Analysis of Ice Layers in the NEEM Firn Column

The physical properties of the stratigraphic layers in the firn column affect gas transport within the firn column and, ultimately, the trapping of gases that reflect past atmospheric compositions. A core from the CO2 firn-air sampling site at NEEM was retrieved in July 2009, and the physical properties of the firn have been analyzed. In the 81m of analyzed firn core, two regions containing ice layers were identified at depths of 29m and 46m. Isotopic analysis provides a depth-age scale that dates these layers to be from 1935 and 1879, respectively. These years were in the two warmest decades of the instrumental temperature record for Greenland. Density, permeability, and isotopic data from these ice layers and surrounding firn will be compared to the historic regional climate, as well as to ice layers found in other Greenland firn cores. The disruption of the firn diffusive column caused by these ice layers will be discussed, as well as implications for firn-air measurements.