Coastal Alaska Research Articles

Ancient bears provide insights into Pleistocene ice age refugia in Southeast Alaska.

During the Late Pleistocene, major parts of North America were periodically covered by ice sheets. However, there are still questions about whether ice-free refugia were present in the Alexander Archipelago along the Southeast (SE) Alaska coast during the last glacial maximum (LGM). Numerous subfossils have been recovered from caves in SE Alaska, including American black (Ursus americanus) and brown (U. arctos) bears, which today are found in the Alexander Archipelago but are genetically distinct from mainland bear populations. Hence, these bear species offer an ideal system to investigate long-term occupation, potential refugial survival and lineage turnover. Here, we present genetic analyses based on 99 new complete mitochondrial genomes from ancient and modern brown and black bears spanning the last ~45,000 years. Black bears form two SE Alaskan subclades, one preglacial and another postglacial, that diverged >100,000 years ago. All postglacial ancient brown bears are closely related to modern brown bears in the archipelago, while a single preglacial brown bear is found in a distantly related clade. A hiatus in the bear subfossil record around the LGM and the deep split of their pre- and postglacial subclades fail to support a hypothesis of continuous occupancy in SE Alaska throughout the LGM for either species. Our results are consistent with an absence of refugia along the SE Alaska coast, but indicate that vegetation quickly expanded after deglaciation, allowing bears to recolonize the area after a short-lived LGM peak.

Spatiotemporal transitions in Pseudo-nitzschia species assemblages and domoic acid along the Alaska coast.

The toxic diatom genus Pseudo-nitzschia is distributed from equatorial to polar regions and is comprised of >57 species, some capable of producing the neurotoxin domoic acid (DA). In the Pacific Arctic Region spanning the Bering, Chukchi, and Beaufort seas, DA is recognized as an emerging human and ecosystem health threat, yet little is known about the composition and distribution of Pseudo-nitzschia species in these waters. This investigation characterized Pseudo-nitzschia assemblages in samples collected in 2018 during summer (August) and fall (October-November) surveys as part of the Distributed Biological Observatory and Arctic Observing Network, encompassing a broad geographic range (57.8° to 73.0°N, -138.9° to -169.9°W) and spanning temperature (-1.79 to 11.7°C) and salinity (22.9 to 32.9) gradients associated with distinct water masses. Species were identified using a genus-specific Automated Ribosomal Intergenic Spacer Analysis (ARISA). Seventeen amplicons were observed; seven corresponded to temperate, sub-polar, or polar Pseudo-nitzschia species based on parallel sequencing efforts (P. arctica, P. delicatissima, P. granii, P. obtusa, P. pungens, and two genotypes of P. seriata), and one represented Fragilariopsis oceanica. During summer, particulate DA (pDA; 4.0 to 130.0 ng L-1) was observed in the Bering Strait and Chukchi Sea where P. obtusa was prevalent. In fall, pDA (3.3 to 111.8 ng L-1) occurred along the Beaufort Sea shelf coincident with one P. seriata genotype, and south of the Bering Strait in association with the other P. seriata genotype. Taxa were correlated with latitude, longitude, temperature, salinity, pDA, and/or chlorophyll a, and each had a distinct distribution pattern. The observation of DA in association with different species, seasons, geographic regions, and water masses underscores the significant risk of Amnesic Shellfish Poisoning (ASP) and DA-poisoning in Alaska waters.

Comprehensive Radar Mapping of Malaspina Glacier (Sít' Tlein), Alaska—The World's Largest Piedmont Glacier—Reveals Potential for Instability

AbstractMalaspina Glacier, located on the coast of southern Alaska, is the world's largest piedmont glacier. A narrow ice‐cored foreland zone undergoing rapid thermokarst erosion separates the glacier from the relatively warm waters of the Gulf of Alaska. Glacier‐wide thinning rates for Malaspina are greater than 1 m/yr, and previous geophysical investigations indicated that bed elevation exceeds 300 m below sea level in some places. These observations together give rise to the question of glacial stability. To address this question, glacier evolution models are dependent upon detailed observations of Malaspina's subglacial topography. Here, we map 2,000 line‐km of the glacier's bed using airborne radar sounding data collected by NASA's Operation IceBridge. When compared to gridded radar measurements, we find that glaciological models overestimate Malaspina's volume by more than 30%. While we report a mean bed elevation 100 m greater than previous models, we find that Malaspina inhabits a broad basin largely grounded below sea level. Several subglacial channels dissect the glacier's bed: the most prominent of these channels extends at least 35 km up‐glacier from the terminus toward the throat of Seward Glacier. Provided continued foreland erosion, an ice‐ocean connection may promote rapid retreat along these overdeepened subglacial channels, with a global sea‐level rise potential of 1.4 mm.

Separated by Space and Time but United by Kinship: Phylogeographical and Phylogenetic History of Two Species of Eleginus (Gadidae) Based on the Polymorphism of Cyt b Mitochondrial DNA Gene

Fishes of the genus Eleginus (Gadidae) are typical representatives of the ichthyofauna of the Northern Hemisphere; they play an important trophic role in the marine ecosystems of the Arctic and North Pacific and serve as targets of commercial and artisanal coastal fishing in many areas of the Russian North and Far East, as well as in areas of the coast of Alaska and northern Japan. The level of knowledge about the intraspecific organization of representatives of the genus Eleginus that is necessary for the rational exploitation of their stocks remains insufficient and their interspecific relationships have so far been analyzed using limited materials. This paper presents the first study of the interspecific relationships and intraspecific structure of navaga (E. nawaga) and saffron cod (E. gracilis) using a large-scale material (986 specimens in 29 samples from most of the species ranges) based on analysis of the polymorphism of mtDNA gene Cyt b. It is shown that they are independent, genetically differentiated species and their comparison with representatives of the genus Microgadus indicates that both species of the genus Eleginus might originate from a common ancestor close to M. proximus, while the divergence in the genus Microgadus occurred much earlier. Data on the haplotypic composition of saffron cod samples inhabiting areas from the Peter the Great Bay to Alaska waters and navaga samples inhabiting areas from the White Sea to the Ob Bay of the Kara Sea are given, which makes it possible to consider the phylogeographic history of both species and their intraspecific organization within the studied areas. Three groups can be distinguished for saffron cod: (1) Pacific–Japanese–Sakhalin group, (2) Chukchi–Bering seas group, and (3) intermediate group, which includes samples from the Sea of Okhotsk and waters of the northern Kurils.

Biomarker evidence of the water mass structure and primary productivity changes in the Chukchi Sea over the past 70 years

The Chukchi Sea has experienced significant changes under global warming in the Common Era, including the shift of primary productivity. However, modern observations are too short to fully investigate the effects of environmental changes in this area. Here, we analyzed lipid biomarkers (e.g. long-chain n-alkanes, n-alkanols, n-alkanoic acids, diols, and sterols) from a sediment core (R07) collected from the Chukchi Sea shelf to determine phytoplankton primary productivity variations and factors influencing these changes over the past 70 years. Similar trends of the abundance of terrestrial ecosystem-derived compounds (e.g. long-chain n-alkanes, n-alkanols, n-alkanoic acids, and C32 1,15-diol) indicate that terrigenous input increased from ca. 1946 towards ca. 1983 and then decreased thereafter. In comparison, biomarkers with marine origin indicate that the ratio of diatoms to dinoflagellates increased after ca. 1983 towards the core-top (ca. 2011). Concurrent changes in terrigenous input and phytoplankton community indicated a shift in water mass structure at ca. 1983 (i.e. the Alaska Coastal Water decreased and the Bering Sea Water increased), which may be attributed to the phase shift of the Arctic Oscillation and/or unsynchronized flow changes in different water masses. Owing to the different water mass properties, the change of water mass structure caused intense water mixing and the resulting high turbidity in the study area, which led to light limitation for phytoplankton growth. These conditions probably account for the reduced phytoplankton primary productivity from ca. 1983 to ca. 2000 in the general trend of increasing. The results indicate that, in addition to global warming and sea ice retreat, other factors, such as change in regional water mass structure (i.e. different water masses), may also have a significant influence on the primary productivity and the phytoplankton community in the Chukchi Sea shelf.

Radarsat Constellation Mission Derived Winter Glacier Velocities for the St. Elias Icefield, Yukon/Alaska: 2022 and 2023

Here we use high resolution (5 m) Radarsat Constellation Mission (RCM) imagery acquired in winters 2022 and 2023 to determine motion across glaciers of the St. Elias Icefield in Yukon/Alaska. Our regional velocity mapping largely conforms with previous studies, with faster motion (>600 m/yr) for the glaciers originating in the Yukon that drain southward and westward to the coast of Alaska and relatively slower motion (100–400 m/yr) for the land terminating glaciers that drain eastward and northeastward and stay within the Yukon. We also identify two new glacier surges within the icefields: the surge of Nàłùdäy (Lowell) Glacier in Winter 2022, and Chitina Glacier in Winter 2023, and track the progression of each surge from January to March utilizing ∼4-day repeat RCM imagery. To evaluate the quality of RCM-derived velocities, we compare our results with 50 simultaneous measurements at three on-ice dGPS stations located on two Yukon glaciers and find the average absolute difference between measurements to be 6.6 m/yr. Our results demonstrate the utility of RCM data to determine glacier motion across large regions with complex topography, to support process-based studies of fast flowing and surge-type glaciers and continue the legacy of velocity products derived from the Radarsat-2 mission.

Aggravation of the Colonial Struggle in the Pacific Ocean in 1760—1770s

The article is devoted to the struggle for colonies in the North Pacific in the context of the interaction between Russia, Great Britain and Spain in the second half of the 18th century, with an emphasis on the voyage of J. Cook to the coast of Alaska. The activity of Russia and the Western European powers related to the intensification of efforts in the northern part of the Pacific Ocean is considered. The article notes that the region studied by us has long attracted the attention of European countries. The factors that contributed to the development of the North-West of America are revealed. The authors show that it was a very complex and multifaceted process, in which various levels of state power, up to the emperors, participated. The importance of the initiative of private commercial companies in the colonization of territories is noted. The authors of the article draw attention to the fact that the expansion of the Spanish Empire became possible due to Madrid’s fears about the strengthening of Russia in the North Pacific. In turn, Great Britain carried out active intelligence activities, which resulted in a phase of military conflict at the end of the 18th century. On the basis of Russian and foreign documents introduced into scientific circulation for the first time, the authors of the article try to show the validity of the fears of the Madrid court regarding Russian colonization, as well as the ambitions of London in this region. Promotion of Russia to the northwest of America was due to economic and political reasons. The access to the Pacific Ocean of Russian private structures was caused by the desire to collect yasak from the indigenous peoples, as well as to obtain furs, which were highly valued in world markets. The article notes the changes in the position of Great Britain, Spain and Russia in relation to the colonies in the 18th century. It is concluded that, in general, the policy of Spain and Great Britain was aimed at curbing the Russian advance in the Pacific Ocean. Russian-Anglo-Spanish relations in the Northwest Pacific at the end of the 17th century and the first half of the 18th century made a significant contribution to the subsequent active colonization of the North Pacific. The article was written using an interdisciplinary approach based on a wide range of sources from domestic and foreign archives.

USA, State of Alaska, Glacier Bay National Park and Preserve, Gulf of Alaska Coast

USA, State of Alaska, Glacier Bay National Park and Preserve, Gulf of Alaska Coast

Интересы США и Канады в арктическом регионе

The purpose of the article is to identify the interests in the Arctic region of such leading countries of the Western Hemisphere as the USA and Canada. Arctic ice is actively melting. If current trends continue, the region will undergo drastic changes with far-reaching consequences. At the same time, the retreating ice is opening up the region for economic development, including through the exploitation of previously inaccessible hydrocarbons and minerals. In September 2011, both the Northern Sea Route (along the northern coast of Russia, formerly known as the Northeast Passage) and the Northwest Passage (along the northern coast of Canada and Alaska) were opened for some time, which could potentially lead to a reduction in shipping lanes in Asia. Increasing human activity in the sparsely populated and climatically difficult Arctic requires new initiatives to ensure the safety of the region's environment, its residents and guests. In this regard, the identification of the basic interests of the Canada and United States in the Arctic zone is of particular importance. The authors used such research methods as system analysis, logical and historical. Due to its geopolitical features and enormous resource potential, the Arctic region concentrates the attention of the leading powers of the modern world. The article analyzes in detail the approaches to defining the borders of the Arctic region of Canada and the United States, provides a retrospective analysis of the development of these territories. The results of the study of the actual data and the literature used showed that in modern Canada, the Arctic is considered as the center of national identity, although the interest of the authorities in this zone has been situational for quite a long time. The authors highlight the reasons why Canada seeks to expand its southern borders into subarctic latitudes. The article examines the stages of the US development of its Arctic zone and the reasons for the increased interest in it among the American authorities at the present stage. In conclusion, the authors conclude that the Arctic zone for the Arctic states of the Western hemisphere is important both in terms of resources and in terms of security. At the same time, the authors identify significant differences in the positions of the United States and Canada, in particular the inability of the two countries to agree on such key issues as the legal status of the Northwest Passage and the maritime border in the Beaufort Sea. This significantly affects not only their internal capabilities, but also their ability to exercise international leadership in the region. The practical and theoretical significance of the work lies in the fact that the Arctic is strategically important for all countries of the Arctic zone, therefore, the identification of their interests in this region is important both for scientific discourse and in the plane of practical policy.

Geohazard Education Trainings Foster Resilience in Rural Alaska

National Science Foundation-funded teacher and community workshops boost disaster preparedness optimism among coastal Alaskan educators, whose communities face an array of natural hazards.

Climate Change Amelioration by Marine Producers: Does Dominance Predict Impact?

AbstractClimate change threatens biodiversity worldwide, and assessing how those changes will impact communities will be critical for conservation. Dominant primary producers can alter local-scale environmental conditions, reducing temperature via shading and mitigating ocean acidification via photosynthesis, which could buffer communities from the impacts of climate change. We conducted two experiments on the coast of southeastern Alaska to assess the effects of a common seaweed species, Neorhodomela oregona, on temperature and pH in field tide pools and tide pool mesocosms. We found that N. oregona was numerically dominant in this system, covering >60% of habitable space in the pools and accounting for >40% of live cover. However, while N. oregona had a density-dependent effect on pH in isolated mesocosms, we did not find a consistent effect of N. oregona on either pH or water temperature in tide pools in the field. These results suggest that the amelioration of climate change impacts in immersed marine ecosystems by primary producers is not universal and likely depends on species' functional attributes, including photosynthetic rate and physical structure, in addition to abundance or dominance.

Diatom and dinoflagellate cyst distribution in surface sediments of the Chukchi Sea in relation to the upper water masses

Diatom and dinoflagellate cyst analyses were performed on 22 surface sediment samples from the Chukchi Sea to document their geographical distributions in one of the most understudied sections of the Arctic Ocean and to examine the influence of upper water masses on these two major groups of phytoplankton. Total concentrations vary from 0.9 to 5.9 × 106 valves g−1 for diatoms and from 0.8 to 12.5 × 103 cysts g−1 for organic-walled dinoflagellate cysts, with the highest values for both groups observed in the southern part of the Chukchi Sea and away from the Bering Strait. Well-preserved microfossils were recovered, with a total of 35 and 88 taxa of dinoflagellate cysts and diatoms, respectively. The most abundant diatoms are Paralia sulcata, Thalassiosira antarctica, Thalassiosira nordenskioeldii, and resting spores of Chaetoceros spp., whereas cysts of phototrophic Alexandrium spp., Operculodinium centrocarpum sensu Wall and Dale (1966), and heterotrophic Islandinium minutum and Brigantedinium spp. were most common in the dinoflagellate cyst assemblages. Cysts of HAB-causing Alexandrium spp. were found in most of the samples, with the highest abundances in Herald Canyon where they contribute ∼56.6% to the cyst assemblage. As expected, cysts produced by heterotrophic dinoflagellates were more abundant where sedimentary diatom concentrations were the highest.Statistical analysis identified three major diatom and dinoflagellate cyst clusters: 1. Sites influenced by the Alaska Coastal Current in the eastern part of the Chukchi Sea are characterized by high abundances of P. sulcata and O. centrocarpum sensu Wall and Dale (1966); 2. The western part and Herald Canyon in the northern part of the Chukchi Sea are distinguished by diatoms Chaetoceros spp., T. antarctica and dinoflagellate cysts of Alexandrium spp. and affected by the Siberian Coastal Current and Bering Shelf Water; and 3. Assemblages in the southern part of the Chukchi Sea are recognized by noticeable abundances of T. nordenskioeldii and cryophilic diatom taxa, and dinoflagellate cysts I. minutum, as well as by overall lower percentages of cysts of Pentapharsodinium dalei and Brigantedinium spp. This work revealed the potential applicability of the combined use of diatoms and dinoflagellate cysts for reconstructions of past dynamic water mass changes in the Chukchi Sea.

Atmospheric Circulation Drivers of Extreme High Water Level Events at Foggy Island Bay, Alaska

The northern coast of Alaska is experiencing significant climatic change enhancing hazards from reduced sea ice and increased coastal erosion. This same region is home to offshore oil/gas activities. Foggy Island Bay is one region along the Beaufort Sea coast with planned offshore oil/gas development that will need to account for the changing climate. High water levels impact infrastructure through coastal erosion and flooding hazards. In this study, 21 high water level events exceeding the top 95th percentile were identified at the gauge in Prudhoe Bay, Alaska (adjacent to Foggy Island Bay) over 1990–2018. All 21 events, and many non-extreme days with elevated water levels, were associated with strong westerly winds according to station records. Storm systems were generally found to be a key driver of westerly winds in the region according to downscaled reanalysis and storm track data. A dynamically downscaled global climate model projection from CMIP5 indicated that days with westerly wind events may become more frequent as storms strengthen and have longer durations by 2100 in the Foggy Island Bay region. Coupled with the anticipated continued decline in sea ice, the northern coast of Alaska may experience more frequent high water events over the next ~80 years.

Seasonal and inter-annual variation in exposure to peregrines (Falco peregrinus) for southbound western sandpipers (Calidris mauri)

BackgroundThe western sandpiper (Calidris mauri) is an early southbound migrant species in North America. The ‘peregrine avoidance’ hypothesis proposes that this timing evolved to reduce exposure to their main predator, the peregrine (Falco peregrinus), along the Pacific flyway.MethodsI evaluate this hypothesis based on 16 years of near-daily (June – October) measures of peregrine presence made on the Fraser River estuary, a major stopover in the Pacific northwest.ResultsExposure to peregrines is lowest for the earliest southbound western sandpipers, and rises steeply as peregrines en route from northern breeding areas begin to arrive in late July or August. Peregrine arrival timing varies greatly between years, shifting in step with the onset of spring along coastal Alaska. Peregrine presence on the Fraser estuary on any date is higher in years with earlier spring onset. On the median adult sandpiper passage date (day-of-year 198) this increases 17-fold over the inter-annual range between the earliest and latest peregrine arrival dates.ConclusionThe pattern of strong and predictable changes in the seasonal pattern of danger quantified here provides a further test of the hypothesis that danger affects migratory timing. Western sandpipers appear to anticipate the exposure level of southward migration, perhaps because they are able to observe spring onset on their Alaskan breeding grounds. They adjust the duration of parental care and length of the breeding season to keep the date of migratory departure from the Arctic relatively invariant in spite of large interannual variation in spring onset. While underway they also adjust aspects of migratory behavior. These observations support the ‘peregrine avoidance’ hypothesis, and suggest that western sandpipers are able to counter, at least partially, the higher migratory danger of early spring years.

Glacier runoff influences biogeochemistry and resource availability in coastal temperate rainforest streams: Implications for juvenile salmon growth

AbstractMeltwater contributions to watersheds are shrinking as glaciers disappear, altering the flow, temperature, and biogeochemistry of freshwaters. A potential consequence of this landscape change is that streamflow patterns within glacierized watersheds will become more homogenous, potentially altering the capacity of watersheds to support Pacific salmon. To assess heterogeneity in stream habitat quality for juvenile salmon in a watershed in the Alaska Coast Mountains, we collected organic matter and invertebrate drift and measured streamwater physical and biogeochemical properties over the main runoff season in two adjacent tributaries, one fed mainly by rain and the other partially by glacier ice/snowmelt. We then used bioenergetic modeling to evaluate how temporal patterns in water temperature and invertebrate drift in each tributary influence juvenile salmon growth potential. Across the study period, average invertebrate drift concentrations were similar in non‐glacierized Montana (0.33 mg m−3) and glacier‐influenced McGinnis Creeks (0.38 mg m−3). However, seasonal patterns of invertebrate drift were temporally asynchronous between the two streams. Invertebrate drift and modeled fish growth were generally higher in McGinnis Creek in the spring and Montana Creek in the Summer. For juvenile salmon, tracking these resource asynchronies by moving between tributaries resulted in 20% greater growth than could be obtained within either stream alone. These results suggest that hydrologic heterogeneity within watersheds may enhance the diversity of foraging and growth opportunities for mobile aquatic organisms, which may be essential for supporting productive and resilient natural salmon runs.

Spatial distribution of arctic sand lance in the Chukchi Sea related to the physical environment

Sand lance or sand eels (Ammodytes spp.) are small planktivorous forage fishes that play an integral role in pelagic ecosystems in the Northern Hemisphere. Arctic sand lance (Ammodytes hexapterus) is prevalent in the North Pacific in the Sea of Okhotsk, northern Bering Sea, Chukchi Sea, and Beaufort Sea. Few studies have focused on this species despite its critical position in energy transfer and trophic food webs. Recent surveys in the Chukchi Sea and Beaufort Sea have noted an increase in the prevalence of this species in concert with reduced ice extent. Sand lance are unique among forage species in having close associations with specific water column conditions as well as a reliance on specific sand substrates for burrowing. Life history and habitat dependency is influenced by both dynamic oceanographic conditions and static benthic substrata. This taxa, therefore, provides a unique opportunity to examine the potential expansion of a boreal species into Arctic marine habitats. We use comprehensive surveys conducted throughout the Chukchi Sea shelf over multiple years to evaluate spatial distribution and abundance relative to oceanographic variables in the water column and sediment composition on the seafloor. We applied logistic regression and generalized additive models to investigate presence and relative abundance of Arctic sand lance and to evaluate spatial distribution, as a function of oceanographic and benthic environmental variables. Spatial distribution shifted considerably between years in response to environmental conditions. Arctic sand lance presence was influenced by surface water mass and positively associated with Alaskan Coastal Water. Relative abundance was positively associated with high surface temperature, low surface salinity, and coarser substrates. Evidence is mounting that the distributions of many boreal species are expanding on the margins of the Arctic. Our research reports increased aggregations of Arctic sand lance in the Chukchi Sea and at the highest latitude on record for this species, at the shelf break of the Arctic Basin.

Dating Coastal Archaeological Wood From Pingusugruk (15th–17th CE), Northern Alaska:

Abstract Along the coasts of northern Alaska, in a treeless tundra environment, the primary wood resource for coastal populations is driftwood, a seasonal and exogenous resource carried by the major rivers of western North America. The potential of Alaskan coastal archaeological wood for tree-ring research was first assessed in the 1940s by archaeologist and tree-ring research pioneer J. L. Giddings. Despite his success, the difficulties of dendrochronological studies on driftwood and the development of radiocarbon dating during the 1950s resulted in the near-abandonment of dendrochronology to precisely date archaeological sites and build long sequences using archaeological wood in Alaska. In this study, we explored the possibilities and limitations of standard ring-width dendrochronological methods for dating Alaskan coastal archaeological wood. We focus on the site of Pingusugruk, a late Thule site (15th–17th CE) located at Point Franklin, northern Alaska. The preliminary results have been obtained from the standard dendrochronological analyses of 40 timber cross-sections from two semi-subterranean houses at Pingusugruk. We cross-correlated individual ring-width series and built floating chronologies between houses before cross-dating them with existing regional 1000-year-long master chronologies from the Kobuk and Mackenzie rivers (available on the International Tree-Ring Databank, ITRDB). Additional work on various dendro-archaeological collections using an interdisciplinary approach (geochemical analyses of oxygen isotopes and radiocarbon dating) will help develop and expand regional tree-ring chronologies and climatic tree-ring sequences in Alaska.

Effects of sub-seabed characteristics on acoustic transmission loss in seismic reflection surveys

Marine seismic reflection surveys are used to study the composition of the seabed and sub-seabed by recording reflections of the field generated by an airgun array from the seafloor with a towed horizontal streamer. The abundance of data within a single survey and the number of publicly available surveys provides substantial opportunity for data-driven acoustic analysis. Here, we consider data from surveys that were conducted off the coasts of Oregon, Washington, British Columbia, and Alaska, covering portions of the Cascadia Subduction Zone and the Queen Charlotte Fault. Throughout the experiments, data was collected at depths ranging from 200 m to 3 km, typically using a 15 km long towed streamer containing 1200 hydrophone groups with 12.5 m spacing. With these datasets, there is a breadth of opportunity for studying the impacts of various seabed features on acoustic propagation. This talk will explore the impacts of seabed and sub-seabed characteristics, bathymetry, reflectivity, etc., on acoustic transmission loss. The data from these experiments, corrected for array design impacts, will be compared directly with computational propagation models. [Work supported by ONR.]

A Numerical Study of Long-Return Period Near-Bottom Ocean Currents in Lower Cook Inlet, Alaska

Lower Cook Inlet (LCI) is an important waterway with very large tides and high marine productivity. Oceanographic forcing in LCI is complex due to a combination of tides, seasonal winds, and large freshwater discharges, as well as inflow from the Alaska Coastal Current. From an analysis of historical current meter data sets, deeper ocean currents of LCI were found to have large differences resulting from the dominance of large tides in the northeast portion of LCI while subtidal contributions to the deeper currents are more important relative to the reduced tidal currents in central and western parts of LCI. To compute the largest values of the near-bottom currents of LCI, a 3D hydrodynamical model was developed over a large model domain extending over the full 300 km length of Cook Inlet as well as a large portion of the adjoining Alaska continental shelf region. At the open model boundaries, nine major tidal height constituents were specified based on National Oceanic and Atmospheric Administration (NOAA) tidal gauge data. The model was forced by the spatially varying winds and freshwater discharges for the six gauged rivers in Cook Inlet. The model was verified using available current meter data in the study area. Model runs were carried out for 21 case studies to derive the near-bottom currents for return periods of 1, 10, and 100 years. Within LCI, the extremal values for near bottom currents arise from quite different forcing regimes. Tidal currents are completely dominant in the northeast portion of LCI while for central and western portions, remote wind forcing over the Alaskan continental shelf current, which generates the Alaska Coastal Current, becomes more important.

Lessons from the Whales.

The cover of this issue shows some of the humpback whales I was privileged to observe this past July. Humpbacks demonstrate a fascinating behavior called bubble-net feeding. These huge animals live most of the year on their own, fending for themselves throughout the ocean. But, during the summer feeding season, many gather along the coast of Alaska to feed on schools of herring. When they do this, a few of these loners instinctively work cooperatively to take full advantage of a feeding opportunity for the good of all involved. There are multiple videos of this available that a Google search will provide. It is an amazing behavior.One thing that has been made clear during the past couple of years is that there are wonderful opportunities for individual human beings to come together for the greater good. As dentists, we historically have thrived on functioning as individuals but also have somehow known that we all benefit when we gather and work together. Our academies and professional organizations are wonderful examples of this. In these environments, we feed on the support, instruction, and camaraderie that they provide. Recent years have also taught us that, indeed, electronic formats can be used effectively for some pursuits. But, at least instinctively, we have seen validated that there is important feeding that is lost when we do not gather. Many of our organizations are feeling the loss of membership unlike at any time in my memory. One clear challenge is the changing mode of practice and practice ownership. Many dentists are now gaining a measure of support, instruction, and camaraderie through their employers. Now, more than ever, we must be aware of this threat to our traditional organizations and work harder than ever to come along side of all members of our profession—finding ways to adapt so that these essential needs are met on a broader scale. We must learn to communicate through technology in even better ways while we strive to create opportunities to gather together that are more attractive to all.The past couple of years have been a tremendous challenge to this journal. The pandemic hit just as we were making a major transition in our publication support structure to enhance our financial viability. The timing of it all was a “perfect storm” that negatively impacted our ability to move from manuscript acceptance to publication in ways never imagined. Recovery from that storm has required many individuals to come together for the common good. It has been a long road of recovery, but we are making headway. We continue to work to decrease the backlog of papers that need to be available online early. We are nearly back on schedule on publication dates for each of our volumes. It has taken dedicated effort on the part of our staff, a new cadre of copy editors and typesetters, a loyal team of reviewers, and authors who have had to tolerate the storm along with us. We hope that our authors will continue to provide excellent submissions, even as we continue in our recovery.Indeed, the humpbacks I observed last summer gave me the opportunity to reflect on many things. I would encourage everyone to take a few minutes to watch an online video of this amazing behavior and to think about how each of us can apply lessons learned from the whales!