Observations of Post-wildfire Landcover Trends in Boreal Alaska Using a Suite of Remote Sensing Approaches

Wildfires are a common occurrence in the boreal ecosystems of the Pacific Northwest. Studies suggest that anthropogenic climate change has fostered more frequent and higher severity fires in recent decades in these forests, which may result in substantial changes in vegetation structure and ecosystem functioning. However, large-scale studies examining the linkages between changing boreal wildfire regimes and vegetation structure have historically been limited in spatial scope due to the broad area and inaccessibility of many boreal regions, including the Alaskan interior. The development and advancement of satellite remote sensing instruments and geospatial analysis techniques provide researchers with unmatched abilities to conduct large-scale studies of boreal fire-vegetation dynamics. This research utilizes publicly available multispectral Landsat imagery, Synthetic Aperture Radar imagery, Digital Elevation Models, wildfire perimeter data, and landcover classification products to gain insights into the linkages between climate, wildfire, and vegetation throughout the entire boreal ecoregion of Alaska. Analyses utilizing existing wildfire and landcover geospatial products suggest significant declines in both fire-adapted black spruce-dominated forests and fire-resistant deciduous forests from 2001 to 2016, of -50.0% and -19.3% landcover area, respectively. However, post-fire recruitment of deciduous forests far exceeds evergreen forest types in regions that had experienced one fire (3.4 times more likely) and two or more fires (4.9 times more likely), between 1970 and 2019. Novel spectral unmixing and fractional coverage analyses using evergreen, deciduous, and early successional endmembers yielded significant monotonic declines in the change in pixel proportion of evergreen forests as a function of wildfire frequency, with -2.36%, -25.35%, and -35.15% for areas of zero, one, and two or more fires, respectively. In contrast, deciduous changes in pixel proportion exhibited higher degradation in non-fire regions (-6.23%) than evergreens, lower magnitude decreases in single-fire areas (-21.59%), and a significant rebound in coverage in regions that burned two or more times over the study period (-10.04%). These findings suggest that deciduous forests are more resistant to wildfire than evergreen-dominated systems, and their recruitment following evergreen-fueled wildfires may moderate the frequency and severity of subsequent local fire regimes

A review of carbon monitoring in wet carbon systems using remote sensing

Carbon monitoring is critical for the reporting and verification of carbon stocks and change. Remote sensing is a tool increasingly used to estimate the spatial heterogeneity, extent and change of carbon stocks within and across various systems. We designate the use of the term wet carbon system to the interconnected wetlands, ocean, river and streams, lakes and ponds, and permafrost, which are carbon-dense and vital conduits for carbon throughout the terrestrial and aquatic sections of the carbon cycle. We reviewed wet carbon monitoring studies that utilize earth observation to improve our knowledge of data gaps, methods, and future research recommendations. To achieve this, we conducted a systematic review collecting 1622 references and screening them with a combination of text matching and a panel of three experts. The search found 496 references, with an additional 78 references added by experts. Our study found considerable variability of the utilization of remote sensing and global wet carbon monitoring progress across the nine systems analyzed. The review highlighted that remote sensing is routinely used to globally map carbon in mangroves and oceans, whereas seagrass, terrestrial wetlands, tidal marshes, rivers, and permafrost would benefit from more accurate and comprehensive global maps of extent. We identified three critical gaps and twelve recommendations to continue progressing wet carbon systems and increase cross system scientific inquiry

Remote Sensing of Environmental Changes in Cold Regions

This Special Issue gathers papers reporting recent advances in the remote sensing of cold regions. It includes contributions presenting improvements in modeling microwave emissions from snow, assessment of satellite-based sea ice concentration products, satellite monitoring of ice jam and glacier lake outburst floods, satellite mapping of snow depth and soil freeze/thaw states, near-nadir interferometric imaging of surface water bodies, and remote sensing-based assessment of high arctic lake environment and vegetation recovery from wildfire disturbances in Alaska. A comprehensive review is presented to summarize the achievements, challenges, and opportunities of cold land remote sensing

SAR (Synthetic Aperture Radar). Earth observing system. Volume 2F: Instrument panel report

The scientific and engineering requirements for the Earth Observing System (EOS) imaging radar are provided. The radar is based on Shuttle Imaging Radar-C (SIR-C), and would include three frequencies: 1.25 GHz, 5.3 GHz, and 9.6 GHz; selectable polarizations for both transmit and receive channels; and selectable incidence angles from 15 to 55 deg. There would be three main viewing modes: a local high-resolution mode with typically 25 m resolution and 50 km swath width; a regional mapping mode with 100 m resolution and up to 200 km swath width; and a global mapping mode with typically 500 m resolution and up to 700 km swath width. The last mode allows global coverage in three days. The EOS SAR will be the first orbital imaging radar to provide multifrequency, multipolarization, multiple incidence angle observations of the entire Earth. Combined with Canadian and Japanese satellites, continuous radar observation capability will be possible. Major applications in the areas of glaciology, hydrology, vegetation science, oceanography, geology, and data and information systems are described

Future Opportunities and Challenges in Remote Sensing of Drought

The value of satellite remote sensing for drought monitoring was first realized more than two decades ago with the application of Normalized Difference Vegetation Index (NDVI) data from the Advanced Very High Resolution Radiometer (AVHRR) for assessing the effect of drought on vegetation, as summarized by Anyamba and Tucker (2012, Chapter 2). Other indices such as the Vegetation Health Index (VHI) (Kogan, 1995) were also developed during this time period and applied to AVHRR NDVI and brightness temperature data for routine global monitoring of drought conditions. These early efforts demonstrated the unique perspective that global imagers like AVHRR could provide for operational drought monitoring through near-daily, synoptic observations of earth’s land surface. However, the advancement of satellite remote sensing for drought monitoring was limited by the relatively few spectral bands on operational global sensors such as AVHRR, along with a relatively short observational record

IGBP Northern Eurasia Study: Prospectus for an Integrated Global Change Research Project

This report was prepared by scientists representing BAHC, IGAC, and GCTE. It is a prospectus for an integrated hydrological, atmospheric chemical, biogeochemical and ecological global change study in the tundra /boreal region of Northern Eurasia. The unifying theme of the IGBP Northern Eurasia Study is the terrestrial carbon cycle and its controlling factors. Its most important overall objective is to determine how these will alter under the rapidly changing environmental conditions. (Also available in Russian.

Comparison of sea-ice freeboard distributions from aircraft data and cryosat-2

The only remote sensing technique capable of obtain- ing sea-ice thickness on basin-scale are satellite altime- ter missions, such as the 2010 launched CryoSat-2. It is equipped with a Ku-Band radar altimeter, which mea- sures the height of the ice surface above the sea level. This method requires highly accurate range measure- ments. During the CryoSat Validation Experiment (Cry- oVEx) 2011 in the Lincoln Sea, Cryosat-2 underpasses were accomplished with two aircraft, which carried an airborne laser-scanner, a radar altimeter and an electro- magnetic induction device for direct sea-ice thickness re- trieval. Both aircraft flew in close formation at the same time of a CryoSat-2 overpass. This is a study about the comparison of the sea-ice freeboard and thickness dis- tribution of airborne validation and CryoSat-2 measure- ments within the multi-year sea-ice region of the Lincoln Sea in spring, with respect to the penetration of the Ku- Band signal into the snow