Thermal Fractionation of Firn Air and the Ice Core Record of Abrupt Interstadial Climate Change

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9725305 Severinghaus This award supports a project to develop and apply a new technique for quantifying temperature changes in the past based on the thermodynamic principle of thermal diffusion, in which gas mixtures in a temperature gradient become fractionated. Air in polar firn is fractionated by temperature gradients induced by abrupt climate change, and a record of this air is preserved in bubbles in the ice. The magnitude of the abrupt temperature change, the precise relative timing, and an estimate of the absolute temperature change can be determined. By providing a gas-phase stratigraphic marker of temperature change, the phasing of methane (with decadal precision) and hence widespread climate change (relative to local polar temperature changes) can be determined (across five abrupt warming events during the last glacial period).