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We investigate for the first time the loss and alteration of past\udatmospheric information from air trapping mechanisms under low-accumulation\udconditions through continuous CH<sub>4</sub> (and CO) measurements. Methane\udconcentration changes were measured over the Dansgaard–Oeschger event 17\ud(DO-17,  ∼  60 000 yr BP) in the Antarctic Vostok 4G-2 ice\udcore. Measurements were performed using continuous-flow analysis combined\udwith laser spectroscopy. The results highlight many anomalous layers at the\udcentimeter scale that are unevenly distributed along the ice core. The anomalous\udmethane mixing ratios differ from those in the immediate surrounding layers\udby up to 50 ppbv. This phenomenon can be theoretically reproduced\udby a simple layered trapping model, creating very localized gas age scale\udinversions. We propose a method for cleaning the record of anomalous values\udthat aims at minimizing the bias in the overall signal. Once the\udlayered-trapping-induced anomalies are removed from the record, DO-17 appears\udto be smoother than its equivalent record from the high-accumulation WAIS\udDivide ice core. This is expected due to the slower sinking and densification\udspeeds of firn layers at lower accumulation. However, the\uddegree of smoothing appears surprisingly similar between modern and DO-17 conditions at\udVostok. This suggests that glacial records of trace gases from low-accumulation sites in the East Antarctic plateau can provide a better time\udresolution of past atmospheric composition changes than previously expected.\udWe also developed a numerical method to extract the gas age distributions in\udice layers after the removal of the anomalous layers based on comparison\udwith a weakly smoothed record. It is particularly adapted for the conditions\udof the East Antarctic plateau, as it helps to characterize smoothing for a\udlarge range of very low-temperature and low-accumulation conditions

Analytical constraints on layered gas trapping and smoothing of atmospheric variability in ice under low-accumulation conditions