Six Strategies for Rehabilitating Land Disturbed by Oil Development in Arctic Alaska

Oil development in arctic Alaska has left a range of disturbed lands that will eventually require rehabilitation. These lands include gravel roads and pads, gravel pits and overburden stockpiles, drilling reserve pits, occasional accidental spills, and other minor disturbances to the tundra. A long-term research program investigating site-specific and cost-effective methods for rehabilitating degraded lands for fish and wildlife habitat has developed six general strategies that are applicable to the range of disturbed conditions. These strategies include 1) flooding of gravel mine sites for fish habitat, 2) creation of wetlands in ponds perched on overburden stockpiles, 3) revegetation of thick gravel fill and overburden to compensate for lost wildlife habitat, 4) removal of gravel fill to help restore wet tundra habitats, 5) restoration of tundra on less severely modified habitats, and 6) remediation of areas contaminated by oil spills, seawater spills, and drilling mud. Although most techniques are in the early stage of evaluation, preliminary results suggest that successful methods are available to create diverse, productive, and self-sustaining communities that are useful to a range of wildlife.Key words: Arctic, Alaska, disturbance, habitat, tundra, oilfield, rehabilitation, revegetation, restoration, wetlandsL'exploitation du pétrole dans la zone arctique de l'Alaska a entraîné une gamme de perturbations sur des terrains qu'il va falloir un jour réhabiliter. Ces derniers comprennent les routes et plates-formes de gravier, les gravières et déblais des terrains de recouvrement, les bassins de réserve de forage, les terrains ayant été le site de déversements accidentels occasionnels et autres perburbations mineures de la toundra. Six stratégies générales applicables à la gamme des terres ayant subi des perturbations ont été développées grâce à un programme de recherche à long terme portant sur les méthodes - rentables et spécifiques à chaque site - de réhabilitation des terres dégradées pour la faune aquatique et terrestre. Ces stratégies comprennent 1) l'inondation de gravières pour l'habitat du poisson, 2) la création de terres humides dans les étangs situés en haut des déblais des terrains de recouvrement, 3) la restauration de la végétation sur les remblais de gravier et déblais épais, pour compenser la perte de l'habitat faunique, 4) l'enlèvement des remblais de gravier comme aide à la restauration des habitats de toundra humide, 5) la restauration de la toundra dans des habitats n'ayant pas subi de modifications aussi sérieuses, et 6) la décontamination de zones ayant subi des déversements de pétrole, d'eau de mer et de boue de forage. Bien que la plupart des techniques en soient au stade préliminaire de l'évaluation, les premiers résultats donnent à penser qu'il existe des moyens efficaces de créer des communautés diverses, productives et autorégulatrices qui permettent la présence d'une flore et d'une faune diversifiées.Mots clés: Arctic, Alaska, perturbation, habitat, toundra, gisement pétrolier, réhabilitation, revégétation, restauration, terres humide

Storm-Surge Flooding on the Yukon-Kuskokwim Delta, Alaska

Coastal regions of Alaska are regularly affected by intense storms of ocean origin, the frequency and intensity of which are expected to increase as a result of global climate change. The Yukon-Kuskokwim Delta (YKD), situated in western Alaska on the eastern edge of the Bering Sea, is one of the largest deltaic systems in North America. Its low relief makes it especially susceptible to storm-driven flood tides and increases in sea level. Little information exists on the extent of flooding caused by storm surges in western Alaska and its effects on salinization, shoreline erosion, permafrost thaw, vegetation, wildlife, and the subsistence-based economy. In this paper, we summarize storm flooding events in the Bering Sea region of western Alaska during 1913 – 2011 and map both the extent of inland flooding caused by autumn storms on the central YKD, using Radarsat-1 and MODIS satellite imagery, and the drift lines, using high-resolution IKONOS satellite imagery and field surveys. The largest storm surges occurred in autumn and were associated with high tides and strong (> 65 km hr-1) southwest winds. Maximum inland extent of flooding from storm surges was 30.3 km in 2005, 27.4 km in 2006, and 32.3 km in 2011, with total flood area covering 47.1%, 32.5%, and 39.4% of the 6730 km2 study area, respectively. Peak stages for the 2005 and 2011 storms were 3.1 m and 3.3 m above mean sea level, respectively—almost as high as the 3.5 m amsl elevation estimated for the largest storm observed (in November 1974). Several historically abandoned village sites lie within the area of inundation of the largest flood events. With projected sea level rise, large storms are expected to become more frequent and cover larger areas, with deleterious effects on freshwater ponds, non-saline habitats, permafrost, and landscapes used by nesting birds and local people.Les régions côtières de l’Alaska sont souvent touchées par d’intenses tempêtes d’origine océanique. La fréquence et l’intensité de ces tempêtes devraient augmenter en raison du changement climatique qui s’opère à l’échelle mondiale. Le delta Yukon-Kuskokwim, dans l’ouest de l’Alaska, du côté est de la mer de Béring, est l’un des systèmes deltaïques les plus imposants de l’Amérique du Nord. Son relief peu accidenté le rend particulièrement susceptible aux marées montantes découlant des tempêtes et aux augmentations du niveau de la mer. Peu d’information existe au sujet de l’ampleur des inondations attribuables aux ondes de tempêtes dans l’ouest de l’Alaska de même que sur leurs effets en matière de salini­sation, d’érosion des berges, de dégel, de pergélisol, de végétation, de faune et d’économie de subsistance. Dans cet article, nous résumons les ondes de tempêtes qui ont eu lieu dans la région de la mer de Béring de l’ouest de l’Alaska entre 1913 et 2011 et nous cartographions à l’aide de Radarsat-1 et de l’imagerie satellitaire MODIS l’étendue des inondations fluviales causées par les tempêtes automnales dans le centre du delta Yukon-Kuskokwim, de même que les lignes de dérive au moyen de l’imagerie satellitaire IKONOS à haute résolution et de levés sur le terrain. Les ondes de tempêtes les plus importantes se sont produites à l’automne. Elles s’accompagnaient de marées hautes et de vents forts (> 65 km h-1) en provenance du sud-ouest. L’étendue maximale des inondations fluviales découlant des ondes de tempêtes a atteint 30,3 km en 2005, 27,4 km en 2006 et 32,3 km en 2011. Au total, la zone inondée couvrait respectivement 47,1 %, 32,5 % et 39,4 % de l’aire de 6 730 km2 visée par l’étude. Le niveau maximal des tempêtes de 2005 et 2011 était de 3,1 m et de 3,3 m au-dessus du niveau moyen de la mer, respectivement, ce qui est presque aussi élevé que la hauteur estimée de 3,5 m au-dessus du niveau moyen de la mer pour la plus grosse des tempêtes observées (en novembre 1974). Plusieurs villages abandonnés au fil des ans se trouvent dans la zone touchée par les plus grandes inondations. Compte tenu de l’élévation projetée du niveau de la mer, la fréquence des tempêtes d’envergure devrait augmenter et les tempêtes devraient couvrir des zones plus grandes, ce qui aura des effets délétères sur les étangs d’eau douce, les habitats non salins, le pergélisol et les paysages dont se servent les oiseaux nicheurs et les gens de la région

Airboat Use and Disturbance of Floating Mat Fen Wetlands in Interior Alaska, U.S.A.

The use of airboats is expanding in Alaska, particularly in the interior. This study describes the nature, magnitude, and distribution of disturbance caused by airboat trails over floating mat fen wetlands in the Tanana Flats near Fairbanks, Alaska. Airphoto interpretation showed over 300 km of airboat trails by 1995, with a 15% expansion of the trail system since 1989. Field sampling was done at 30 trail and adjacent control sites along this trail system to assess changes in hydrology, soils, and vegetation. Water velocities in the trails at two-thirds of the sites were at least an order of magnitude greater than velocities of less than 1.5 cm/sec in the control areas. On average, 30 cm of the 0.5-0.75 m thick floating mat has been removed or eroded by airboat traffic at the sampling locations. Nearly all emergent floating mat vegetation has been destroyed (5% cover remaining on average) so that the trails resemble a highly visible open water stream channel 2-3 m wide through the floating mats. Although the recovery and regrowth potential of floating mats in trails is high, recovery is unlikely in trails with continuing use.En Alaska, l'utilisation des hydroglisseurs est à la hausse, surtout à l'intérieur des terres. Cette étude décrit la nature, l'amplitude et la distribution des perturbations causées par le sillage des hydroglisseurs sur les zones humides de vasières à mattes flottantes situées dans les plaines marécageuses de Tanana près de Fairbanks (en Alaska). L'interprétation de photos a montré que, en 1995, les sillages d'hydroglisseurs s'étendaient sur plus de 300 km, ce qui correspond à une augmentation de 15 p. cent du réseau depuis 1989. On a procédé à un échantillonnage sur le terrain à 30 emplacements de sillages et aires témoins adjacentes le long du réseau en vue d'évaluer les changements dans l'hydrologie, les sols et la végétation. Dans deux tiers des emplacements, la vitesse de l'eau dans les sillages était d'au moins un ordre de grandeur supérieure aux vitesses de moins de 1,5 cm/sec dans les zones témoins. Aux endroits d'échantillonnage, 30 cm en moyenne de la matte flottante épaisse de 0,5 à 0,75 m a été enlevée ou érodée par la circulation de l'hydroglisseur. Presque toute la végétation de la matte flottante émergée a été détruite (il reste en moyenne 5 p. cent du couvert) de sorte que les sillages sont très visibles et forment un chenal d'eau ouverte de 2 à 3 m de large à travers les mattes flottantes. Bien que le potentiel de recouvrement et de repousse des mattes flottantes dans les sillages soit élevé, il est peu probable que ce recouvrement ait lieu dans les sillages qui sont utilisés de façon continue

Scaling-up permafrost thermal measurements in western Alaska using an ecotype approach

Permafrost temperatures are increasing in Alaska due to climate change and in some cases permafrost is thawing and degrading. In areas where degradation has already occurred the effects can be dramatic, resulting in changing ecosystems, carbon release, and damage to infrastructure. However, in many areas we lack baseline data, such as subsurface temperatures, needed to assess future changes and potential risk areas. Besides climate, the physical properties of the vegetation cover and subsurface material have a major influence on the thermal state of permafrost. These properties are often directly related to the type of ecosystem overlaying permafrost. In this paper we demonstrate that classifying the landscape into general ecotypes is an effective way to scale up permafrost thermal data collected from field monitoring sites. Additionally, we find that within some ecotypes the absence of a moss layer is indicative of the absence of near-surface permafrost. As a proof of concept, we used the ground temperature data collected from the field sites to recode an ecotype land cover map into a map of mean annual ground temperature ranges at 1 m depth based on analysis and clustering of observed thermal regimes. The map should be useful for decision making with respect to land use and understanding how the landscape might change under future climate scenarios

Permafrost Database Development, Characterization, and Mapping for Northern Alaska

List of Figures - ii List of Tables - iii Acknowledgements - iii Introduction - 1 Study Area - 2 Methods - 2 Permafrost Data Compilation - 2 Geomorphic Units - 3 Classification - 3 Mapping - 3 Permafrost-soil Landscapes - 4 Classification - 4 Mapping - 4 Permafrost Characteristics and Vulnerability - 5 Web-based Data Distribution - 5 Results and Discussion - 6 Permafrost Data Compilation - 6 Geomorphic Units - 12 Classification and Descriptions - 12 Mapping - 12 Permafrost-Soil Landscapes - 20 Classification and Descriptions - 20 Landscape Profiles - 20 Mapping - 29 Permafrost Characteristics and Vulnerability - 34 Web-based Data Distribution - 40 Summary and Conclusion - 41 Literature Cited - 4

Effect of permafrost thaw on CO2 and CH4 exchange in a western Alaska peatland chronosequence

Permafrost soils store over half of global soil carbon (C), and northern frozen peatlands store about 10% of global permafrost C. With thaw, inundation of high latitude lowland peatlands typically increases the surface-atmosphere flux of methane (CH4), a potent greenhouse gas. To examine the effects of lowland permafrost thaw over millennial timescales, we measured carbon dioxide (CO2) and CH4 exchange along sites that constitute a ~1000 yr thaw chronosequence of thermokarst collapse bogs and adjacent fen locations at Innoko Flats Wildlife Refuge in western Alaska. Peak CH4 exchange in July (123 ± 71 mg CH4–C m−2 d−1) was observed in features that have been thawed for 30 to 70 (\u3c100) yr, where soils were warmer than at more recently thawed sites (14 to 21 yr; emitting 1.37 ± 0.67 mg CH4–C m−2 d−1 in July) and had shallower water tables than at older sites (200 to 1400 yr; emitting 6.55 ± 2.23 mg CH4–C m−2 d−1 in July). Carbon lost via CH4 efflux during the growing season at these intermediate age sites was 8% of uptake by net ecosystem exchange. Our results provide evidence that CH4 emissions following lowland permafrost thaw are enhanced over decadal time scales, but limited over millennia. Over larger spatial scales, adjacent fen systems may contribute sustained CH4 emission, CO2 uptake, and DOC export. We argue that over timescales of decades to centuries, thaw features in high-latitude lowland peatlands, particularly those developed on poorly drained mineral substrates, are a key locus of elevated CH4 emission to the atmosphere that must be considered for a complete understanding of high latitude CH4 dynamics

Airborne electromagnetic imaging of discontinuous permafrost

The evolution of permafrost in cold regions is inextricably connected to hydrogeologic processes, climate, and ecosystems. Permafrost thawing has been linked to changes in wetland and lake areas, alteration of the groundwater contribution to stream flow, carbon release, and increased fire frequency. But detailed knowledge about the dynamic state of permafrost in relation to surface and groundwater systems remains an enigma. Here, we present the results of a pioneering ~1,800 line-kilometer airborne electromagnetic survey that shows sediments deposited over the past ~4 million years and the configuration of permafrost to depths of ~100 meters in the Yukon Flats area near Fort Yukon, Alaska. The Yukon Flats is near the boundary between continuous permafrost to the north and discontinuous permafrost to the south, making it an important location for examining permafrost dynamics. Our results not only provide a detailed snapshot of the present-day configuration of permafrost, but they also expose previously unseen details about potential surface – groundwater connections and the thermal legacy of surface water features that has been recorded in the permafrost over the past 1,000 years. This work will be a critical baseline for future permafrost studies aimed at exploring the connections between hydrogeologic, climatic, and ecological processes, and has significant implications for the stewardship of Arctic environments

The Alaska Arctic Vegetation Archive (AVA-AK)

The Alaska Arctic Vegetation Archive (AVA-AK, GIVD-ID: NA-US-014) is a free, publically available database archive of vegetation-plot data from the Arctic tundra region of northern Alaska. The archive currently contains 24 datasets with 3,026 non-overlapping plots. Of these, 74% have geolocation data with 25-m or better precision. Species cover data and header data are stored in a Turboveg database. A standardized Pan Arctic Species List provides a consistent nomenclature for vascular plants, bryophytes, and lichens in the archive. A web-based online Alaska Arctic Geoecological Atlas (AGA-AK) allows viewing and downloading the species data in a variety of formats, and provides access to a wide variety of ancillary data. We conducted a preliminary cluster analysis of the first 16 datasets (1,613 plots) to examine how the spectrum of derived clusters is related to the suite of datasets, habitat types, and environmental gradients. Here, we present the contents of the archive, assess its strengths and weaknesses, and provide three supplementary files that include the data dictionary, a list of habitat types, an overview of the datasets, and details of the cluster analysis