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• 1. [Article] Carbon isotopes show snowpack acts as a valuable moisture subsidy to mountain forests in the Oregon Cascades

  This study examines climatological influences, particularly that of snowpack, on tree growth and stable carbon isotope discrimination (Δ¹³C) from ~1980 to 2013 at two sites located in the upper reaches ...

  Citation × Citation Citation Abstract Copy Title: Carbon isotopes show snowpack acts as a valuable moisture subsidy to mountain forests in the Oregon Cascades Author: Ratcliff, Christopher J. This study examines climatological influences, particularly that of snowpack, on tree growth and stable carbon isotope discrimination (Δ¹³C) from ~1980 to 2013 at two sites located in the upper reaches of the McKenzie River watershed of the Oregon Cascade Mountains. We tested the use of Δ¹³C values from latewood, corroborated by tree-ring width chronologies as precipitation proxies to develop correlations between moisture stress and climate variables. Tree species at each site included Douglas-fir and mountain hemlock. Interpolated meteorological and snowpack data included snow water equivalent (SWE), precipitation, atmospheric temperature, vapor pressure deficit (VPD), relative humidity (RH), and a metric estimating growing season length. Significant correlations between latewood Δ¹³C and winter SWE at each site indicated the importance of winter snowpack to our selected tree species (r = 0.35, r = 0.43). Late summer precipitation and relative humidity (RH) were also significantly correlated with Δ¹³C (r = 0.49, r = 0.46; r = 0.43, r = 0.44). High correlations at both sites reinforced that late summer VPD was the primary driver of Δ¹³C (r = - 0.67, r = -0.61), which is often associated with moisture stress. This was further supported by correlations between air temperature and Δ¹³C (r = -0.46, r = -0.47), which drives much of the variation in VPD. Growing season length also showed significance in mountain hemlocks at the site with longer average snowpack (r = -0.22, r = -0.44). Moisture supplied by spring snow melt is a seasonably limited resource, nonetheless both sites clearly showed that snowpack acts as a valuable moisture subsidy to coniferous mountain forests in the Oregon Cascades. This study acts as a useful case study for future investigations into the relationship between snowpack and forest health in the Pacific North West. Title: Carbon isotopes show snowpack acts as a valuable moisture subsidy to mountain forests in the Oregon Cascades Author: Ratcliff, Christopher J. This study examines climatological influences, particularly that of snowpack, on tree growth and stable carbon isotope discrimination (Δ¹³C) from ~1980 to 2013 at two sites located in the upper reaches of the McKenzie River watershed of the Oregon Cascade Mountains. We tested the use of Δ¹³C values from latewood, corroborated by tree-ring width chronologies as precipitation proxies to develop correlations between moisture stress and climate variables. Tree species at each site included Douglas-fir and mountain hemlock. Interpolated meteorological and snowpack data included snow water equivalent (SWE), precipitation, atmospheric temperature, vapor pressure deficit (VPD), relative humidity (RH), and a metric estimating growing season length. Significant correlations between latewood Δ¹³C and winter SWE at each site indicated the importance of winter snowpack to our selected tree species (r = 0.35, r = 0.43). Late summer precipitation and relative humidity (RH) were also significantly correlated with Δ¹³C (r = 0.49, r = 0.46; r = 0.43, r = 0.44). High correlations at both sites reinforced that late summer VPD was the primary driver of Δ¹³C (r = - 0.67, r = -0.61), which is often associated with moisture stress. This was further supported by correlations between air temperature and Δ¹³C (r = -0.46, r = -0.47), which drives much of the variation in VPD. Growing season length also showed significance in mountain hemlocks at the site with longer average snowpack (r = -0.22, r = -0.44). Moisture supplied by spring snow melt is a seasonably limited resource, nonetheless both sites clearly showed that snowpack acts as a valuable moisture subsidy to coniferous mountain forests in the Oregon Cascades. This study acts as a useful case study for future investigations into the relationship between snowpack and forest health in the Pacific North West. Close

• 2. [Article] Climate Change and Oregon’s Water Future

  Presented at The Oregon Water Conference, May 24-25, 2011, Corvallis, OR.

  Citation × Citation Citation Abstract Copy Title: Climate Change and Oregon’s Water Future Author: Campana, Michael E. Year: 2011 Presented at The Oregon Water Conference, May 24-25, 2011, Corvallis, OR. Title: Climate Change and Oregon’s Water Future Author: Campana, Michael E. Year: 2011 Presented at The Oregon Water Conference, May 24-25, 2011, Corvallis, OR. Close

• 3. [Article] Carbon isotopes show snowpack acts as a valuable moisture subsidy to mountain forests in the Oregon Cascades

  This study examines climatological influences, particularly that of snowpack, on tree growth and stable carbon isotope discrimination (Δ¹³C) from ~1980 to 2013 at two sites located in the upper reaches ...

  Citation × Citation Citation Abstract Copy Title: Carbon isotopes show snowpack acts as a valuable moisture subsidy to mountain forests in the Oregon Cascades Author: Ratcliff, Christopher J. This study examines climatological influences, particularly that of snowpack, on tree growth and stable carbon isotope discrimination (Δ¹³C) from ~1980 to 2013 at two sites located in the upper reaches of the McKenzie River watershed of the Oregon Cascade Mountains. We tested the use of Δ¹³C values from latewood, corroborated by tree-ring width chronologies as precipitation proxies to develop correlations between moisture stress and climate variables. Tree species at each site included Douglas-fir and mountain hemlock. Interpolated meteorological and snowpack data included snow water equivalent (SWE), precipitation, atmospheric temperature, vapor pressure deficit (VPD), relative humidity (RH), and a metric estimating growing season length. Significant correlations between latewood Δ¹³C and winter SWE at each site indicated the importance of winter snowpack to our selected tree species (r = 0.35, r = 0.43). Late summer precipitation and relative humidity (RH) were also significantly correlated with Δ¹³C (r = 0.49, r = 0.46; r = 0.43, r = 0.44). High correlations at both sites reinforced that late summer VPD was the primary driver of Δ¹³C (r = - 0.67, r = -0.61), which is often associated with moisture stress. This was further supported by correlations between air temperature and Δ¹³C (r = -0.46, r = -0.47), which drives much of the variation in VPD. Growing season length also showed significance in mountain hemlocks at the site with longer average snowpack (r = -0.22, r = -0.44). Moisture supplied by spring snow melt is a seasonably limited resource, nonetheless both sites clearly showed that snowpack acts as a valuable moisture subsidy to coniferous mountain forests in the Oregon Cascades. This study acts as a useful case study for future investigations into the relationship between snowpack and forest health in the Pacific North West. Title: Carbon isotopes show snowpack acts as a valuable moisture subsidy to mountain forests in the Oregon Cascades Author: Ratcliff, Christopher J. This study examines climatological influences, particularly that of snowpack, on tree growth and stable carbon isotope discrimination (Δ¹³C) from ~1980 to 2013 at two sites located in the upper reaches of the McKenzie River watershed of the Oregon Cascade Mountains. We tested the use of Δ¹³C values from latewood, corroborated by tree-ring width chronologies as precipitation proxies to develop correlations between moisture stress and climate variables. Tree species at each site included Douglas-fir and mountain hemlock. Interpolated meteorological and snowpack data included snow water equivalent (SWE), precipitation, atmospheric temperature, vapor pressure deficit (VPD), relative humidity (RH), and a metric estimating growing season length. Significant correlations between latewood Δ¹³C and winter SWE at each site indicated the importance of winter snowpack to our selected tree species (r = 0.35, r = 0.43). Late summer precipitation and relative humidity (RH) were also significantly correlated with Δ¹³C (r = 0.49, r = 0.46; r = 0.43, r = 0.44). High correlations at both sites reinforced that late summer VPD was the primary driver of Δ¹³C (r = - 0.67, r = -0.61), which is often associated with moisture stress. This was further supported by correlations between air temperature and Δ¹³C (r = -0.46, r = -0.47), which drives much of the variation in VPD. Growing season length also showed significance in mountain hemlocks at the site with longer average snowpack (r = -0.22, r = -0.44). Moisture supplied by spring snow melt is a seasonably limited resource, nonetheless both sites clearly showed that snowpack acts as a valuable moisture subsidy to coniferous mountain forests in the Oregon Cascades. This study acts as a useful case study for future investigations into the relationship between snowpack and forest health in the Pacific North West. Close

• 4. [Article] Regional Scale Modeling of Climate, Cryosphere, and Freshwater Discharge in Changing Coastal Mountain Environments

  The glaciated coastal mountain watersheds that drain into the Gulf of Alaska (GOA) provide a model laboratory to explore the challenges of hydrological modeling and study the impact of climate and glacier ...

  Citation × Citation Citation Abstract Copy Title: Regional Scale Modeling of Climate, Cryosphere, and Freshwater Discharge in Changing Coastal Mountain Environments Author: Beamer, Jordan P. The glaciated coastal mountain watersheds that drain into the Gulf of Alaska (GOA) provide a model laboratory to explore the challenges of hydrological modeling and study the impact of climate and glacier cover change on regional hydrology. The region is data-sparse and contains a complex assemblage of topography and land cover, including a system of mountain glaciers that are retreating at some of the highest rates on Earth. The high rates of runoff from precipitation and glacial melt delivered by coastal rivers influence ocean circulation patterns, rates of global sea level rise, and provide spawning habitat for the large salmon populations. Physically-based hydrological modeling of the major water budget components of the GOA, driven using historical reanalysis weather data and land cover, reveals that the modeled water budget components, particularly precipitation input, vary widely between commonly-used weather products. The majority of the large freshwater flux into the GOA is derived from distributed coastal streams rather than the large inland rivers. The modeled seasonal aggregated GOA hydrograph is dominated by the spring and early summer snowmelt, and supplemented by late summer glacial ice melt. Model results demonstrate good agreement with NASA Gravity Recovery and Climate Experiment (GRACE) satellite data in terms of annual amplitudes and long term losses (ice loss), and suggest that existing GRACE solutions, previously reported to represent glacier mass balance alone, are actually measuring the full water budget of land and ice surfaces. An ensemble of climate models and future emissions scenarios were paired with systematically altered land cover to test the sensitivity of the hydrologic system to changes in regional climate patterns and glacier coverage representative of late twenty first century conditions. Compared with the hindcast simulations, the model results forced with increased regional air temperatures and precipitation inputs and reduced glacier cover produce an increase in the annual GOA freshwater discharge volume. The seasonal GOA hydrograph is flattened due to increased winter runoff from more winter rainfall and less snow accumulation, and lower levels of snowmelt and glacier ice contribution. Large uncertainties exist in the direction of change in the glacier runoff component, primarily due to uncertainties that exist in predicting glacier response to climate change. Hydrological modeling with high resolution and inclusion of relevant physical processes can produce significantly improved products that are of high value to and in demand by numerous other scientific communities. However, the value and accuracy of the output from the hydrologic model is highly dependent on the weather forcing quality. Given the considerable importance of quality weather forcing for hydrologic modeling, it is imperative to assess the suitability of multiple products by evaluating local and regional performance and accounting for uncertainty. Additional efforts should be made to improve the spatial resolution of the reanalysis through downscaling and to strategically increase the number of weather stations at high elevations and incorporate that data into weather forcing datasets. Title: Regional Scale Modeling of Climate, Cryosphere, and Freshwater Discharge in Changing Coastal Mountain Environments Author: Beamer, Jordan P. The glaciated coastal mountain watersheds that drain into the Gulf of Alaska (GOA) provide a model laboratory to explore the challenges of hydrological modeling and study the impact of climate and glacier cover change on regional hydrology. The region is data-sparse and contains a complex assemblage of topography and land cover, including a system of mountain glaciers that are retreating at some of the highest rates on Earth. The high rates of runoff from precipitation and glacial melt delivered by coastal rivers influence ocean circulation patterns, rates of global sea level rise, and provide spawning habitat for the large salmon populations. Physically-based hydrological modeling of the major water budget components of the GOA, driven using historical reanalysis weather data and land cover, reveals that the modeled water budget components, particularly precipitation input, vary widely between commonly-used weather products. The majority of the large freshwater flux into the GOA is derived from distributed coastal streams rather than the large inland rivers. The modeled seasonal aggregated GOA hydrograph is dominated by the spring and early summer snowmelt, and supplemented by late summer glacial ice melt. Model results demonstrate good agreement with NASA Gravity Recovery and Climate Experiment (GRACE) satellite data in terms of annual amplitudes and long term losses (ice loss), and suggest that existing GRACE solutions, previously reported to represent glacier mass balance alone, are actually measuring the full water budget of land and ice surfaces. An ensemble of climate models and future emissions scenarios were paired with systematically altered land cover to test the sensitivity of the hydrologic system to changes in regional climate patterns and glacier coverage representative of late twenty first century conditions. Compared with the hindcast simulations, the model results forced with increased regional air temperatures and precipitation inputs and reduced glacier cover produce an increase in the annual GOA freshwater discharge volume. The seasonal GOA hydrograph is flattened due to increased winter runoff from more winter rainfall and less snow accumulation, and lower levels of snowmelt and glacier ice contribution. Large uncertainties exist in the direction of change in the glacier runoff component, primarily due to uncertainties that exist in predicting glacier response to climate change. Hydrological modeling with high resolution and inclusion of relevant physical processes can produce significantly improved products that are of high value to and in demand by numerous other scientific communities. However, the value and accuracy of the output from the hydrologic model is highly dependent on the weather forcing quality. Given the considerable importance of quality weather forcing for hydrologic modeling, it is imperative to assess the suitability of multiple products by evaluating local and regional performance and accounting for uncertainty. Additional efforts should be made to improve the spatial resolution of the reanalysis through downscaling and to strategically increase the number of weather stations at high elevations and incorporate that data into weather forcing datasets. Close

• 5. [Article] Snow water equivalent, snowpack surface debris concentrations, and micrometeorological conditions over snow in burned and unburned forest sites for three years following fire

  See the related paper: Gleason, Kelly E; Nolin, Anne W; Roth, Travis R (2013) Charred forests increase snowmelt: Effects of burned woody debris and incoming solar radiation on snow ablation. Geophysical ...

  Citation × Citation Citation Abstract Copy Title: Snow water equivalent, snowpack surface debris concentrations, and micrometeorological conditions over snow in burned and unburned forest sites for three years following fire Author: Nolin, Anne W, Gleason, Kelly E See the related paper: Gleason, Kelly E; Nolin, Anne W; Roth, Travis R (2013) Charred forests increase snowmelt: Effects of burned woody debris and incoming solar radiation on snow ablation. Geophysical Research Letters, 40: 4654-4661. DOI: 10.1002/grl.50896. Title: Snow water equivalent, snowpack surface debris concentrations, and micrometeorological conditions over snow in burned and unburned forest sites for three years following fire Author: Nolin, Anne W, Gleason, Kelly E See the related paper: Gleason, Kelly E; Nolin, Anne W; Roth, Travis R (2013) Charred forests increase snowmelt: Effects of burned woody debris and incoming solar radiation on snow ablation. Geophysical Research Letters, 40: 4654-4661. DOI: 10.1002/grl.50896. Close

• 6. [Article] Dynamics of a recovering Arctic bird population: the importance of climate, density dependence, and site quality

  The Appendix is available online: http://dx.doi.org/10.1890/14-1591.1.sm

  Citation × Citation Citation Abstract Copy Title: Dynamics of a recovering Arctic bird population: the importance of climate, density dependence, and site quality Author: Bruggeman, Jason E., Nigro, Debora, Swem, Ted, Kennedy, Patricia L., Andersen, David E. The Appendix is available online: http://dx.doi.org/10.1890/14-1591.1.sm Title: Dynamics of a recovering Arctic bird population: the importance of climate, density dependence, and site quality Author: Bruggeman, Jason E., Nigro, Debora, Swem, Ted, Kennedy, Patricia L., Andersen, David E. The Appendix is available online: http://dx.doi.org/10.1890/14-1591.1.sm Close

• 7. [Article] Dynamics of a recovering Arctic bird population: the importance of climate, density dependence, and site quality

  Appendix A is available online: http://dx.doi.org/10.1890/14-1591.1.sm

  Citation × Citation Citation Abstract Copy Title: Dynamics of a recovering Arctic bird population: the importance of climate, density dependence, and site quality Author: Bruggeman, Jason E., Nigro, Debora, Andersen, David E., Kennedy, Patricia L., Swem, Ted Appendix A is available online: http://dx.doi.org/10.1890/14-1591.1.sm Title: Dynamics of a recovering Arctic bird population: the importance of climate, density dependence, and site quality Author: Bruggeman, Jason E., Nigro, Debora, Andersen, David E., Kennedy, Patricia L., Swem, Ted Appendix A is available online: http://dx.doi.org/10.1890/14-1591.1.sm Close

• 8. [Article] Understanding the impact of climate change on snowpack extent and measurement in the Columbia River Basin and nested sub basins

  Shifting climate patterns in the Columbia River basin are affecting snow pack, and, as a result, stream flow throughout the region. In the Oregon Cascades, ever growing populations, and their associated ...

  Citation × Citation Citation Abstract Copy Title: Understanding the impact of climate change on snowpack extent and measurement in the Columbia River Basin and nested sub basins Author: Brown, Aimee Lyn Shifting climate patterns in the Columbia River basin are affecting snow pack, and, as a result, stream flow throughout the region. In the Oregon Cascades, ever growing populations, and their associated activities, place increasing stress on an already over allocated hydrologic system. Political pressures, including the possibility of renegotiation or termination of the Columbia River Treaty between the United States and Canada; societal pressures, including a desire for ecosystem services and fish habitat; and economic pressures, including a need for adequate streamflow for hydropower generation and irrigation, all necessitate a better understanding of current and future snow pack. This work focuses on analyzing the ability of the current snowpack measurement system to represent and capture snowpack in the Columbia River basin and its sub basins under both today’s climate and future climates. In addition, this work develops a more comprehensive knowledge of the impact climate warming will have on snow-covered areas across the region. To determine the efficacy of current snow water equivalence (SWE) measurement sites, the locations and characteristics of sites in the McKenzie River Basin, a sub basin of the Columbia River basin, were considered. SWE was distributed through the basin using the physically based model, SnowModel. SWE values at the four SNOTEL sites in the basin ranged from 0.18-0.37 m at peak SWE. Three of the sites had SWE values greater than 180% of average SWE of the snow covered area. Using elevation, aspect and slope, a 16-node binary regression tree explained controlling variables on SWE at the basin scale. As expected, elevation is the primary determinant in SWE distribution, however, the influence of different parameters shifted throughout the accumulation and ablation seasons. Updated high resolution PRISM precipitation and temperature data are used to map areas within the Columbia River basin and two nested sub basins that are at risk of turning from winter snow dominated precipitation regimes to winter rain dominated under warming scenarios ranging from 1-3°C. Within the Columbia River basin, the Oregon Cascades exhibit the greatest degree of sensitivity to changes in precipitation. Under a 2°C warming scenario, an increase that the International Panel on Climate Change finds highly likely to occur within the next 30 years, 30% of current-day snow covered area in Oregon’s Willamette River Basin will be at risk of turning from snow to rain. The water storage that will be lost if such a change does occur (0.73 km3) is equivalent to more than 8 months worth of water at the current rate of water use in the basin. Data from nine regional stations in the National Oceanic and Atmospheric Administration (NOAA) National Weather Service (NWS) Cooperative Observer Program were used to validate placement of snow by the model. The conclusions of this work suggest that the placement of snow measurement sites requires refinement and improvement if the measurements are to accurately represent basin wide snowpack today and in the future. Water and natural resource managers will find the results presented here useful for siting future measurement locations that capture and represent SWE during times of interest. While political, societal and economic pressures will only increase, these findings provide early steps for the creation of a more robust system that has the potential to help stakeholders make informed decisions about their water resources, their communities and their needs. Title: Understanding the impact of climate change on snowpack extent and measurement in the Columbia River Basin and nested sub basins Author: Brown, Aimee Lyn Shifting climate patterns in the Columbia River basin are affecting snow pack, and, as a result, stream flow throughout the region. In the Oregon Cascades, ever growing populations, and their associated activities, place increasing stress on an already over allocated hydrologic system. Political pressures, including the possibility of renegotiation or termination of the Columbia River Treaty between the United States and Canada; societal pressures, including a desire for ecosystem services and fish habitat; and economic pressures, including a need for adequate streamflow for hydropower generation and irrigation, all necessitate a better understanding of current and future snow pack. This work focuses on analyzing the ability of the current snowpack measurement system to represent and capture snowpack in the Columbia River basin and its sub basins under both today’s climate and future climates. In addition, this work develops a more comprehensive knowledge of the impact climate warming will have on snow-covered areas across the region. To determine the efficacy of current snow water equivalence (SWE) measurement sites, the locations and characteristics of sites in the McKenzie River Basin, a sub basin of the Columbia River basin, were considered. SWE was distributed through the basin using the physically based model, SnowModel. SWE values at the four SNOTEL sites in the basin ranged from 0.18-0.37 m at peak SWE. Three of the sites had SWE values greater than 180% of average SWE of the snow covered area. Using elevation, aspect and slope, a 16-node binary regression tree explained controlling variables on SWE at the basin scale. As expected, elevation is the primary determinant in SWE distribution, however, the influence of different parameters shifted throughout the accumulation and ablation seasons. Updated high resolution PRISM precipitation and temperature data are used to map areas within the Columbia River basin and two nested sub basins that are at risk of turning from winter snow dominated precipitation regimes to winter rain dominated under warming scenarios ranging from 1-3°C. Within the Columbia River basin, the Oregon Cascades exhibit the greatest degree of sensitivity to changes in precipitation. Under a 2°C warming scenario, an increase that the International Panel on Climate Change finds highly likely to occur within the next 30 years, 30% of current-day snow covered area in Oregon’s Willamette River Basin will be at risk of turning from snow to rain. The water storage that will be lost if such a change does occur (0.73 km3) is equivalent to more than 8 months worth of water at the current rate of water use in the basin. Data from nine regional stations in the National Oceanic and Atmospheric Administration (NOAA) National Weather Service (NWS) Cooperative Observer Program were used to validate placement of snow by the model. The conclusions of this work suggest that the placement of snow measurement sites requires refinement and improvement if the measurements are to accurately represent basin wide snowpack today and in the future. Water and natural resource managers will find the results presented here useful for siting future measurement locations that capture and represent SWE during times of interest. While political, societal and economic pressures will only increase, these findings provide early steps for the creation of a more robust system that has the potential to help stakeholders make informed decisions about their water resources, their communities and their needs. Close