Aboveground biomass is a critical element of the global carbon cycle, both in terms of the large magnitudes of carbon stored in aboveground woody material, and the ecological carbon-climate…

This federal contract award, valued at $714,989.00, was granted by the National Aeronautics and Space Administration (NASA) to the University of Texas at Austin (UT Austin) to develop improved biomass estimation models using data from the ICESat-2 satellite. The project aims to create updated boreal biomass maps for the circumpolar region and explore the use of ICESat-2 data for biomass estimation in temperate and tropical forests, following the expected decommissioning of the GEDI laser altimeter system. UT Austin, a prominent public research university, will leverage its expertise in aerospace engineering, remote sensing, and climate modeling to achieve the research objectives. No set-aside designation was used for this award. The project is part of a larger effort to improve the understanding of the global carbon cycle and the role of aboveground biomass, which is critical for climate and carbon cycle modeling.

Aboveground biomass is a critical element of the global carbon cycle, both in terms of the large magnitudes of carbon stored in aboveground woody material, and the ecological carbon-climate feedbacks related to disturbances from pests and fire that are particularly important for carbon cycling in global ecosystems. Baseline aboveground biomass maps provide modeling groups with important constraints on climate and carbon cycle models, and enable the long-term monitoring of changes to aboveground biomass stocks in the future. In 2018, NASA launched two laser altimeter systems (gedi and icesat-2) that are able to map forest structure and are producing global biomass products. Although gedi s primary science objectives are related to quantifying forest structure, IT is limited in its spatial coverage collecting data between ~51.6 degrees north and south as IT is on the international space station. Until recently, high resolution biomass maps have been largely unavailable across the boreal system due to a lack of active remote sensing data sensitive to forest structure at the spatial scales of boreal forest processes (~30M 1 HA). The launch of icesat-2 has allowed for the creation of a circa 2020 boreal biomass product for the entire circumpolar region. However, a parameter missing from the icesat-2 biomass allometric models was canopy cover due to the influence of surface reflectance on the canopy cover estimate. One research objective of this effort is to explore whether other icesat-2 derived vertical structure metrics (i.e. foliage profiles or surrogates to canopy cover) calculated at 30 m improve biomass estimation for the boreal domain. Based on these results, we will calculate a circa 2025 icesat-2 boreal biomass product in the same manner as for the 2020 epoch. With gedi likely being decommissioned from the ISS in march 2023, icesat-2 will be the only space-based laser altimeter capable of measuring canopy structure over all ecosystem types including temperate and tropical forest. A second goal of this proposal is to better understand the operating bounds of icesat-2 s usability for biomass estimation beyond the boreal domain. An objective for this research is to establish icesat-2 biomass models for temperate and tropical forests using the gedi open field data and the icesat-2 simulator. Based upon the gedi simulator and a pre-launch icesat-2 simulation methodology, an icesat-2 version of the gedi simulator has been developed to simulate icesat-2 data and IT has been thoroughly tested and validated. Through the use of simulated icesat-2 data, we will validate the icesat-2 biomass models for temperate and tropical forests against the open reference data sets utilized by the gedi mission for the creation of their biomass products.