Development of a Parameterization for Mesoscale Hydrological Modeling and Application to Landscape and Climate Change in the Interior Alaska Boreal Forest Ecosystem PDF Download
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Author: Abraham Melesse Endalamaw
Publisher:
ISBN:
Category : Biotic communities
Languages : en
Pages : 506
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Book Description
The Interior Alaska boreal forest ecosystem is one of the largest ecosystems on Earth and lies between the warmer southerly temperate and colder Arctic regions. The ecosystem is underlain by discontinuous permafrost. The presence or absence of permafrost primarily controls water pathways and ecosystem composition. As a result, the region hosts two distinct ecotypes that transition over a very short spatial scale - often on the order of meters. Accurate mesoscale hydrological modeling of the region is critical as the region is experiencing unprecedented ecological and hydrological changes that have regional and global implications. However, accurate representation of the landscape heterogeneity and mesoscale hydrological processes has remained a big challenge. This study addressed this challenge by developing a simple landscape model from the hill-slope studies and in situ measurements over the past several decades. The new approach improves the mesoscale prediction of several hydrological processes including streamflow and evapotranspiration (ET). The impact of climate induced landscape change under a changing climate is also investigated. In the projected climate scenario, Interior Alaska is projected to undergo a major landscape shift including transitioning from a coniferous-dominated to deciduous-dominated ecosystem and from discontinuous permafrost to either a sporadic or isolated permafrost region. This major landscape shift is predicted to have a larger and complex impact in the predicted runoff, evapotranspiration, and moisture deficit (precipitation minus evapotranspiration). Overall, a large increase in runoff, evapotranspiration, and moisture deficit is predicted under future climate. Most hydrological climate change impact studies do not usually include the projected change in landscape into the model. In this study, we found that ignoring the projected ecosystem change could lead to an inaccurate conclusion. Hence, climate-induced vegetation and permafrost changes must be considered in order to fully account for the changes in hydrology.
Author: Abraham Melesse Endalamaw
Publisher:
ISBN:
Category : Biotic communities
Languages : en
Pages : 506
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Book Description
The Interior Alaska boreal forest ecosystem is one of the largest ecosystems on Earth and lies between the warmer southerly temperate and colder Arctic regions. The ecosystem is underlain by discontinuous permafrost. The presence or absence of permafrost primarily controls water pathways and ecosystem composition. As a result, the region hosts two distinct ecotypes that transition over a very short spatial scale - often on the order of meters. Accurate mesoscale hydrological modeling of the region is critical as the region is experiencing unprecedented ecological and hydrological changes that have regional and global implications. However, accurate representation of the landscape heterogeneity and mesoscale hydrological processes has remained a big challenge. This study addressed this challenge by developing a simple landscape model from the hill-slope studies and in situ measurements over the past several decades. The new approach improves the mesoscale prediction of several hydrological processes including streamflow and evapotranspiration (ET). The impact of climate induced landscape change under a changing climate is also investigated. In the projected climate scenario, Interior Alaska is projected to undergo a major landscape shift including transitioning from a coniferous-dominated to deciduous-dominated ecosystem and from discontinuous permafrost to either a sporadic or isolated permafrost region. This major landscape shift is predicted to have a larger and complex impact in the predicted runoff, evapotranspiration, and moisture deficit (precipitation minus evapotranspiration). Overall, a large increase in runoff, evapotranspiration, and moisture deficit is predicted under future climate. Most hydrological climate change impact studies do not usually include the projected change in landscape into the model. In this study, we found that ignoring the projected ecosystem change could lead to an inaccurate conclusion. Hence, climate-induced vegetation and permafrost changes must be considered in order to fully account for the changes in hydrology.
Author: Katrina Bennett
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 510
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Book Description
The high latitude regions of the globe are responding to climate change at unprecedented magnitudes and rates. As the climate warms, extreme hydroclimate events are likely to change more than the mean events, and it is the extreme changes that present a risk to society, the economy and the environment of the north. The subarctic boreal forest is one of the largest ecosystems in the world and is greatly understudied with respect to hydroclimate extremes. Thus, defining a baseline for changing extremes is the first step towards planning and implementing adaptation measures to reduce risk and costs associated with the changing extremes. This thesis focuses on quantitative analysis of extreme events using historical data and future model projections of changing temperature, precipitation and streamflow in the Interior forested region of boreal Alaska. Historically, shifts in the climate have resulted in declining magnitudes of peak flow for snow dominated and glacial Interior Alaskan basins. However, changes are variable and dependent upon watershed topography, permafrost conditions, and glacial extents. Therefore, adjacent basins respond in considerably different ways to the same climate drivers. For example, peak streamflow events in the adjacent Salcha and Chena River basins had different responses to changes in climate. In the higher elevation Salcha basin, maximum streamflow increased as spring temperatures increased but in the lower elevation Chena, winter precipitation was a control on increases in maximum streamflow, while both were influenced by the Pacific Decadal Oscillation. Analysis of hydrologic change must take this variability into account to understand extreme hydroclimate responses and correctly account for process shifts. To examine future changes in peak streamflow, the implementation and parameterization of hydrologic models to simulate hydroclimate extremes is required. In the northern latitudes of the world, there is a sparse observational station network that may be used for evaluation and correction of hydrologic models. This presents a limitation to science in these regions of the globe and has led to a paucity of research results and consequently, a lack of understanding of the hydrology of northern landscapes. Input of observations from remote sensing and the implementation of models that contain parameterizations specific to northern regions (i.e. permafrost) is one aim of this thesis. Remote sensing of snow cover extent, an important indicator of climate change in the north, was positively validated at snow telemetry sites across Interior Alaska. Input of the snow cover extent observations into a hydrologic model used by the Alaska Pacific River Forecast Center for streamflow flood forecasting improved discharge estimates for poorly observed basins, whereas the discharge estimates in basins with good quality river discharge observations improved little. Estimates of snow water equivalent were improved compared to station results and the adaptation of the model parameters indicated that the model is more robust, particularly during the snowmelt period when model simulations are error prone. Use of two independent hydrologic models and multiple global climate models (GCMs) and emission scenarios to simulate changes in future hydroclimate extremes indicated that large regime shifts are projected for snowmelt dominated basins of Interior Alaska. The Chena River basin, nearby Fairbanks, Alaska, is projected to be rainfall dominated by the 2080s, with smaller snowmelt peaks. Return intervals for flooding will increase by one-and-one half to double the flow volume magnitude compared to the historical return interval. Frequency of extreme streamflow events will increase five times the mean increase. These changes in extreme streamflow events necessitate further research on the implications for infrastructure, ecology and economy to constrain risk associated with the projected regime shift in boreal forested watersheds of Interior Alaska.
Author: Robert H. Prucha
Publisher:
ISBN:
Category : Chuitna River Watershed (Alaska)
Languages : en
Pages : 158
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Book Description
This document is an assessment of the potential impacts of climate change on the Chuitna River watershed hydrologic system. Available geology, soils, climate, surface and groundwater, and vegetation data were used to develop a 3-dimensional integrated conceptual flow model of the surface and subsurface flow system within the watershed. The model predicts that for even minimum increases in air temperature and precipitation, significant changes in hydrology are projected to occur in the Chuitna River watershed during the 2080 to 2100 time period.
Author: M. J. Kirkby
Publisher:
ISBN:
Category : Hidrologia
Languages : en
Pages : 0
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Author: Benjamin V. Gaglioti
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 476
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The climate is now changing rapidly at high-latitudes, and observing how the Arctic and sub-Arctic environment responded to prehistoric climate changes can hold valuable lessons as we adapt in the future. This dissertation presents four studies that use biogeochemical proxies to reconstruct environmental changes in northern Alaska over the last 40,000 years (40 ka). These records are used to infer how the environment responded to climate changes at different locations and over varying spatial and temporal scales. The first study presents a time series of stable oxygen isotopes contained in radiocarbon-dated (14C) willow wood to quantify the nature and rates of climate change on the North Slope of Alaska over the last 40 ka. The second study examines how past temperature fluctuations affected permafrost thaw and the release of ancient carbon over the last 14.5 ka by compiling 14C-age offsets in the sediment of a small lake in the Brooks Range foothills. In the third study, I document human-caused changes to boreal wildfire frequency near the city of Fairbanks to test whether the primeval forest type and permafrost in the surrounding watershed will be vulnerable to more frequent fires in the future. The fourth study examines how ice age (40-9 ka) climate changes impacted the activity of sand dunes, vegetation productivity, and the dynamics of permafrost recorded in a unique sedimentary exposure located near the Arctic Coastal Plain on Alaska’s North Slope. Overall, I present several new and interesting approaches and findings stemming from this work. Ancient willow isotopes show that between 17 and 8 ka, during the time when ice sheets were in retreat worldwide, temperatures fluctuated widely on the North Slope mostly in concert with those in Greenland. Most notably, rapid changes in temperature and moisture occurred during the initial deglacial warming (ca. 16 ka), and during the Younger Dryas cold period (12.9-11.7 ka). These climate trends were amplified on the North Slope by changes in sea-ice extent in adjacent seas, which also controlled the availability of local precipitation evaporated from these seas. However, these warming and cooling trends were occasionally dampened by the advent of more maritime climate accompanying sea-level rise during the early Holocene, and by the breakdown of the atmospheric circulation patterns created by continental ice sheets in North America during the last glacial maximum. Over the last 7 ka, a gradual, insolation-driven cooling trend ended in ca. AD 1850 when the exceptional rates of recent warming began that continue to today. I found that the vegetation, permafrost and sand dunes in Arctic Alaska were sensitive to external climate forcing, but their responses were moderated by strong, internal feedbacks, including the temperature-buffering effects that thick peat layers have on the underlying permafrost. Prior to peat buildup in the early Holocene, the timing of sedimentary transitions indicate permafrost and aeolian processes were highly responsive to the volatile climate during the last ice age, which included Greenland interstadials. This incessant ice age climate change, coupled with the complex biophysical landscape responses that are particular to the unglaciated Arctic, helped maintain the ecological mosaic of the Mammoth Steppe ecosystem. Prehistoric warming events triggered permafrost thaw and the release of ancient carbon during the Bølling-Allerød (14.5-12.9 ka) and early Holocene warm period (11.7-8.0 ka), and this release is likely to occur again given enough warming. In the boreal forest watershed near Fairbanks, Alaska, the current ecological regime has remained intact despite a three-fold increase in pre-settlement wildfires during the Fairbanks gold rush (1902-1940). Once continued warming surpasses the buffering effects of the current internal feedbacks of the North Slope and boreal forest and the threshold for change is reached, more dynamic aeolian and permafrost processes may again dominate as they did on the more unstable and diverse ice age landscape. Overall, the results of this work will be useful for understanding how climate and landscape change in northern Alaska will respond to global climate forcing in the future.
Author: Francis Stuart Chapin (III)
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 7
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Human activities are altering many factors that determine the fundamental properties of ecological and social systems. Is sustainability a realistic goal in a world in which many key process controls are directionally changing? To address this issue, we integrate several disparate sources of theory to address sustainability in directionally changing social-ecological systems, apply this framework to climate-warming impacts in Interior Alaska, and describe a suite of policy strategies that emerge from these analyses. Climate warming in Interior Alaska has profoundly affected factors that influence landscape processes (climate regulation and disturbance spread) and natural hazards, but has only indirectly influenced ecosystem goods such as food, water, and wood that receive most management attention. Warming has reduced cultural services provided by ecosystems, leading to some of the few institutional responses that directly address the causes of climate warming, e.g., indigenous initiatives to the Arctic Council. Four broad policy strategies emerge: (i) enhancing human adaptability through learning and innovation in the context of changes occurring at multiple scales; (ii) increasing resilience by strengthening negative (stabilizing) feedbacks that buffer the system from change and increasing options for adaptation through biological, cultural, and economic diversity; (iii) reducing vulnerability by strengthening institutions that link the high-latitude impacts of climate warming to their low-latitude causes; and (iv) facilitating transformation to new, potentially more beneficial states by taking advantage of opportunities created by crisis. Each strategy provides societal benefits, and we suggest that all of them be pursued simultaneously.
Author: J. Yarie
Publisher:
ISBN:
Category :
Languages : en
Pages : 4
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Book Description
A modified version of the LINKAGES ecosystem simulation model is used to access the changes in the role of forests in the interior of Alaska to act as a source or sink of carbon over a fifty-year period. The study area is the Tanana Valley State Forest (TVSF). The TVSF occupies an area of 5523 hectares along the Tanana River from the Canadian Border to the confluence of the Tanana River and the Yukon River. The current inventory for the TVSF is used to develop a starting state for the model for ten vegetation classes. The model is run with the current climate until the current stand age for the various vegetation types is reached. Then a 5 deg C increase in mean annual temperature and a doubling in precipitation distributed evenly over the year is gradually added to the model. The model was then used to develop an average estimate of the atmospheric carbon sequestering for the current vegetation distribution of the productive forest types in the TVSF. This value was estimated as 392 g M-2 yr-1 for a 490,000-hectare area of interior Alaska.
Author: Rohini Kumar
Publisher:
ISBN:
Category :
Languages : en
Pages : 180
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Author: Chad Babcock
Publisher:
ISBN:
Category :
Languages : en
Pages : 113
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The United State Forest Service’s (USFS) Forest Inventory and Analysis (FIA) program is charged by Congress to monitor the nation’s forestlands—survey growth, mortality and composition, among other aspects related to the status and trends of United States (US) forests. To accomplish this, the FIA repeatedly inventories a massive network of sample plots that spans most of the country’s forests. Although the FIA’s permanent forest inventory network is the largest in the world, it does not represent the entirety of the nation’s forested landscape. Interior Alaska contains approximately 15 percent of the nation’s total forestland but, until recently, has not been included in the FIA’s monitoring efforts. Being one of the most vulnerable ecosystems to climate change in the US, it is pivotal to begin monitoring the dynamics of interior Alaska’s forested landscape. The vastness of the remote Alaskan landscape makes thorough field-only inventories prohibitively expensive—we need new and innovative methods to track forest dynamics in Alaska. The USFS and NASA’s Carbon Monitoring System jointly funded a pilot project in 2013 titled Monitoring Forest Carbon Stocks in Interior Alaska to examine the potential of airborne and spaceborne remote sensing technologies to augment sparse collections of field data to obtain carbon estimates with acceptable levels of precision. This study will yield first-ever regional estimates of carbon stocks for interior Alaska’s Tanana Valley leveraging FIA inventory data—an important initial step in the process of developing a forest monitoring system for Alaska’s wilderness. The research summarized in the following dissertation examines several statistical methods for coupling field and remotely sensed information to estimate aboveground biomass and carbon stocks that can potentially be used for tracking forest carbon dynamics of interior Alaska. Both design- and model-based inferential paradigms are considered. This research is strongly focused on the appropriate characterization of uncertainty in the form of standard errors and confidence intervals. Results form this research will help decision makers meet the challenges of environmental change by providing statistically rigorous methodologies that can estimate interior Alaskan carbon stocks. Having reliable and transparent estimates of carbon and biomass stocks can inform carbon management choices about the role Alaskan forestlands play in the global carbon system.
Author: 蔡磊
Publisher:
ISBN:
Category : Atmospheric circulation
Languages : en
Pages : 316
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This thesis includes four studies that explore and compare the impacts of four contributing factors resulting in regional climate change on the North Slope of Alaska based on a numerical simulation approach. These four contributing factors include global warming due to changes in radiative forcing, sea ice decline, earlier Arctic lake ice-off, and atmospheric circulation change over the Arctic. A set of dynamically downscaled regional climate products has been developed for the North Slope of Alaska over the period from 1950 up to 2100. A fine grid spacing (10 km) is employed to develop products that resolve detailed mesoscale features in the temperature and precipitation fields on the North Slope of Alaska. Processes resolved include the effects of topography on regional climate and extreme precipitation events. The Representative Concentration Pathway (RCP) 4.5 scenario projects lower rates of precipitation and temperature increase than RCP8.5 compared to the historical product. The increases of precipitation and temperature trends in the RCP8.5 projection are higher in fall and winter compared to the historical product and the RCP4.5 projection. The impacts of sea ice decline are addressed by conducting sensitivity experiments employing both an atmospheric model and a permafrost model. The sea ice decline impacts are most pronounced in late fall and early winter. The near surface atmospheric warming in late spring and early summer due to sea ice decline are projected to be stronger in the 21st century. Such a warming effect also reduces the total cloud cover on the North Slope of Alaska in summer by destabilizing the atmospheric boundary layer. The sea ice decline warms the atmosphere and the permafrost on the North Slope of Alaska less strongly than the global warming does, while it primarily results in higher seasonal variability of the positive temperature trend that is bigger in late fall and early winter than in other seasons. The ongoing and projected earlier melt of the Arctic lake ice also contributes to regional climate change on the Northern coast of Alaska, though only on a local and seasonal scale. Heat and moisture released from the opened lake surface primarily propagate downwind of the lakes. The impacts of the earlier lake ice-off on both the atmosphere and the permafrost underneath are comparable to those of the sea ice decline in late spring and early summer, while they are roughly six times weaker than those of sea ice decline in late fall and early winter. The permafrost warming resulted from the earlier lake ice-off is speculated to be stronger with more snowfall expected in the 21st century, while the overall atmospheric warming of global origin is speculated to continue growing. Two major Arctic summer-time climatic variability patterns, the Arctic Oscillation (AO) and the Arctic Dipole (AD), are evaluated in 12 global climate models in Coupled Model Intercomparison Program Phase 5 (CMIP5). A combined metric ranking approach ranks the models by the Pattern Correlation Coefficients (PCCs) and explained variances calculated from the model-produced summer AO and AD over the historical period. Higher-ranked models more consistently project a positive trend of the summer AO index and a negative trend of summer AD index in their RCP8.5 projections. Such long-term trends of large-scale climate patterns will inhibit the increase in air temperature while favoring the increase in precipitation on the North Slope of Alaska. In summary, this thesis bridges the gaps by quantifying the relative importance of multiple contributing factors to the regional climate change on the North Slope of Alaska. Global warming is the leading contributing factor, while other factors primarily contribute to the spatial and temporal asymmetries of the regional climate change. The results of this thesis lead to a better understanding of the physical mechanisms behind the climatic impacts to the hydrological and ecological changes of the North Slope of Alaska that have been become more severe and more frequent. They, together with the developed downscaling data products, serve as the climatic background information in such fields of study.
