Now showing items 1-20 of 8808

    • EarthScope publications database

      Sims, Nealey; Tasa, Keir; Larsen, Jessica; Tape, Carl (2020-08-04)
      We compile a database of EarthScope science publications though May 11, 2020. The database is preserved as a Google Scholar profile available at https://scholar.google.com/citations?user=ZKI-0gUAAAAJ&hl=en&authuser=3
    • Non-linear glacier response to calving events, Jakobshavn Isbræ, Greenland

      Cassoto, Ryan; Fahnestock, Mark; Amundson, Jason M.; Truffer, Martin; Boettcher, Margaret S.; De La Pena, Santiago; Howat, Ian (International Glaciological Society, 2018-11-29)
      Jakobshavn Isbræ, a tidewater glacier that produces some of Greenland’s largest icebergs and highest speeds, reached record-high flow rates in 2012 (Joughin and others, 2014). We use terrestrial radar interferometric observations from August 2012 to characterize the events that led to record-high flow. We find that the highest speeds occurred in response to a small calving retreat, while several larger calving events produced negligible changes in glacier speed. This non-linear response to calving events suggests the terminus was close to flotation and therefore highly sensitive to terminus position. Our observations indicate that a glacier’s response to calving is a consequence of two competing feedbacks: (1) an increase in strain rates that leads to dynamic thinning and faster flow, thereby promoting desta- bilization, and (2) an increase in flow rates that advects thick ice toward the terminus and promotes restabilization. The competition between these feedbacks depends on temporal and spatial variations in the glacier’s proximity to flotation. This study highlights the importance of dynamic thinning and advective processes on tidewater glacier stability, and further suggests the latter may be limiting the current retreat due to the thick ice that occupies Jakobshavn Isbræ’s retrograde bed.
    • Data Submission Package for Manuscript 'Model-predicting Matschie's Tree Kangaroo in Papua New Guinea'

      Falk Huettmann et al. (30-Jul-20)
      These are the GIS data used for modeling Matschie's Tree Kangaroo (Huon Tree Kangaroo) in Papua New Guinea PNG; for details please see metadata. THe manuscript is currently in revision phase.
    • Active seismic studies in valley glacier settings: strategies and limitations

      Zechmann, Jenna M.; Booth, Adam D.; Truffer, Martin; Gusmeroli, Alessio; Amundson, Jason M.; Larsen, Christopher S. (International Glaciological Society, 2018-09-20)
      Subglacial tills play an important role in glacier dynamics but are difficult to characterize in situ. Amplitude Variation with Angle (AVA) analysis of seismic reflection data can distinguish between stiff tills and deformable tills. However, AVA analysis in mountain glacier environments can be problem- atic: reflections can be obscured by Rayleigh wave energy scattered from crevasses, and complex basal topography can impede the location of reflection points in 2-D acquisitions. We use a forward model to produce challenging synthetic seismic records in order to test the efficacy of AVA in crevassed and geo- metrically complex environments. We find that we can distinguish subglacial till types in moderately cre- vassed environments, where ‘moderate’ depends on crevasse spacing and orientation. The forward model serves as a planning tool, as it can predict AVA success or failure based on characteristics of the study glacier. Applying lessons from the forward model, we perform AVA on a seismic dataset col- lected from Taku Glacier in Southeast Alaska in March 2016. Taku Glacier is a valley glacier thought to overlay thick sediment deposits. A near-offset polarity reversal confirms that the tills are deformable.
    • Restructuring Alaska: An Alaska Oil, Gas and Industry Economic Treatise

      Reynolds, Douglas (None, 2020-07-31)
      This paper in the form of a treatise is about how to improve Alaska’s overall socio-economic welfare. It explains economic issues in Alaska starting with the Trans-Alaska (oil) Pipeline System (TAPS) and how TAPS interacts with Alaska’s oil industry and induces risk averse reactions by the state. It also explains how an alternative oil pipeline can replace TAPS in order to reduce Alaska’s expensive oil tax credits. The treatise also explains some of the issues surrounding how the oil tax credits work or don’t work including such interactions as how oil exploration is carried out, why shale-oil will not easily be developed in Alaska and how the credits subsidize Anchorage’s area energy costs to the detriment of the state as a whole. Ideas for economic development of the state are given including building natural gas infrastructure and how to set up electric utilities to maximize their value to the state. An alternative for Anchorage energy needs is a simple natural gas pipeline to Fairbanks with rail connection to Anchorage and eventually the use of TAPS for natural gas. An incentivized management system for monopoly electric power utilities is explained which can provide better cheaper electric power and an incentivized management system for a state owned oil company is explained which can help Alaska negotiate with OPEC to Alaska’s advantage. Aspects of the university and education funding are explained.
    • Tracking icebergs with time-lapse photography and sparse optical flow, LeConte Bay, Alaska, 2016–2017

      Kienholtz, Christian; Amundson, Jason M.; Motyka, Roman J.; Jackson, Rebecca H.; Mickett, John B.; Sutherland, David A.; Nash, Jonathan D.; Winters, Dylan S.; Dryer, William P.; Truffer, Martin (International Glaciological Society, 2019-03-07)
      We present a workflow to track icebergs in proglacial fjords using oblique time-lapse photos and the Lucas-Kanade optical flow algorithm. We employ the workflow at LeConte Bay, Alaska, where we ran five time-lapse cameras between April 2016 and September 2017, capturing more than 400 000 photos at frame rates of 0.5–4.0 min−1 . Hourly to daily average velocity fields in map coordinates illustrate dynamic currents in the bay, with dominant downfjord velocities (exceeding 0.5 m s−1 intermittently) and several eddies. Comparisons with simultaneous Acoustic Doppler Current Profiler (ADCP) measurements yield best agreement for the uppermost ADCP levels (∼ 12 m and above), in line with prevalent small icebergs that trace near-surface currents. Tracking results from multiple cameras compare favorably, although cameras with lower frame rates (0.5 min−1 ) tend to underestimate high flow speeds. Tests to determine requisite temporal and spatial image resolution confirm the importance of high image frame rates, while spatial resolution is of secondary importance. Application of our procedure to other fjords will be successful if iceberg concentrations are high enough and if the camera frame rates are sufficiently rapid (at least 1 min−1 for conditions similar to LeConte Bay).
    • Direct observations of submarine melt and subsurface geometry at a tidewater glacier

      Sutherland, D. A.; Jackson, R. H.; Kienholtz, C.; Amundson, J. M.; Dryer, W. P.; Duncan, D.; Eidam, E. F.; Motyka, R. J.; Nash, J. D. (American Association for the Advancement of Science, 2019-07-26)
      Ice loss from the world’s glaciers and ice sheets contributes to sea level rise, influences ocean circulation, and affects ecosystem productivity. Ongoing changes in glaciers and ice sheets are driven by submarine melting and iceberg calving from tidewater glacier margins. However, predictions of glacier change largely rest on unconstrained theory for submarine melting. Here, we use repeat multibeam sonar surveys to image a subsurface tidewater glacier face and document a time-variable, three-dimensional geometry linked to melting and calving patterns. Submarine melt rates are high across the entire ice face over both seasons surveyed and increase from spring to summer. The observed melt rates are up to two orders of magnitude greater than predicted by theory, challenging current simulations of ice loss from tidewater glaciers.
    • Metadata of six NCEAS data sets in Elith et al. 2020

      Elith, J.; Graham, C.H.; Valavi, R.; Abegg, M.; Bruce, C.; Ford, A.; Guisan, A.; Hijmans, R.J.; Huettmann, F.; Lohmann, L.G.; et al. (7/29/2020)
      The publication by Elith et al. 2020 publishes data from Elith et al. 2006 and consists of six data set; metadata descriptions provided here. Data are found in OSF and as an R package; details provided in Elith et al. 2020 and/or with authors.
    • Alaska Earthquakes Poster

      Gardine, Lea; West, Michael; Grassi, Beth (2020-06)
      Alaska is one of the most seismically active places in the world. This poster connects the geographic distribution of earthquakes from the Alaska Earthquake Center catalog with the core concepts that drive Alaska seismicity. Rupture patches, how plate tectonics forms faults throughout Alaska, and how the angle of the sinking Pacific Plate affects earthquake distribution and creates volcanoes are some of the key concepts represented.
    • Subseasonal changes observed in subglacial channel pressure, size, and sediment transport

      Gimbert, Florent; Tsai, Victor C.; Amundson, Jason M.; Bartholomaus, Timothy, C.; Walter, Jacob I. (American Geophysical Union, 2016-04-07)
      Water that pressurizes the base of glaciers and ice sheets enhances glacier velocities and modulates glacial erosion. Predicting ice flow and erosion therefore requires knowledge of subglacial channel evolution, which remains observationally limited. Here we demonstrate that detailed analysis of seismic ground motion caused by subglacial water flow at Mendenhall Glacier (Alaska) allows for continuous measurement of daily to subseasonal changes in basal water pressure gradient, channel size, and sediment transport. We observe intermittent subglacial water pressure gradient changes during the melt season, at odds with common assumptions of slowly varying, low-pressure channels. These observations indicate that changes in channel size do not keep pace with changes in discharge. This behavior strongly affects glacier dynamics and subglacial channel erosion at Mendenhall Glacier, where episodic periods of high water pressure gradients enhance glacier surface velocity and channel sediment transport by up to 30% and 50%, respectively. We expect the application of this framework to future seismic observations acquired at glaciers worldwide to improve our understanding of subglacial processes.
    • A mass-flux perspective of the tidewater glacier cycle

      Amundson, Jason M. (International Glaciological Society, 2016-04-06)
      I explore the tidewater glacier cycle with a 1-D, depth- and width-integrated flow model that includes a mass-flux calving parameterization. The parameterization is developed from mass continuity arguments and relates the calving rate to the terminus velocity and the terminus balance velocity. The model demonstrates variable sensitivity to climate. From an advanced, stable configuration, a small warming of the climate triggers a rapid retreat that causes large-scale drawdown and is enhanced by positive glacier-dynamic feedbacks. Eventually, the terminus retreats out of deep water and the terminus velocity decreases, resulting in reduced drawdown and the potential for restabilization. Terminus readvance can be initiated by cooling the climate. Terminus advance into deep water is difficult to sustain, however, due to negative feedbacks between glacier dynamics and surface mass balance. Despite uncertainty in the precise form of the parameterization, the model provides a simple explanation of the tidewater glacier cycle and can be used to evaluate the response of tidewater glaciers to climate variability. It also highlights the importance of improving parameterizations of calving rates and of incorporating sediment dynamics into tidewater glacier models.
    • Subglacial discharge at tidewater glaciers revealed by seismic tremor

      Bartholomaus, Timothy C.; Amundson, Jason M.; Walter, Jacob I.; O'Neel, Shad; West, Michael E.; Larsen, Christopher F. (American Geophysical Union, 2015-08-10)
      Subglacial discharge influences glacier basal motion and erodes and redeposits sediment. At tidewater glacier termini, discharge drives submarine terminus melting, affects fjord circulation, and is a central component of proglacial marine ecosystems. However, our present inability to track subglacial discharge and its variability significantly hinders our understanding of these processes. Here we report observations of hourly to seasonal variations in 1.5–10 Hz seismic tremor that strongly correlate with subglacial discharge but not with basal motion, weather, or discrete icequakes. Our data demonstrate that vigorous discharge occurs from tidewater glaciers during summer, in spite of fast basal motion that could limit the formation of subglacial conduits, and then abates during winter. Furthermore, tremor observations and a melt model demonstrate that drainage efficiency of tidewater glaciers evolves seasonally. Glaciohydraulic tremor provides a means by which to quantify subglacial discharge variations and offers a promising window into otherwise obscured glacierized environments.
    • Alaska's economy and the pandemic

      Guettabi, Mouhcine (2020-06-30)
      The Alaska economy has emerged from its longest recession in 2019. The decline in economic activity and government revenues was due to the severe decline in oil prices which resulted in deep spending cuts and significant private sector job losses. The current pandemic has resulted in a significant shock to all facets of the Alaska economy. In this paper, we provide a little bit of background on the Alaska economy, present new high frequency data to asses the extent of the current damage, and then present a forecast for the next 6, 12, and 18 months. In 2020, we anticipate the economy to end the year with almost 25,000 fewer jobs than in 2019. The decrease would represent a 7.4% relative to the previous year. In 2021, we expect the economy to slowly start regaining the jobs lost the previous year and grow at a rate of 2.2%. In 2022, we anticipate a continuing climb for the economy as it is expected to grow at 1.1% percent. By the end of 2022, the Alaska economy should be at about 95% of the pre-pandemic levels. It is important to note there are significant downside risks which could negatively influence the employment outlook.
    • Seasonal and interannual variations in ice melange and its impact on terminus stability, Jakobshavn Isbræ, Greenland

      Cassotto, Ryan; Fahnestock, Mark; Amundson, Jason M.; Truffer, Martin; Joughin, Ian (International Glaciological Society, 2014-09-29)
      We used satellite-derived surface temperatures and time-lapse photography to infer temporal variations in the proglacial ice melange at Jakobshavn Isbræ, a large and rapidly retreating outlet glacier in Greenland. Freezing of the melange-covered fjord surface during winter is indicated by a decrease in fjord surface temperatures and is associated with (1) a decrease in ice melange mobility and (2) a drastic reduction in iceberg production. Vigorous calving resumes in spring, typically abruptly, following the steady up-fjord retreat of the sea-ice/ice-melange margin. An analysis of pixel displacement from time-lapse imagery demonstrates that melange motion increases prior to calving and subsequently decreases following several events. We find that secular changes in ice melange extent, character and persistence can influence iceberg calving, and therefore glacier dynamics over daily-to-monthly timescales, which, if sustained, will influence the mass balance of an ice sheet.
    • Dynamic jamming of iceberg-choked fjords

      Peters, Ivo R.; Amundson, Jason M.; Cassotto, Ryan; Fahnestock, Mark; Darnell, Kristopher N.; Truffer, Martin; Zhang, Wendy W. (American Geophysical Union, 2015-02-02)
      We investigate the dynamics of ice mélange by analyzing rapid motion recorded by a time-lapse camera and terrestrial radar during several calving events that occurred at Jakobshavn Isbræ, Greenland. During calving events (1) the kinetic energy of the ice mélange is 2 orders of magnitude smaller than the total energy released during the events, (2) a jamming front propagates through the ice mélange at a rate that is an order of magnitude faster than the motion of individual icebergs, (3) the ice mélange undergoes initial compaction followed by slow relaxation and extension, and (4) motion of the ice mélange gradually decays before coming to an abrupt halt. These observations indicate that the ice mélange experiences widespread jamming during calving events and is always close to being in a jammed state during periods of terminus quiescence. We therefore suspect that local jamming influences longer timescale ice mélange dynamics and stress transmission.
    • The morphology of supraglacial lake ogives

      Darnell, K.N.; Amundson, J.M.; Cathles, L.M.; MacAyeal, D.R. (International Glaciological Society, 2013-02-12)
      Supraglacial lakes on grounded regions of the Greenland and Antarctic ice sheets sometimes produce ‘lake ogives’ or banded structures that sweep downstream from the lakes. Using a variety of remote-sensing data, we demonstrate that lake ogives originate from supraglacial lakes that form each year in the same bedrock-fixed location near the equilibrium-line altitude. As the ice flows underneath one of these lakes, an ‘image’ of the lake is imprinted on the ice surface both by summer- season ablation and by superimposed ice (lake ice) formation. Ogives associated with a lake are sequenced in time, with the downstream ogives being the oldest, and with spatial separation equal to the local annual ice displacement. In addition, lake ogives can have decimeter- to meter-scale topographic relief, much like wave ogives that form below icefalls on alpine glaciers. Our observations highlight the fact that lake ogives, and other related surface features, are a consequence of hydrological processes in a bedrock-fixed reference frame. These features should arise naturally from physically based thermodynamic models of supraglacial water transport, and thus they may serve as fiducial features that help to test the performance of such models.
    • Alaska Native Claims Settlement Act: Selected Bibliography

      Sharp, Suzanne; Rowan, Irene; Antonson, Jo; Ongtooguk, Paul; Puller, Gordon; Templeton, Willie (Institute of Social and Economic Research, University of Alaska Anchorage, 2011-04-01)
      ISER prepared this list of books, reports, and other resources on the Alaska Native Claims Settlement Act for the ANCSA @ 40 Committee. It is the most comprehensive such list we are aware of, but there are likely additional resources yet to be identified. Some of these resources are now out of print and may be available at used bookstores or at libraries. More recent publications can be obtained from the publishers or at bookstores. You can also find resources on websites, as noted in the citations.
    • Quantifying expert opinion with discrete choice models: Invasive elodea's influence on Alaska salmonids

      Little, Joseph; Hayward, Gregory D. (Elsevier, 2020-10-01)
      Scientific evidence should inform environmental policy, but rapid environmental change brings high ecological uncertainty and associated barriers to the science-management dialogue. Biological invasions of aquatic plants are a worldwide problem with uncertain ecological and economic consequences. We demonstrate that the discrete choice method (DCM) can serve as a structured expert elicitation alternative to quantify expert opinion across a range of possible but uncertain environmental outcomes. DCM is widely applied in the social sciences to better understand and predict human preferences and trade-offs. Here we apply it to Alaska's first submersed invasive aquatic freshwater plant, Elodea spp. (elodea), and its unknown effects on salmonids. While little is known about interactions between elodea and salmonids, ecological research suggests that aquatic plant invasions can have positive and negative, as well as direct and indirect, effects on fish. We use DCM to design hypothetical salmonid habitat scenarios describing elodea's possible effect on critical environmental conditions for salmonids: prey abundance, dissolved oxygen, and vegetation cover. We then observe how experts choose between scenarios that they believe could support persistent salmonid populations in elodea-invaded salmonid habitat. We quantify the relative importance of habitat characteristics that influence expert choice and investigate how experts trade off between habitat characteristics. We take advantage of Bayesian techniques to estimate discrete choice models for individual experts and to simulate expert opinion for specific environmental management situations. We discuss possible applications and advantages of the DCM approach for expert elicitation in the ecological context. We end with methodological questions for future research.
    • Pod Cast US Shale-Oil Production Peak

      Reynolds, Douglas (2020-07-08)
      This paper, in the form of a Pod Cast, estimates a U.S. shale-oil production trend forecast and explores potential consequences of that trend on U.S. and World macroeconomic conditions and growth prospects. It explains the economics of the Hubbert curve including a literature review both pro and con. It explains the relationship of shale-oil and shale-gas. It falsifies various U.S. shale-oil trend hypotheses using logic and econometrics. It then presents oil price expectations based on an analyses of entropy-economic relationships, physical energy characteristics, new-institutional economic theories of OPEC, and OPEC+ game-theoretic plays. Covid-19, OPEC+ and macro-economic principles are analyzed for their potential market changing effects using Schwartzian futurology methodology. A comparison of the current global civilization to past civilizations is also carried out.
    • When Uŋalaqłiq danced: stories of strength, suppression & hope

      Qassataq, Ayyu; Stern, Charlene B.; Black, Jessica C.; John-Shields, Agatha (2020-05)
      In the late 1800’s, Uŋalaqłiq (Unalakleet), a predominantly Iñupiaq community along the Norton Sound in Western Alaska, was missionized by the Evangelical Covenant Church. Missionaries were integral in establishing a localized education system under the direction of General Agent of Education, Sheldon Jackson, in the early 1900’s. By 1915, the community was no longer engaging in ancestral practices such as deliberating, teaching and hosting ceremonies within the qargi. Nor were they uplifting shared history and relationships between villages or expressing gratitude for the bounty of the lands through traditional songs, dances, or celebrations such as the Kivgiq Messenger Feast. This research outlines events that occurred in Uŋalaqłiq around the turn of the 20th century and analyzes how those events influenced the formation of the education system and its ongoing impacts to Native peoples and communities today. The intent of this research is to help grow a shared understanding of how this history continues to shape our lived experience as modern day Native peoples and to lay a foundation to promote healing and strength through the potential revival of ancestral traditions that have kept us healthy and strong for thousands of years.