Abstract
Shallow permafrost distribution and characteristics are important for predicting ecosystem feedbacks to a changing climate over decadal to century timescales because they can drive active layer deepening and land surface deformation, which in turn can significantly affect hydrologic and biogeochemical responses, including greenhouse gas dynamics. As part of the U.S. Department of Energy Next-Generation Ecosystem Experiments- Arctic, we have investigated shallow Arctic permafrost characteristics at a site in Barrow, Alaska, with the objective of improving our understanding of the spatial distribution of shallow permafrost, its associated properties, and its links with landscape microtopography. To meet this objective, we have acquired and integrated a variety of information, including electric resistance tomography data, frequency-domain electromagnetic induction data, laboratory core analysis, petrophysical studies, high-resolution digital surface models, and color mosaics inferred from kite-based landscape imaging. The results of our study provide a comprehensive and high-resolution examination of the distribution and nature of shallow permafrost in the Arctic tundra, including the estimation of ice content, porosity, and salinity. Among other results, porosity in the top 2 m varied between 85% (besides ice wedges) and 40%, and was negatively correlated with fluid salinity. Salinity directly influenced ice and unfrozen water content and indirectly influenced the soil organic matter content. A relatively continuous but depth-variable increase in salinity led to a partially unfrozen saline layer (cryopeg) located below the top of the permafrost. The cryopeg environment could lead to year-round microbial production of greenhouse gases. Results also indicated a covariability between topography and permafrost characteristics including icewedge and salinity distribution. In addition to providing insight about the Arctic ecosystem, through integration of lab-based petrophysical results with field data, this study also quantified the key controls on electric resistivity at this Arctic permafrost site, including salinity, porosity, water content, ice content, soil organic matter content, and lithologic properties.
| Original language | English |
|---|---|
| Pages (from-to) | WA247-WA263 |
| Journal | Geophysics |
| Volume | 81 |
| Issue number | 1 |
| DOIs | |
| State | Published - Mar 16 2015 |
| Externally published | Yes |
Funding
The Next-Generation Ecosystem Experiments (NGEE Arctic) project is supported by the Office of Biological and Environmental Research in the DOE Office of Science. This NGEE-Arctic research is supported through contract number DE-AC02-05CH11231 to Lawrence Berkeley National Laboratory. Data sets are available from Dafflon et al. (2015) or by contacting the authors. Logistical support in Barrow was provided by UMIAQ, LLC. The authors thank S. Wullschleger (NGEE-Arctic PI, ORNL), N. Quinn (LBNL) for lending us EM38 tools, A. Kemna (University of Bonn) for providing 2D complex resistivity imaging codes, C. Tweedie (University of Texas at El Paso) for providing LiDAR data, C. Tweedie and S. Vargas (University of Texas at El Paso) for providing advice in kite-based aerial imaging, A. Kholodov (University of Alaska at Fairbanks) for his help with field coring efforts, V. Ro-manovsky (University of Alaska at Fairbanks) for providing soil temperature data, and D. Graham (ORNL) for drilling core Z0#146.