An Earth System Data Record for Land Surface Freeze-Thaw State: Quantifying Terrestrial Water Mobility Constraints to Global Ecosystem Processes

Principal Investigator (PI): John Kimball, Numerical Terradynamic Simulation Group, University of Montana
Co-Investigator (Co-PI): Kyle McDonald, NASA's Jet Propulsion Laboratory

The goal of this project is to develop an Earth System Data Record (ESDR) quantifying global vegetated land surface freeze/thaw state dynamics over a long-term data record of more than 25 years. The freeze/thaw ESDR (F/T-ESDR) is being developed using multi-frequency satellite passive and active microwave remote sensing time series spanning multiple missions and sensors, including passive microwave radiometery from the Scanning Multichannel Microwave Radiometer (SMMR), Special Sensor Microwave Imager (SSM/I) and Advanced Microwave Scanning Radiometer for EOS (AMSR-E), and radar scatterometer data from SeaWinds. These records are global in extent and provide a contiguous time series extending from 1979 onward with some overlap between missions.

The science justification, algorithms, calibration and validation approaches for the F/T-ESDR are well established, having been developed from an extensive heritage of past NASA Earth Science research. The transition of the land surface between predominantly frozen and non-frozen conditions in seasonally frozen environments occurs each year over more than 50 million km2 of the global biosphere, affecting surface hydrological activity, meteorological conditions and trace gas dynamics profoundly. Spatial patterns and timing of landscape freeze/thaw (F/T) state transitions show substantial variability with measurable impacts to climate, hydrological, ecological and biogeochemical processes. Satellite microwave remote sensing is uniquely capable of detecting and monitoring a range of related biophysical processes associated with the measurement of landscape F/T status. Major landscape hydrological and ecological processes embracing the remotely-sensed F/T signal include the timing and spatial dynamics of seasonal snow melt and associated soil thaw, ice breakup in large rivers and lakes, vegetation growing seasons and productivity, and the seasonal switch of the land surface between a net source of atmospheric CO₂ in winter and a terrestrial carbon sink following thawing in spring. Thus the F/T state variable provides a surrogate measure of water mobility in the landscape and the interactions between terrestrial water, carbon and energy cycles.

The F/T-ESDR will provide a consistent and well calibrated record of the spatial pattern, temporal variability and long-term changes in terrestrial F/T state dynamics, enabling accurate assessment of associated changes in terrestrial growing seasons and vegetation productivity, seasonal snow cover, permafrost and land-atmosphere energy, water and carbon exchanges. The enhanced precision and consistent temporal record provided by the F/T-ESDR will improve measurement and diagnosis of climate change trajectories and impacts to the global biosphere. Anticipated applications of the F/T-ESDR include global change assessment and monitoring, numerical weather forecasting, hydrological and biospheric assessment and forecasting.

Visit ESDR Freeze/Thaw

Distributed by NASA's National Snow and Ice Data Center (NSIDC) Distributed Active Archive Center (NSIDC DAAC)