We will combine EOS optical and passive microwave remote sensing measurements to assess seasonal freeze-thaw state and associated biophysical constraints on vegetation productivity for the terrestrial high latitudes. We will employ radiometric brightness temperature measurements from AMSR-E in combination with MODIS-based vegetation productivity estimates to quantify the seasonal freeze-thaw constraints to vegetation productivity. We will enlist remote sensing data from SSM/I and AVHRR in a retrospective analysis extending from 1988 over the duration of this investigation to quantify the spatial patterns, temporal anomalies and recent trends in seasonal freeze-thaw dynamics and associated impacts on northern terrestrial productivity and carbon sequestration and respiration processes. The domain of this study is the pan-boreal vegetated land mass above 50 deg. N latitude, inclusive of the pan-Arctic terrestrial drainage, with specific relevance to regions experiencing seasonal freezing.
We address the research questions 1) How are northern freeze-thaw dynamics changing with a warming climate? and 2) How are recent temporal anomalies and trends in freeze-thaw patterns affecting terrestrial productivity and trace gas exchange with the atmosphere? This investigation will establish a new, combined AMSR-E/MODIS product suite, initiating a new long-term, contiguous freeze-thaw record quantifying spatial and temporal variability in the seasonal constraints on northern vegetation productivity and land-atmosphere CO2 exchange. This effort builds on our previous work in developing SSM/I passive microwave-based freeze-thaw mapping capabilities and AMSR-E based methods for retrieving soil temperature and moisture information over boreal/Arctic biomes. We have also established the biophysical significance of the satellite remote sensing derived freeze-thaw variable and elucidated the linkages between terrestrial freeze-thaw patterns, vegetation productivity and atmospheric CO2. We will now expand our past research to enlist ASMR-E based freeze/thaw and soil temperature fields with satellite optical-IR based productivity measures to improve assessment of biophysical constraints related to freeze/thaw state afforded by the lower frequency AMSR-E sensor in quantifying recent global warming impacts to growing season dynamics and the northern carbon cycle.
We address the Integrated Science Data Analysis component of the NRA, presenting an innovative approach combining AMSR-E and MODIS to develop a new capability for addressing the major NASA Earth Science Research Strategy science questions: How are global ecosystems changing? and How do ecosystems respond to and affect global environmental change? The proposed study also addresses NASA Earth Science Research Strategy goals by quantifying regional carbon sources and sinks and associated environmental drivers, as well as improving documentation and understanding of how the regional carbon cycle is changing.
