Arctic Slope Research Articles

Stratigraphy and paleontology (plant and arthropod fossils) from the Late Neogene Niguanak site, Arctic Slope, Northern Alaska

ABSTRACT Motivated by the need for more paleodata for Pliocene paleoclimate data-model comparison, we revisited unpublished investigations of a fossiliferous site on the Niguanak River in Arctic North America. Analyses of the samples indicates forested conditions during an early phase of sedimentation in which environments were perhaps similar to those near tree line in the modern Anchorage area or farther south along the Pacific coast, whereas during a later phase of sedimentation, environments were characterized by shrub tundra vegetation and were possibly similar to the present-day conditions in the interior of southern Seward Peninsula. We describe the site stratigraphy and discuss the macrofossils and pollen recovered from the sediments, their paleoecological implications, and their significance for paleoclimate and sea ice. Mean annual temperatures were found to be 12.7°C warmer than current, with a pattern of much warmer winters, and less difference in summer warming as observed at other Pliocene Arctic sites. Finally, we discuss possible age assignments for the sediments, based on regional stratigraphy and geomorphology, and the probable sequence of evolution of arctic borderland climate and ecosystems.

Sibling Species Amblyraja hyperborea and A. jenseni in Slope Waters of Eastern Canada: An Ecomorphological Description

Deepwater survey data and specimens collected from the Grand Banks to Baffin Bay in the Northwest Atlantic were used to examine the distribution, morphometrics, meristics and maturity of two siblings, Amblyraja hyperborea and A. jenseni. Our study confirmed that the two species occupy different locations, their distributions separated by Davis Strait, a biogeographic break separating Atlantic from Arctic waters. A. hyperborea with a smaller maximum size and size at maturity inhabited colder Arctic slope waters in Baffin Bay while larger A. jenseni were located in warmer Atlantic slope waters. Despite their distributional separation and thus reproductive isolation, spine counts and body morphology were almost indistinguishable between species. Only upper jaw teeth row count and difference in the size of spines on the mid-rear wings differentiated the two species. Also, for both species, the proportion of dorsal fins joined, disc shape and relative tail length changed with total length. Secondary reproductive anatomy, clasper length and vas deferens weight, shell gland and uterus weight underwent initial acceleration in growth when the gonads transitioned to stage 2 (adolescent, maturing). Also, YOY A. hyperborea were found to distribute at shallower depths than larger stages, constituting a nursery, which was not observed for A. jenseni.

Associations between opioid overdose deaths and drugs confiscated by law enforcement and submitted to crime laboratories for analysis, United States, 2014–2019: an observational study

The overdose epidemic in the United States (US) continues to generate unprecedented levels of mortality. There is urgent need for a national data system capable of yielding high-quality, timely, and actionable information on existing and emerging drugs. Public health researchers have started using law enforcement forensic laboratory data to obtain surveillance information on illicit drugs. This study is the first to use drug reports from the entire US to examine correlations between a changing drug supply and increasing opioid-involved overdose deaths (OOD) on a national scale. This study is observational and investigates associations between law enforcement drug reports and OOD for the US from 2014 to 2019. OOD data are from the Centers for Disease Control and Prevention's National Vital Statistics System restricted-use multiple cause of death files. The US Drug Enforcement Administration's National Forensic Laboratory Information System (NFLIS) contains forensic laboratory-tested drug exhibit information for the entire US (NFLIS-Drug). Counts of forensic laboratory reports and OOD were aggregated for each state by month, quarter, and year. A difference-in-differences framework was used to estimate contemporaneous and lagged associations. Between 2014 and 2019 in the US, 249,522 OOD were reported, with the annual number nearly doubling from 28,723 to 50,179. OOD involving illicitly manufactured fentanyls (IMF) also increased substantially during this period, from 19.4% to 72.9%. In addition, 3,817,438 forensic laboratory reports in the US that were reported to NFLIS-Drug contained an opioid, stimulant, or benzodiazepine. Reports of fentanyl and fentanyl-related compounds (FFRC) had the strongest association with OOD. Each additional FFRC exhibit was associated with a 2.97% (95% CI: 1.7%, 4.1%) increase in OOD per 100,000 persons per quarter. Adding to the emerging consensus, protracted growth in IMF supply was more strongly associated with OOD than all other illicit drugs reported to NFLIS-Drug over the study time period. Findings demonstrate NFLIS-Drug data usefulness for research that require proxy indicators for the illicit drugs supply. A concerted effort between public health and public safety to make NFLIS-Drug more timely could strengthen its utility as a national, public health, drug surveillance system. Sangeetha Arctic Slope Mission Services, LLC, ASMS Contract No. ASM5-00017.

Unrecorded Tundra Fires of the Arctic Slope, Alaska USA

Few fires are known to have burned the tundra of the Arctic Slope north of the Brooks Range in Alaska, USA. A total of 90 fires between 1969 and 2022 are known. Because fire has been rare, old burns can be detected by the traces of thermokarst and distinct vegetation they leave in otherwise uniform tundra, which are visible in aerial photograph archives. Several prehistoric tundra burns have been found in this way. Detection of tundra fires in this sparsely populated and remote area has been historically inconsistent and opportunistic, relying on reports by aircraft pilots. Fire reports have been logged into an administrative database which, out of necessity, has been used to scientifically evaluate changes in the fire regime. To improve the consistency of the record, we completed a systematic search of Landsat Collection 2 for the Brooks Range Foothills ecoregion over the period 1972–2022. We found 57 unrecorded tundra burns, about 41% of the total, which now numbers 138. Only 15% and 33% of all fires appear in MODIS and VIIRS satellite-borne thermal anomaly products, respectively. The fire frequency in the first 37 years of the record is 0.89 y−1 for natural ignitions that spread ≥10 ha. Frequency in the last 13 years is 2.5 y−1, indicating a nearly three-fold increase in fire frequency.

Sea surface height anomaly and geostrophic current velocity from altimetry measurements over the Arctic Ocean (2011–2020)

Abstract. Satellite altimetry missions flying over the ice-covered Arctic Ocean have opened the possibility of further understanding changes in the ocean beneath the sea ice. This requires complex processing of satellite signals emerging from the sea surface in leads within the sea ice, with efforts to generate consistent Arctic-wide datasets of sea surface height ongoing. The aim of this paper is to provide and assess a novel gridded dataset of sea surface height anomaly and geostrophic velocity, which incorporates both the ice-covered and open ocean areas of the Arctic. Data from the CryoSat-2 mission in the period 2011–2020 were gridded at monthly intervals, up to 88∘ N, using the Data-Interpolating Variational Analysis (DIVA) method. To examine the robustness of our results, we compare our dataset to independent satellite data, mooring time series and Arctic-wide hydrographic observations. We find that our dataset is well correlated with independent satellite data at monthly timescales. Comparisons to in situ ocean observations show that our dataset provides reliable information on the variability of sea surface height and surface geostrophic currents over geographically diverse regions of the Arctic Ocean and different dynamical regimes and sea ice states. At all comparison sites we find agreement with in situ observed variability at seasonal to interannual timescales. Furthermore, we find that our geostrophic velocity fields can resolve the variability of boundary currents wider than about 50 km, a result relevant for studies of Arctic Ocean circulation. Additionally, large-scale seasonal features emerge. Sea surface height exhibits a wintertime Arctic-wide maximum, with the highest amplitude over the shelves. Also, we find a basin-wide seasonal acceleration of Arctic slope currents in winter. We suggest that this dataset can be used to study not only the large-scale sea surface height and circulation, but also the regionally confined boundary currents. The dataset is available in netCDF format from PANGAEA at https://doi.org/10.1594/PANGAEA.931869 (Doglioni et al., 2021d).

A large frozen debris avalanche entraining warming permafrost ground—the June 2021 Assapaat landslide, West Greenland

A large landslide (frozen debris avalanche) occurred at Assapaat on the south coast of the Nuussuaq Peninsula in Central West Greenland on June 13, 2021, at 04:04 local time. We present a compilation of available data from field observations, photos, remote sensing, and seismic monitoring to describe the event. Analysis of these data in combination with an analysis of pre- and post-failure digital elevation models results in the first description of this type of landslide. The frozen debris avalanche initiated as a 6.9 * 106 m3 failure of permafrozen talus slope and underlying colluvium and till at 600–880 m elevation. It entrained a large volume of permafrozen colluvium along its 2.4 km path in two subsequent entrainment phases accumulating a total volume between 18.3 * 106 and 25.9 * 106 m3. About 3.9 * 106 m3 is estimated to have entered the Vaigat strait; however, no tsunami was reported, or is evident in the field. This is probably because the second stage of entrainment along with a flattening of slope angle reduced the mobility of the frozen debris avalanche. We hypothesise that the initial talus slope failure is dynamically conditioned by warming of the ice matrix that binds the permafrozen talus slope. When the slope ice temperature rises to a critical level, its shear resistance is reduced, resulting in an unstable talus slope prone to failure. Likewise, we attribute the large-scale entrainment to increasing slope temperature and take the frozen debris avalanche as a strong sign that the permafrost in this region is increasingly at a critical state. Global warming is enhanced in the Arctic and frequent landslide events in the past decade in Western Greenland let us hypothesise that continued warming will lead to an increase in the frequency and magnitude of these types of landslides. Essential data for critical arctic slopes such as precipitation, snowmelt, and ground and surface temperature are still missing to further test this hypothesis. It is thus strongly required that research funds are made available to better predict the change of landslide threat in the Arctic.

Temporal and Spatial Variations in Particle Fluxes on the Chukchi Sea and East Siberian Sea Slopes From 2017 to 2018

Time-series sediment traps were deployed on the Chukchi Sea and East Siberian Sea slopes from August 2017 to August 2018 with the aim of elucidating the temporal and spatial variations in particle fluxes and identifying the main processes affecting those variations. Particle fluxes showed a typical seasonal pattern, with high values in summer and low values in other seasons, and a large inter-annual variation was observed only on the East Siberian Sea slope, where particle fluxes were one order of magnitude higher in early August 2018 than in late August 2017. This large inter-annual variation in particle flux resulted from the episodic intrusion of nutrient-enriched shelf water in the East Siberian Sea, which enhanced biological production at the surface and particle fluxes. The Chukchi Sea slope was influenced by the inflow of Anadyr Water, with high salinity and high nutrient concentrations, which had little annual variability. Therefore, particle flux showed little inter-annual variation on the Chukchi Sea slope. Under-ice phytoplankton blooms were observed in both the Chukchi Sea and East Siberian Sea slopes, and increases in particulate organic carbon (POC) flux and the C:N ratio under the sea ice were related to transparent exopolymer (TEP) production by ice algae. On the East Siberian Sea slope, particle fluxes increased slightly from 115 to 335 m, indicating lateral transport of suspended particulate matter; POC and lithogenic particles may be laterally transported to the slope as nutrient-rich shelf waters flowed from the East Siberian Sea to the Makarov Basin. Annual POC fluxes were 2.3 and 2.0 g C m–2 year–1 at 115 and 335 m, respectively, on the East Siberian Sea slope and was 2.1 g C m–2 year–1 at 325 m on the Chukchi Sea slope. Annual POC fluxes were higher on the Chukchi Sea and East Siberian Sea slopes than in Arctic basins, lower than on Arctic shelves, and generally similar to those on western Arctic slopes.

Periglacial slopewash dominated by solute transfers and subsurface erosion on a High Arctic slope

AbstractArctic slope hydrology studies suggest that water follows preferential subsurface flow paths known as water tracks. While subsurface flow is usually expected to transport only dissolved solids, periglacial studies have indicated some evidence of lessivage associated with flow through sorted patterned ground. We investigated the transport of dissolved and suspended sediments in water tracks on a polar desert slope, and linked this transport to slope and flow path geomorphology. Solute transfer was dominated by carbonate weathering products, and concentrations of other ions increased disproportionately when the active layer thawed. Suspended sediment transport occurred in water tracks, but fluxes were supply‐limited, indicating competent subsurface mechanical erosion. Solute mass fluxes were 5–10 times greater than sediment fluxes. In this dry landscape dominated by snowmelt, surface seepage leads to sediment deposition, while subsurface flow promotes lessivage. A conceptual model of nivation slopes is presented, taking into consideration the influence of flow path morphology and adaptation of the hydrological system to localized water sources from wind‐drifted snowbanks. Climate‐driven permafrost degradation and the increased frequency of rainfall events may result in new sediment sources and changes in flow pathways, modifying the physico‐chemical properties and ecology of downstream receiving waters.

The Impact of USArray on Earthquake Monitoring in Alaska

AbstractSeismic network coverage in Alaska has fundamentally changed with the presence of the USArray Transportable Array (TA) stations. These new stations provided an unprecedented opportunity to expand earthquake reporting in areas of Alaska that have not previously been instrumented. The Alaska Earthquake Center (AEC) has been incorporating all TA data into its standard earthquake analysis. The TA network is currently the second largest contributor of phase picks in the Alaska earthquake catalog, after the AK network operated by the AEC. Recent increases in reported earthquakes (about 45,000 in 2017 and 55,000 in 2018) are directly attributable to the additional TA stations, especially in the northern and western mainland Alaska. In some regions, the earthquake detection threshold decreased by as much as two units of magnitude. With the TA installation complete in 2017, the detection threshold over the entire mainland Alaska region is M∼1.5. The new stations have also led to a decrease in hypocentral location errors, which are now more uniform over the entire mainland Alaska region. The uniformity of the TA network made it possible, for the first time, to make quantitatively valid comparisons of microseismic activity in different parts of the state. Among other observations, this uniform coverage helped demonstrate that the quiescence that has long been inferred in the central and western Arctic Slope region appears to be real, and not just an artifact of network coverage. This combined network should, with time, provide vastly better data for seismic hazard assessments in an area of increasing national interest.

Sources and sink of black carbon in Arctic Ocean sediments

The concentrations and carbon isotopic (13C, 14C) compositions of total organic carbon (TOC) and black carbon (BC) were measured for four sediment cores collected from the shelf to slope in the Arctic Ocean. Contents of TOC and BC ranged from 0.46% to 1.94% and 0.04% to 0.13% by dry weight, and BC accounted for 3.5% to 15.2% of the TOC preserved in the shelf and slope sediments. Sediment of the Chukchi shelf contained relatively high BC contents compared with the sediments of the Arctic slope, suggesting strong influence from the river and terrestrial inputs to the shelf region. Radiocarbon measurements revealed that the ages of BC are in the range of 7330 to 29,700 years (before present) and they are 4093 to 7723 years older than the 14C ages of TOC preserved in the same sediment depths. Based on an isotopic mass balance model, we calculated that fossil fuel combustion contributed 62–96%, and biomass burning contributed 4–38% of the BC pool in the sediments of the study area. This “slow-cycling” old BC is an important fraction of the inert organic carbon pool preserved in the sediments, and represents a significant sink of atmospheric CO2 and global carbon cycle. With the thawing permafrost caused by continuous global warming, the size of this BC pool mobilized and exported by rivers to the Arctic Ocean could increase in the future.

Proxies for heat fluxes to the Arctic Ocean through Fram Strait

Oceanic fluxes through Fram Strait may significantly contribute to climate variations in the Arctic. However, their observations are difficult. Here, a 26-year numerical model simulation is used to derive oceanic proxies for interannual variability in heat fluxes through Fram Strait. It is found that variability in the cross-slope gradient of sea surface height (SSH) across the West Spitsbergen Current (WSC) can explain about 90% of the variance of winter and annual mean volume transports of Atlantic water at 79°N. Given the strong covariance between the simulated heat flux in the slope current along Svalbard and the corresponding volume transport, variability of the SSH gradient across the WSC is also found to account for about 80% of the variance of heat flux associated with the northward flow through Fram Strait. Moreover, variations in the SSH gradient across the Arctic Slope Current (ASC) northeast of Svalbard at 31°E explain about 85% of the variance of heat flux there and about 80% of the variance of the net heat flux upstream through Fram Strait. Finally, about 85% and 75% of the variance of the net heat flux through Fram Strait is associated with anomalies of the eastward volume transport and depth-averaged core velocity in the ASC, respectively. These relations indicate that monitoring of the flow in the ASC, even with a single current meter mooring, or of the SSH gradient across this current derived from either in situ or remote measurements may provide useful proxies for the heat import to the Arctic Ocean.

Water runoff vs modern climatic warming in mountainous cryolithic zone in North-East Russia

The article presents the results of studying the effects of current climatic warming for both surface and subsurface water runoffs in North-East Russia, where the Main Watershed of the Earth separates it into the Arctic and Pacific continental slopes. The process of climatic warming is testified by continuous weather records during 80-100 years and longer periods. Over the Arctic slope and in the northern areas of the Pacific slope, climatic warming results in a decline in a total runoff of rivers whereas the ground-water recharge becomes greater in winter low-level conditions. In the southern Pacific slope and in the Sea of Okhotsk basin, the effect of climatic warming is an overall increase in total runoff including its subsurface constituents. We believe these peculiar characters of river runoff there to be related to the cryolithic zone environments. Over the Arctic slope and the northern Pacific slope, where cryolithic zone is continuous, the total runoff has its subsurface constituent as basically resulting from discharge of ground waters hosted in seasonally thawing rocks. Warmer climatic conditions favor growth of vegetation that needs more water for the processes of evapotranspiration and evaporation from rocky surfaces in summer seasons. In the Sea of Okhotsk basin, where the cryolithic zone is discontinuous, not only ground waters in seasonally thawing layers, but also continuous taliks and subpermafrost waters participate in processes of river recharges. As a result, a greater biological productivity of vegetation cover does not have any effect on ground-water supply and river recharge processes. If a steady climate warming is provided, a continuous cryolithic zone can presumably degrade into a discontinuous and then into an island-type permafrost layer. Under such a scenario, there will be a general increase in the total runoff and its subsurface constituent. From geoecological viewpoints, a greater runoff will have quite positive effects, whereas some minor negative consequences of it can be successfully prevented.

Seasonal and interannual variability of the Arctic sea ice: A comparison between AO-FVCOM and observations

A high-resolution (up to 2 km), unstructured-grid, fully ice-sea coupled Arctic Ocean Finite-Volume Community Ocean Model (AO-FVCOM) was used to simulate the sea ice in the Arctic over the period 1978–2014. The spatial-varying horizontal model resolution was designed to better resolve both topographic and baroclinic dynamics scales over the Arctic slope and narrow straits. The model-simulated sea ice was in good agreement with available observed sea ice extent, concentration, drift velocity and thickness, not only in seasonal and interannual variability but also in spatial distribution. Compared with six other Arctic Ocean models (ECCO2, GSFC, INMOM, ORCA, NAME, and UW), the AO-FVCOM-simulated ice thickness showed a higher mean correlation coefficient of ∼0.63 and a smaller residual with observations. Model-produced ice drift speed and direction errors varied with wind speed: the speed and direction errors increased and decreased as the wind speed increased, respectively. Efforts were made to examine the influences of parameterizations of air-ice external and ice-water interfacial stresses on the model-produced bias. The ice drift direction was more sensitive to air-ice drag coefficients and turning angles than the ice drift speed. Increasing or decreasing either 10% in water-ice drag coefficient or 10° in water-ice turning angle did not show a significant influence on the ice drift velocity simulation results although the sea ice drift speed was more sensitive to these two parameters than the sea ice drift direction. Using the COARE 4.0-derived parameterization of air-water drag coefficient for wind stress did not significantly influence the ice drift velocity simulation.

Mesoscale Climatology and Variation of Surface Winds over the Chukchi–Beaufort Coastal Areas

Abstract The detailed mesoscale climatology of surface winds in the Chukchi–Beaufort Seas and adjacent Arctic Slope region is analyzed using the recently developed Chukchi–Beaufort High-Resolution Atmospheric Reanalysis (CBHAR). Within the study area, surface winds are mainly driven by the prevailing synoptic weather patterns of the Beaufort high and Aleutian low and are further modulated by local geographic features through thermodynamic and dynamic processes. Sea breezes, up- or downslope winds, and the mountain barrier jets are all clearly captured by CBHAR. Sea breezes emerge in June–September and last most of the day, with a maximum spatial extent 100 km inland and 50 km offshore and maximum speed around 1–3 m s−1 in the late afternoon [~1500 Alaska standard time (AKST)]. Thermodynamic impacts of mountains on the surface winds vary from time to time. Drainage flows begin to build at the mountaintop in September and reach the strongest during November–February, occupying the entire slope. Upslope winds demonstrate a clear diurnal cycle during summer, starting to build around 0900 local time, reaching the maximum strength around 1500 local time and continuing until 2100 local time. The mountain barrier jets (MBJs) are found to be most active around the Chukotka Mountains during cold seasons. Both sea breezes and MBJs are also subject to variations and changes in response to adjusted large-scale atmosphere circulation. Storm activities can inhibit the development of sea breezes. Different responses from the Beaufort high and Aleutian low to anomalies in large-scale circulations play a vital role in the variations of MBJ activities over the Chukotka Mountains.

Sediment color cycles and their causes in the western Arctic Ocean and Bering Sea

A challenge that limits high-latitude paleo-environment investigations is the lack of foraminiferal shell-bearing sediments for stratigraphy constructions. In the Arctic, the Mn-rich brown layers have been proposed as a new approach to establish glacial-interglacial timescale stratigraphy, but their formation mechanisms remain unclear. Until now, only a limited number of sediment cores with Mn-rich brown layers have been studied, and it has been argued that these layers were formed by diagenesis. During past several years, China expeditions have collected many sediment cores from the western Arctic Ocean and Bering Sea offering an opportunity to investigate sediment color cycles in these regions. In this study, we have studied 14 sediment cores from wide geographic and topographic regions including basin, continental slope, continental shelf, and off-shore deep-sea. First, core images were taken by a line scan camera and high-resolution color reflectance was measured by a spectrometer. Second, core sediments were scanned at 1 cm resolution by an XRF core scanner to obtain element content variations. Third, sediment layers with maxima and minima Mn based on XRF data were analyzed by ICP-OES and ICP-MS to crosscheck the reliability of XRF results and provide precise element concentration. Our results show that 9 cores from slope and basin of the western Arctic bear color cycles which can be effectively indicated by a */ b * ratios, as a * is chromatic value from green to red while b * is chromatic value from blue to yellow. In each of these cores, a */ b * ratios co-vary with contents of Mn and some other redox sensitive trace elements such as Cu, Co, Ni, and especially Mo. Data comparison shows that MnO and Mo concentrations at peak values in the cores gradually decrease, respectively, from 5.22% and 80 ppm on the slope to nearly 1% and 30 ppm in the central basin, whereas minimal MnO and Mo concentrations in these cores always stay around 0.1% and <10 ppm, respectively. By contrast, the 5 sediment cores from Bering Sea, continental shelf and off-shore deep-sea of the Western Arctic show (i) no cycle in color, a */ b *, Mn, or Mo, (ii) no correlation between a */ b *, Mn, or Mo, and (iii) generally very low MnO and Mo contents comparable to average values of weathered continents. Based on independent stratigraphy of several cores and considering previous work in this region, we propose the following mechanism for the formation of sediment color cycles in the Western Arctic. During interglacial, a substantial amount of weathered terrigenous Mn-bearing minerals and Mn2+ containing waters are transported by rivers into continental shelves of the Arctic Ocean, where many minerals are subsequently weathered to release additional Mn2+. Although upper waters on continental shelves are oxidizing, bottom waters are more reducing due to the respiration of organic matter, which prevents Mn2+ in waters from being oxidized into MnO x deposits in sediments. This leaves significant amount of Mn2+ to be transported to the Arctic basin by Pacific waters entered through the Bering Strait. Furthermore, Mn-bearing debris carried by sea ice during winter is moved towards the Arctic basin during summer. On the Arctic slope, Mn2+ is oxidized and deposited in the form of MnO x due to little organic matter, making sediments brown color. Also, most Mn-bearing debris is deposited because summer sea ice boundary is located around the slope. Remaining Mn2+ is then further dispersed into other areas in oxidizing waters by ocean currents and is eventually deposited to form brown sediments at depth. While during glacial periods, cold climate and reduced continent exposure due to more extensive ice cover would decrease Mn transportation to the Arctic, resulting in the formation of yellow or dark-grey sediments with low-Mn. If diagenetic influences can be taken into account, cycles of color and Mn content could be used as indicators for glacial-interglacial cycles in the Western Arctic.

Circulation in the Arctic Ocean: Results from a high-resolution coupled ice-sea nested Global-FVCOM and Arctic-FVCOM system

A high-resolution unstructured-grid global-regional nested ice-current coupled FVCOM system was configured for the Arctic Ocean and used to examine the impact of model resolution and geometrical fitting on the basin-coastal scale circulation and transport in the pan-Arctic. With resolving steep bottom slope and irregular coastal geometry, the model was capable of simulating the multi-scale circulation and its spatial variability in the Arctic Basin and flow through the Bering Strait, Fram Strait and Canadian Archipelago. The model-simulated annual-mean velocities were in good agreement with observations within the measurement uncertainty and variability due to insufficient sampling. The errors in the flow direction varied with the flow speed, larger in the weak velocity zone and smaller as the velocity increased. In the upper 50-m layer, the annual-mean circulation pattern was dominated by the wind- and ice-drifting-induced anticyclonic circulation in the Arctic Basin and a relatively strong cyclonic slope current along the edge of the continental shelf. In the deep 200–600-m layer, a relatively permanent cyclonic circulation occurred along the steep bottom slope. These annual-mean circulations accounted for ∼85% of the total kinetic energy variance. De-trending the mean flow, an empirical orthogonal function (EOF) analysis showed that the semi-annual and seasonal variability of the sub-tidal flow was dominated by the first and second modes that accounted for ∼46% and ∼30% of the total variance in the upper 50-m layer and ∼58% and 20% in the deep 200–600-m layer. Consistent with observations, the AO-FVCOM-simulated cyclonic slope flow was characterized by a large positive topostrophy. Sensitivity experiment results with various grid configurations suggested that the currents over slopes, narrow straits and water passages featured topographic and baroclinic frontal dynamical scales associated with bathymetric slope and internal Rossby deformation radius. Over the Arctic slope, since these two scales are in the same order, the along-slope current could be captured, as the cross-isobath model resolution was refined to resolve the steep bottom topography. Under this condition, there is no need to add Neptune forcing into the momentum equations. The accuracy of the estimation of the transport through the strait and narrow water passage was affected by the model resolution. In Fram Strait where the flow is characterized by strong lateral current shear resulting from the Atlantic inflow and Arctic outflow, the transport estimation could have a significant uncertainty due to both horizontal and vertical sampling resolutions.

Circumpolar oil-and-gas-bearing basins of the arctic part of the North American continent

Major geotectonic elements of the reviewed territory of the Arctic part of the North American continent are the Hyperborean Precambrian Platform, the Franklin folding belt, the northern part of the Precambrian Canadian platform, and the Mesozoic folding belt of Canada and Alaska. The rise of the Arctic slope of Alaska, the Beaufort Sea, and the Sverdrup basin are located in the southern margins of the Hyperborean Platform. The structure and peculiarities of development of these structural elements are genetically related to the evolution of this platform, as well as the current state of petroleum potential of the most promising exploration region of Arctic in the 21st century. The forced exploration of the Arctic regions of the United States and Canada has become an important milestone in the current development of the world energetics. Up to 100 oil, gas, and gas condensate fields have been discovered as a result of violent studies, and the potential oil and gas reserves in the Arctic part of the North American continent have been estimated to 30 billiion t and 50 trillion cubic meters, respectively. Many prospects are related to the continental slopes of all three above-mentioned basins; the total potential reserves of slopes are estimated as 10–12 billion t of oil and 20–25 trillion cubic meters of gas.

In the Warming Arctic Seas

In the Warming Arctic Seas

Temperature data acquired from the DOI/GTN-P Deep Borehole Array on the Arctic Slope of Alaska, 1973–2013

Abstract. A homogeneous set of temperature measurements obtained from the DOI/GTN-P Deep Borehole Array between 1973 and 2013 is presented; DOI/GTN-P is the US Department of the Interior contribution to the Global Terrestrial Network for Permafrost (GTN-P). The 23-element array is located on the Arctic Slope of Alaska, a region of cold continuous permafrost. Most of the monitoring wells are situated on the Arctic coastal plain between the Brooks Range and the Arctic Ocean, while others are in the foothills to the south. The data represent the true temperatures in the wellbores and surrounding rocks at the time of the measurements; they have not been corrected to remove the thermal disturbance caused by drilling the wells. With a few exceptions, the drilling disturbance is estimated to have been on the order of 0.1 K or less by 1989. Thus, most of the temperature measurements acquired during the last 25 yr are little affected by the drilling disturbance. The data contribute to ongoing efforts to monitor changes in the thermal state of permafrost in both hemispheres by the Global Terrestrial Network for Permafrost, one of the primary subnetworks of the Global Terrestrial Observing System (GTOS). The data will also be useful for refining our basic understanding of the physical conditions in permafrost in Arctic Alaska, as well as providing important information for validating predictive models used for climate impact assessments. The processed data are available from the Advanced Cooperative Arctic Data and Information Service (ACADIS) repository at doi:10.5065/D6N014HK.

Toward Producing the Chukchi–Beaufort High-Resolution Atmospheric Reanalysis (CBHAR) via the WRFDA Data Assimilation System

Abstract The Weather Research and Forecasting Model (WRF) and its variational data assimilation system (WRFDA) are applied to the Chukchi–Beaufort Seas and adjacent Arctic Slope region for high-resolution regional atmospheric reanalysis study. To optimize WRFDA performance over the study area, a set of sensitivity experiments are carried out to analyze the model sensitivity to model background errors (BEs) and the assimilation of various observational datasets. Observational data are assimilated every 6 h and the results are verified against unassimilated observations. In the BE sensitivity analyses, the results of assimilating in situ surface observations with a customized, domain-dependent BE are compared to those using the WRF-provided global BE. It is found that the customized BE is necessary in order to achieve positive impacts from WRFDA assimilation for the study area. When seasonal variability is incorporated into the customized BE, the impacts are minor. Sensitivity analyses examining the assimilation of different datasets via WRFDA demonstrate that 1) positive impacts are always seen through the assimilation of in situ surface and radiosonde measurements, 2) assimilating Quick Scatterometer (QuikSCAT) winds improves the simulation of the 10-m wind field over ocean and coastal areas, and 3) selectively assimilating Moderate Resolution Imaging Spectroradiometer (MODIS) retrieved profiles under clear-sky and snow-free conditions is essential to avoid degradation of assimilation performance, while assimilation of Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) retrievals has little impact, most likely due to limited data availability. Based on the sensitivity results, a 1-yr (2009) experimental reanalysis is conducted and consistent improvements are achieved, particularly in capturing mesoscale processes such as mountain barrier and sea-breeze effects.