The distribution of suspended particles in the Southern Beaufort Sea

The Mackenzie River estuary serves as an avenue for suspended particles to pass seaward. The horizontal distribution of surface suspended particles is compartible with the distribution of low-salinity surface waters. The water structure in the shelf area is highly stratified in summer due to a thin upper layer of low-salinity which has a high concentration of suspended particles. The concentration of suspended particles decreases with depth, but near the bottom a turbid layer had often been observed. It is likely that bottom current energy high enough to erode and maintain in suspension the bottom sediments below 15m in diameter does occur over this shelf area.     

Development of an integrated fisheries co-management framework for new and emerging commercial fisheries in the Canadian Beaufort Sea

The Canadian Beaufort Sea is one of the last places on Earth that has not experienced large-scale commercial fisheries. The aboriginal people of the western Canadian Arctic, the Inuvialuit, have become increasingly concerned about the potential effects of large-scale commercial operations on key subsistence species of fish and marine mammals and the marine ecosystem upon which they depend. A 1984 comprehensive land settlement agreement (treaty) between Canada and the Inuvialuit established a co-management regime for limited aspects of fish and marine mammal resource management, and gave the Inuvialuit rights to subsistence fisheries and existing commercial fisheries but no preference for new commercial fisheries. The Fisheries Joint Management Committee (the fisheries co-management body), the Canada Department of Fisheries and Oceans, the Inuvialuit Regional Corporation and the Inuvialuit Game Council have developed an integrated fisheries management framework agreement for the review and assessment of any proposed commercial fisheries within the Canadian Beaufort Sea. The agreement provides clarity and transparency for decision making and strengthens the protection of fish stocks. The development of the framework depended upon a history of cooperation between the parties and a bridging initiative by the Fisheries Joint Management Committee and an NGO that brought together the Inuvialuit and the government.     

Phytoplankton community adaptation to changing light levels in the southern Beaufort Sea,Canadian Arctic

The chlorophyll a specific absorption coefficient of phytoplankton, a_φ^∗(λ) is an important parameter to determine for primary production models and for the estimation of phytoplankton physiological condition. Knowledge of this parameter at high latitudes where nutrient rich cold water submitted to low incident light is a common environment is almost nonexistent. To address this issue, we investigated the light absorption properties of phytoplankton as a function of irradiance, temperature, and nutrients using a large data set in the southern Beaufort Sea during the open water to ice cover transition period. The a_φ^∗(λ) tended to increase from autumn when open water still existed to early winter when sea ice cover was formed, resulting from a biological selection of smaller-size phytoplankton more efficient to absorb light. There was no significant correlation between a_φ^∗(λ) and irradiance or temperature for both seasons. However, a_φ^∗(λ) showed a significant positive correlation with NO₃ + NO₂. Implications of the results for phytoplankton community adaptation to changing light levels are discussed.     

Shelf Waves in the Beaufort Sea in a High-Resolution Ocean Model

Oceanology - The article examines low-frequency oscillations of sea level over the Beaufort Sea shelf simulated in a high-resolution regional configuration of the Massachusetts Institute of...     

Late Holocene paleoceanography and climate variability over the Mackenzie Slope (Beaufort Sea,Canadian Arctic)

Late Holocene paleoceanography and climate variability of the Southeastern Beaufort Sea (Canadian Arctic) have been investigated on the basis of sedimentary cores collected over the Mackenzie Slope. Piston, trigger and box cores were sampled at station 803 in 2004 aboard the CCGS Amundsen at 218 m water depth. The chronology of the piston core is constrained by 4 AMS-¹⁴C dates, as the sedimentation rate in the box core is assessed from ²¹⁰Pb data. We obtain a continuous composite sequence covering the last 4600 years, with a sedimentation rate of ~ 140 cm.kyr^? 1. Transfer functions (modern analogue technique) based on dinoflagellate cyst (dinocyst) assemblages were used to reconstruct the evolution of sea-surface conditions over the time period covered by the cores.Palynological data reveal that dinocyst assemblages are dominated by Operculodinium centrocarpum sensu lato (mean of 43.3%) throughout the core, with the accompanying taxa Brigantedinium spp. (19.6%), Islandinium minutum (15.6%) and cysts of Pentapharsodinium dalei (13.7%). Four zones have been established on the basis of dinocyst relative abundances. Dinocyst assemblage zone 1 (D1), from 4600 to 2700 cal years BP, is dominated by O. centrocarpum (mean of 49.0%). In zone D2 (2700–1500 cal years BP), the relative abundances of O. centrocarpum decrease (34.4%) in favour of the opportunistic, heterotrophic taxa Brigantedinium spp. (28.8%) and cysts of Polykrikos sp. var. arctic/quadratus (2.8%). Dinocyst zone D3 (1500–30 cal years BP or 450–1920 AD) is characterised by the high relative abundance of the peridinioid taxa I. minutum (19.9%). The last zone (D4), spanning from 1920 to 2004 AD, is again dominated by O. centrocarpum (44.5%), and shows low relative abundances of Brigantedinium spp. and cf. Echinidinium karaense.Quantitative reconstructions of past sea-surface parameters (August sea-surface temperature: SST, August sea-surface salinity: SSS, and duration of sea-ice cover) indicate relatively stable conditions over the last 4.6 kyr, with episodic cooling events (SST of ~ 1.5 °C below the modern value of 6 °C) that took place between 700 and 1820 AD. We associate the last and the longest of these cooling events (1560–1820 AD) with the Little Ice Age. Reconstructed SSS shows decadal oscillations since 1920 AD that we tentatively associate with the accumulation of freshwater by the Beaufort Gyre and the subsequent Great Salinity Anomalies. Our data suggest that similar salinity anomalies could have occurred ca. 1860 and 1790 AD.Stable isotopic data show a slight increase in δ¹³C values (from ~?27.1‰ at the base to ~?25.8‰ at the top) over the last 4.6 kyr that we associate with the gradual increase in atmospheric CO₂ concentration as recorded by Antarctic ice cores. Variations in the δ¹⁵N profile suggest variations in Pacific water influence from 4600 to ~ 1300 cal years BP, associated with centennial scale shifts of the Arctic Oscillation phases.     

GIS Based Marine Platinum Exploration, Goodnews Bay Region, Southwest Alaska

Goodnews Bay, southwest Alaska, is known for platinum (Pt) reserve that extends offshore in the Bering Sea. To assess the nearshore placer potential we first collated marine Pt concentrations available since 1960 in a geographic information system (GIS) database. Subsequently, in 2005, we collected 23 pipe dredge sediment samples and 26 vibracores from unexplored sites and analyzed them for Pt. This sampling was supplemented by magnetic (Sea Spy) and seismic (side scan, geoacoustic and datasonic bubble pulser) surveys. Integrating results of geospatial analysis of Pt concentrations with geophysical analysis using GIS techniques led to delineate four locations encouraging for further Pt exploration. Of these, two locations fall close to paleochannels and drowned ultramafic source, while the other two coincide with high energy environments in the Goodnews Bay and close to the Carter Bay.     

中国远洋渔业发展历程及其特征

自1985年起,我国远洋渔业经历空白期(1949—1971年)、积极筹备期(1972—1984年)、起步期(1985—1990年)、快速发展期(1991—1997年)、调整期(1998—2006年)和优化期(2007年至今)6个发展阶段。我国远洋渔业快速发展,得益于国家适时出台的一系列扶持政策及指导意见。我国远洋渔业法律法规体系已初步建立,并在不断完善。金枪鱼、鱿鱼、南极磷虾和竹荚鱼为我国远洋渔业的主要品种。我国远洋渔业事业仍存在发展后劲不足,捕捞方式落后,国际合作门槛进一步提高,过度依赖海外市场等问题。远洋渔业仍需政府部门大力扶持,进一步深化供给侧结构性改革,对渔船进行升级换代,大力培养国际渔业履约团队,国内外市场协同发展。     

The ICE-MOSES experiment: Mapping permafrost zones electrically beneath the Beaufort Sea

A novel variation of the geophysical technique known as MOSES, for Magnetometric Off-Shore Electrical Sounding, has been developed to map the electrical properties of the sea floor in Aretic regions. The particular target is the permafrost layer under the Beaufort Sea, a layer containing frozen or partially frozen sediment from 100 to 600 m thick underlying shallow sea water, typically 10 to 100 m deep, and several tens of metres of soft sediment. A detailed knowledge of the location and physical properties of the permafrost layer is essential for accurate interpretation of reflection seismic data. The permafrost can contain pockets, regions or layers of gas hydrate. The latter is both a possible resource and a hazard to drilling operations or hydrocarbon production. A local map of the permafrost zone is essential geotechnical information required prior to the construction of an offshore structure or pipeline.The MOSES method is particularly suitable for offshore electrical mapping as it can be made relatively insensitive to the shielding effects of the highly conductive sea water, in sharp contrast to many other electrical techniques. The transmitter is a vertical, long-wire bipole, extending from the sea surface to the sea floor. A commutated current is fed to two large electrodes: one near the sea surface and the other on the sea floor. The return current is through the sea water and the subjacent sediment. The receiver consists of two horizontal orthogonal coils located on the sea floor, and the data are measurements of two components of the magnetic field as a function of frequency and transmitter-receiver horizontal separation.The electrical conductivity of a sample of frozen material is much smaller than that of unfrozen or partially frozen sediment of the same type. Frozen and unfrozen thin layers are often observed sequentially throughout the geological section. The resistivity measured as a function of depth by an electrical logging tool is consequently highly variable. The resulting depth-averaged resistivity, the resistivity resolved by a surface electrical method, is macro-an-isotropic. An experimental design study reveals that both the vertical and horizontal averaged resistivities could be determined in a MOSES sounding without vertical scale distortion.A test of the methodology in very shallow water was conducted in the spring of 1986 at a site, approximate coordinates (70° N, 134.5° W), 85 km north-west of the town of Tuktoyaktuk. The instrumentation was lowered and subsequently recovered through holes in the ice which covers the Beaufort Sea at that time of the year. The transmitter power was obtained from a single lead-acid battery. Transmitter-receiver separations ranged from 10 to 300 m. A rapid increase in sediment resistivity with depth was observed. The higher resistivity values are consistent with those expected for a partially frozen zone.     

Upwelling in the Alaskan Beaufort Sea: Atmospheric forcing and local versus non-local response

The spin up and relaxation of an autumn upwelling event on the Beaufort slope is investigated using a combination of oceanic and atmospheric data and numerical models. The event occurred in November 2002 and was driven by an Aleutian low storm. The wind field was strongly influenced by the pack-ice distribution, resulting in enhanced winds over the open water of the Chukchi Sea. Flow distortion due to the Brooks mountain range was also evident. Mooring observations east of Barrow Canyon show that the Beaufort shelfbreak jet reversed to the west under strong easterly winds, followed by upwelling of Atlantic Water onto the shelf. After the winds subsided a deep eastward jet of Atlantic Water developed, centered at 250 m depth. An idealized numerical model reproduces these results and suggests that the oceanic response to the local winds is modulated by a propagating signal from the western edge of the storm. The disparity in wave speeds between the sea surface height signal—traveling at the fast barotropic shelf wave speed—versus the interior density signal—traveling at the slow baroclinic wave speed—leads to the deep eastward jet. The broad-scale response to the storm over the Chukchi Sea is investigated using a regional numerical model. The strong gradient in windspeed at the ice edge results in convergence of the offshore Ekman transport, leading to the establishment of an anti-cyclonic gyre in the northern Chukchi Sea. Accordingly, the Chukchi shelfbreak jet accelerates to the east into the wind during the storm, and no upwelling occurs west of Barrow Canyon. Hence the storm response is fundamentally different on the Beaufort slope (upwelling) versus the Chukchi slope (no upwelling). The regional numerical model results are supported by additional mooring data in the Chukchi Sea.     

Linkages among halocline variability,shelf-basin interaction,and wind regimes in the Beaufort Sea demonstrated in pan-Arctic Ocean modeling framework

To address the mechanisms controlling halocline variability in the Beaufort Sea, the relationship between halocline shoaling/deepening and surface wind fields on seasonal to decadal timescales was investigated in a numerical experiment. Results from a pan-Arctic coupled sea ice-ocean model demonstrate reasonable performances for interannual and decadal variations in summer sea ice extent in the entire Arctic and in freshwater content in the Canada Basin. Shelf-basin interaction associated with Pacific summer and winter transport depends on basin-scale wind patterns and can have a significant influence on halocline variability in the southern Beaufort Sea. The eastward transport of fresh Pacific summer water along the northern Alaskan coast and Ekman downwelling north of the shelf break are commonly enhanced by cyclonic wind in the Canada Basin. On the other hand, basin-wide anti-cyclonic wind induces Ekman upwelling and blocks the eastward current in the Beaufort shelf-break region. Halocline shoaling/deepening due to shelf-water transport and surface Ekman forcing consequently occur in the same direction. North of the Barrow Canyon mouth, the springtime down-canyon transport of Pacific winter water, which forms by sea ice production in the Alaskan coastal polynya, thickens the halocline layer. The model result indicates that the penetration of Pacific winter water prevents the local upwelling of underlying basin water to the surface layer, especially in basin-scale anti-cyclonic wind periods.     

东海区科技兴海产业示范基地发展模式研究与探索

科技兴海是我国推动海洋经济发展和产业结构调整的重大举措。文章概述东海区科技兴海产业示范基地的建设情况,明确其有力促进具有鲜明特色的海洋战略性新兴产业的集聚发展和海洋经济的转型升级,总结市场运营的"临港模式"、政府主导的"厦门模式"、特色产业的"大丰模式"和地方特色的"诏安模式"等发展经验,提出突出特色,形成独具一格的发展模式;定位清晰,政府服务和市场运营相辅相成;凝聚产业,以品牌提升产业链核心价值;形成示范,创新支持方式和管理模式的示范基地发展建议。     

Classification of the Alaskan Beaufort Sea Coast and estimation of carbon and sediment inputs from coastal erosion

A regional classification of shoreline segments along the Alaskan Beaufort Sea Coast was developed as the basis for quantifying coastal morphology, lithology, and carbon and mineral sediment fluxes. We delineated 48 mainland segments totaling 1,957 km, as well as 1,334 km of spits and islands. Mainland coasts were grouped into five broad classes: exposed bluffs (313 km), bays and inlets (235 km), lagoons with barrier islands (546 km), tapped basins (171 km) and deltas (691 km). Sediments are mostly silts and sands, with occasional gravel, and bank heights generally are low (2–4 m), especially for deltas (<1 m). Mean annual erosion rates (MAER) by coastline type vary from 0.7 m/year (maximum 10.4 m/year) for lagoons to 2.4 m/year for exposed bluffs (maximum 16.7 m/year). MAERs are much higher in silty soils (3.2 m/year) than in sandy (1.2 m/year) to gravelly (–0.3 m/year) soils. Soil organic carbon along eroding shorelines (deltas excluded) range from 12 to 153 kg/m² of bank surface down to the water line. We assume carbon flux out from depositional delta sediments is negligible. Across the entire Alaskan Beaufort Sea Coast, estimated annual carbon input from eroding shorelines ranges from –47 to 818 Mg/km/year (Metric tones/km/year) across the 48 segments, average 149 Mg/km/year (for 34 nondeltaic segments), and total 1.8×10⁵ Mg/year. Annual mineral input from eroding shorelines ranges from –1,863 (accreting) to 15,752 Mg/km/year, average 2,743 Mg/km/year, and totals 3.3 ×10⁶ Mg/year.     

Evidence for multiple Quaternary ice advances and fan development from the Amundsen Gulf cross-shelf trough and slope,Canadian Beaufort Sea margin

The seismic stratigraphy and sedimentary architecture of the Amundsen Gulf Trough and adjacent slope, Canadian Beaufort Sea margin, are investigated using a grid of 2-D seismic reflection data. The inner-shelf of the Amundsen Gulf Trough is interpreted to be composed predominantly of exposed or near-surface bedrock, overlain by a spatially-discontinuous veneer of glacimarine to open-marine sediment. There is a seaward transition from exposed bedrock on the inner-shelf to a thick (up to 500 m) outer-shelf prograding wedge of acoustically semi-transparent sediment. Eight seismic sequences, divided into four megasequences, are described from the outer-shelf stratigraphy. Eight till sheets are identified from Megasequences A to C, providing evidence for at least eight Quaternary ice-stream advances through the Amundsen Gulf Trough to the shelf break. A trough-mouth fan with a minimum volume of about 10,000 km³ is present on the adjacent slope. The Amundsen Gulf ice stream probably represented the most northwesterly marine-terminating ice stream of the Laurentide Ice Sheet through much of the Quaternary, providing a major route for ice and sediment transfer to the Arctic Ocean. The youngest till sheet within the Amundsen Gulf Trough, Megasequence D, was probably deposited by a subsidiary ice stream, the Anderson ice stream, subsequent to retreat of the last, Late Wisconsinan Amundsen Gulf ice stream. This provides evidence of dynamic ice-sheet behaviour and the reorganisation of the northwest Laurentide Ice Sheet margin during the last deglaciation. A number of buried glacigenic landforms, including palaeo-shelf break gullies and a grounding-zone wedge with a volume of 90 km³, are described from the Amundsen Gulf Trough stratigraphy. Lateral grounding-zone wedges are identified at the northern and southern lateral margins of the Amundsen Gulf and M'Clure Strait troughs, respectively, and are interpreted to have been formed roughly contemporaneously by ice streams in Amundsen Gulf and M'Clure Strait.     

国家海域动态监视监测管理系统运行现状及发展趋势探讨

文章从业务体系、系统功能、监测业务、系统数据、系统应用等方面对国家海域动态监视监测管理系统运行现状进行总结,并指出系统目前存在的主要问题,在此基础上从业务体系建设、管理制度建设、监测业务拓展、应用系统优化、数据体系建设、辅助决策支持、联动监管机制、系统安全建设等方面进行系统发展趋势探讨。     

In situ microbial degradation of Prudhoe Bay crude oil in Beaufort Sea sediments

This study examined the fate of Prudhoe Bay crude oil in nearshore sediments of the Beaufort Sea, in situ, with emphasis on the rôle of microorganisms in the weathering process. The results indicate that oil is degraded in Arctic sediments very slowly; only after 1 year's exposure was biodegradation evident. Several factors probably contributed to the slow rate of microbial weathering, including: limited populations of hydrocarbon utilising microorganisms; localised high oil concentrations; low temperatures; limiting nutrient concentrations (unfavourable C:N and C:P ratios); low oxygen tensions and limited circulation of interstitial waters in fine-grained sediments. Abiotic weathering of the oil was also slow, with limited loss of low molecular weight aliphatic and aromatic hydrocarbons during 2 years' exposure. Significant features of the overall weathering process were: lack of initial loss of low molecular weight compounds; aliphatic compounds were not preferentially degraded over aromatic compounds and C₁₇, and lower molecular weight normal alkanes were preferentially degraded over higher molecular weight alkanes. The results of this study indicate that hydrocarbons will persist relatively unaltered for several years if Beaufort Sea sediments are contaminated with petroleum.     

Spatial variation in shallow sediment methane sources and cycling on the Alaskan Beaufort Sea Shelf/Slope

The MITAS (Methane in the Arctic Shelf/Slope) expedition was conducted during September, 2009 onboard the U.S. Coast Guard Cutter (USCGC) Polar Sea (WAGB-11), on the Alaskan Shelf/Slope of the Beaufort Sea. Expedition goals were to investigate spatial variations in methane source(s), vertical methane flux in shallow sediments (<10 mbsf), and methane contributions to shallow sediment carbon cycling. Three nearshore to offshore transects were conducted across the slope at locations approximately 200 km apart in water column depths from 20 to 2100 m. Shallow sediments were collected by piston cores and vibracores and samples were analyzed for sediment headspace methane (CH₄), porewater sulfate (SO₄²⁻), chloride (Cl⁻), and dissolved inorganic carbon (DIC) concentrations, and CH₄ and DIC stable carbon isotope ratios (δ¹³C). Downward SO₄²⁻ diffusion rates estimated from sediment porewater SO₄²⁻ profiles were between −15.4 and −154.8 mmol m⁻² a⁻¹ and imply a large spatial variation in vertical CH₄ flux between transects in the study region. Lowest inferred CH₄ fluxes were estimated along the easternmost transect. Higher inferred CH₄ flux rates were observed in the western transects. Sediment headspace ${\mathrm{\delta }}^{13}{\text{C}}_{{\text{CH}}_4}$ values ranged from −138 to −48‰, suggesting strong differences in shallow sediment CH₄ cycling within and among sample locations. Measured porewater DIC concentrations ranged from 2.53 mM to 79.39 mM with δ¹³C_DIC values ranging from −36.4‰ to 5.1‰. Higher down-core DIC concentrations were observed to occur with lower δ¹³C where an increase in ${\mathrm{\delta }}^{13}{\text{C}}_{{\text{CH}}_4}$ was measured, indicating locations with active anaerobic oxidation of methane. Shallow core CH₄ production was inferred at the two western most transects (i.e. Thetis Island and Halkett) through observations of low ${\mathrm{\delta }}^{13}{\text{C}}_{{\text{CH}}_4}$ coupled with elevated DIC concentrations. At the easternmost Hammerhead transect and offshore locations, ${\mathrm{\delta }}^{13}{\text{C}}_{{\text{CH}}_4}$ and DIC concentrations were not coupled suggesting less rapid methane cycling. Results from the MITAS expedition represent one of the most comprehensive studies of methane source(s) and vertical methane flux in shallow sediments of the U.S. Alaskan Beaufort Shelf to date and show geospatially variable sediment methane flux that is highly influenced by the local geophysical environment.     

2002年和2003年夏季波弗特海海冰叶绿素a和小型生物的研究

海冰在极地海洋中是个较为独特的生境,海冰卤道系统中的光照强度、温度、盐度和生存空间随着季节更替发生显著变化[1].春天,在北极新冰和多年冰的底部冰藻旺发,随后浮游植物生产力上升[2,3].     

Evidence for gas hydrate occurrences in the Canadian Arctic Beaufort Sea within permafrost-associated shelf and deep-water marine environments

The presence of a wedge of offshore permafrost on the shelf of the Canadian Beaufort Sea has been previously recognized and the consequence of a prolonged occurrence of such permafrost is the possibility of an underlying gas hydrate regime. We present the first evidence for wide-spread occurrences of gas hydrates across the shelf in water depths of 60–100 m using 3D and 2D multichannel seismic (MCS) data. A reflection with a polarity opposite to the seafloor was identified ∼1000 m below the seafloor that mimics some of the bottom-simulating reflections (BSRs) in marine gas hydrate regimes. However, the reflection is not truly bottom-simulating, as its depth is controlled by offshore permafrost. The depth of the reflection decreases with increasing water depth, as predicted from thermal modeling of the late Wisconsin transgression. The reflection crosscuts strata and defines a zone of enhanced reflectivity beneath it, which originates from free gas accumulated at the phase boundary over time as permafrost and associated gas hydrate stability zones thin in response to the transgression. The wide-spread gas hydrate occurrence beneath permafrost has implications on the region including drilling hazards associated with the presence of free gas, possible overpressure, lateral migration of fluids and expulsion at the seafloor. In contrast to the permafrost-associated gas hydrates, a deep-water marine BSR was also identified on MCS profiles. The MCS data show a polarity-reversed seismic reflection associated with a low-velocity zone beneath it. The seismic data coverage in the southern Beaufort Sea shows that the deep-water marine BSR is not uniformly present across the entire region. The regional discrepancy of the BSR occurrence between the US Alaska portion and the Mackenzie Delta region may be a result of high sedimentation rates expected for the central Mackenzie delta and high abundance of mass-transport deposits that prohibit gas to accumulate within and beneath the gas hydrate stability zone.     

The nearshore western Beaufort Sea ecosystem: Circulation and importance of terrestrial carbon in arctic coastal food webs

The nearshore shelf of the Beaufort Sea is defined by extreme physical and biological gradients that have a distinctive influence on its productivity and trophic structure. Massive freshwater discharge from the Mackenzie River, along with numerous smaller rivers and streams elsewhere along the coast, produce an environment that is decidedly estuarine in character, especially in late spring and summer. Consequently, the Beaufort coast provides a critical habitat for several species of amphidromous fishes, some of which are essential to the subsistence lifestyle of arctic native populations. Because of its low in situ productivity, allochthonous inputs of organic carbon, identifiable on the basis of isotopic composition, are important to the functioning of this arctic estuarine system. Coastal erosion and river discharge are largely responsible for introducing high concentrations of suspended sediment from upland regions into the nearshore zone. The depletion in the ¹³C content of invertebrate and vertebrate consumers, which drops about 4–5‰ eastward along the eastern Alaskan Beaufort Sea coast, may reflect the assimilation of this terrestrial organic matter into local food webs. In addition, the large range in ¹³C values of fauna collected in the eastern Beaufort (nearly 8‰) compared to the same species in the northeastern Chukchi (3‰), indicate a lower efficiency of carbon transfer between trophic levels in the eastern Beaufort. The wider spread in stable isotope values in the eastern Beaufort may also reflect a decoupling between benthic and pelagic components. Isotopic tracer studies of amphidromous fishes in the Simpson Island barrier island lagoon revealed that terrestrial (peat) carbon may contribute as much as 30–50% of their total dietary requirements. On the eastern Alaska Beaufort Sea coast, the δ¹³C values of arctic cod collected in semi-enclosed lagoons were more depleted, by 3–4‰, compared to fish collected in the coastal Beaufort Sea. Calculations from isotopic mixing equations indicate cod from lagoons may derive 70% of their carbon from terrestrial sources. The δ¹⁵N values of lagoon fish were also 4‰ lower than coastal specimens, reflective of the lower δ¹⁵N values of terrestrially derived nitrogen (0–1.5‰ compared to 5–7‰ for phytoplankton). The role of terrestrial carbon in arctic estuarine food webs is especially important in view of the current warming trend in the arctic environment and the role of advective processes that transport carbon along the nearshore shelf. Biogeochemical studies of the arctic coastal estuarine environment may provide more insights into the function of these biologically complex ecosystems.