reflecting marked climatic warming at the end of the last glaciation. Around 11,000
14C yr B.P., δ
18O
Si decreases by 1.7‰, suggesting a temperature decrease of 3.5–8.9 °C at the onset of the Younger Dryas (YD) in southwestern Alaska. Climatic recovery began ca. 10,740
14C yr B.P., as inferred from the increase of δ
18O
Si to a maximum of 23.9‰ near the end of the YD. Our data reveal that a YD climatic reversal in southwestern coastal areas of Alaska occurred, but the YD climate did not return to full-glacial conditions.
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