Now showing items 1-20 of 52

    • Two Years of High-Resolution Airborne Imagery and Value-Added Products for the Barrow Environmental Observatory

      Cherry, Jessica; Lovick, Joe; Crowder, Kerri; Cunningham, Keith; Schroder, Julien (2013-12)
      Optical and thermal infrared imagery were collected by UAF at the Arctic NGEE Intensive sites in 2012 and 2013.
    • Conceptualization and Application of Arctic Tundra Landscape Evolution Using the Alaska Thermokarst Model

      Bolton, W. Robert; Romanovsky, Vladimir; McGuire, A. David; Lara, Mark (2015-05)
      Thermokarst topography forms whenever ice-rich permafrost thaws and the ground subsides due to the volume loss when excess ice transitions to water. The Alaska Thermokarst Model (ATM) is a large-scale, state-and-transition model designed to simulate transitions between [non-]thermokarst landscape units, or cohorts. The ATM uses a frame-based methodology to track transitions and proportion of cohorts within a 1- km2 grid cell. In the arctic tundra environment, the ATM tracks thermokarst related transitions between wetland tundra, graminoid tundra, shrub tundra, and thermokarst lakes. The transition from one cohort to another due to thermokarst processes can take place if seasonal thaw of the ground reaches ice-rich soil layers either due to pulse disturbance events such as a large precipitation event, wildfire, or due to gradual active layer deepening that eventually reaches ice-rich soil. The protective layer is the distance between the ground surface and ice-rich soil. The protective layer buffers the ice-rich soils from energy processes that take place at the ground surface and is critical to determining how susceptible an area is to thermokarst degradation. The rate of terrain transition in our model is determined by the soil ice-content, the drainage efficiency (or ability of the landscape to store or transport water), and the probability of thermokarst initiation. Tundra types are allowed to transition from one type to another (i.e. a wetland tundra to a graminoid tundra) under favorable climatic conditions. In this study, we present our conceptualization and initial simulation results of the ATM for an 1792 km2 area on the Barrow Peninsula, Alaska. The area selected for simulation is located in a polygonal tundra landscape under varying degrees of thermokarst degradation. The goal of this modeling study is to simulate landscape evolution in response to thermokarst disturbance as a result of climate change.
    • Climate Divisions for Alaska Based on Objective Methods

      Bieniek, Peter A.; Bhatt, Uma S.; Thoman, Richard L.; Angeloff, Heather; Partain, James; Papineau, John; Fritsch, Frederick; Holloway, Eric; Walsh, John E.; Daly, Chris; et al. (2012-12)
      Alaska climate regions first drawn by Fitton (1930) [Fitton]. Divisions outlined by Searby (1968) currently used by the National Climatic Data Center [NCDC]. Climate regions updated by Shulski and Wendler (2007) [ACRC]. None are based on primarily objective methods. Useful for seasonal forecasting and many other research applications.
    • 2016 Snow Melt in the NGEE-Arctic Teller Research Watershed

      Busey, Robert; Wilson, Cathy; Iwahana, Go; Bolton, W. Robert; Cohen, Lily (2016-12)
      In April 2016, daily transects were made across the Teller Road Basin to begin the several year process of characterizing the largest event in the northern hydrologic year: snow melt. This year was an experiment to see how much could be accomplished (a full suite of time intensive measurements) during this interval.
    • Uncertainties in Arctic Precipitation

      Majhi, Ipshita; Alexeev, Vladimir; Cherry, Jessica; Groisman, Pavel; Cohen, Judah (2012-12)
      It is crucial to measure precipitation accurately to predict future water budget with confidence. In our study, we aim to understand and compare precipitation datasets and discrepancies associated with them. We divide our datasets into three classes-raw data (data that have only been preprocessed to minimum quality control);corrected products (data that have been adjusted by their respective authors); finally, a reanalysis dataset (a combination of observed data and model output).
    • Scenarios to prioritize observing activities on the North Slope, AK

      Lee, Olivia; Lassuy, Dennis; Payne, John; Vargas, Juan Carlos; Eicken, Hajo (2016-03)
      The North Slope of Alaska is experiencing rapid changes in response to interacting climate and socioeconomic drivers. The North Slope Science Initiative (NSSI) is using scenarios as a tool to identify plausible, spatially explicit future states of resource extraction activities on the North Slope and adjacent seas through the year 2040. The objective of the scenarios process is to strategically assess research and monitoring needs on the North Slope. The participatory scenarios process involved stakeholder input (including Federal, State, local, academic, industry and non-profit representatives) to identify key drivers of change related to resource extraction activities on the North Slope. While climate change was identified as a key driver in the biophysical system, economic drivers related to oil and gas development were also important. Expert-reviewed informational materials were developed to help stakeholders obtain baseline knowledge and stimulate discussions about interactions between drivers, knowledge gaps and uncertainties. Map-based scenario products will allow mission-oriented agencies to jointly explore where to prioritize research investments and address risk in a complex, changing environment. Scenarios consider multidecadal timescales. However, tracking of indicator variables derived from scenarios can lead to important insights about the trajectory of the North Slope social-environmental system and inform management decisions to reduce risk on much shorter timescales. The inclusion of stakeholders helps provide a broad spectrum of expert viewpoints necessary for considering the range of plausible scenarios.
    • Scenarios in Social-Ecological Systems: Co-Producing Futures in Arctic Alaska

      Lovecraft, A. L.; Eicken, H. (2016-12)
      Scenarios are used to think ahead in rapidly changing, complex, and competitive environments, and make crucial decisions in absence of complete information about the future. Currently, at many regional scales of governance, there is a growing need for legitimate tools that enable the actors (e.g., governments, corporations, organized interests) at local-scales to address pressing concerns in the midst of uncertainty. This is particularly true of areas experiencing rapidly changing environments (e.g., drought, floods, diminishing sea ice, erosion) and complex social problems (e.g., remote communities, resource extraction, threatened cultures). Scenario exercises produce neither forecasts of what is to come nor are they visions of what participants would like to happen. Rather, they produce pertinent evidence-based information related to questions of “what would happen if...” and thus provide the possibility of strategic decision- making to plan research that promotes community resilience.
    • Propagation of tsunami-induced acoustic-gravity waves in the atmosphere

      Alexeev, Vladimir A.; Nicolsky, Dmitry J. (2012-12)
      A dynamical core of an atmospheric GCM is utilized for assessing the qualitative picture of propagation of atmospheric acoustic-gravity waves in response to perturbations generated by tsunami waves at the surface. Both resting isothermal atmosphere and model- generated atmosphere with realistic stratification and circulation features were considered. Shallow water tsunami model was run in two different configurations: ocean of equal depth of 4 km and ocean with realistic continents and bottom topography. Amplitude and timing of atmospheric response is analyzed as a function of vertical stratification and configuration of atmospheric jets. This approach has a potential for early tsunami detection by measuring changes in electric properties of the upper atmosphere in response to acoustic-gravity waves generated by tsunami.
    • A Synthesis of Terrestrial Carbon Balance of Alaska and Projected Changes in the 21st Century: Implications for Climate Policy and Carbon Management

      McGuire, A. D. (2015-01)
      To better understand how carbon responses to changes in climate and other drivers in Alaska might influence national climate and carbon management policies, the U.S. Geological Survey, in collaboration with the USDA Forest Service and university scientists, has conducted a comprehensive assessment of the historical (1960-2009) and projected (2010-2099) carbon balance for Alaska. This assessment of carbon dynamics in Alaska includes (1) syntheses of soil, vegetation, and surface water carbon stocks and fluxes in Alaska, and (2) state of the art models of fire dynamics, vegetation change, forest management, permafrost dynamics, and upland, wetland, and surface water ecosystem carbon dynamics. Here we report on progress in the soils synthesis, fire and vegetation dynamics synthesis, and syntheses of upland, wetland, and inland waters components. The terrestrial reporting regions for soil, upland, and wetland components of this assessment are based on the four large terrestrial Landscape Conservation Cooperatives (LCC) in Alaska: (1) the Arctic, (2) the Western Alaska, (3) the Northwest Boreal, and (4) the North Pacific. The reporting regions for the inland waters’ component of this assessment are based on the six main hydrologic regions of Alaska: the Southeast, the South-Central, Southwest, Yukon, Northwest and Arctic Slope.
    • Arctic Ecosystem Changes from Gloal Community Earthc System Model (CESM) and Regional Arctic System Model (RASM)

      Jin, Meibing; Deal, Clara; Maslowski, Wieslaw; Roberts, Andrew; Marina, Frants; Robert, Osinski; Craig, Anthony (2016-02)
      The Arctic Ocean is currently experiencing rapid and large environmental changes related to global warming. Many small scale physical processes, such as mesoscale eddies, mixed layer dynamics, ocean boundary and coastal currents, varying sea ice edges, upwelling can influence nutrient transport, light availability and ocean stratification, thus are critical for understanding marine primary production and carbon cycling in the Arctic Ocean. A high-resolution pan-Arctic regional earth system model (RASM) was developed to investigate the ecosystem response to climate changes in seasonal to decadal scales. Here we show some initial results from the high resolution ecosystem model and comparison with results from coarse resolution global community earth system model. Both models include coupled ice algal submodel at the bottom of sea ice and intermediate NPZD pelagic ecosystem submodel in water column.
    • NONLINEARITIES, SCALE-DEPENDENCE, AND INDIVIDUALISM OF BOREAL FOREST TREES TO CLIMATE FORCING

      Wolken, J. M.; Mann, D. H.; Loyd, A. H.; Rupp, T. Scott; Hollingsworth, T. N.; Grant, T. A. III (2014-02)
      Changes in climate are affecting tree growth, fire regimes and the geographic ranges of species (Beck et al. 2011; Kelly et al. 2013). Increasing our understanding of how boreal tree species respond to climate warming is critical for predicting the future states of the boreal forest and assessing the global impacts of these changes. Black spruce (Picea mariana [Mill.] B.S.P.) is the most abundant tree species in the Interior Alaskan boreal forest. Although it grows in a variety of community types (Hollingsworth et al. 2006), it is the only tree species found at the coldest, wettest sites on the landscape. Despite its abundance, very little is known about the climate-growth relationships of black spruce, as the majority of dendrochronological studies in Interior Alaska involve white spruce growing at treeline.
    • Effect of thaw depth on fluxes of CO2 and CH4 in manipulated Arctic coastal tundra of Barrow, Alaska

      Kim, Yongwon; Oechel, Walter C. (2015-04)
      The manipulation treatment consisted of draining, controlling, and flooding treated sections by adjusting standing water. Inundation increased CH4 emission by a factor of 4.3 compared to non-flooded sections. This may be due to the decomposition of organic matter under a limited oxygen environment by saturated standing water. On the other hand, CO2 emission in the dry section was 3.9-fold higher than in others. CH4 emission tends to increase with deeper thaw depth, which strongly depends on the water table; however, CO2 emission is not related to thaw depth. Quotients of global warming potential (GWPCO2) (dry/control) and GWPCH4 (wet/control) increased by 464 and 148 %, respectively, and GWPCH4 (dry/control) declined by 66 %. This suggests that CO2 emission in a drained section is enhanced by soil and ecosystem respiration, and CH4 emission in a flooded area is likely stimulated under an anoxic environment by inundated standing water. The findings of this manipulation experiment during the autumn period demonstrate the different production processes of CO2 and CH4, as well as different global warming potentials, coupled with change in thaw depth. Thus the outcomes imply that the expansion of tundra lakes leads the enhancement of CH4 release, and the disappearance of the lakes causes the stimulated CO2 production in response to the Arctic climate change.
    • Using local knowledge, hydrologic, and climate data to develop a driftwood harvest model in interior Alaska

      Jones, Chas; Hinzman, Larry D.; Kielland, Knut (2011-12)
      Rural Alaskan residents are concerned that the character of the summer discharge in the Yukon River is changing, which is affecting their ability to harvest driftwood. The Yukon River flows northwesterly through British Columbia and the Yukon Territory before flowing southwest through Alaska. In most summers, residents of Tanana, Alaska harvest driftwood from the Yukon River during two different periods. Typically, driftwood accompanies high flows on the Yukon River associated with spring break‐up. A few weeks later, a second series of driftwood appears, associated with the “2nd rise,” which is reported to occur during early June. This study examines the nature of the differential timing of high flow events in the Yukon River. Many communities in interior Alaska have grown to rely upon driftwood as an important source of wood, which is used in construction, carving, and as a fuel source. Increasingly, villages in rural Alaska are trying to lessen their dependence upon expensive fossil fuels. To achieve this goal, a number of Alaskan villages have recently installed wood chip‐fired boilers to generate heat and/or electricity and additional boilers are slated to be installed in rural Alaska in the near future. These boilers are largely fed by driftwood, a cheap and easily processed wood source. Some Tanana residents have expressed concern that in recent years, driftwood was not readily available because the “2nd rise” flood event was absent. This is disconcerting for rural Alaskans that are becoming increasingly reliant upon the driftwood flows. Our goal is to determine if the perceived changes in driftwood availability are related to changes in river hydrology and if predicted changes in hydrology may affect driftwood flows and the livelihoods of rural Alaskans.
    • On-shelf transport of oceanic zooplankton in the Bering Sea.

      Gibson, Georgina; Coyle, Ken; Hedstrom, Kate; Curchitser, Enrique (2012-10)
      Neocalanus are zooplankton that require deep water to successfully reproduce so tend to occur in oceanic and shelf-break habitats. Shelf-break fronts in the Eastern Bering Sea reduce cross-shelf advection over the outer-shelves potentially retarding on-shelf transport of the oceanic copepods. South-Easterly winds October-May are thought to increase on-shelf flow over the southern shelf. Because Neocalanus are large-bodied with a high energy content they are an important food source for juvenile stages of commercially important fish such as pollock, capelin and salmon in the Bering Sea. Annual differences in forage and commercial fish stocks in the Bering Sea may depend on climatic and oceanographic conditions promoting on- shelf transport of Neocalanus. Timing of on-shelf transport of Neocalanus, and the key physical processes determining the degree and extent of this transport are unclear.
    • Processes Controlling Spatial Snow Distribution Variability at the Macro-Scale Level in Cold Regions

      Filhol, Simon; Sturm, Matthew (2014-02)
      Spatial snow distribution is a result of interactions between snow flakes and other factors such as vegetation, wind , topography. The accumulation of snow can be seen as a surface evolving snowfall after snowfall. The resulting snow depth distribution is the difference of the upper and lower surface of the snow. The lower interface of the snowpack changes winter to winter, but is fairly stable throughout a given winter. On the other hand, the upper surface’s morphology is incrementally evolving under external forces. Through three experiments, where external forces are isolated from each other, we attempt at understanding how they - vegetation, wind, and topography - interact with the snow pack, and ultimately control snow distribution.
    • Conceptualization of Arctic Tundra Landscape Transitions Using the Alaska Thermokarst Model

      Bolton, W. Robert; Romanovsky, Vladimir; McGuire, A. David; Lara, Mark (2015-09)
      Thermokarst topography forms whenever ice-rich permafrost thaws and the ground subsides due to the volume loss when excess ice transitions to water. The Alaska Thermokarst Model (ATM) is a large-scale, state-and-transition model designed to simulate landscape transitions between landscape units, or cohorts, due to thermokarst. The ATM uses a frame-based methodology to track transitions and proportion of cohorts within a 1-km2 grid cell. In the arctic tundra environment, the ATM tracks landscape transitions between non-polygonal ground (meadows), low center polygons, coalescent low center polygons, flat center polygons, high center polygons, ponds and lakes. The transition from one terrestrial landscape type to another can take place if the seasonal ground thaw penetrates underlying ice-rich soil layers either due to pulse disturbance events such as a large precipitation event, wildfire, or due to gradual active layer deepening. The protective layer is the distance between the ground surface and ice-rich soil. The protective layer buffers the ice-rich soils from energy processes that take place at the ground surface and is critical to determining how susceptible an area is to thermokarst degradation. The rate of terrain transition in our model is determined by the soil ice-content, the drainage efficiency (or ability of the landscape to store or transport water), and the probability of thermokarst initiation. Using parameterizations derived from small-scale numerical experiments, functional responses of landscape transitions will be developed and integrated into NGEE-Arctic climate-scale (CLM) modeling efforts.
    • Investigation of retrieved snow depth by microwave remote sensing with in-situ field data

      Kim, Yongwon; Enomoto, Hiroyuki (2015-04)
      AMSR-E/AMSR2 is provided the brightness temperature data with more channels, higher spatial resolution and frequent coverage. New snow algorism techniques of remote sensing for snow depth and snow-melting area can be carried out using these in-situ data. We have conducted snow survey from 2006 to now, which is mainly on March and occasionally on January and April/May when seasonal snow melts. The sites are located at an interval of ca. 32-km along the Dalton Highway (Fig. 1). Snow density, snow depth and temperature were measured in snow-pit wall observation at each site. Snow water equivalent (SWE) was calculated by multiplying snow-column snow density by snow depth. As the results, the response of SWE to snow depth showed a positively linear relationship (R2 > 0.90).
    • Scenarios use to engage scientists and decision-makers in a changing Arctic

      Lee, Olivia; Eicken, Hajo; Moreno, Juan Carlos Vargas; Lassuy, Dennis; Payne, John (2016-09)
      Scenarios provide a framework to develop adaptive Arctic policies that consider the best available science to address complex relationships and key uncertainties in drivers of change. These drivers may encompass biophysical factors such as climate change, socioeconomic drivers, and wild- cards that represent low likelihood but influential events. Three spatially explicit scenarios were identified with respect to the focal question: What is the future of energy development, resource extraction and supporting activities on the North Slope and adjacent seas through 2040? The NSSI science needs will guide recommendations for future research and monitoring and could improve policy guidance.
    • Conceptualization and Application of the Alaska Thermokarst Model

      Bolton, W. Robert; Lara, Mark; Genet, Helene; Romanovsky, Vladimir; McGuire, A. David (2016-06)
      Thermokarst topography forms whenever ice-rich permafrost thaws and the ground subsides due to the volume loss when ground ice transitions to water. The Alaska Thermokarst Model (ATM) is a large- scale, state-and-transition model designed to simulate transitions between landscape units affected by thermokarst disturbance. The ATM uses a frame-based methodology to track transitions and proportion of cohorts within a 1-km2 grid cell. In the arctic tundra environment, the ATM tracks thermokarst-related transitions among wetland tundra, graminoid tundra, shrub tundra, and thermokarst lakes. In the boreal forest environment, the ATM tracks transitions among forested permafrost plateau, thermokarst lakes, collapse scar fens and bogs. The spatial distribution of cohorts [landcover] is required to initialize and run the ATM. The initial landcover distribution is based upon analysis of compiled remote sensing data sets (SPOT-5, Inferometric Synthetic Aperture Radar, and LandSat8 OLI) at 30-m resolution. Remote sensing analysis and field measurements from previous and ongoing studies are used to determine the ice-content of the soil, the drainage efficiency (or the ability of the landscape to store or transport water), the cumulative probability of thermokarst initiation, distance from rivers, lake dynamics (increasing, decreasing, or stable), and other factors which help determine landscape transition rates. Tundra types are allowed to transition from one type to another (for example, wetland tundra to graminoid tundra) under favorable climatic conditions.
    • Model-data synthesis and high resolution simulation of the Bering Sea

      Panteleev, G.; Zhang, J.; Kurapov, A.; Durski, S.; Stroh, J.; Weingartner, T.; Woodgate, R. (2014-03)
      The Bering Sea is the source of over 50% of the total US fish catch and the home to immense populations of birds and marine mammals. This extraordinarily productive ecosystem is vulnerable to climate regime shifts that have occurred over the past decades. These regime shifts are closely linked to warming and cooling of the atmosphere and ocean, and the coincident retreat or expansion of the sea ice cover with strong interannual and decadal variability. Here we investigate changes in the Bering ice/ocean system in recent years. One of key tools for this investigation is the Bering Ecosystem STudy ice-ocean Modeling and Assimilation System (BESTMAS) for synthesis and modeling of the Bering ice/ocean system.