Kenai Peninsula Research Articles

Predicting live and dead tree basal area of bark beetle affected forests from discrete-return lidar

Bark beetle outbreaks have killed large numbers of trees across North America in recent years. Lidar remote sensing can be used to effectively estimate forest biomass, but prediction of both live and dead standing biomass in beetle-affected forests using lidar alone has not been demonstrated. We developed Random Forest (RF) models predicting total, live, dead, and percent dead basal area (BA) from lidar metrics in five different beetle-affected coniferous forests across western North America. Study areas included the Kenai Peninsula of Alaska, southeastern Arizona, north-central Colorado, central Idaho, and central Oregon, U.S.A. We created RF models with and without intensity metrics as predictor variables and investigated how intensity normalization affected RF models in Idaho. RF models predicting total BA explained the most variation, whereas RF models predicting dead BA explained the least variation, with live and percent dead BA models explaining intermediate levels of variation. Important metrics varied between models depending on the type of BA being predicted. Generally, height and density metrics were important in predicting total BA, intensity and density metrics were important in predicting live BA, and intensity metrics were important in predicting dead and percent dead BA. Several lidar metrics were important across all study areas. Whether needles were on or off beetle-killed trees at the time of lidar acquisition could not be ascertained. Future work, where needle conditions at the time of lidar acquisition are known, could improve upon our analysis and results. Although RF models predicting live, dead, and percent dead BA did not perform as well as models predicting total BA, we concluded that discrete-return lidar can be used to provide reasonable estimations of live and dead BA. Our results also showed which lidar metrics have general utility across different coniferous forest types.

Tardigrades of Alaska: distribution patterns, diversity and species richness

During the summer of 2010, a biotic survey of tardigrades was conducted along a latitudinal transect in central Alaska from the Kenai Peninsula, via Fairbanks and the Arctic Circle to the coastal plain. Work was centred at the Toolik and Bonanza Creek Long Term Ecological Research Network sites and supplemented by opportunistic collections from the Kenai Peninsula and Anchorage areas. The 235 samples collected at 20 sites over 10 degrees of latitude yielded 1463 tardigrades representing two classes, three orders, 10 families, 23 genera and 73 species from 142 positive samples. A total of 50 species are new to Alaska, increasing the state’s known species richness to 84. Several environmental metrics, such as pH, substrate, elevation, location and habitat were measured, recorded and analysed along the latitudinal gradient. Contrary to expectations, pH did not appear to be a predictor of tardigrade abundance or distribution. Density and species richness were relatively consistent across sites. However, the assemblages were highly variable within and between sites at only 14-20% similarity. We detected no correlation between species diversity and latitudinal or environmental gradients, though this may be affected by a high (59.9%) occurrence of single-species samples (containing individuals of only one species). Estimates of species richness were calculated for Alaska (118) and the Arctic (172). Our efforts increased the number of known species in Alaska to 84, and those results led us to question the validity of the estimate numbers. Keywords: Tardigrade; Alaska; distribution; latitudinal gradient; pH; species richness (Published: 22 May 2013) Citation: Polar Research 2013, 32 , 18793, http://dx.doi.org/10.3402/polar.v32i0.18793

Character, mass, distribution, and origin of tephra-fall deposits from the 2009 eruption of Redoubt Volcano, Alaska—Highlighting the significance of particle aggregation

The 2009 eruption of Redoubt Volcano included 20 tephra-producing explosions between March 15, 2009 and April 4, 2009 (UTC). Next-Generation radar (NEXRAD) data show that plumes reached heights between 4.6km and 19km asl and were distributed downwind along nearly all azimuths of the volcano. Explosions lasted between <1 and 31min based on the signal duration at a distal seismic station (86km). From Moderate Resolution Imaging Spectroradiometer (MODIS) imagery and field data, we estimate that over 80,000km2 received at least minor ash fall (>0.8mm thick), including communities along the Kenai Peninsula (80–100km) and the city of Anchorage (170km). Trace ash (<0.8mm) was reported as far as Fairbanks, 550km NNE of the volcano. We estimate the total mass of tephra-fall deposits at 54.6×109kg with a total DRE volume of 20.6×106m3.On March 15, a small (4.6km asl) phreatic explosion containing minor, non-juvenile ash, erupted through the summit ice cap. The first five magmatic explosions (events 1–5) occurred within a 6-hour period on March 23. Plumes rose to heights between 5.5km and 14.9km asl during 2- to 20-minute-duration explosions, and were dispersed mainly along a NNE trajectory. Trace ash fall was reported as far as Fairbanks. Owing to a shift in wind direction and heavy snowfall during these events, field discrimination among many of these layers was possible. All deposits comprise a volumetrically significant amount of particle aggregates, yet only event 5 deposits contain coarse clasts including glacier ice. The most voluminous tephra fall was deposited on March 24 (event 6) from a 15minute explosion that sent a plume to 18.3km asl, and dispersed tephra to the WNW. Within 10km of the vent, this deposit contains 1–11cm pumice clasts in a matrix of 1–2mm aggregate lapilli. A small dome was presumably emplaced between March 23 and March 26 and was subsequently destroyed during 1–14minute magmatic explosions of events 7–8 (March 26) that sent plumes between 8.2km and 19km asl. Ash fell along a broad swath to the ESE, covering communities along the Kenai Peninsula with up to 1mm of ash. Proximal deposits are largely composed of aggregate lapilli of 1–2mm with very little coarse juvenile material. Events 9–18 (March 27) sent plumes between 5.2km and 15.5km asl during <1–11-minute-long explosions. Ash clouds dispersed along trajectories to the NE, ENE and N and event 17 deposited up to 1mm of ash on upper Kenai Peninsula and Anchorage. A moderate-size dome was emplaced between March 29 and April 4 and was subsequently destroyed during event 19 on April 4 which lasted 31min and sent ash to 15.2km asl. The proximal deposit is principally composed of dense dome rock, unlike earlier events, indicating that event 19 was likely caused by dome failure. The cloud dispersed to the SE along a narrow trajectory and up to 1–2mm of ash fell on the lower Kenai Peninsula.Particle size data showing a preponderance of fine ash, even in the most proximal locations, along with the abundance of aggregate lapilli documented in most samples, confirms that particle aggregation played a significant role in the 2009 eruption and induced premature fallout of fine ash.

Early Holocene glacial retreat isolated populations of river otters (Lontra canadensis) along the Alaskan coast

Pleistocene climatic oscillations have resulted in high rates of speciation. Lesser known are speciation events related to recent glacial retreats. During the early Holocene many Alaskan coastal glaciers receded, exposing much of the Kodiak Island Archipelago (KOD), the Kenai Peninsula, and Prince William Sound (PWS). Using fecal DNA analyses on samples collected in KOD, PWS, Kenai Fjords National Park (KEFJ), Katmai National Park and Preserve (KATM), and Vancouver Island, British Columbia (BC), we found isolation by distance to be an important mechanism for the divergence of populations of river otters ( Lontra canadensis (Schreber, 1777)) along the Pacific coast. Nonetheless, our results also demonstrated that KOD river otters appear to be more isolated genetically from their mainland conspecifics (approximately 50 km away), as river otters inhabiting PWS are from those in BC (over 2500 km away). In addition, KATM and KOD otters likely differentiated from one ancestral stock that inhabited the southwestern shores of Alaska during the Pleistocene and was isolated from more easterly populations by distance. The low genetic diversity among KOD river otters, compared with similar subpopulations in PWS, is likely the result of a founder effect and limited gene flow among the different islands within the Archipelago. Our observation that glacial retreat, rising sea levels, and formation of the Gulf of Alaska Coastal Current in the early Holocene likely led to divergence of populations of river otters, a highly mobile semiaquatic mammal, highlights the potential for future speciation events related to current climate change and ocean currents in coastal animal populations.

Practical Estimation of Near-surface Bulk Density Variations Across the Border Ranges Fault System, Central Kenai Peninsula, Alaska

We demonstrate a near-surface density estimation approach in an area without exposed outcrop or where outcrop occurrences do not adequately represent the subsurface rock densities based on the Nettleton (1939) - Parasnis (1952) technique as extended by Rao and Murty (1973) . We applied this technique in the central Kenai Peninsula, Alaska where the region is cut by a major fault zone, the Border Ranges fault system, that juxtaposes two terranes with greatly varying geological and geophysical properties. The Kenai Peninsula region can be generally divided into two different geologic settings: recent fluvial and glacial deposits of the Cook Inlet basin to the west and accreted metamorphic terranes of the Kenai Mountains to the east. Our study region includes glacial cover, deep lakes, and large topographically-driven gravity gradients between the Kenai Mountains and Cook Inlet. We selected 11 gravity loops from ∼580 gravity points collected in 2009, which have 10–20 gravity points per loop; nine loops (A to I) are located in the Quaternary glacial and alluvial deposits and two loops (J and K) are in Cretaceous metamorphic rocks of the Kenai Mountains. Inversion of the free-air anomaly data gave estimates of near-surface rock densities and their associated uncertainties. Our inversion results are comparable to values obtained from density logs in the Cook Inlet basin ranging from 1.64 to 2.60 g/cm3 with an average uncertainty of 0.12 g/cm3. Estimated densities for the accreted metamorphic terrane in the eastern peninsula of 2.89 ± 0.02 and 2.86 ± 0.01 g/cm3 are slightly higher than measured densities from hand rock samples.

Modification of a Kenai eddy along the Alaskan Stream

A Kenai eddy was studied through analyses of satellite altimeter data and hydrographic data from shipboard and Argo float observations. This eddy formed in December 2006 south of the Kenai Peninsula and propagated southwestward along the Alaskan Stream. The eddy held horizontally uniform warm core water in January 2007. In late winter 2007, this core water was cooled from the top and a subsurface temperature maximum was formed around 26.5σθ. Two years later in summer 2009, warm and low‐dissolved‐oxygen (low‐DO) water characterized by a temperature maximum around 26.5σθ was observed again in the eddy core and was likely the remnant of original core water. At the same time, cold and high‐DO water intrusions occurred in the eddy core, suggesting that strong modification of core water was ongoing. After summer 2009, the core water was fully changed through interaction with another eddy.

Tsugacorticium kenaicum (Hymenochaetales, Basidiomycota), a new corticioid genus and species from Alaska.

The new corticioid genus and species, Tsugacorticium kenaicum from Alaska, is described. Primarily found on attached, dead, corticate branches of mountain hemlock in the Kenai Peninsula, T. kenaicum is characterized by small, soft, white to yellow basidiomata, thickened subhymenium, much branched dendrohyphidia, and small globose to subglobose basidiospores. Although morphologically similar to Dendrothele (Agaricales) and Dendrocorticium (Corticiales), phylogenetic analyses of the nuclear large subunit ribosomal RNA gene place this taxon in the Rickenellaceae clade in the Hymenochaetales. Tsugacorticium kenaicum is described, illustrated, and compared to morphologically similar and phylogenetically related taxa.

ALASKAN RIBES L. AND RUBUS L. PLANT SPECIES SURVEYED FOR VIRUSES

Alaska’s domesticated and native Ribes and Rubus genera have virtually gone unchecked for pathogen detections. Cultivated Ribes species are predominantly found in home gardens and landscape areas along highways and in cities. In 2008, while surveying native plants for diseases in North Central Alaska near the town of North Pole, mottled leaves were readily visible on wild raspberries (Rubus strigosus L.) growing in agricultural berms and on recent clearings next to forests. In 2009 and 2010, other sites close to the original sites were observed to have similar symptoms. Initial protein extracts from partially purified preparations revealed a putative coat protein about 30 kDa. Mechanical transmission occurred in Nicotiana benthamiana and Chenopodium quinoa. Virion RNA preparations contained two dominant bands about 5.9 kb and 1.9 kb. Based on these biological parameters and similarities with Raspberry bushy dwarf virus, leaf sap and purified virion from infected raspberry and N. benthamiana were assayed for RBDV by ELISA and western blot. Leaf samples were also tested specifically for RBDV by RT-PCR. Negative results indicated that RBDV was not the causal agent involved in the native raspberry disease. Commercial raspberries growing near infected wild plants did not have symptoms and did not test positive for viruses. Another virus was discovered and detected from domesticated black and red currants (Ribes nigrum L. and R. rubrum L.) in 2008 and 2010 on the Kenai Peninsula, Alaska. Diseased plants usually contained leaves with vein-clearing that developed into large spots. Field collected leaf samples tested positive for vitivirus using a RT-PCR assay adapted for vitivirus detection. Direct sequencing of the ca. 200 bp PCR product resulted in nucleotides that were most similar to species in the genus Vitivirus when analyzed in BLAST. This is the first time that viruses have been detected in currants and raspberries from Alaska and the first report of a vitivirus from Ribes spp.

SKS splitting beneath Alaska: Regional variability and implications for subduction processes at a slab edge

Many aspects of subduction zone geodynamics remain poorly understood, including the pattern of flow in the mantle surrounding subducting slabs. Because of the relationship between deformation and seismic anisotropy, measurements of shear wave splitting in subduction zones can shed light on this pattern of flow. While observations of splitting in subduction zones are numerous and robust, the source and geodynamical implications of the anisotropy remain imperfectly constrained. The Alaska subduction zone, associated with the subduction of the Pacific plate beneath North America, is a particularly complex tectonic setting. Dramatic lateral variations in slab morphology, seismicity, and volcanic character are present beneath the region, and previous splitting observations and modeling studies have suggested the possibility of significant along-strike mantle flow in the region. Here we present SKS splitting measurements from more than 50 stations of the permanent broadband AK network located throughout Alaska. Splitting patterns show significant regional variability, but proximate stations often exhibit similar splitting behavior. Stations in southern Alaska exhibit nearly trench-normal fast directions, while in southeasternmost Alaska fast directions trend parallel to the plate boundary. A group of stations in the eastern part of the array exhibit predominantly null splitting, while stations to the northwest of this group tend to exhibit ~1s or more of splitting with fast directions that are roughly NE–SW. Stations east of the Kenai Peninsula region exhibit complicated splitting patterns that suggest complex anisotropy. We discuss a number of potential factors that may contribute to the complexity in splitting patterns observed in Alaska, including frozen anisotropic structure in the overriding plate lithosphere, asthenospheric shear due to absolute plate motion, trench-parallel flow in the mantle wedge, two-dimensional entrained flow beneath the slab, and mantle upwelling at the slab edge.

Bark-beetle-attacked trees produced more charcoal than unattacked trees during a forest fire on the Kenai Peninsula, Southern Alaska

Alaskan boreal forests frequently suffer from outbreaks of bark beetles and fires, factors that appear to combine to alter charcoal production. Charcoal (black carbon) production in forest ecosystems is an important pathway to clarify for a more complete understanding of the effects of fire on carbon cycling in boreal forests. In this study, we aimed to clarify the effects of prevalent outbreaks of the spruce beetle, Dendroctonus rufipennis (Kirby), on charcoal production during forest fires in boreal forests. Snags with prefire damage by the spruce beetle (infested snags) have significantly more charcoal than those undamaged before fire (noninfested snags). This increased amount of charcoal in spruce beetle-damaged trees was probably the result of dried biomass in the canopies of these trees. The results of this study suggest that with changing environmental conditions, the proliferation of insect damage in the boreal forest can modify the effects of fire on carbon sink via a change in the amount of charcoal production.

What is in a Name? The Predicament of Ethnonyms in the Sugpiaq-Alutiiq Region of Alaska

Aleut, Alutiiq, Sugpiaq, Russian, Pacifi c Eskimo, Unegkuhmiut, and Chugach Eskimo are all different names that have been used to identify the group of Native people living on the Lower Kenai Peninsula of Alaska. While most of these ethnonyms are par- tially based on particular characteristics, they also carry specifi c social-political agendas that are embedded in the names themselves. Names are a powerful medium in communicating meaning about historical context and the actors who move within specifi c historical events. In this paper I draw on historical and ethnographic information to shed light on the different nomenclature used in the past, as well as currently in this region. By organizing names into a schema through an historical overview, I highlight the signifi cance of the relationship between historical legacies and contemporary articulations of ethnonyms. Furthermore, after exploring the origins of ethno- nyms and analyzing the different implications that are closely associated with them, the paper concludes with a better approach for understanding agency in the politics of ethnic identity construction.

Integrating Traditional and Scientific Knowledge through Collaborative Natural Science Field Research: Identifying Elements for Success

We discuss two recent projects to examine the role of collaborative environmental fieldwork both in research and in the interactions between academically trained researchers and experienced local residents. The Bidarki Project studied black leather chitons (Katharina tunicata) in the lower Kenai Peninsula, Alaska. Its conclusion that chiton declines are part of a serial decline of intertidal invertebrates drew on collaborative fieldwork, archaeological data, historical records, and interviews with local residents. The Siku-Inuit-Hila Project studied sea ice in Barrow, Alaska; Clyde River, Nunavut; and Qaanaaq, Greenland. Quantitative data from locally maintained observation sites were supplemented by knowledge exchanges among hunters from the communities and by discussion in local working groups to develop an understanding of the physical dynamics and human uses of sea ice at each locale. We conclude that careful planning and preparation, along with the effort to build strong personal relationships, can increase the likelihood that collaborative fieldwork will be productive, enjoyable, and rewarding.

The quiet world: saving Alaska's wilderness kingdom, 1879-1960

A riveting history of America's most beautiful natural resources, The Quiet World documents the heroic fight waged by the U.S. federal government from 1879 to 1960 to save wild Alaska--Mount McKinley, the Tongass and Chugach national forests, Gates of the Arctic, Glacier Bay, Lake Clark, and the Coastal Plain of the Beaufort Sea, among other treasured landscapes--from the extraction industries. Award-winning historian Douglas Brinkley traces the wilderness movement in Alaska, from John Muir to Theodore Roosevelt to Aldo Leopold to Dwight D. Eisenhower, with narrative verve. Basing his research on extensive new archival material, Brinkley shows how a colorful band of determined environmentalists created the Arctic National Wildlife Refuge just before John F. Kennedy became president. Brinkley introduces a lively gallery of characters influential in preserving Alaska's wilderness resources: the indomitable U.S. Supreme Court justice William O. Douglas, who championed the Brooks Range; charming Ivy League explorer Charles Sheldon, who led the campaign to create Denali National Park; intrepid Bob Marshall, who cofounded The Wilderness Society; hermit illustrator Rockwell Kent, who lived in isolation on Fox Island like a modern Thoreau; nature photographer Ansel Adams, whose image Mount McKinley and Wonder Lake set off a tsunami of public interest in America's tallest peak; and U.S. Fish and Wildlife biologist Rachel Carson, who promoted proper ocean stewardship; among many more. Wildlife fervently comes to life in The Quiet World Brinkley tells incredible stories about the sea otters in the Aleutians, moose in the Kenai Peninsula, and birdlife across the Yukon Delta expanse while exploring the devastating effects that reckless overfishing, seal slaughter, and aerial wolf hunting have wrought on Alaska's once-abundant fauna. While taking into account Exxon Valdez-like oil spills, The Quiet World mainly celebrates how the U.S. government has preserved many of Alaska's great wonders for future generations to enjoy.

Invasion Prediction on Alaska Trails: Distribution, Habitat, and Trail Use

AbstractLittle is known about the relationship between frequency of occurrence and the expected maximum distance a nonnative species might spread along a trail once introduced to an ecological system with high native species integrity. Understanding how colonization and invasive plant habitat degradation occur in largely intact ecosystems is challenging. Determining which nonnative species are most likely to spread might be possible, given a suite of environmental or trail conditions. Spread may be linked to a particular set of environmental conditions, or to type and level of trail use. A field study conducted on trails in Forest Service and State Park lands on the Kenai Peninsula, Alaska, was designed to determine frequency and spread distance of all nonnative vascular plant species per 100-m segments keyed to vegetation type, canopy cover class, aspect, trail use level, and trail use type. Although the maximum total number of nonnative species decreased with increased distances from trailheads, the average number of species remained nearly constant. Common dandelion, broadleaf plantain, and annual bluegrass exhibited consistent presence per canopy cover class or vegetation type. A nested subset analysis revealed a significant reduction in nonnative species presence beyond a 500-m distance from a trailhead and a moderately strong nestedness pattern. High-use trails exhibited the greatest numbers of nonnative species at the farthest distances from the trailhead and contained a greater number of less common nonnative species. Alaska and other northern biomes have relatively few widespread invasive problems, offering an opportunity to limit ecosystem degradation by invasion. Results suggest that control strategies might focus on high-use trails with open-canopy habitats to prevent spread.

Aleut baseball: Cultural creation and innovation through a sporting event

Aleut baseball is a popular game played by the Sugpiat of Nanwalek and Port Graham on the lower Kenai Peninsula of Alaska. Despite its resemblance to American baseball and Russian lapta, Aleut baseball should be considered a Sugpiaq cultural novelty. Ranging from recreational to competitive, the game is a communal occasion, which often brings together Sugpiaq villages and communities. This article presents some of the profound elements that make Aleut baseball expressive of Sugpiaq culture, and a channel for renegotiating and re-energising established norms and values. Furthermore, looking at Aleut baseball through Victor Turner’s concept of play, the authors argue that sports and games provide immense opportunities for cultural innovation and experimentation, as well as for strengthening of group identity. Finally, the article explores the capacity of sports and games to link global perceptions with local realities.

Breakdown rates, nutrient concentrations, and macroinvertebrate colonization of bluejoint grass litter in headwater streams of the Kenai Peninsula, Alaska

Grass litter can be a dominant detritus type in many streams. However, use of this C source in stream food webs often is viewed as insignificant because of its relatively slow breakdown rates and low nutritional quality. We deployed leaf packs containing senesced bluejoint grass (Calamagrostis canadensis) across a natural nutrient gradient of 6 salmon-rearing headwater streams on the lower Kenai Peninsula, Alaska. We hypothesized that litter-colonizing microbes would use dissolved stream nutrients and enhance breakdown rates, litter nutrient concentrations, and densities of macroinvertebrates across streams. Leaf-pack mass and nutrient concentrations were measured on the material at 0 (predeployment), 2, 4, 6, and 8 wk in all streams. Breakdown rates were calculated from the mass measurements with an exponential decay model. Macroinvertebrate composition and abundance were measured at 8 wk in all streams and every 2 wk in 1 stream. Breakdown rates of bluejoint litter were relatively low (20–30% mass loss over 2 mo), but similar to rates found in previous studies of senesced grass litter. Weighted regressions showed that bluejoint breakdown rates in the 6 streams were significantly (p < 0.05) related to dissolved stream nutrient concentrations (r2 = 0.94 and 0.67 for dissolved inorganic N and PO4-P, respectively), litter nutrient concentration (r2 = 0.72 and 0.96 for leaf % N and % P, respectively), total macroinvertebrates/g (r2 = 0.73), and nonmetric multidimensional scaling-axis-1 scores of macroinvertebrate community structure (r2 = 0.80). Litter nutrients changed after just 2 wk and were increasingly and significantly related to stream nutrient concentrations over time. NMS ordination showed that succession of macroinvertebrates on leaf packs from one stream followed a distinct direction over time, and a large shift in macroinvertebrate community structure occurred between weeks 6 and 8, a result potentially indicating a consumer response to microbial conditioning. The abundance and diversity of macroinvertebrate taxa using bluejoint litter provide evidence that it is an important habitat and energy pathway for consumers in headwater streams of the Kenai Peninsula. In addition, climate change has the potential to change terrestrial vegetation assemblages, which drive differences in stream nutrient concentrations in this region. If N-fixing shrubs become more abundant in the future, litter-decomposition rates will be positively affected by increases in both stream and leaf-litter nutrient concentrations.

Comment on “Wetland drying and succession across the Kenai Peninsula Lowlands, south-central Alaska”Appears in Can. J. For. Res. 35: 1931-1941 (2005).

Klein et al. (2005, Can. J. For. Res. 35: 1931–1941) compare aerial photographs and report dramatically lower lake levels on the northern Kenai Peninsula, Alaska. They hypothesize that the lower lake levels may be caused by a decline in moisture surplus driven by climate change. However, the reported decline in surplus appears to be insufficient to explain the lower lake levels. Here I develop a simple sensitivity analysis to test their hypothesis and also show how tectonic processes such as the Great Alaskan earthquake could dramatically lower lake levels by fracturing an underlying aquitard. Tectonic processes, therefore, could potentially alter forest succession and wetland ecosystems by inducing hydrologic changes that mimic changes in climate.

Reply to comment by Gracz on “Wetland drying and succession across the Kenai Peninsula Lowlands, south-central Alaska”Appears in the Can. J. For. Res. 35: 1931–1941.

Gracz (2011, Can. J. For. Res. 41: 425–428) proposes that the Good Friday earthquake of 1964 caused falling lake levels and drying wetlands on Alaska’s Northern Kenai Lowlands (NKL). His hypothesis states that the earthquake increased hydraulic conductivity by fracturing a leaky confining layer, accelerating drainage of surface water into regional aquifers. We counter that a single model of draining does not apply across the heterogeneity of geomorphology and soils on the NKL. In particular, the NKL’s glacial history precludes uniform application of a subsurface hydrologic model for lake draining and the nature of peat-based wetlands precludes its application to wetland drying. Instead, small, yet cumulative, climatic reductions in moisture surplus explain both observed lake level declines and vegetation changes. Moreover, and unlike a climatic hypothesis, a seismic hypothesis fails to explain lake drying elsewhere in Alaska. Although it is likely that the earthquake influenced some hydrologic features in the NKL, it is unlikely that a single hydrologic model based on a simple mechanical cause, e.g., downward drainage, adequately explains the changes observed across the whole NKL. Conversely, we maintain that the uniformity of the vegetation response seen across different landscapes, including wetlands, forests, and alpine areas, throughout the state of Alaska strongly supports a climatic hypothesis.

A data assimilative, coupled physical–biological model for the Coastal Gulf of Alaska

A data assimilative, coupled physical–biological model for the Coastal Gulf of Alaska (CGOA) is used to investigate the extent to which improvements to oceanic circulation yield improvements to lower trophic level ecosystem predictions, especially in relation to mesoscale variability at the shelfbreak. The ocean circulation component is an implementation of the Regional Ocean Modeling System (ROMS), the lower trophic level ecosystem component is a six-compartment Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) model with iron limitation, and the data assimilation component is the adjoint-based, four-dimensional variational (4D-Var) system available in ROMS. Assimilated observations consist of weekly satellite sea surface height and temperature, as well as bimonthly in situ temperature and salinity measurements. Simulation results for 1998–2002 indicate that assimilation of physical observations significantly improves the accuracy with which the model reproduces the frequency, duration, and intensity of eddy events along the CGOA shelfbreak. Improvements to oceanic mesoscale processes lead to substantial improvements to the biological response predicted by the NPZD model. Observed and simulated correlations between eddy kinetic energy and surface chlorophyll concentrations suggest that ecosystem dynamics at the shelfbreak is tied to eddy activity in the northern CGOA (i.e., off the Kenai Peninsula and Kodiak Island). In the southern CGOA (i.e., off the Shumagin Islands), mesoscale processes and ecosystem response at the shelfbreak are uncorrelated, as eddies tend to occur during winter when phytoplankton growth is severely light-limited. Based on observation and control vector impact calculations for physical (eddy kinetic energy) and biological (surface chlorophyll concentrations) processes, improvements to oceanic circulation and ecosystem dynamics are primarily associated with the assimilation of satellite sea surface height observations, and occur mainly through adjustments of the model initial conditions. These similarities in the observation and control vector impacts lend further evidence to the linkages between mesoscale activity and primary production along the CGOA shelfbreak.

A new satellite-derived glacier inventory for western Alaska

AbstractGlacier inventories provide the baseline data to perform climate-change impact assessment on a regional scale in a consistent and spatially representative manner. In particular, a more accurate calculation of the current and future contribution to global sea-level rise from heavily glacierized regions such as Alaska is much needed. We present a new glacier inventory for a large part of western Alaska (including Kenai Peninsula and the Tordrillo, Chigmit and Chugach mountains), derived from nine Landsat Thematic Mapper scenes acquired between 2005 and 2009 using well-established automated glacier-mapping techniques (band ratio). Because many glaciers are covered by optically thick debris or volcanic ash and partly calve intowater, outlineswere manually edited in these wrongly classified regions during post-processing. In total we mapped ~8830 glaciers (&gt;0.02 km2) with a total area of ~16 250 km2. Large parts of the area (47%) are covered by a few (31) large (&gt;100 km2) glaciers, while glaciers less than 1 km2 constitute only 7.5% of the total area but 86% of the total number. We found a strong dependence of mean glacier elevation on distance from the ocean and only a weak one on aspect. Glacier area changes were calculated for a subset of 347 selected glaciers by comparison with the Digital Line Graph outlines from the US Geological Survey. The overall shrinkage was ~23% between 1948–57 and 2005–09.