NOAA/WDS Paleoclimatology - Lake Mackenzie, Subtropical East Australian Glacial and Holocene Surface Air Temperature Reconstruction

Branched glycerol dialkyl glycerol tetraether (GDGT) distributions observed in a sediment core from Lake McKenzie were utilized to quantitatively reconstruct the pattern of mean annual air temperature (MAAT) from coastal subtropical eastern Australia between 37 and 18.3 cal ka BP and 14.0 cal ka BP to present. Both the reconstructed trend and amplitude of MAAT changes from the top of the sediment core were nearly identical to a local instrumental MAAT record from Fraser Island, providing confidence that in this sediment core branched GDGTs could be used to produce a quantitative record of past MAAT. The reconstructed trend of MAAT during 37 to 18.3 cal ka BP and timing of the Last Glacial Maximum (LGM) in the Lake McKenzie record were in agreement with previously published nearby marine climate records. The amplitude of lower-than-present MAAT during the LGM potentially provides information on the latitude of separation of the Tasman Front from the East Australian current in the subtropical western Pacific. The Lake McKenzie record shows an earlier onset of near modern day warm temperatures in the early Holocene compared to marine records and the presence of a warmer than present day period during the mid-Holocene.

本研究利用麦肯齐湖（Lake McKenzie）一处沉积物岩芯中测得的支链甘油二烷基甘油四醚（branched glycerol dialkyl glycerol tetraether, GDGT）分布数据，对澳大利亚东部亚热带沿海区域在37~18.3距今校准千年（cal ka BP）以及14.0距今校准千年至今时段的年平均气温（mean annual air temperature, MAAT）变化模式开展了定量重建。沉积物岩芯顶部重建得到的年平均气温变化趋势与波动幅度，均与弗雷泽岛的本地实测年平均气温记录高度吻合，这证实了该岩芯中的支链GDGT可用于构建古年平均气温的定量序列。37~18.3 cal ka BP时段的年平均气温重建趋势，以及麦肯齐湖记录所反映的末次盛冰期（Last Glacial Maximum, LGM）出现时间，均与已发表的邻近海域气候记录相符。末次盛冰期期间气温低于现代的波动幅度，可为亚热带西太平洋区域塔斯曼海锋（Tasman Front）与东澳洋流（East Australian Current）的分离纬度提供相关约束信息。相较于海洋气候记录，麦肯齐湖记录显示全新世（Holocene）早期的近现代暖温期出现时间更早，且全新世中期存在一段气温高于现代的时段。