Sediment and nutrient delivery from thermokarst features in the foothills of the North Slope, Alaska : potential impacts on headwater stream ecosystems

Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 113 (2008): G02026, doi:10.1029/2007JG000470.Permafrost is a defining characteristic of the Arctic environment. However, climate warming is thawing permafrost in many areas leading to failures in soil structure called thermokarst. An extensive survey of a 600 km2 area in and around the Toolik Lake Natural Research Area (TLNRA) revealed at least 34 thermokarst features, two thirds of which were new since ∼1980 when a high resolution aerial survey of the area was done. Most of these thermokarst features were associated with headwater streams or lakes. We have measured significantly increased sediment and nutrient loading from thermokarst features to streams in two well-studied locations near the TLNRA. One small thermokarst gully that formed in 2003 on the Toolik River in a 0.9 km2 subcatchment delivered more sediment to the river than is normally delivered in 18 years from 132 km2 in the adjacent upper Kuparuk River basin (a long-term monitoring reference site). Ammonium, nitrate, and phosphate concentrations downstream from a thermokarst feature on Imnavait Creek increased significantly compared to upstream reference concentrations and the increased concentrations persisted over the period of sampling (1999–2005). The downstream concentrations were similar to those we have used in a long-term experimental manipulation of the Kuparuk River and that have significantly altered the structure and function of that river. A subsampling of other thermokarst features from the extensive regional survey showed that concentrations of ammonium, nitrate, and phosphate were always higher downstream of the thermokarst features. Our previous research has shown that even minor increases in nutrient loading stimulate primary and secondary production. However, increased sediment loading could interfere with benthic communities and change the responses to increased nutrient delivery. Although the terrestrial area impacted by thermokarsts is limited, the aquatic habitat altered by these failures can be extensive. If warming in the Arctic foothills accelerates thermokarst formation, there may be substantial and wide-spread impacts on arctic stream ecosystems that are currently poorly understood.The results presented in this report are based upon work supported by the U.S. National Science Foundation under grants to the Arctic Hyporheic project (OPP- 0327440) and the Arctic Long-Term Ecological Research Program (DEB- 9810222)

Engineering preferentially aligned nitrogen vacancy centre ensembles in CVD grown diamond

Here we report a method for improving the magnetic field sensitivity of an ensemble of Nitrogen Vacancy NV centres in C 12 enriched diamond aligned along the [111] crystal axis. The preferentially aligned NV centres are fabricated by a Plasma Enhanced Chemical Vapour Deposition PECVD process and their concentration is quantitatively determined by analysing the confocal microscopy images. We further observe that annealing the samples at high temperature 1500 degrees C in vacuum leads to a conversion of substitutional nitrogen into NV centres. This treatment also increases the coherence time of the NV centres electron spins up to 40 mu s, which corresponds to enhancement of the sensitivity by a factor of three. However, this procedure also leads to a loss of the preferential alignment by 3

A yearlong comparison of plot‐scale and satellite footprint‐scale 19 and 37 GHz brightness of the Alaskan North Slope

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95289/1/jgrd9836.pd

(EIN)FACH? : Komplexität, Wissen, Fortschritt und die Grenzen der Germanistik

Spätestens seit den gesellschaftlichen Modernisierungsschüben in den sechziger Jahren identifiziert auch die Germanistik Erkenntnis- und Wissenszuwachs, ja allgemeiner den "Fortschritt" ihres Fachs, mit Komplexitätserhöhung. Vor diesem Hintergrund erscheint es mir wenig plausibel, die seitdem erfolgten inneren Ausdifferenzierungen und interdisziplinären Grenzüberschreitungen als durch Identitätsverlust, Zerstreuung und Desintegration gekennzeichnete Niedergangsszenarien zu beschreiben. Die Veränderungen gehorchen der immanenten Logik germanistischer Forschung, einer "disziplinierten", auf Leistung ausgerichteten, an kooperativen Großforschungsvorhaben partizipierenden Wissensproduktion

Why theory matters:Analytical strategies of critical psychology

Based on Critical Psychology from the Standpoint of the Subject the article describes analytical concerns and strategies of critical psychology. In a first step, the development of critical psychologies is located in current discussions on the production of knowledge, and three different typical approaches and major steps toward situated critique as a practice of mutual recognition are delineated. This shift, it is argued, has led to a historically new relevance of critique, and two basic analytical elements of critical research are introduced: Everyday conflictuality as the initiating moment of critique as well as the importance of theory for critical inquiry. On this basis a variety of analytic strategies and concepts are presented which inform Critical Psychology from the Standpoint of the Subject and suggest a constituent move from partial perspectives toward situated generalization

Analyzing the Impacts of Off-Road Vehicle (ORV) Trails on Watershed Processes in Wrangell-St. Elias National Park and Preserve, Alaska

Trails created by off-road vehicles (ORV) in boreal lowlands are known to cause local impacts, such as denuded vegetation, soil erosion, and permafrost thaw, but impacts on stream and watershed processes are less certain. In Wrangell-St. Elias National Park and Preserve (WRST), Alaska, ORV trails have caused local resource damage in intermountain lowlands with permafrost soils and abundant wetlands and there is a need to know whether these impacts are more extensive. Comparison of aerial photography from 1957, 1981, and 2004 coupled with ground surveys in 2009 reveal an increase in trail length and number and show an upslope expansion of a trail system around points of stream channel initiation. We hypothesized that these impacts could also cause premature initiation and headward expansion of channels because of lowered soil resistance and greater runoff accumulation as trails migrate upslope. Soil monitoring showed earlier and deeper thaw of the active layer in and adjacent to trails compared to reference sites. Several rainfall-runoff events during the summer of 2009 showed increased and sustained flow accumulation below trail crossings and channel shear forces sufficient to cause headward erosion of silt and peat soils. These observations of trail evolution relative to stream and wetland crossings together with process studies suggest that ORV trails are altering watershed processes. These changes in watershed processes appear to result in increasing drainage density and may also alter downstream flow regimes, water quality, and aquatic habitat. Addressing local land-use disturbances in boreal and arctic parklands with permafrost soils, such as WRST, where responses to climate change may be causing concurrent shifts in watershed processes, represents an important challenge facing resource managers