NOAA/WDS Paleoclimatology - Chipman fire data from Upper Capsule Lake, North Slope, Alaska - IMPD USUP-001

STUDY NOTES: Chronology and macroscopic charcoal counts (number of pieces >125 microns) from lake sediments, Upper Capsule Lake, North Slope, Alaska. Provided Keywords: tundra fire-regimes, Arctic, Alaska Additional Information: Contact person: Feng Sheng Hu Sample storage location: University of Illinois, Urbana. Sampling date: 1997 Site size(ha): 1.1 Location description: Tussock-sedge, dwarf shrub tundra State/Province: Alaska Water depth(cm): 5.7 Sampling device: All cores were taken with a combination of 7.5 cm livingstone, 5 cm livingstone, and 7.5 cm polycarbonate tube; Analysis method: Macroscopic charcoal counts (>125 microns). Please see Chipman et al. 2015 for details
ABSTRACT SUPPLIED BY ORIGINATOR: Anthropogenic climate change has altered many ecosystem processes in the Arctic tundra and may have resulted in unprecedented fire activity. Evaluating the significance of recent fires requires knowledge from the paleofire record because observational data in the Arctic span only several decades, much shorter than the natural fire rotation in Arctic tundra regions. Here we report results of charcoal analysis on lake sediments from four Alaskan lakes to infer the broad spatial and temporal patterns of tundra-fire occurrence over the past 35 000 years. Background charcoal accumulation rates are low in all records (0-0.05 pieces cm-2 yr-1), suggesting minimal biomass burning across our study areas. Charcoal peak analysis reveals that the mean fire-return interval (FRI; years between consecutive fire events) ranged from ca. 1650 to 6050 years at our sites, and that the most recent fire events occurred from ca. 880 to 7030 years ago, except for the CE 2007 Anaktuvuk River Fire. These mean FRI estimates are longer than the fire rotation periods estimated for the past 63 years in the areas surrounding three of the four study lakes. This result suggests that the frequency of tundra burning was higher over the recent past compared to the late Quaternary in some tundra regions. However, the ranges of FRI estimates from our paleofire records overlap with the expected values based on fire-rotation-period estimates from the observational fire data, and the differences are statistically insignificant. Together with previous tundra-fire reconstructions, these data suggest that the rate of tundra burning was spatially variable and that fires were extremely rare in our study areas throughout the late Quaternary. Given the rarity of tundra burning over multiple millennia in our study areas and the pronounced effects of fire on tundra ecosystem processes such as carbon cycling, dramatic tundra ecosystem changes are expected if anthropogenic climate change leads to more frequent tundra fires.