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Abstract (from http://www.sciencedirect.com/science/article/pii/S1873965215000110): The goal of this study was to assess the importance of the 2007 sea ice retreat for hydrologic conditions on the Alaskan North Slope, and how this may have influenced the outbreak of tundra fires in this region. This study concentrates on two years, 2007 and 1996, with different arctic sea ice conditions and tundra fire activity. The year of 2007 is characterized by a low summer sea ice extent (second lowest) and high tundra fire activity, while 1996 had high sea ice extent, and few tundra fires. Atmospheric lateral boundary forcing from the NCEP/NCAR Reanalysis drove the Weather Research and Forecast (WRF) model, along with varying...
Abstract: To test the effects of altered hydrology on organic soil decomposition, we investigated CO2 and CH4 production potential of rich-fen peat (mean surface pH = 6.3) collected from a field water table manipulation experiment including control, raised and lowered water table treatments. Mean anaerobic CO2 production potential at 10 cm depth (14.1 ± 0.9 μmol C g-1 d-1) was as high as aerobic CO2 production potential (10.6 ± 1.5 μmol C g-1 d-1), while CH4 production was low (mean of 7.8 ± 1.5 nmol C g-1 d-1). Denitrification enzyme activity indicated a very high denitrification potential (197 ± 23 μg N g-1 d-1), but net reduction suggested this was a relatively minor pathway for anaerobic CO2 production. Abundances...
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Water is a key ecosystem service that provides life to vegetation, animals, and human communities. The distribution and flow of water on a landscape influences many ecological functions, such as the distribution and health of vegetation and soil development and function. However, the future of many important water resources remains uncertain. Reduced snowfall and snowpack, earlier spring runoff, increased winter streamflow and flooding, and decreased summer streamflow have all been identified as potential impacts to water resources due to climate change. These factors all influence the water balance in the Pacific Coastal Temperate Rainforest (PCTR). Ensuring healthy flow and availability of water resources is...
Abstract (from http://onlinelibrary.wiley.com/doi/10.1002/hyp.9934/abstract): Adaptation planning in Alaska, as in other snowy parts of the world, will require snow projections, yet snow is a challenging variable to measure, simulate and downscale. Here we describe the construction and evaluation of 771-m-resolution gridded historical and statistically downscaled projections of snow/rain partitioning for the state of Alaska at decadal temporal resolution. The method developed here uses observational data to describe the relationship between average monthly temperature and the fraction of wet days in that month receiving snow, the snow-day fraction. Regionally and seasonally specific equations were developed to...
Abstract: Arctic tundra ecosystems have experienced unprecedented change associated with climate warming over recent decades. Across the Pan-Arctic, vegetation productivity and surface greenness have trended positively over the period of satellite observation. However, since 2011 these trends have slowed considerably, showing signs of browning in many regions. It is unclear what factors are driving this change and which regions/landforms will be most sensitive to future browning. Here we provide evidence linking decadal patterns in arctic greening and browning with regional climate change and local permafrost-driven landscape heterogeneity. We analyzed the spatial variability of decadal-scale trends in surface greenness...
Abstract (from http://onlinelibrary.wiley.com/doi/10.1002/2016GB005548/full): Burn area and the frequency of extreme fire events have been increasing during recent decades in North America, and this trend is expected to continue over the 21st century. While many aspects of the North American carbon budget have been intensively studied, the net contribution of fire disturbance to the overall net carbon flux at the continental scale remains uncertain. Based on national scale, spatially explicit and long-term fire data, along with the improved model parameterization in a process-based ecosystem model, we simulated the impact of fire disturbance on both direct carbon emissions and net terrestrial ecosystem carbon balance...
Abstract (from http://www.sciencedirect.com/science/article/pii/S0168192316303446): Across a global network of eddy covariance flux towers, two relatively new open-path infrared gas analyzers (IRGAs), the IRGASON and the EC150, are increasingly used to measure net carbon dioxide (CO2) fluxes (Fc_OP). Differences in net CO2 fluxes derived from open- and closed-path IRGAs in general remain poorly constrained. In particular, the performance of the IRGASON and the EC150 for measuring Fc_OP has not been characterized yet. These IRGAs measure CO2 absorption, which is scaled with air temperature and pressure before converting it to instantaneous CO2 density. This sensor-internal conversion is based on a slow-response thermistor...
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For thousands of years, Pacific lamprey and Pacific eulachon have been important traditional foods for Native American tribes of the Columbia River Basin and coastal areas of Oregon and Washington. These fish have large ranges – spending part of their lives in the ocean and part in freshwater streams – and they require specific environmental conditions to survive, migrate, and reproduce. For these reasons, Pacific lamprey and Pacific eulachon are likely threatened by a variety of climate change impacts to both their ocean and freshwater habitats. However, to date, little research has explored these impacts, despite the importance of these species to tribal communities. This project will evaluate the effects of...
Abstract (from http://onlinelibrary.wiley.com/doi/10.1111/gcb.13612/full): Rich fens are common boreal ecosystems with distinct hydrology, biogeochemistry and ecology that influence their carbon (C) balance. We present growing season soil chamber methane emission (FCH4), ecosystem respiration (ER), net ecosystem exchange (NEE) and gross primary production (GPP) fluxes from a 9-years water table manipulation experiment in an Alaskan rich fen. The study included major flood and drought years, where wetting and drying treatments further modified the severity of droughts. Results support previous findings from peatlands that drought causes reduced magnitude of growing season FCH4, GPP and NEE, thus reducing or reversing...
Abstract (from http://onlinelibrary.wiley.com/doi/10.1111/gcb.12757/abstract): The landscape of the Barrow Peninsula in northern Alaska is thought to have formed over centuries to millennia, and is now dominated by ice-wedge polygonal tundra that spans drained thaw-lake basins and interstitial tundra. In nearby tundra regions, studies have identified a rapid increase in thermokarst formation (i.e., pits) over recent decades in response to climate warming, facilitating changes in polygonal tundra geomorphology. We assessed the future impact of 100 years of tundra geomorphic change on peak growing season carbon exchange in response to: (i) landscape succession associated with the thaw-lake cycle; and (ii) low, moderate,...
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Snow is extremely important to a wide range of natural processes in Alaska. Snow cover helps regulate the earth’s temperature and stores water on the landscape. As it melts, snow hydrates the soil and replenishes the freshwater supplies of streams and lakes, providing water for vegetation, wildlife, and human activities such as agriculture and electricity generation. Understanding present and future snow conditions under climate change is critical for managing Alaska’s natural resources, yet many scientists, land managers, and policymakers lack this information at useful scales. Hence, the goal of this project was to produce an advanced snow modeling system for part of the Arctic that predicts a variety of factors...
Abstract (from http://www.nature.com/nature/journal/v520/n7546/full/nature14338.html): Large quantities of organic carbon are stored in frozen soils (permafrost) within Arctic and sub-Arctic regions. A warming climate can induce environmental changes that accelerate the microbial breakdown of organic carbon and the release of the greenhouse gases carbon dioxide and methane. This feedback can accelerate climate change, but the magnitude and timing of greenhouse gas emission from these regions and their impact on climate change remain uncertain. Here we find that current evidence suggests a gradual and prolonged release of greenhouse gas emissions in a warming climate and present a research strategy with which to...
Abstract (from http://onlinelibrary.wiley.com/doi/10.1002/2014JG002683/abstract): Changes in vegetation and soil properties following permafrost degradation and thermokarst development in peatlands may cause changes in net carbon storage. To better understand these dynamics, we established three sites in Alaska that vary in permafrost regime, including a black spruce peat plateau forest with stable permafrost, an internal collapse scar bog formed as a result of thermokarst, and a rich fen without permafrost. Measurements include year-round eddy covariance estimates of carbon dioxide (CO2 ), water, and energy fluxes, associated environmental variables, and methane (CH4 ) fluxes at the collapse scar bog. The ecosystems...
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Abstract: We present an inverse modeling approach for reconstructing the effective thermal conductivity of snow on a daily basis using air temperature, ground temperature and snow depth measurements. The method is applied to four sites in Alaska. To validate the method we used measured snow densities and snow water equivalents. The modeled thermal conductivities of snow for the two interior Alaska sites have relatively low values and reach their maximum near the end of the snow season, while the conductivities at the two sites on the Alaskan North Slope are higher and reach their maximum earlier in the snow season. We show that the reconstructed daily thermal conductivities allow for more accurate modeling of ground...
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Permafrost is a layer of perennially frozen soil that primarily exists in and around the Arctic and Antarctic regions of the world. While a shallow near-surface soil layer (called active layer) thaws during the summer and re-freezes in the winter, the underlying permafrost remains perennially frozen, often underlying buildings, roads, and other infrastructure. As warmer temperatures become more common, thawing of permafrost could have major consequences for Alaska. Where thawing has already occurred, dramatic changes in ecosystems and existing infrastructure are evident. For example, thawing permafrost along the ocean shore and riverbanks in Northern Alaska is causing substantial coastal erosion and is impacting...
map background search result map search result map Assessing Permafrost Changes and Related Impacts on Alaskan Infrastructure and Communities Projecting the Future Distribution and Flow of Water in Alaskan Coastal Forest Watersheds Modeling and Predicting Future Changes in Snowfall and Snow Cover in Alaska Assessing Climate Change Impacts on Pacific Lamprey and Pacific Eulachon The Effect of Snow: How to Better Model Ground Surface Temperatures The Effect of Snow: How to Better Model Ground Surface Temperatures Assessing Permafrost Changes and Related Impacts on Alaskan Infrastructure and Communities Projecting the Future Distribution and Flow of Water in Alaskan Coastal Forest Watersheds Modeling and Predicting Future Changes in Snowfall and Snow Cover in Alaska Assessing Climate Change Impacts on Pacific Lamprey and Pacific Eulachon