Coastal Alaska Research Articles

Wave resource characterization at regional and nearshore scales for the U.S. Alaska coast based on a 32-year high-resolution hindcast

A wave resource characterization was performed for the southern coast of Alaska based on a 32-year hindcast covering the period from 1979 to 2010. The characterization closely followed International Electrotechnical Commission (IEC) Technical Specifications. An unstructured-grid Simulating WAves Nearshore (SWAN) model, which had an approximate spatial resolution of 300 m within 30 km from the nearest shoreline, was developed. Extensive model validation and error characterization was performed. The model was found to perform well with an average absolute percent error of 8.6% in significant wave height, averaged over 18 buoys. Statistics for the six IEC wave resource parameters were calculated and aggregated at 20 km from shore to quantify the incident wave power and its variability at a regional scale. The southern coast of the Aleutian Archipelago was found to have the most available wave energy in the region. A nearshore resource assessment was performed by evaluating resource hotspots located 1 km from shore. More than 28% of the nearshore stations analyzed had an Optimum Hotspot Identifier value of at least 5 [kW/m] at diverse water depths, thereby positioning Alaska as a promising location for wave energy development.

Large Precipitation Gradients along the South Coast of Alaska Revealed by Spaceborne Radars

Large Precipitation Gradients along the South Coast of Alaska Revealed by Spaceborne Radars

Understanding growth and age of red tree corals (Primnoa pacifica) in the North Pacific Ocean.

Massive, long-lived deep-sea red tree corals (Primnoa pacifica) form a solid, layered axis comprised of calcite and gorgonin skeleton. They are abundant on the outer continental shelf and upper slope of the Northeast Pacific, providing habitat for fish and invertebrates. Yet, their large size and arborescent morphology makes them susceptible to disturbance from fishing activities. A better understanding of their growth patterns will facilitate in-situ estimates of population age structure and biomass. Here, we evaluated relationships between ages, growth rates, gross morphological characteristics, and banding patterns in 11 colonies collected from depths of ~141–335 m off the Alaskan coast. These corals ranged in age from 12 to 80 years old. They grew faster radially (0.33–0.74 mm year-1) and axially (2.41–6.39 cm year-1) than in previously measured older colonies, suggesting that growth in P. pacifica declines slowly with age, and that basal diameter and axial height eventually plateau. However, since coral morphology correlated with age in younger colonies (< century), we developed an in-situ age estimation technique for corals from the Northeast Pacific Ocean providing a non-invasive method for evaluating coral age without removing colonies from the population. Furthermore, we determined that annual bands provided the most accurate means for determining coral age in live-collected corals, relative to radiometric dating. Taken together, this work provides insight into P. pacifica growth patterns to inform coastal managers about the demographics of this ecologically important species. With this new ability to estimate the age of red tree corals in-situ, we can readily determine the age-class structure and consequently, the maturity status of thickets, using non-invasive video survey techniques when coupled with mensuration systems such as lasers or stereo-cameras. Enhanced surveys could identify which populations are most vulnerable to disturbance from human activities, and which should be highlighted for protection.

Passes of the Aleutian Islands: First detailed description

AbstractWe derived the first detailed and accurate estimates of the location, cross‐sectional area, length, and depth of the Aleutian Island passes, which are important bottlenecks for water exchange between the North Pacific Ocean and the Bering Sea. Our pass descriptions utilized original bathymetric data from hydrographic smooth sheets, which are of higher resolution than the navigational chart data used for earlier pass size estimates. All of the westernmost Aleutian passes, from Kavalga to Semichi, are larger (18%–71%) than previously reported, including Amchitka Pass (+23%), the largest in the Aleutians. Flow through Chugul Pass, previously reported as the largest pass in the Adak Island area, is blocked on the north side by Great Sitkin and several other islands. Collectively, these smaller passes (Asuksak, Great Sitkin, Yoke, and Igitkin) are only about half the size of Chugul Pass. The important oceanographic and ecological boundary of Samalga Pass occurs in a location where the cumulative openings of the eastern Aleutian passes equal the minimal opening of Shelikof Strait, carrier of the warmer, fresher water of the Alaska Coastal Current that eventually flows northward, through Samalga and the other eastern passes, into the Bering Sea and Arctic Ocean.

False Pass, Alaska: Significant changes in depth and shoreline in the historic time period

AbstractGlobal ocean circulation is limited partly by the small passes of Alaska's Aleutian Islands, which restrict North Pacific Ocean water from flowing north into the Bering Sea and eventually to the Arctic, but the size and shape of these Aleutian passes are poorly described. While quantitatively redefining all of the Aleutian passes, we determined that the easternmost pass, with the cryptic name of False Pass, and with an unusual configuration of having both northern and southern inlets, had two or more inlets to the Bering Sea in the recent past, but that it has only a single northern inlet now (15,822 m2), roughly equivalent in size to the southern inlet, Isanotski Strait (15,969 m2). Navigational charts depict the opposite: two inlets to the Bering Sea now, but just one in older charts (1926–43). This discrepancy inspired a thorough review of the hydrographic history from which we concluded that the second northern inlet did exist and hypothesize that it was a remnant of multiple former openings, or a single large opening, potentially allowing greater northward flow of warmer, fresher Alaska Coastal Current water. While the shoreline changes that we document here are often regarded as minor, ephemeral events, we document similar, nearby, permanent shoreline shifts which changed Ikatan Island into a peninsula and which shifted the Swanson Lagoon outlet over 3 km to the east.

Sustaining an Alaska Coastal Community: Integrating Place Based Well-Being Indicators and Fisheries Participation

The incorporation of human dimensions into ecosystem-based fisheries management has largely focused on metrics of economic welfare. Yet researchers have demonstrated the variety of well-being that is derived from fisheries as well as the need for localized and collaborative scientific efforts that result in appropriately contextualized metrics. This article presents the results of a project intended to address these needs and inform the North Pacific fisheries management process with a set of indicators that are related to multiple dimensions of human well-being and links to fisheries participation. The article showcases a mechanism of applying a well-being framework and participatory methods to develop locally relevant quantitative indicators for one of the most highly engaged fishing communities in Alaska - Sitka. These indicators can be used to track how fishery shocks may reverberate through social systems and affect fishing communities. Furthermore, the discussion of the multifaceted well-being indicators presents information on local values and complex dynamics between community well-being and fisheries that are difficult to conceptualize and integrate into management decisions. Ultimately, this work can facilitate a more comprehensive incorporation of human dimensions into ecosystem-based frameworks in fisheries management, contextualizing that expansion within locally relevant narratives that engage stakeholders in resource management.

Prediction of Northern Hemisphere Regional Sea Ice Extent and Snow Depth Using Stratospheric Ozone Information

AbstractThe forecast potential of springtime ozone on April surface temperatures at particular locations in the Northern Hemisphere has been previously reported. Evidence suggests that early springtime Arctic stratospheric ozone acts as a proxy for extreme events in the winter polar vortex. Here, using a state‐of‐the‐art chemistry‐climate model, reanalysis and observations, we extend the forecast potential of ozone on surface temperatures to aspects of the Northern Hemisphere cryosphere. Sea ice fraction and sea ice extent differences between years of March high and low Arctic stratospheric ozone extremes show excellent agreement between an ensemble of chemistry‐climate model simulations and observations, with differences occurring not just in April but extending through to the following winter season in some locations. Large snow depth differences are also obtained in regional locations in Russia and along the southeast coast of Alaska. These differences remain elevated until early summer, when snow cover diminishes. Using a conditional empirical model in a leave‐three‐out cross validation method, March total column ozone is able to accurately predict the sign of the observed sea ice extent and snow depth anomalies over 70% of the time during an ozone extreme year, especially in the region of the Bering strait and the Greenland Sea, which could be useful for shipping routes and for testing climate models.

Interannual variation in the coastal distribution of a juvenile gadid in the northeast Pacific Ocean: The relevance of wind and effect on recruitment

AbstractDrift of propagules occurs within many populations inhabiting flow fields. This affects the number of propagules that rejoin their source population (recruitment) and plays a role in adaptive spatial redistribution. We focus on the cause and consequence of interannual variation in geographic distribution of population density among five cohorts of young‐of‐the‐year (age‐0) juvenile walleye pollock Gadus chalcogrammus in the western Gulf of Alaska (GOA). The coastal GOA is a wind‐driven advective system. Walleye pollock spawn during spring and their eggs and larvae drift southwestward; by late summer, age‐0 juveniles are variously distributed over the shelf. We found that high population densities of age‐0 juveniles (ca. 6 months old) near the southwestward exit of the Alaska Coastal Current from the GOA corresponded with high abundance of larvae from the major spawning area upstream, but did not translate into high abundance at older ages. Further, offshore and upwelling‐favorable winds were associated with the high downstream abundance and presumed export. In contrast, downwelling‐favorable (northeasterly) wind during and shortly after spawning (April–May) was associated with high recruitment at age 1. Finally, we found that recruitment also increased with apparent retention of age‐0 juveniles in favorable habitat upstream near the main spawning area. We hypothesize that wind‐related retention in superior upstream habitat favors recruitment. Our results argue for including wind‐driven transport in future walleye pollock recruitment models. We encourage more work on the juvenile stage of marine fishes aimed at understanding how transport and species‐specific habitat suitability interact to affect population response to large‐scale forcing.

Spatial genetic structure in Themisto libellula (Amphipoda: Hyperiidae) from the coastal Gulf of Alaska, Bering and Chukchi seas

Arctic marine ecosystems are undergoing rapid biogeographic responses to climate changes following the highest warming rates observed around the globe in recent decades. These drastic changes undoubtfully affect gene flow and genetic structure in the polar and subpolar regions. Here, we examine the genetic structure of the cold-water holozooplankton hyperiid Themisto libellula (Amphipoda: Hyperiidae), a key species in the Arctic ecosystem, using molecular population genetic approach. For the first time, we examine and compare populations across the Arcto-Pacific sector of the species biographical range from the northern Gulf of Alaska through the northern Chukchi Sea. We hypothesized that the complex history of the North Pacific and Amerasian Arctic marked by periodic intermissions and restrictions of the dominant northward flow resulted in vicariant differentiation of T. libellula along the latitudinal gradient. Mitochondrial and Rad-sequencing analyses revealed little genetic differentiation between closely connected Arctic populations in the Arctic Chukchi and Bering seas. In contrast, population from sub-Arctic glacial fjords in the Gulf of Alaska were distinct with few shared COI haplotypes. Strong FST estimates (FST = 0.16) based on 5197 neutral SNPs between the Gulf of Alaska and Bering Sea populations indicated very limited exchanges despite an existing connection between the areas via the Alaska Coastal Current. Our results suggest strong opportunities for genetic differentiation among marine zooplankton populations along the Pacific Alaskan coast and from the Arctic marginal seas.

Beluga dive behavior relative to fronts and stratified layers near Barrow Canyon, Alaska

We report on the first beluga whale (Delphinapterus leucas), an adult female, from the Eastern Chukchi Sea (ECS) stock to be tagged with a Satellite Relay Data Logger (SRDL) that included a miniaturized Conductivity, Temperature, and Depth (CTD) sensor capable of collecting temperature (T) and salinity (S) profiles as the beluga dove. Prior work speculated that ECS belugas may target fronts and stratified regimes between water masses, because these boundaries may aggregate zooplankton, which in turn may attract fish that belugas prey upon. However, the SRDLs used in those studies were not capable of collecting CTD data necessary to identify water masses. The CTD-SRDL transmitted for 71 days, 8 July–17 September 2019, providing 492 time-depth profiles, indicating the shape and duration of beluga dives, and 255 CTD profiles, providing information on the location of water masses and ocean stratification used by the animal. We found that this beluga typically targeted fronts and stratified layers between water masses or colder water masses of Pacific origin. Of particular significance, we found that within the main summering area in Barrow Canyon, dives were co-located with the frontal zone between relatively warm and fresh Alaskan Coastal Water (derived from river discharge), and colder, saltier water of Pacific origin.

Directionality of ambient noise in the Mississippi embayment

SUMMARYCross-correlations of ambient seismic noise from 277 broad-band stations within the Mississippi embayment (ME) with at least 1 month of recording time between 1990 and 2018 are used to estimate source locations of primary and secondary microseisms. We investigate source locations by analysing the azimuthal distribution of the signal-to-noise ratios (SNRs) and positive/negative amplitude differences. We use 84 stations with 1 yr of continuous recordings to explore seasonal variations of SNRs and amplitude differences. We also investigate the seasonal ambient noise ground motions using 2-D frequency–wavenumber (FK) analysis of a 50-station array. We observe that: (1) two major azimuths can be identified in the azimuthal distribution of SNRs and amplitude differences. We also observe two minor azimuths in the seasonal variation of SNRs, amplitude differences and 2-D FK power spectra. Monthly 2-D FK power spectra reveal that two energy sources are active in the Northern Hemisphere winter and two relatively weak sources are active in summer. (2) Backprojection suggests that primary microseisms originate along the coasts of Australia or New Zealand, Canada and Alaska, Newfoundland or Greenland and South America. (3) Secondary microseisms are generated in the deep water of the northern and southern Pacific Ocean, along the coasts of Canada and Alaska associated with near-shore reflections and in the deep water of south of Greenland. (4) Weak energy is observed in the third quadrant of the azimuthal distribution of amplitude differences of sedimentary Rayleigh and Love waves in the period band of 1–5 s and correlates with the direction of widening of the basin.

Stratification in the northern Bering Sea in early summer of 2017 and 2018

We investigated spatial and interannual variation in the physical environment in the northern Bering Sea focusing on stratification, which is one factor affecting biological production in Arctic/subarctic regions. In particular, we analyzed in situ data obtained onboard the training ship Oshoro Maru in early summer in 2017 and 2018. We found that stratification in the areas just north of St. Lawrence Island (around 64.5°N and west of 168.5°W) and south/southwest of St. Lawrence Island was significantly weaker in 2018 than in 2017. These results are consistent with the extremely low sea-ice extent present in the winter of 2017/2018, which would have resulted in less freshwater being supplied to the surface layers and a warmer and less saline bottom water. Conversely, stratification was as strong in 2018 as in 2017 in the area close to the Alaska mainland, including the Bering Strait area, suggesting that the Alaskan Coastal Water dominates stratification in this area in early summer. Moreover, we found that the weakly stratified water column in the Bering Strait area stratified quickly shortly after the occurrence of strong northerly winds, likely because of the Ekman transport of warm and low-salinity Alaskan Coastal Water from the east.

Historical distribution of kelp forests on the coast of British Columbia: 1858–1956

The quantification of kelp forest distribution across space and time is critical to support decision-makers responsible for habitat management and conservation. Spatial data such as aerial photos and satellite imagery are key for deriving kelp distribution; however, they have only become available at an adequate quality within the 20th and 21st centuries. In this study, British Admiralty (BA) charts created between 1858 and 1956 covering the British Columbia coast and portions of the adjacent Washington and Alaska coast were used to create a digital historical baseline map of kelp presence. A total of 137 BA charts were scanned at 200 DPI, georeferenced, and kelp features were manually digitized following a rigorous method considering the scale and quality of the data. An accuracy assessment of the digitized kelp features concluded that 99% of the kelp features occurred in expected areas within a depth of less than 40 m, and only about 1% of the features occurred entirely outside of this depth. Recently mapped kelp forests in similar areas reaffirmed the results of the produced baseline map. Potential sources of uncertainty should be considered when working with the historic BA charts such as the surveyor's method for defining floating kelp features, the artistic ability of the cartographer when transcribing the information from the surveys to the BA charts, and the regional seasonality of kelp cover. The outcome of this research shows that the historical BA charts are an unconventional but extremely rich source of baseline coastal habitat data from the 19th century. The methods conducted are simple and robust and could be applied to other regions where historical charts with sufficient quality exist.

Summer Changes in Water Mass Characteristics and Vertical Thermohaline Structure in the Eastern Chukchi Sea, 1974–2017

Hydrographic data from the World Ocean Database 2013 and the Chinese National Arctic Research Expedition were used to investigate the summertime changes in the eastern Chukchi Sea from 1974 to 2017. Owing to the Pacific inflow and timing of the sea ice retreat, water masses and vertical thermohaline structures in the eastern Chukchi Sea have changed but with regional differences. The entire eastern Chukchi Sea warmed up with significant temperature increase in the central shelf; however, the surface and bottom salinity in the southern, central, and northern shelves exhibited different trends. The northward extension of the Pacific Summer Water after 1997 influenced the summer hydrography significantly. Moreover, the data reveal changes in the characteristics of various water masses. Both Bering Summer Water (BSW) and Pacific Winter Water in the deeper layer became saltier, whereas the Alaskan Coastal Water in the upper layer became fresher after 1997. The previous definition of the BSW should be modified to include the warming water mass in the southern Chukchi Sea in the more recent years. Furthermore, the vertical thermohaline structure over the Chukchi shelves experienced considerable changes in its characteristics due to the combined effects of the Pacific inflow and surface forcing.

The effect of oceanographic variability on the distribution of larval fishes of the northern Bering and Chukchi seas

We investigated the pelagic habitat requirements of Arctic larval fish and the effects of interannual variability of ocean conditions on their distribution. We examined the distribution of larval Arctic cod, Bering flounder, yellowfin sole and capelin in the Chukchi and northern Bering seas during two years with different oceanographic conditions. We found that despite marked changes in water mass distribution, the distributions of larval fishes were not significantly different between the two years. In both years, Arctic cod and Bering flounder were found in cold, high salinity shelf waters advected from the south and influenced by winter cooling (Chukchi Winter Water and Anadyr Water mix). Yellowfin sole and capelin distributions were also similar from year-to-year but they were only found in warm, low salinity Alaska Coastal Water. The cold, high salinity water masses had elevated large copepod biomass, and the Alaska Coastal Water had elevated small copepod biomass. Thus, we propose that these water masses provided different but nonetheless potentially profitable foraging habitat for the four species of larval fishes. We conclude by suggesting that the timing and location of spawning of these species has evolved such that larval offspring are distributed in suitable foraging habitat despite interannual variability in ocean conditions. This study provides a baseline of Arctic larval fish distribution and insight into the degree of climate variability that might be expected to impact early life history stages of larval fish. Our results also increase the knowledge of the mechanistic links between oceanography and the early life history of fish. Because growth and survival of early life stages of fish often drives population change, our results contribute to the understanding of the impacts of climate change on Arctic fish populations.

The impacts of coastal erosion on Alaska’s North Slope communities: a co-production assessment of land use damages and risks

ABSTRACT The impacts of coastal erosion on municipal infrastructure and property have been widely documented within coastal Alaska. Less is known, however, about erosion-related impacts on natural resource-based land uses that contribute to the well-being of Alaska’s Native residents. This study explores erosion impacts on resource-based land uses on Alaska’s North Slope. The study utilized a collaborative mapping workshop approach, in which research participants defined major categories of land use impacts, identified locations most at risk, and described key local and regional effects of erosion. The study findings highlight three critical types of land use impacts associated with coastal erosion. These include: (1) disruption of subsistence hunting; (2) losses associated with damaged military radar assets (DEW-Line); and, (3) constrained hydrocarbon related development opportunities on land controlled by Native corporations. Through specification of locally relevant land use impacts, the study findings contribute to a better understanding of how climate change is undermining cryosphere-related ecosystem services, particularly buffering cultural and economic activity from coastal storms. The study results reinforce the utility and value of co-production approaches for Arctic climate impact assessments. Through integration of local perspectives on erosion risks, the study contributes to collective regional knowledge about climate change risks to Arctic communities.

Marine bird response to forage fish during winter in subarctic bays

AbstractDespite the importance of understanding marine bird response to prey fish, few studies have examined this relationship during winter. Over a 5‐year period, we conducted synoptic marine bird and hydroacoustic forage fish surveys during early (November) and late (March) winter to characterize the factors influencing marine bird and forage fish dynamics at two spatial scales (fish school and bay) within subarctic bays of coastal Alaska, USA. Over 40% of observed marine birds were associated with a fish school (within 150 m of a fish school), although only 20% of fish schools were associated with birds. Seasonally, we recorded significantly more schools during early winter. The marine bird community also shifted from being comprised primarily of marbled murrelets (Brachyramphus marmoratus) and large gulls (Larus spp.) in early winter to common murres (Uria aalge) in late winter. At the school level, marine birds were more likely to be associated with shallow fish schools within 500 m of shore and in smaller prey patches. At the bay level, gull abundance was positively associated with the total number of fish schools recorded, while diving birds were more abundant when fish schools were higher in the water column, in shallower bottom depths, and in areas with more eel grass habitat. Our results indicate the importance of temporal, habitat, and fish school variables as drivers of marine bird presence and abundance, underscoring the complexity of predator–prey dynamics in the marine environment during winter.

Collaborative Study and Preservation of Coastal Alaskan Native Watercraft and Material Culture

ABSTRACT The Alutiiq Museum and Archaeological Repository in Kodiak, Alaska, and the Peabody Museum of Archaeology and Ethnology, Harvard University in Cambridge, MA, partnered to study and preserve endangered Alaska Native material culture and traditional knowledge by focusing on skin-based kayaks and associated objects. The Alutiiq Museum identified kayaks and related gear as being potentially instrumental in fostering intergenerational community dialogue around Alutiiq language, arts, and science as building blocks of cultural revitalization. The resulting project and partnership stemmed from 2003 consultations and grew through collaborative design and implementation. Staff at both museums and consultants worked collaboratively to meet their respective and collective needs and goals. This article shares the process to achieve the study, preservation, educational exchange, and accessibility of historic Alutiiq material culture and traditional knowledge regarding collections at the Peabody Museum. Collections included four kayaks and nearly 130 kayak-related items of marine mammal skins including gutskin, wood, and flexible plant-based materials. The two museums’ and communities’ ongoing partnership is presented, along with highlighted components of university and community engagement. Workshops and class seminars with Alutiiq scholars and artists, university students, museum curators, and conservators engaged the visiting public and researchers in teaching and conservation activities.

Climate- and Disturbance-Driven Changes in Subsistence Berries in Coastal Alaska: Indigenous Knowledge to Inform Ecological Inference

Berry-producing plants are a key subsistence resource in Indigenous Alaskan communities. Coastal, high-latitude regions are particularly impacted by global climate change because their location at the land-sea ecotone subjects them to both terrestrial stressors and shifting ocean dynamics. Although changes in near-shore vegetation communities have been previously documented for the sub-Arctic coastal region of Alaska, we know little about vegetation dynamics in the permafrost-underlain portions of the landscape that support berry communities. To fill this gap, surveys were administered in four communities within the Yukon-Kuskokwim Delta to identify observations of changes in berry resources and integrate Indigenous Knowledge of drivers of changes with climate projections. We found that while many participants identified changes in berry phenology, abundance, and habitat related to climate drivers, important differences in responses were identified at the community level. Regional consensus can be used in combination with climate projections to forecast potential future impacts to berry resources, while distinctions at the community level can help to account for impacts of local scale disturbances and importance of social context.

The tip of the iceberg: Three case studies of spill risk assessments used in environmental impact statements

Environmental impact statements (EISs) are based on science produced about specific project proposals, which results in a large body of grey literature. Spill risk estimates are part of that body of work. This is a critique the spill risk models cited in EISs for proposed drilling on the Alaskan Coastal Plain, the Pebble Mine transportation corridor, and Arctic offshore drilling, which are scored against published standards of best practices for ecological risk assessments. After a detailed peer review of Arctic offshore drilling risks, the findings and results from internal and external review processes of those reports are described. The amount of grey literature cited in recent EISs and how the alphanumeric ratings of draft EISs changed in 2017 are shown. Suggestions of how agencies, scientists, and peer reviewed journals can contribute to meaningful review of grey literature in regulatory science are offered.