Plot-scale analysis of interactions between climate, vegetation, and permafrost at Toolik Lake, Alaska (1995 - 2018)
Abstract
Air temperatures across the Arctic have increased in recent decades, and through complex feedbacks, vegetation and permafrost (frozen ground) are responding as climate warming continues. This study investigates the trends and interactions of observed air, soil-surface temperature (SST), and active-layer thickness (ALT) at Toolik Lake on the Alaskan North Slope between 1995 and 2017, as well as vegetation change over time.
Time series between 1995 and 2017 at CALM site U12B, a 1 ha plot near Toolik Lake, reveal an increase in mean summer (Jun-Aug) air temperatures and a slight decrease in mean summer SST. In winter (Dec-Feb), the plot experienced an overall increase in SST and a slight increase in air temperatures. Deepening mean maximum ALT reflects the annual warming air and SST. Using aerial photographs, normalized difference vegetation index (NDVI) maps were produced for peak greenness in 1995 and 2017 within the 1 ha plot. A water track located within the study site, dominated by low shrubs, had the highest NDVI values compared to the surrounding tussock tundra. An increase in greenness along the edges of the water track in 2017 relative to 1995, as well as a visual comparison of the orthomosaics and photo-derived digital elevation models (DEMs), reveals the water track widening by nearly 4.5 m and growth of the shrubs adjacent to it. In nearly every year during the 23-yr observation period, mean winter SST at sensors positioned along the water track remained above -6°C, introducing the possibility of overwinter decomposition and nutrient mineralization. Since 2009, sensors in non-water track areas have recorded mean winter SST consistently above -8°C, signifying an increase in mean winter SST throughout the plot that could have important implications for winter microbial activity. Incorporating air and soil-surface temperatures, ALT, and vegetation dynamics into a time series demonstrates the complexity of feedbacks in a changing Arctic environment. These results may have strong implications for biogeochemical feedbacks and ecosystem processes.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B31F2566R
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCESDE: 0475 Permafrost;
- cryosphere;
- and high-latitude processes;
- BIOGEOSCIENCESDE: 1640 Remote sensing;
- GLOBAL CHANGE