Western Beaufort Sea Research Articles

Bowhead and Beluga Whale Distributions, Sighting Rates, and Habitat Associations in the Western Beaufort Sea in Summer and Fall 2009–16, with Comparison to 1982–91

We analyzed data from line-transect aerial surveys for marine mammals conducted in the western Beaufort Sea (shore to 72˚ N, 140˚–157˚ W) from July to October of 2009–16 to investigate the distribution, behaviors, sighting rates, and habitat use preferences of bowhead and beluga whales. The habitat use data allowed for direct comparison with data collected in the same area from 1982 to 1991. Both species are ice-adapted, migrating through leads in sea ice in spring, and are seasonal inhabitants of the western Beaufort Sea during summer and fall. From 2009 to 2016, bowheads were seen in all survey months, with the highest overall sighting rate (whales per km) in August. Bowhead sighting rates were highest in the whales’ preferred habitats: outer shelf habitat (51–200 m depth) in July and inner shelf-shallow habitat (≤ 20 m depth) in August, September, and October. Beluga whales were also seen in all survey months, with highest overall sighting rate in July. Beluga whales were overwhelmingly associated with continental slope habitat (201–2000 m depth) in all months. Bowhead distribution and depth preferences in summer months of 2009–16 differed from those observed in 1982–91, when bowheads were not seen during limited survey effort in July and preferred outer continental shelf habitat in August. These differences indicate that bowhead whale preference for shallow shelf habitat now occurs earlier in summer than it used to. Beluga distribution and depth preference remained similar between 1982–91 and 2009–16, with strong preference for continental slope during both periods. Differences in sea ice cover habitat association for both species are likely due more to the relative lack of sea ice in recent years compared to the earlier period than to shifts in habitat preference. Habitat partitioning between bowhead and beluga whales in the western Beaufort Sea remained evident except in July, when both species used continental slope habitat. In July – October 2009–16, the distribution, sighting rates, and behavior of both bowheads and belugas in the western Beaufort showed considerable interannual variation, which underscores the importance of annual sampling to accurate records of the complex western Beaufort Sea ecosystem.

E&P Notes (February 2018)

E&P Notes Industry Poised for Stronger Performance in 2018 Joel Parshall, JPT Features Editor The global oil industry appears poised for stronger performance in 2018, having benefitted from the financial discipline and cost-cutting innovation driven by several years of low oil prices and looking ahead to somewhat more stable market conditions. While oil prices have recently risen above $60/bbl, likely reflecting a number of short-term supply disruptions and concerns over Middle East tensions, forecasts generally call for prices to fluctuate sustainably between $40/bbl and $60/bbl and end the year in the higher part of that range. “Higher prices in or above that range will increase supply as countries lessen compliance with production quotas and United States shale production keeps increasing,” said Moody’s Investors Services in its 2018 industry outlook. ‘Supergiant’ Zohr Gas Field Off Egypt Comes On Stream Matt Zborowski, Technology Writer Eni confirmed on 20 December that the Zohr field has started gas production from the Shorouk block offshore Egypt. The launch comes less than 2½ years after the Italian firm discovered the enormous deposit, which is estimated to hold more than 30 Tcf of gas in place. The field is flowing 350 MMcf/D and is slated to produce 1 Bcf/D by the middle of next year, Egypt’s petroleum ministry said. The project’s first phase includes six subsea wells, with gas transported 180 km to an onshore plant at Port Said for processing and use in Egypt’s national grid. The second phase will comprise 14 more wells to be drilled by the end of 2019. The field sits in 1500 m of water. Schlumberger Buys Weatherford’s US Fracturing Assets Weatherford has sold its US pressure pumping and pump-down perforating assets to Schlumberger for $430 million in cash, abruptly ending a planned joint venture that was to begin operations on 1 January. The parties agreed to revised deal terms that reflect an asset sale, abandoning the previously announced OneStim joint venture that had received US Department of Justice approval in November 2017. Schlumberger will take ownership of Weatherford’s US pressure pumping and pump-down perforating related facilities and supplier and customer contracts. Additionally, 100 Weatherford employees associated with the business will transfer to Schlumberger. Oil Discoveries Fall to Lowest Level in 70 Years Unconventional output may be booming, but the low oil prices of the past 3 years have led to the lowest level of oil discoveries in the past 70 years. Oil companies discovered less oil and gas in 2017—7 billion BOE—than any year on record, the Norwegian research firm Rystad Energy said in a December report. “We haven’t seen anything like this since the 1940s,” said Sonia MladÁ Passos, a senior analyst at Rystad. “We have to face the fact that the low discovered volumes on a global level represent a serious threat to the supply levels some 10 years down the road.” Big Discoveries Prompt US Agencies To Lift Recoverable Resource Estimates in Alaska Matt Zborowski, Technology Writer The US Department of the Interior (DOI) has increased its estimate of undiscovered, technically recoverable resources in parts of Alaska’s federal, state, and tribal lands and waters following recent, bigger-than-expected discoveries. The revisions include a large jump in estimated onshore oil resources. The assessment—conducted by DOI agencies the Bureau of Ocean Energy Management (BOEM), Bureau of Land Management, and US Geological Survey (USGS)—shows approximately 17.6 billion bbl of oil and 50 Tcf of gas in the National Petroleum Reserve-Alaska (NPR-A), the Western Beaufort Sea, nearby state and native lands, and state waters.

Calibrating a Viscoelastic Sea Ice Model for Wave Propagation in the Arctic Fall Marginal Ice Zone

AbstractThis paper presents a wave‐in‐ice model calibration study. Data used were collected in the thin ice of the advancing autumn marginal ice zone of the western Arctic Ocean in 2015, where pancake ice was found to be prevalent. Multiple buoys were deployed in seven wave experiments; data from four of these experiments are used in the present study. Wave attenuation coefficients are calculated utilizing wave energy decay between two buoys measuring simultaneously within the ice covered region. Wavenumbers are measured in one of these experiments. Forcing parameters are obtained from simultaneous in‐situ and remote sensing observations, as well as forecast/hindcast models. Cases from three wave experiments are used to calibrate a viscoelastic model for wave attenuation/dispersion in ice cover. The calibration is done by minimizing the difference between modeled and measured complex wavenumber, using a multi‐objective genetic algorithm. The calibrated results are validated using two methods. One is to directly apply the calibrated viscoelastic parameters to one of the wave experiments not used in the calibration and then compare the attenuation from the model with measured data. The other is to use the calibrated viscoelastic model in WAVEWATCH III® over the entire western Beaufort Sea and then compare the wave spectra at two remote sites not used in the calibration. Both validations show reasonable agreement between the model and the measured data. The completed viscoelastic model is believed to be applicable to the fall marginal ice zone dominated by pancake ice.

Trends in sea-ice cover within bowhead whale habitats in the Pacific Arctic

The range of the Bering-Chukchi-Beaufort (BCB) population of bowhead whales (Balaena mysticetus) extends across the seasonally ice-covered waters of the Pacific Arctic region. The majority of whales summer in the eastern Beaufort Sea and winter in the Bering Sea, migrating across the Chukchi Sea in fall and spring. As arctic sea-ice extent rapidly diminishes, the increasing length and variability of the open water season is changing bowhead habitat substantially, with many areas now regularly ice-free when whales are present. This study examines changes in the number of open water days (OWD) between 1979 and 2014 within annual bowhead whale core-use areas as defined by satellite tagging data, and within the western Beaufort Sea (140–157°W; to 72°N) sampled by fall aerial surveys. Ice cover has decreased more in the core-use areas in the northern extent of the range than in core-use areas in the southern extent. The numbers of OWD within the core-use areas near Point Barrow and along the northern Chukotka Coast during peak use have increased by 13 and 10 days/decade, respectively. The most dramatic reductions in sea-ice cover have taken place in the western Beaufort Sea where the number of OWD on the shelf and slope have increased by 20 and 25 days/decade, respectively. In contrast, sea-ice cover has not significantly changed within the winter core-use area near the Gulf of Anadyr. Using aerial survey data, we found that bowheads in the Beaufort Sea during the fall migration have a preference for being closer to shore than to the ice edge, and that their distance to shore decreases as the fraction of open water increases. This distribution may be due to increased feeding opportunities closer to shore as a result of greater upwelling along the shelf break when the ice cover is farther from shore. Furthermore, the aerial survey data also revealed a substantial shift westward toward Point Barrow in the whales’ use of the western Beaufort Sea during fall in the period 1997–2014 compared to 1982–1996. The extent and timing of sea-ice coverage has changed relatively little over time in the Bering Sea. Bowheads typically migrate north prior to spring ice melt and retreat; therefore, large changes in the timing of the spring migration are not expected. We anticipate that bowheads will spend increasingly more time within summer and fall feeding areas, delaying their arrival to wintering areas in the Bering Sea. Reduced ice coverage and thickness in the southern Chukchi Sea may make wintering there more common in the future. Summer and fall movements may be more variable as productivity and zooplankton aggregations in existing feeding areas are altered in response to sea ice thinning and retreat, and as new areas become available.

Acoustic propagation from the Canadian Basin to the Chukchi Shelf

The Pacific Arctic Region, encompassing the Bering, Chukchi, Western Beaufort, and Eastern Siberian shelves and seas, has experienced decadal changes in atmospheric conditions, seasonal sea-ice coverage, and seawater temperature. In the summer of 2016, the Canada Basin Acoustic Propagation Experiment (CANAPE) was conducted to understand the changing soundscape and to explore the use of acoustic signals as a remote sensing tool in the modern Arctic. During the experiment, low-frequency signals from five tomographic sources located in the Canada Basin were recorded by a short vertical line array of hydrophones deployed from a research vessel. The recordings were made at seven stations located in the Canada Basin, on the continental rise, and on the Chukchi Shelf. The propagation distances ranged from 50 km to 500 km, and the propagation conditions changed from ducted by the Beaufort Lens in the basin to upward refracting on the continental shelf. Multiple measurements of the sound speed profile were acquire...

Using biological traits and environmental variables to characterize two Arctic epibenthic invertebrate communities in and adjacent to Barrow Canyon

The Arctic's Barrow Canyon, located in the northeastern Chukchi and western Beaufort seas, supports a rich and diverse benthic ecosystem and is often termed an ecological “hotspot” of productivity. Within and adjacent to Barrow Canyon, the epibenthic invertebrate communities vary, with biomass and taxonomic distributions related to habitat variation. Here we asked if the patterns observed are due to Barrow Canyon's variation in near-seafloor physical hydrography, and whether differences in taxonomic distribution also reflect differences in functional properties of the epibenthic invertebrate community. Data were collected using a standardized 83–112 bottom trawl during two surveys in and adjacent to Barrow Canyon: the northeast Chukchi Sea survey in 2013 and the western Beaufort Sea survey in 2008. A portion of the Beaufort Sea survey also used a liner to retain smaller organisms. A suite of nine environmental variables were examined, that included depth, bottom water temperature, bottom hardness as measured by acoustics, and circulation model hindcast current speed. They explained 18–47% of observed variance for each of the three data sets (Chukchi Sea, Beaufort Sea lined net (LN), Beaufort Sea unlined net (UN)). In the Chukchi Sea, bottom hardness and depth were significant variables. In the Beaufort Sea LN hauls, depth, bottom temperature, and the mean current speed on the day of sampling were significant variables and in the Beaufort Sea UN hauls, depth was the only significant variable. Of the 150+ collected taxa from each survey, ~20 made up 90% of the total biomass in the Beaufort and Chukchi Seas, and six of the 20 taxa were common to both study areas. We used biological traits analysis (BTA) of body morphology, trophic, and reproductive traits to further characterize the epibenthos at the head of Barrow Canyon in the Chukchi Sea and into Barrow Canyon in the Beaufort Sea. Although the Chukchi and Beaufort seas differed taxonomically in abundance and distribution, they were functionally similar based on the biological traits we examined. A traits analysis can advance knowledge of a community of organisms; however, it is most informative if used as a complement to a taxonomic composition analysis of abundance and distribution.

Environmental drivers of benthic fish distribution in and around Barrow Canyon in the northeastern Chukchi Sea and western Beaufort Sea

We investigate the relationships between Arctic fish and their environment with the goal of illustrating mechanisms of climate change impacts. A multidisciplinary research survey was conducted to characterize fish distribution and oceanographic processes in and around Barrow Canyon in the northeastern Chukchi Sea in summer 2013. Benthic fish were sampled with standard bottom trawl survey methods. Oceanographic data were collected at each trawl station. The density of Arctic cod (Boreogadus saida), the most abundant species, was related to bottom depth, salinity and temperature. Arctic cod were more abundant in deep, cold and highly saline water in Barrow Canyon, which was likely advected from the Chukchi Shelf or from the Arctic Basin. We hypothesize that Arctic cod occupied Barrow Canyon to take advantage of energy-rich copepods transported in these water masses. Arctic cod were similarly more abundant in deep, cold and high salinity water in the Beaufort Sea, documented by a comparable multidisciplinary survey conducted in 2008. These linkages between oceanographic variables and benthic fish distribution and abundance suggest that advection, sea-ice dynamics and pelagic-benthic coupling are important for the ecology of benthic Arctic fishes. These processes have been and will likely continue to be impacted by climate change. Our results improve the understanding of the mechanistic linkages between climate change and benthic Arctic fish ecology.

Beluga whales in the western Beaufort Sea: Current state of knowledge on timing, distribution, habitat use and environmental drivers

The seasonal and geographic patterns in the distribution, residency, and density of two populations (Chukchi and Beaufort) of beluga whales (Delphinapterus leucas) were examined using data from aerial surveys, passive acoustic recordings, and satellite telemetry to better understand this arctic species in the oceanographically complex and changing western Beaufort Sea. An aerial survey data-based model of beluga density highlights the Beaufort Sea slope as important habitat for belugas, with westerly regions becoming more important as summer progresses into fall. The Barrow Canyon region always had the highest relative densities of belugas from July-October. Passive acoustic data showed that beluga whales occupied the Beaufort slope and Beaufort Sea from early April until early November and passed each hydrophone location in three broad pulses during this time. These pulses likely represent the migrations of the two beluga populations: the first pulse in spring being from Beaufort animals, the second spring pulse Chukchi belugas, with the third, fall pulse a combination of both populations. Core-use and home range analyses of satellite-tagged belugas showed similar use of habitats as the aerial survey data, but also showed that it is predominantly the Chukchi population of belugas that uses the western Beaufort, with the exception of September when both populations overlap. Finally, an examination of these beluga datasets in the context of wind-driven changes in the local currents and water masses suggests that belugas are highly capable of adapting to oceanographic changes that may drive the distribution of their prey.

Food habits of Arctic staghorn sculpin (Gymnocanthus tricuspis) and shorthorn sculpin (Myoxocephalus scorpius) in the northeastern Chukchi and western Beaufort Seas

Arctic staghorn sculpin (Gymnocanthus tricuspis) and shorthorn sculpin (Myoxocephalus scorpius) belong to Cottidae, the second most abundant fish family in the western Arctic. Although considered important in food webs, little is known about their food habits throughout this region. To address this knowledge gap, we examined and compared the diets of 515 Arctic staghorn sculpin and 422 shorthorn sculpin using stomachs collected over three summers in the northeastern Chukchi Sea (2010–2012) and one summer in the western Beaufort Sea (2011). We used permutational multivariate analysis of variance (PERMANOVA) and non-metric multidimensional scaling (nMDS) to compare sculpin diets between regions and selected size classes. Differences in mouth morphologies and predator size versus prey size relationships were examined using regression techniques. Arctic staghorn sculpin and shorthorn sculpin diet compositions differed greatly throughout the Chukchi and Beaufort Seas. Regardless of body size, the smaller-mouthed Arctic staghorn sculpin consumed mostly benthic amphipods and polychaetes, whereas the larger-mouthed shorthorn sculpin shifted from a diet composed of benthic and pelagic macroinvertebrates as smaller individuals to shrimps and fish prey as larger individuals. Within shared habitats, the sculpins appear to partition prey, either by taxa or size, in a manner that suggests no substantial overlap occurs between species. This study increases knowledge of sculpin feeding ecology in the western Arctic and offers regional, quantitative diet information that could support current and future food web modeling efforts.

Regional diving behavior of Pacific Arctic beluga whales Delphinapterus leucas and possible associations with prey

Two populations of beluga whales Delphinapterus leucas in the Pacific Arctic make seasonal migrations to regions characterized by diverse bathymetry and hydrography, yet there is limited information contrasting behavior and foraging across regions. We used satellite-linked timedepth recorders attached to 30 belugas from 1997 to 2012 to infer the depths at which belu- gas forage seasonally and regionally. We also examined the correspondence between patterns of beluga diving and the vertical distribution of a primary prey species, Arctic cod Boreogadus saida, within the western Beaufort Sea. A suite of regional diving metrics revealed that beluga dive behavior varied among regions and sometimes between populations. Estimates of occupancy time at depth, in addition to maximum and modal dive depths for 6 h periods, suggested that Eastern Chukchi Sea and Beaufort Sea belugas were regularly diving to the seafloor in shallow shelf regions. Along slope margins and in the deep Canada Basin (>3000 m), specific portions of the water column were more frequently targeted. The greatest maximum daily dive depths were >900 m in the Canada Basin. Arctic cod were most abundant at 200�300 m in the western Beaufort Sea, and beluga dives within the survey area also most frequently targeted these depths. These results are consistent with a hypothesis that Arctic cod are a primary prey item for Pacific Arctic belugas and suggest that foraging belugas dive to depths that maximize prey encounters. In the context of a rapidly transforming Arctic ecosystem increasingly exposed to anthropogenic activi- ties, our results quantify the ecological importance of key regions for these 2 populations.

Variability in the summer diets of juvenile polar cod (Boreogadus saida) in the northeastern Chukchi and western Beaufort Seas

Polar cod (Boreogadus saida) is an important link between top predators and lower trophic levels in high-latitude marine ecosystems. Previous findings describe differences in its diet throughout the western Arctic; however, the causes of this variation are not well known. This study examined the diets of juvenile polar cod collected via demersal trawling methods over three summers in the northeastern Chukchi Sea (2010–2012) and one summer in the western Beaufort Sea (2011) to determine the amount of variability explained by biological, spatial, and interannual factors. Prey were identified, measured for length, and aggregated by percent mean weight into taxonomically coarse prey categories for analysis. Within seas, variation in juvenile polar cod diet composition was significantly related to body size, latitude, longitude, depth, and interannual (Chukchi Sea only) factors. Canonical correspondence analysis indicated body size was the most important factor contributing to the total variance in juvenile polar cod diet in the Chukchi and Beaufort Seas. Body size-based diet differences between the Chukchi and Beaufort Seas were evaluated using non-metric multidimensional scaling. This method revealed that similar-sized polar cod consumed similar-sized prey in both seas, but their diets were more benthically influenced in the Chukchi Sea and more pelagically influenced in the Beaufort Sea. Juvenile polar cod diet compositions vary by body size and region of inhabitance throughout their distribution. Here, we show that body size was the primary factor explaining variation in the summer diet of juvenile polar cod within the Chukchi and Beaufort Seas.

Seasonal spatial patterns in seabird and marine mammal distribution in the eastern Chukchi and western Beaufort seas: Identifying biologically important pelagic areas

The Chukchi and Beaufort seas are undergoing rapid climate change and increased human activity. Conservation efforts for upper trophic level predators such as seabirds and marine mammals require information on species’ distributions and identification of important marine areas. Here we describe broad-scale distributions of seabirds and marine mammals. We examined spatial patterns of relative abundance of seabirds and marine mammals in the eastern Chukchi and western Beaufort seas during summer (15 June–31 August) and fall (1 September–20 November) from 2007 to 2012. We summarized 49,206km of shipboard surveys for seabirds and 183,157km of aerial surveys for marine mammals into a grid of 40-km×40-km cells. We used Getis-Ord Gi∗ hotspot analysis to test for cells with higher relative abundance than expected when compared to all cells within the study area. We identified cells representing single species and taxonomic group hotspots, cells representing hotspots for multiple species, and cells representing hotspots for both seabirds and marine mammals. The locations of hotspots varied among species but often were located near underwater canyons or over continental shelf features and slopes. Hotspots for seabirds, walrus, and gray whales occurred primarily in the Chukchi Sea. Hotspots for bowhead whales and other pinnipeds (i.e., seals) occurred near Barrow Canyon and along the Beaufort Sea shelf and slope. Hotspots for belugas occurred in both the Chukchi and Beaufort seas. There were three hotspots shared by both seabirds and marine mammals in summer: off Wainwright in the eastern Chukchi Sea, south of Hanna Shoal, and at the mouth of Barrow Canyon. In fall, the only identified shared hotspot occurred at the mouth of Barrow Canyon. Shared hotspots are characterized by strong fronts caused by upwelling and currents, and these areas can have high densities of euphausiids in summer and fall. Due to the high relative abundance of animals and diversity of taxa, these sites are clearly important areas of congregation for seabirds and marine mammals that should be prioritized in the development of management and conservation plans.

Effects of recent decreases in arctic sea ice on an ice-associated marine bird

Recent major reductions in summer arctic sea ice extent could be expected to be affecting the distributions and life histories of arctic marine biota adapted to living adjacent to sea ice. Of major concern are the effects of ice reductions, and associated increasing SST, on the most abundant forage fish in the Arctic, Arctic cod (Boreogadus saida), the primary prey for the region’s upper trophic level marine predators. The black guillemot (Cepphus grylle mandtii) is an ice-obligate diving seabird specializing in feeding on Arctic cod and has been studied annually since 1975 at a breeding colony in the western Beaufort Sea. The data set is one of the few allowing assessment of the response of an upper trophic marine predator to recent decadal changes in the region’s cryosphere. Analysis of oceanographic conditions north of the colony from 1975 to 2012 for the annual period when parents provision young (mid-July to early September), found no major regime shifts in ice extent or SST until the late 1990s with major decreases in ice and increases in SST in the first decade of the 21st Century. We examined decadal variation in late summer oceanographic conditions, nestling diet and success, and overwinter adult survival, comparing a historical period (1975–1984) with a recent (2003–2012) one. In the historical period sea ice retreated an average of 1.8km per day from 15 July to 1 September to an average distance of 95.8km from the colony, while in the recent period ice retreat averaged 9.8km per day to an average distance of 506.9km for the same time period. SST adjacent to the island increased an average of 2.9°C between the two periods.While Arctic cod comprised over 95% of the prey provided to nestlings in the historical period, in the recent period 80% of the years had seasonal decreases, with Arctic cod decreasing to <5% of the nestling diet, and nearshore demersals, primarily sculpin (Cottidae), comprising the majority of the diet. A five-fold increase in the rate of nestling starvation and reductions in nestling growth and fledging mass were associated with the shift from Arctic cod. Annual adult survival during the nonbreeding season (September–May), showed no significant difference between the two periods, indicating no major change in availability of Arctic cod or other prey in the wintering area in the Bering Sea. Our findings of a substantial decrease in Arctic cod availability in late summer in response to decreased ice extent and increasing SST have implications for the entire Arctic given the ongoing and predicted basin-wide reductions in sea ice.

Fish communities across a spectrum of habitats in the western Beaufort Sea and Chukchi Sea

The increased scientific interest in the Arctic due to climate change and potential oil and gas development has resulted in numerous surveys of Arctic marine fish communities since the mid-2000s. Surveys have been conducted in nearly all Arctic marine fish habitats: from lagoons, beaches and across the continental shelf and slope. This provides an opportunity only recently available to study Arctic fish communities across a spectrum of habitats. We examined fish survey data from lagoon, beach, nearshore benthic, shelf pelagic and shelf benthic habitats in the western Beaufort Sea and Chukchi Sea. Specifically, we compare and contrast relative fish abundance and length (a proxy for age) among habitats and seas. We also examined ichthyoplankton presence/absence and abundance of dominant taxa in the shelf habitat. Our synthesis revealed more similarities than differences between the two seas. For example, our results show that the nearshore habitat is utilized by forage fish across age classes, and is also a nursery area for other species. Our results also indicated that some species may be expanding their range to the north, for example, Chinook Salmon. In addition, we documented the presence of commercially important taxa such as Walleye Pollock and flatfishes (Pleuronectidae). Our synthesis of information on relative abundance and age allowed us to propose detailed conceptual models for the life history distribution of key gadids in Arctic food webs: Arctic and Saffron Cod. Finally, we identify research gaps, such as the need for surveys of the surface waters of the Beaufort Sea, surveys of the lagoons of the Chukchi Sea, and winter season surveys in all areas. We recommend field studies on fish life history that sample multiple age classes in multiple habitats throughout the year to confirm, resolve and interpret the patterns in fish habitat use that we observed.

Physical and morphological properties of sea ice in the Chukchi and Beaufort Seas during the 2010 and 2011 NASA ICESCAPE missions

Physical and morphological properties of sea ice in the Chukchi and western Beaufort seas were measured during the 2010 and 2011 June−July ICESCAPE (Impacts of Climate on the Eco-Systems and Chemistry of the Arctic Pacific Environment) missions aboard the USCGC Healy. Observations of ice conditions, including ice thicknesses, types, and concentrations of primary, secondary, and tertiary categories were reported at 2-h intervals while the ship was in transit using the Antarctic Sea ice Processes and Climate (ASPeCt) protocol. On-ice surveys of ice thickness, melt-pond depth, and ice properties (including profiles of internal temperature, salinity, and isotopic composition) were conducted at 21 total ice stations (12 in 2010 and 9 in 2011). Comparison to historical ship-based observations confirms a multi-decadal transition from a multiyear to thinner, first year -dominated seasonal sea-ice pack in the region, with much earlier ice retreat than in past decades. The ice encountered was predominantly (>98%) first year, with un-deformed ice thicknesses ranging from 0.73 to 1.2m. Pond coverage was extensive, averaging 29% in 2010 and 19% in 2011, resulting in considerable light absorption in the ice and transmission of light to the ocean. Enhanced melting near the ice edge is consistent with transport of Pacific-origin heat and/or ice-albedo feedbacks. Sediment entrainment was visible in 7.5% and 10.9% of the ice in 2010 and 2011, respectively. Overall, the results indicate a regime shift in the characteristics of the ice cover has occurred in the region over recent decades, with substantive implications for thermodynamic forcing, light availability in the upper ocean, and biological and biogeochemical processes in the ice and water column beneath. The results presented have applications for the interpretation of optical and biological measurements in the Chukchi Sea and serve as record of ice conditions for assessing long-term change.

Seasonal ice loss in the Beaufort Sea: Toward synchrony and prediction

AbstractThe seasonal evolution of sea ice loss in the Beaufort Sea during 1979–2012 is examined, focusing on differences between eastern and western sectors. Two stages in ice loss are identified: the Day of Opening (DOO) is defined as the spring decrease in ice concentration from its winter maximum below a value of 0.8 areal concentration; the Day of Retreat (DOR) is the summer decrease below 0.15 concentration. We consider three aspects of the subject, i.e., (i) the long‐term mean, (ii) long‐term linear trends, and (iii) interannual variability. We find that in the mean, DOO occurs earliest in the eastern Beaufort Sea (EBS) owing to easterly winds which act to thin the ice there, relative to the western Beaufort Sea (WBS) where ice has been generally thicker. There is no significant long‐term trend in EBS DOO, although WBS DOO is in fact trending toward earlier dates. This means that spatial differences in DOO across the Beaufort Sea have been shrinking over the past 33 years, i.e., these dates are becoming more synchronous, a situation which may impact human and marine mammal activity in the area. Retreat dates are also becoming more synchronous, although with no statistical significance over the studied time period. Finally, we find that in any given year, an increase in monthly mean easterly winds of ∼1 m/s during spring is associated with earlier summer DOR of 6–15 days, offering predictive capability with 2–4 months lead time.

Temporal peaks in beluga whale (Delphinapterus leucas) acoustic detections in the northern Bering, northeastern Chukchi, and western Beaufort Seas: 2010–2011

Two populations of beluga whales (Delphinapterus leucas) migrate annually between their summering grounds in the eastern Chukchi and eastern Beaufort Seas, and overwintering areas in the Bering Sea. To contribute to the understanding of migratory streams of this highly vocal species, we investigated temporal peaks in acoustic detections from 4-year-long (2010–2011) recorders located in the northeastern Chukchi (inshore and offshore), western Beaufort, and northern Bering Seas. Beluga calls were detected throughout summer (July–August) in the western Beaufort; other studies suggest these animals are likely from the eastern Chukchi population. In autumn (September–November), calls were detected in the western Beaufort and northeastern Chukchi, which were likely from both the eastern Beaufort and eastern Chukchi populations. A strong peak at the inshore northeastern Chukchi site occurred in late-November; this peak is likely to be from the eastern Chukchi population. During spring, beluga calls were detected in the northeastern Chukchi and western Beaufort in two distinct vocal peaks (early- and late-May). The timing was consistent with the hypothesis that both vocal peaks were caused by the eastern Beaufort population. This suggests that migration of populations can be discriminated when temporal differences between vocal peaks are large enough to be identified as independent events. Our study results complement and support the population identity of peaks suggested by satellite telemetry, aerial surveys, and other acoustical studies. Passive acoustic monitoring improves our understanding of the migratory timing of beluga populations for management and conservation in a region undergoing rapid change.

Landfast sea ice extent in the Chukchi and Beaufort Seas: The annual cycle and decadal variability

Through analysis of over 2500 synthetic aperture radar (SAR) scenes spanning the period 1996–2008, we have compiled the most comprehensive dataset to date on landfast sea ice extent and its annual cycle in the Chukchi and Beaufort Seas. Our results show that landfast ice in the central and western Beaufort Sea forms earlier, breaks up later, occupies deeper water and extends further from shore than that in the Chukchi Sea. The differences in the timing of the annual landfast ice cycle are largely due to regional contrasts in the southward advance of pack ice in early winter and the onset of spring thaw. On the other hand, we suggest that the differences in landfast ice extent between the two seas are related to the number and distribution of recurring grounded ice features. These grounded features appear as “nodes” where the seaward landfast ice edge (SLIE) persistently recurs in multiple years. In the Beaufort Sea there are several such nodes that occur in water depths around 20m, giving rise to the similarity between the average SLIE location and the 20m isobath. We attribute the narrower landfast ice in the Chukchi Sea and lack of a consistent relationship with bathymetry to the sparsity of nodes in the Chukchi Sea. In comparing our results with data from the period 1973–76, we find that landfast ice extent in the Beaufort Sea has not changed significantly in the last four decades. However, in the Chukchi Sea our results show the landfast ice width has decreased by a coast-wide average of 13km over this period. We again attribute this difference between the two seas to the distribution of recurring grounded ice features. Over the 12 annual cycles in the study period, we identify trends indicating that landfast ice is forming later and disappearing earlier by approximately one week per decade. Although these trends are not statistically significant, they are in agreement with an overall shortening of the landfast ice season by as much as two months over the past three decades, revealed by a comparison with earlier findings for the period 1973–77.

Panmixia in Alaskan populations of the snow crab Chionoecetes opilio (Malacostraca: Decapoda) in the Bering, Chukchi, and Beaufort Seas

Decreasing sea ice in the Arctic is expected to impact marine ecosystems, and to lead to increased human activity in the form of shipping traffic, fishing pressure, and mineral resource exploration and extraction. In the face of these pressures, we examine genetic population structure in the snow crab Chionoecetes opilio (Fabricius, 1788), throughout its distribution in Alaskan waters, to determine degrees of population connectivity between the Arctic and more southerly portions of the species’ range. Snow crabs are widely distributed on the high-latitude continental shelves of North America, where they support a valuable commercial fishery in the United States and Canada. Fishing pressure in United States waters is currently concentrated in the Bering Sea, but large populations of snow crab also occur farther north in the Chukchi and Beaufort Seas. These northern stocks are not well studied, and not yet targeted by fisheries, although commercial-sized individuals were recently reported in areas of the Western Beaufort Sea. We used seven polymorphic microsatellite markers to examine tissue samples from 573 individual crabs collected at 12 sampling locations distributed across the Bering, Chukchi, and Beaufort Seas. These data indicate that Alaskan snow crabs constitute one large, panmictic population. Connectivity between fishery areas in the south and unexploited regions farther north thus appears to be substantial, perhaps due to a lengthy larval dispersal period and highly mobile adult population.

Dive Behavior of Eastern Chukchi Beluga Whales (&lt;i&gt;Delphinapterus leucas&lt;/i&gt;), 1998–2008

We provide an exploratory description of the dive behavior of 23 beluga whales of the eastern Chukchi Sea stock, tagged with satellite-linked time and depth recorders at Point Lay, Alaska, between 1998 and 2007. Because of differences in how transmitters were parameterized, we analyzed data from tags deployed from 1998 to 2002 (n = 20 tags) and data from tags deployed in 2007 (n = 3 tags) separately. Using cluster analysis, we found three basic dive types in the 1998–2002 dataset. “Shallow” diving behavior was characterized by dives mostly 50 m in depth. “Intermediate” diving behavior was characterized by having one mode near the surface and a second mode near 250 m. “Deep” diving behavior was characterized by having one mode near the surface and a second mode more than 400 m from the surface. The average number of dives per hour ranged from 5.1 (SD = 2.1) to 9.8 (SD = 2.9) across dive types, with the fewest dives per hour in the deep diving category. In general, duration of dives ranged from 1 to 18 minutes; however, dives up to 21 minutes occurred in the deepest diving category. We found little evidence that dive behavior of the belugas in our sample varied by sex or age. In general, belugas dove more deeply in the eastern Beaufort Sea than in the western Beaufort or Chukchi Seas. The depths to which belugas most commonly dive in Barrow Canyon and along the Beaufort shelf break (200–300 m) correspond to the boundary where colder Pacific water overlies warmer Atlantic water, which is probably where Arctic cod (Boreogadus saida) are most dense. Diving depths within the Arctic Basin suggest that belugas are foraging mostly within the warm layer of Atlantic Water (~200–1000 m).