The age reconstruction of the bottom part of the Siple Dome Ice Core Makoto Suwa 1*, Jinho Ahn 2, Bruce Barnett 1, Michael Bender 1, Ed Brook 3, Martin Wahlen 2 and James White 4 1 Department of Geosciences, Princeton University, Princeton, NJ, USA 2 Scripps Institution of Oceanography, University of California San Diego, CA, USA 3 Department of Geology and Program in Environmental Science, Washington State University, Vancouver, WA, USA 4 Institute for Arctic and Alpine Research, and Department of Geological Sciences, University of Colorado, Boulder, CO, USA. *To whom correspondence should be addressed:

Vostok Ice Core Siple Dome Ice Core 97.6 Ka Extrapolated time scale > 97.6 ka temperature proxy δ 18 O of atmospheric O 2 CH 4 CO 2

Bottom section of the Siple Dome Ice Core CH 4 cut off = 800ppbv CO 2 cut off = 300ppmv ~3-4% δDδD δ 18 O of atmospheric O 2 CH 4 CO 2 total gas content ~40% δ 15 N of atmospheric N 2

Method ka Use δ 18 O – CO 2 to constrain age for the bottom part of the Siple Dome Ice Core. Use CH 4 to validate the age reconstruction Vostok δ 18 O – CO 2

100 ka Method 1 Vostok δ 18 O – CO 2

Method 2 Use CH 4 – δ 18 O – CO 2 to constrain age for the bottom part of the Siple Dome Ice Core. Vostok CH 4 – δ 18 O – CO ka 97.6 ka

Method 1 Method 1 (δ 18 O – CO 2 to constrain age) δDδD δ 18 O of atmospheric O 2 CH 4 CO 2

Method 2 Method 2 (CH 4 – δ 18 O – CO 2 to constrain age) δDδD δ 18 O of atmospheric O 2 CH 4 CO 2

Method 1 Method 1 (δ 18 O – CO 2 to constrain age) ka m m

Method 2 Method 2 (CH 4 – δ 18 O – CO 2 to constrain age) ka m m

Conclusions Most of the bottom ice (below 976 m) is from 100 ka – 135 ka Most of the bottom ice (below 976 m) is from 100 ka – 135 ka Our results suggest that disturbance of the ice starts between m and m below surface, i.e. stratigraphy is undisturbed up to ka Our results suggest that disturbance of the ice starts between m and m below surface, i.e. stratigraphy is undisturbed up to ka We do not find ice from the warmest period of the last interglacial, MIS–5e. We do not find ice from the warmest period of the last interglacial, MIS–5e. The bottom-most 5m of ice has anomaly low δD record.  Could have been formed at a higher elevation site and flowed into the Siple Dome area. The total gas content of this ice is 3-4% lower, and δ 15 N is ~40% higher than for samples right above this section. The bottom-most 5m of ice has anomaly low δD record.  Could have been formed at a higher elevation site and flowed into the Siple Dome area. The total gas content of this ice is 3-4% lower, and δ 15 N is ~40% higher than for samples right above this section.

97 ka ~ 300 ka

Method 1 Method 1 (δ 18 O – CO 2 to constrain age) δDδD δ 18 O of atmospheric O 2 CH 4 CO 2

Method 2 Method 2 (CH 4 – δ 18 O – CO 2 to constrain age) δDδD δ 18 O of atmospheric O 2 CH 4 CO 2

Method 1 Method 1 (δ 18 O – CO 2 to constrain age) ka m m

Method 1 Method 1 (δ 18 O – CO 2 to constrain age) δDδD δ 18 O of atmospheric O 2 CH 4 CO 2

Method 1 Method 1 (δ 18 O – CO 2 to constrain age)