Table. S1. Snow and ice sample list.


Fig. S1. Melting device for ice core analysis. Upper panel: Top view of the melting head. Lower panel: Cross-section of the melting head. The ice core samples were melted using a device developed by our group that enabled us to obtain water only from the inner portion of the cores; the 20 mm thick outer layer was remained intact. For the Austdomen ice core samples taken in 1999 by the Japanese Arctic Glaciological Expedition (JAGE) (Motoyama et al., 2001), dating was calculated by the delta 18O described by Watanabe and colleagues (2001) and Isaksson and colleagues (2003). In this experiment, the following three cores were studied: 6.34–6.78 m in depth (dated at 1991 year), 12.02–12.55 m in depth (dated at 1980 year) and 50.78–51.28 m in depth (dated at 1900 year). The ice cores analysed in this study consisted of superimposed ice (Motoyama et al., 2001). Complete separation of the inner and outer cores is required to avoid contamination by bacteria that can adhere to the cores during drilling and storage. To determine whether any contamination had occurred during handling or due to ice core cracks, a solution of ∼ 2 ng μl−1 bacterial plasmid vector was applied to the surface of the core samples. The vector contaminant was not amplified from the inner part of ice core samples, but amplified only with the outer layer of ice core samples by 45 cycles of PCR with vector-specific primers. Therefore, we proceeded with further DNA analyses on the inner portion of ice core samples.

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