T7 Polar and Alpine Changes

Sunday, 22 October 2017
8:00 AM - 12:00 PM
Room 612

RADIONUCLIDE PROFILES AND CARBON ACCRUAL IN PERMAFROST SOIL AT TOOLIK LAKE, ALASKA

Paper number: T7-3
Program: Technical Sessions
Time: 8:30 AM – 8:45 AM

Authors

Abstract

The response of the Arctic terrestrial carbon cycle to climate change is one of the largest uncertainties affecting climate change predictions and research. Current models give a wide, varying estimate of the fate of currently frozen permafrost carbon as the high-latitude climate warms. This study is investigating permafrost soil cores taken in 2016 from a 22-year snow fence experiment in Toolik, AK and will compare the radionuclide isotope depth profiles (7Be, 137Cs and 210Pb), carbon contents, and carbon stable isotope ratios of cores taken at different locations beneath varying winter snow depths. Be-7 activities were measurable only in the top 1-3 cm, corresponding to canopy thickness of current-year growth. Profiles of excess 210Pb were normalized to cumulative dry mass vs. depth to obtain accumulation rates of organic horizons assuming constant initial 210Pb concentration (i.e. CIC model) in the accumulating material. The resulting age profiles were compared to the depth of the 137Cs peak that was deposited in 1963, yielding perfect agreement in some but not all cases. Results indicate nearly constant mass accumulation rates within each core profile, but different rates depending on snow depth. Previous studies have shown that 210Pb deposition is determined by the daily fluctuations in precipitation and by its concentration in ground-level air, with the annual deposition flux being driven by weather variations. Local topography may also play a significant role in the 210Pb accumulation variability. Therefore, the CIC model may not accurately represent the conditions at the Toolik Lake site. Work in progress will involve normalizing the 210Pb activities to the organic carbon content of the samples to better understand the response of the soil carbon system to changing snow depth as a proxy for climate warming.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-297215

© Copyright 2017 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.