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Title: Greenhouse gas balance over thaw-freeze cycles in discontinuous zone permafrost

Peat in the discontinuous permafrost zone contains a globally significant reservoir of carbon that has undergone multiple permafrost-thaw cycles since the end of the mid-Holocene (~3700 years before present). Periods of thaw increase C decomposition rates which leads to the release of CO 2 and CH 4 to the atmosphere creating potential climate feedback. In this paper, to determine the magnitude and direction of such feedback, we measured CO 2 and CH 4 emissions and modeled C accumulation rates and radiative fluxes from measurements of two radioactive tracers with differing lifetimes to describe the C balance of the peatland over multiple permafrost-thaw cycles since the initiation of permafrost at the site. At thaw features, the balance between increased primary production and higher CH 4 emission stimulated by warmer temperatures and wetter conditions favors C sequestration and enhanced peat accumulation. Flux measurements suggest that frozen plateaus may intermittently (order of years to decades) act as CO 2 sources depending on temperature and net ecosystem respiration rates, but modeling results suggest that—despite brief periods of net C loss to the atmosphere at the initiation of thaw—integrated over millennia, these sites have acted as net C sinks via peat accumulation. In greenhouse gasmore » terms, the transition from frozen permafrost to thawed wetland is accompanied by increasing CO 2 uptake that is partially offset by increasing CH 4 emissions. Finally, in the short-term (decadal time scale) the net effect of this transition is likely enhanced warming via increased radiative C emissions, while in the long-term (centuries) net C deposition provides a negative feedback to climate warming.« less
Authors:
ORCiD logo [1] ;  [2] ;  [3] ;  [4] ;  [3] ;  [5] ;  [1] ; ORCiD logo [1]
  1. Florida State Univ., Tallahassee, FL (United States). Earth Ocean and Atmospheric Sciences
  2. Gulf Coast State College, Panama City, FL (United States). Natural Sciences
  3. Christopher Newport Univ., Newport News, VA (United States). Organismal and Environmental Biology
  4. Univ. of New Hampshire, Durham, NH (United States). Earth Systems Research Center
  5. Univ. of Alabama, Tuscaloosa, AL (United States). Geological Sciences
Publication Date:
Grant/Contract Number:
SC0004632; SC0010580; SC0012088; SC0016440
Type:
Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Biogeosciences
Additional Journal Information:
Journal Volume: 122; Journal Issue: 2; Journal ID: ISSN 2169-8953
Publisher:
American Geophysical Union
Research Org:
Florida State Univ., Tallahassee, FL (United States); Christopher Newport Univ., Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 59 BASIC BIOLOGICAL SCIENCES; 58 GEOSCIENCES; peatland; greenhouse gas; carbon balance; radiative forcing; discontinuous permafrost zone
OSTI Identifier:
1466676
Alternate Identifier(s):
OSTI ID: 1402166