Late Holocene tundra fires and linkages to climate and vegetation in northern Alaska

Charcoal particles in lake-sediments can reveal past fires and linkages to climate and vegetation change. We use analyses of charcoal accumulation rates from two lakes (Lake I4 and Kirk Lake) on the Alaskan North Slope to reconstruct past fire activity, and charcoal morphology to identify changes in fuel sources. This dataset contains 1) chronological data for both lake-sediment cores used to construct age-depth models (Pb-210 and radiocarbon), 2) magnetic susceptibility measurements for both cores, 3) macroscopic charcoal particle counts for both sites at three size fractions (90-125µm, 125-250µm, and >250µm), and 4) charcoal morphology (classes defined in associated Arctic Science publication). 

Methods
 210Pb data was generated vis gamma spectrometry on a Mirion HPGe small anode germanium (SAGe) well detector. Activities for 210Pb (46.5 keV) and 226Ra (calculated from average of 214Pb (351.9 keV) and 214Bi (609.3 keV) activities) presented. 

Radiocarbon ages were measured from macrofossil material extracted from cores and submitted to the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) for AMS 14C dating. Reported 14C ages were calibrated with the INTCAL 20 dataset  using CALIB version 8.2. 

Magnetic susceptibility was measured on split core surfaces (continuous measurements) on a Geotek MSCL-S system with a Barrington MS-C point meter. 

Charcoal particles were sieved from measured volumes of wet sediment with a sieve cascade of 90, 125, and 250 µm, and particles counts were enumerated for each size fraction. 

Charcoal morphologies for all particles >90 µm were identified (see publication for full methodology and references). Morphotypes M and P are irregular particles with and without structure, morphotypes S and C are geometric particles with and without structure, and morphotypes F and D are elongated particles with and without ramifications.