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Published: February 21, 2017
Posted: April 21, 2017


Large thermokarst along the Selawik River in Alaska, where degradation of ice-rich permafrost causes subsidence and increased variability in topography across the Arctic landscape. The Department of Energy-supported next-generation ecosystem experiments—Arctic project seeks to understand how thawing permafrost affects feedbacks to the climate system. [Image courtesy Oak Ridge National Laboratory]


Observational Needs for Estimating Alaskan Soil Carbon Stocks Under Current and Future Climate

A geospatial analysis optimized the distribution of observation locations needed for reducing uncertainties in soil carbon stock estimates.

The Science 
Researchers used a geospatial approach that integrates existing observations with the multivariate spatial heterogeneity of soil-forming factors. The approach was developed to identify the optimal number and spatial distribution of observation sites needed to improve estimates of soil organic carbon stocks under current and projected future climatic conditions.

The Impact
The magnitude, vulnerability, and spatial distribution of soil carbon stocks are major sources of uncertainty in projected carbon-climate feedbacks attributed to the permafrost region. Study results provide a spatially optimized set of locations designed to guide new field observations for constraining the uncertainties in soil carbon estimates and providing robust spatial benchmarks for Earth system model results.

Summary
Representing land surface spatial heterogeneity is a scientific challenge that is critical for designing observation schemes to reliably estimate soil properties. Researchers led by Argonne National Laboratory developed a geospatial approach to identify an optimum distribution of observation sites for improving the characterization of soil organic carbon stocks across Alaska. By using environmental data expected to influence soil formation as proxies for representing the spatial distribution of soil organic carbon stocks, the scientists determined that complementing data from existing samples with 484 new observation sites would be needed to characterize average whole-profile soil organic carbon stocks across Alaska at a confidence interval of 5 kg C m-2. Estimates to depths of 0 m to 1 m and 0 m to 2 m with the same level of confidence would require 309 and 446 new observation sites, respectively. New observation needs are greater for scrub (mostly tundra) than forest land cover types, and ecoregions in southwestern Alaska are among the most under-sampled. The number and locations of required observations are not greatly altered by changes in climatic variables through 2100 as projected by Intergovernmental Panel on Climate Change emission scenarios. Study results serve as a guide for future sampling efforts to reduce existing uncertainty in soil organic carbon observations and improve benchmarks for Earth system model results.

Contacts (BER PM)
Daniel Stover
SC-23.1
Daniel.Stover@science.doe.gov (301-903-0289)

(PI Contact)
Julie D. Jastrow
Argonne National Laboratory
jdjastrow@anl.gov (630-252-3226)

(Corresponding Author Contact)
Umakant Mishra
Argonne National Laboratory
umishra@anl.gov (630-252-1108)

Funding
This study was supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research, Climate and Environmental Sciences Division, Terrestrial Ecosystem Science program under contract DE-AC02-06CH11357 to Argonne National Laboratory.

Publication
U. W. A. Vitharana, U. Mishra, J. D. Jastrow, R. Matamala, and Z. Fan, “Observational needs for estimating Alaskan soil carbon stocks under current and future climate.” Journal of Geophysical Research: Biogeosciences (2017). [DOI:10.1002/2016JG003421] (Reference link)

Topic Areas:

  • Research Area: Terrestrial Ecosystem Science
  • Research Area: Carbon Cycle, Biosequestration
  • Research Area: Climate and Earth System Modeling
  • Mission Science: Climate

Division: SC-23.1 Climate and Environmental Sciences Division, BER


 

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