Climate Effects on Firn Permeability Are Preserved Within a Firn Column

Abstract

AbstractWe have investigated the impacts of short‐term climatic events on firn‐permeability evolution, by analyzing density and permeability measurements from the NEEM 2009 S2 firn core from the North Greenland Eemian Ice Drilling (NEEM) site in Greenland. Our results indicate that the firn layers from 27.4 to 34.9‐m depth display the expected density but unexpected permeability values, indicating a change in firn permeability during the years 1917 to 1940. The δ18O and accumulation rates from a compilation of NEEM shallow cores indicate that 1928, 1929, and 1933 were significantly warmer years, and that 1928 and 1933 also had significantly higher accumulation rates. These results suggest that the sharp rise in Arctic temperature during the late 1920s and early 1930s caused metamorphism of the near‐surface firn, which was preserved in the layers at depth. Conversely, the average density remained undisturbed throughout this warm period. Our results show that climate fluctuations, especially increased temperature, permanently change the firn permeability. Without taking these changes into consideration, estimates of Δage will be inaccurate.