Project Funding: 2014 - 2017

NRA: 2012 NASA: Interdisciplinary Research in Earth Science   

Funded by NASA

Abstract:
We propose to produce the first-ever remote sensing based maps of soil profile characteristics in Alaska permafrost landscapes using time series of airborne P-band synthetic aperture radar. Our guiding hypothesis is that long wavelength P-band synthetic aperture radar backscatter measurements are sensitive to soil profile structure, moisture and thermal dynamics that are responsive to permafrost conditions, and can be used to improve regional estimation of surface hydrology and carbon cycle processes. The radar observations will be conducted using the Airborne Microwave Observatory of Subcanopy and Subsurface (AirMOSS) instrument, and the permafrost soil properties will be retrieved using techniques developed for the AirMOSS Earth Ventures 1 (EV-1) mission. Primary permafrost soil properties to be examined include soil active layer moisture profile and freeze-thaw state variability, and depth to permafrost table. The AirMOSS retrievals will be guided and validated by detailed ground network measurements of soil and permafrost conditions, and forward model simulations of radar backscatter properties and parameter retrieval uncertainty analyses. The AirMOSS retrievals will be used to inform a succession of land surface hydrology and terrestrial carbon (CO2) flux simulations to investigate the impact of permafrost soil dynamics and surface hydrologic information on regional carbon flux simulations. First, the AirMOSS retrievals will be used to constrain soil conditions within the NASA GEOS-5 land surface modeling and data assimilation system, which will be enhanced to better account for the temporal and spatial evolutions of soil active layer dynamics in permafrost landscapes, and their associated impacts to land surface hydrology and energy budgets. Next, the resulting land model predictions will be used as primary forcings within a terrestrial carbon flux model constrained by independent regional tower carbon flux measurements and supporting biophysical data to produce current estimates and prognoses of terrestrial carbon fluxes, including vegetation productivity, ecosystem respiration and soil decomposition processes, and the potential of these vulnerable ecosystems to shift from a predominant sink to a source of atmospheric CO2. The resulting data sets and models will provide a unique opportunity to assess the climate feedbacks in permafrost systems and the potential tipping points they enable. There are numerous synergies with other NASA missions. The proposed activities will directly support algorithm refinement, validation and potential improvement of the Level 4 soil moisture (L4_SM) and carbon (L4_C) products of the NASA Soil Moisture Active Passive (SMAP) mission, scheduled for launch in 2014. The proposed activities will also provide critical datasets for planning and initiating the NASA-led Arctic Boreal Vulnerability Experiment (ABoVE), which will focus on permafrost landscapes of Alaska and northwest Canada. The proposed AirMOSS campaigns and data products will encompass the same data acquisition areas as the NASA Carbon in Arctic Reservoirs Vulnerability (CARVE) EV-1 mission. A recent CARVE mission descope involved the loss of radar land surface retrievals to accompany airborne atmospheric trace gas (CO2, CH4) profile measurements; the proposed activities will fill this information void using AirMOSS P-band measurements of permafrost soil properties and higher order surface hydrology and terrestrial carbon flux products, and enabling value added science return by leveraging information from both AirMOSS and CARVE. The proposed research addresses NASA Earth Science goal to advance Earth system science to meet the challenges of climate and environmental change. Under this goal, it seeks to answer the questions of (1) how is the global Earth system changing, (2) what are the sources of change in the Earth system and their magnitudes and trends, and (3) how will the Earth system change in the future.

Publications:

Tabatabaeenejad, A., Burgin, M., Duan, X., Moghaddam, M. 2015. P-Band Radar Retrieval of Subsurface Soil Moisture Profile as a Second-Order Polynomial: First AirMOSS Results. IEEE Transactions on Geoscience and Remote Sensing. 53(2), 645-658. DOI: 10.1109/TGRS.2014.2326839

More details may be found in the following project profile(s):

• North American Carbon Program (NACP) Project Profile
• NASA Arctic-Boreal Vulnerability Experiment (ABoVE) Project Profile