Stable carbon isotope ratio analyses on trace methane from ice samples

►We present an isotope ratio mass spectrometer method to measure ice sample δ13CH4. ► We use a unique post-combustion trapping to produce a high amplitude sample peak. ► We require only ~ 165 pmol of CH4 (~ 30-150 g of ice, CH4 mixing ratio dependent). ► Precision was evaluated with atmospheric air, artificial and GISP2 ice samples. ► Precision is < ± 0.3 ‰ (1σ) and our GISP2 results are in line with published data.