Geophysical Observations of Organic Matter and Soil Moisture Interactions during Freezing and Thawing of Alaskan Boreal Permafrost
Abstract
Organic matter distribution within the soil column of interior Alaska's syngenetic ice-cemented permafrost influences the soil moisture distribution during freeze and thaw processes. Soil moisture behavior, in turn, influences freeze/thaw dynamics within the seasonally thawed permafrost active layer. Here we use geophysical time-lapse measurements of soil moisture and thaw depth to answer the question, "How does organic matter distribution affect soil moisture behavior within the active layer of Interior Alaska boreal forest permafrost?" In situ measurements of organic matter distribution and thaw depth supplement geophysical observations from borehole nuclear magnetic resonance (NMR), ground-penetrating radar (GPR), and electrical resistivity tomography (ERT) to produce images of soil moisture distribution from August, 2018 to October, 2019. Borehole NMR measurements provide depth-specific soil moisture and pore size distribution observations; GPR soundings yield depth-averaged soil moisture estimates; and ERT identifies areas of frozen versus unfrozen regions from two-dimensional and three-dimensional subsurface assessments. This suite of analyses focused on soil moisture distribution in relation to organic matter concentrations helps to explain the dynamic distribution of liquid water during freezing and thawing. Our improved observations of key processes within the active layer help constrain thaw pattern projections within the boreal forest of interior Alaska.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMNS11B0627S
- Keywords:
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- 0702 Permafrost;
- CRYOSPHERE;
- 0738 Ice;
- CRYOSPHERE;
- 0758 Remote sensing;
- CRYOSPHERE;
- 0794 Instruments and techniques;
- CRYOSPHERE