Local Variability of Ice Core Ammonium and Black Carbon Records From Tunu and Summit, Greenland: Implications for Long‐Term Biomass Burning Reconstructions

Paleoclimate reconstructions of wildfire using ice cores often rely on high‐resolution aerosol records of refractory black carbon (rBC) or ammonium (NH 4 + ). The interpretation of such records, however, can be hindered by uncertainties related to long‐range atmospheric transport, spatial distribution and strength of emissions, as well as glaciochemical noise introduced to the record during and after deposition. Here, we use arrays of parallel ice cores collected from two sites in Greenland, each with differing characteristics including accumulation rate, elevation, and meteorology, to assess the spatial variability and site representativeness of their rBC and NH 4 + records. The higher accumulation site, Summit, was found to preserve a more coherent signal of both aerosols across multiple ice core records and was more representative of the total site signal than the lower accumulation site, Tunu. Representativeness analyses indicate that a single core at Summit is as representative of the theoretical total site signal as a combined three core composite record from Tunu for rBC and NH 4 + at annual resolution. This work suggests that high temporal resolution records of these aerosols using a single core from either site have considerable uncertainties, highlighting the need for careful consideration of the effects of site conditions on aerosol representativeness for wildfire reconstruction.