The ecology of benthic carbon cycling in the northern Bering and Chukchi Seas

Thesis (Ph.D.) University of Alaska Fairbanks, 198

Organic matter remineralization in marine sediments : A Pan-Arctic synthesis

Natural Environment Research Council (GrantNumber(s): NE/J023094/1; Grant recipient(s): Ursula Witte) ArcticNet (GrantNumber(s): Hotspot biodiversity project; Grant recipient(s): Philippe Archambault)Peer reviewedPublisher PD

An Independent Review of USGS Circular 1370: An Evaluation of the Science Needs to Inform Decisions on Outer Continental Shelf Energy Development in the Chukchi and Beaufort Seas, Alaska

Reviews the U.S. Geological Survey's findings and recommendations on Alaska's Arctic Ocean, including geology, ecology and subsistence, effect of climate change on, and impact of oil spills. Makes recommendations for data management and other issues

Arctic Ocean Primary Productivity: The Response of Marine Algae to Climate Warming and Sea Ice Decline

Highlights: 1. Satellite estimates of ocean primary productivity (i.e., the rate at which marine algae transform dissolved inorganic carbon into organic material) were higher in 2018 (relative to the 2003-17 mean) for three of the nine investigated regions (the Eurasian Arctic, Bering Sea, and Baffin Bay). 2. All regions continue to exhibit positive trends over the 2003-18 period, with the strongest trends for the Eurasian Arctic, Barents Sea, Greenland Sea, and North Atlantic. 3. The regional distribution of relatively high (low) chlorophyll-a concentrations can often be associated with a relatively early (late) breakup of sea ice cover

The Potential for Using Little Diomede Island as a Platform for Observing Environmental Conditions in Bering Strait

The Pacific waters that enter the Arctic via the Bering Strait exert a major influence on the Arctic Ocean’s stratification, ice cover, and ecosystem. We demonstrate the potential of a shore-based laboratory to monitor the water masses that flow predominantly northward past Little Diomede Island in the center of the Bering Strait into the Arctic Ocean. We determined near-surface water column salinity, inorganic nutrient concentrations, natural fluorescence associated with chlorophyll, and the oxygen isotope composition of seawater, both in summer during the open-water period and in late winter under ice-covered conditions, by pumping ashore water from shallow depths near the island. Additional surveys were undertaken within 5 km of the island to assess the influence of local sources of nutrients. Water mass variability was much greater during the open-water period than under ice-covered conditions, presumably because the relatively immobile ice cover attenuates wind forcing and the decrease in run-off reduces cross-shelf gradients. The mean oxygen isotope composition of the summer (?18O = -1.11‰) and late winter (?18O = -0.98) collections, however, was close to that which has been established for Bering Sea waters in the Pacific-dominated upper halocline of the Arctic Ocean (-1.1‰) particularly considering the higher seasonal flow of runoff in the summer. A comparison with data from shipboard sampling at various locations across the Bering Strait indicates that the oxygen isotope composition of near-surface water sampled at Diomede varies in response to wind-forcing. If the least saline (< 30.5) water near the Alaska coast is excluded, the ?18O values of Diomede and shipboard samples cannot be distinguished statistically. This similarity suggests that the water sampled from the island also reasonably represents the ?18O value of Bering Sea waters that contribute to the upper halocline of the Arctic Ocean. Effects of benthic recycling, human activity, and seabird nesting on nutrient concentrations appeared to be concentrated within ~200 m of the island. Our results are discussed in the practical context of availability of electricity, interested local residents, and a geotechnical study indicating that it is feasible to construct and operate a more permanent undersea water intake system to improve environmental observation capabilities in the Bering Strait region.Les eaux du Pacifique qui entrent dans l’Arctique par le détroit de Béring ont une influence majeure sur la stratification, le couvert de glace et l’écosystème de l’océan Arctique. Dans ce rapport nous présentons des données qui démontrent le potentiel d’un laboratoire basé à terre dans le but de surveiller les masses d’eau qui circulent principalement vers le nord au-delà de l’île Little Diomede au centre du détroit de Béring jusqu’à l’océan Arctique. Nous avons déterminé la salinité de la colonne d’eau près de la surface, la concentration des nutriments inorganiques, la fluorescence naturelle associée avec la chlorophylle, ainsi que la composition en isotope d’oxygène de l’eau de mer. Ces données ont été recueillies pendant la période estivale en eaux ouvertes et à la fin de l’hiver sous des conditions de couvert de glace en pompant à terre l’eau provenant d’aires peu profondes près de l’île. Des études supplémentaires ont été entreprises à moins de 5 km de l’île afin d’évaluer l’influence des sources locales de nutriments. La variabilité des masses d’eaux était plus grande pendant la période sans couvert de glace que pendant les conditions de couvert de glace. Ceci était vraisemblablement dû à l’atténuation de la force exercée par le vent sous le couvert de glace relativement immobile et à une réduction des gradients à travers le plateau provenant d’une réduction du ruissellement. La composition moyenne en isotope d’oxygène des collections de l’été (?18O = -1.11‰) et de fin d’hiver (?18O = -0.98‰) étaient cependant près de celle qui a été établie pour les eaux de la mer de Béring dans l’halocline supérieure de l’océan Arctique dominée par les eaux du Pacifique (?18O = -1.1‰), particulièrement compte tenu du flux saisonnier de ruissellement plus élevé pendant l’été. Une comparaison avec des données recueillies par bateau à plusieurs locations à travers le détroit de Béring indique que la composition en isotope d’oxygène près de la surface des eaux mesurée à Diomede varie en réponse à la force du vent. Lorsque l’eau moins saline (< 30.5) près de la côte de l’Alaska est exclue, les valeurs ?18O de Diomede et des échantillons recueillis par bateau ne peuvent être distingués statistiquement. Cette similarité suggère que l’eau échantillonnée à partir de l’île représente aussi raisonnablement les valeurs ?18O des eaux de la mer de Béring qui contribuent à l’halocline supérieure de l’océan Arctique. Les conséquences du recyclage benthique, des activités anthropogéniques et de la nidification des oiseaux de mer sur les concentrations de nutriments semblent être concentrées à moins de ~200m de l’île. Nos résultats sont interprétés dans le contexte pratique de la disponibilité de l’électricité, de l’intérêt des résidents locaux et d’une étude géotechnique qui indique qu’un système permanent de prise d’eau sous-marin peut être construit et opéré afin d’améliorer les capacités d’observation environnementale dans la région du détroit de Béring

Modeling Marine Protected Areas for Threatened Eiders in a Climatically Changing Bering Sea

Delineating protected areas for sensitive species is a growing challenge as changing climate alters the geographic pattern of habitats as well as human responses to those shifts. When human impacts are expected within projected ranges of threatened species, there is often demand to demarcate the minimum habitat required to ensure the species\u27 persistence. Because diminished or wide-ranging populations may not occupy all viable (and needed) habitat at once, one must identify thresholds of resources that will support the species even in unoccupied areas. Long-term data on the shifting mosaic of critical resources may indicate ranges of future variability. We addressed these issues for the Spectacled Eider (Somateria fischeri), a federally threatened species that winters in pack ice of the Bering Sea. Changing climate has decreased ice cover and severely reduced the eiders\u27 benthic prey and has increased prospects for expansion of bottom trawling that may further affect prey communities. To assess long-term changes in habitats that will support eiders, we linked data on benthic prey, sea ice, and weather from 1970 to 2001 with a spatially explicit simulation model of eider energy balance that integrated field, laboratory, and remote-sensing studies. Areas estimated to have prey densities adequate for eiders in 1970–1974 did not include most areas that were viable 20 years later (1993–1994). Unless the entire area with adequate prey in 1993–1994 had been protected, the much reduced viable area in 1999–2001 might well have been excluded. During long non-foraging periods (as at night), eiders can save much energy by resting on ice vs. floating on water; thus, loss of ice cover in the future might substantially decrease the area in which prey densities are adequate to offset the eiders\u27 energy needs. For wide-ranging benthivores such as eiders, our results emphasize that fixed protected areas based on current conditions can be too small or inflexible to subsume long-term shifts in habitat conditions. Better knowledge of patterns of natural disturbance experienced by prey communities, and appropriate allocation of human disturbance over seasons or years, may yield alternative strategies to large-scale closures that may be politically and economically problemati

Modification of NO, PO, and NO/PO During Flow Across the Bering and Chukchi Shelves: Implications for Use as Arctic Water Mass Tracers

The NO and PO tracers (9[NO3-] + 02 and 135[PO4-] + 02, respectively,) and their derivative NO/PO have found increasing use in Arctic water mass analyses for identifying the specific basin or shelf areas from which surface waters originate, based upon assumed differences in Pacific- and Atlantic-derived content and basin-to-basin differences within the Arctic. Following shipboard sampling in June-September 1993 and May-June 1994, both north and south of Bering Strait, we have found evidence that Pacific-derived waters flowing north to Bering Strait do not necessarily have any unique NO, PO, or NO/PO identity that would permit unequivocal use as a water mass tracer. In particular, NO/PO ratios in the Bering Sea continental shelf (\u3c150 m) waters varied from 0.7 to 1.1, which encompasses ratios previously reported for Arctic continental shelf and Atlantic origin waters in the Arctic Ocean. The highest NO/PO ratios (~ 1) in the Bering Sea were observed to the southwest of St. Lawrence Island, close to where high nutrient waters are first upwelled onto the shelf, and seasonally early in the biological production cycle. By contrast, later in the summer, north of Bering Strait, at the depth of the Arctic Ocean nutrient maximum, the highest concentrations of silica (~60 μM) were associated with low NO/PO ratios (-0.7). Apparent increases in the proportions of sea ice melt in these waters, inferred from 180 and salinity regressions, were associated with lower NO/PO ratios. This pattern, the potential for sea-air exchange, and a significant relationship between decreases in nitrate/phosphate ratios and both NO/PO ratios and silica concentrations indicate that biological and physical processes north and south of Bering Strait affect the fidelity of these nutrient-based tracers. These results indicate the need for consideration of shelf-based processes before NO/PO ratios and other nutrient-based tracers can be successfully applied as Arctic circulation tracers. Copyright 1999 by the American Geophysical Union

Distributions of nuclear fuel-reprocessing tracers in the Arctic Ocean: Indications of Russian river influence

Radionuclide sampling in 1986 and 1993 in the Canada Basin, and in 1993 in the Amundsen Basin and on the adjacent Laptev shelf, provides new insights into the origin, timing, pathways, and mechanisms for dispersal of non-fallout radioactive tracers in the Arctic Ocean. First, samples from the Beaufort Sea shelf, slope, and adjacent basin show a four-fold increase in 129I concentrations from 1986 to 1993. Second, anthropogenic non-fallout radionuclide concentrations in the Beaufort Sea increase with proximity to slope boundary currents. Third, there is evidence for riverine contributions of anthropogenic radionuclides to surface waters of the Amundsen Basin and the Laptev continental shelf. This evidence includes high surface water burdens of 237Np and 129I, with the maximum in anthropogenic 129I found in the least saline and most 18O-depleted waters, consistent with an origin in high-latitude runoff. Additionally, the 237Np/129I atom ratios in the Laptev Sea and Amundsen Basin in 1993 were significantly lower than observed elsewhere in the Arctic Ocean and can be reasonably explained by 129I added during transit of the Russian shelves. The 240Pu/239Pu ratios in the water column were mostly near 0.18, consistent both with stratospheric bomb fallout and with the discharged-weighted mean Sellafield ratio during 1966-1985. In the least saline water samples collected at the most shallow Laptev shelf station, however, the Pu ratios were lower, consistent with a non-European nuclear fuel reprocessing source. There are clear secondary maxima in 237Np and 129I near 1000 m in the Amundsen Basin, likely associated with the Barents Sea branch of Atlantic water. Finally, the 129I/salinity and 129I/δ18O relationships in the Amundsen and Canada Basins at middepths are indistinguishable, suggesting effective horizontal dispersion

Developing an observational design for epibenthos and fish assemblages in the Chukchi Sea

Accepted manuscript version, licensed CC BY-NC-ND 4.0. Published version available at https://doi.org/10.1016/j.dsr2.2018.11.005.In light of ongoing, and accelerating, environmental changes in the Pacific sector of the Arctic Ocean, the ability to track subsequent changes over time in various marine ecosystem components has become a major research goal. The high logistical efforts and costs associated with arctic work demand the prudent use of existing resources for the most comprehensive information gain. Here, we compare the information that can be gained for epibenthic invertebrate and for demersal fish assemblages reflecting coverage on two different spatial scales: a broader spatial coverage from the Arctic Marine Biodiversity Observing Network (AMBON, 67 stations total), and the spatial coverage from a subset of these stations (14 stations) that reflect two standard transect lines of the Distributed Biological Observatory (DBO). Multivariate cluster analysis was used to discern community similarity patterns in epibenthic invertebrate and fish communities. The 14 stations reflecting the two DBO lines captured about 57% of the epibenthic species richness that was observed through the larger-scale AMBON coverage, with a higher percentage on the more southern DBO3 than the northern DBO4 line. For demersal fishes, both DBO lines captured 88% of the richness from the larger AMBON spatial coverage. The epifaunal assemblage clustered along the south-north and the inshore-offshore axes of the overall study region. Of these, the southern DBO3 line well represented the regional (southern) epifaunal assemblage structure, while the northern DBO4 line only captured a small number of the distinct assemblage clusters. The demersal fish assemblage displayed little spatial structure with only one coastal and one offshore cluster. Again, this structure was well represented by the southern DBO3 line but less by the northern DBO4 line. We propose that extending the coverage of the DBO4 line in the northern Chukchi Sea farther inshore and offshore would result in better representation of the overall northern Chukchi epifaunal and fish assemblages. In addition, the multi-annual stability of epifaunal and, to a lesser extent also fish assemblages, suggests that these components may not need to be sampled on an annual basis and sampling every 2–3 years could still provide sufficient understanding of long-term changes. Sampling these assemblages every few years from a larger region such as covered by the AMBON project would create the larger-scale context that is important in spatial planning of long-term observing

Past, present, and future : a science program for the Arctic Ocean linking ancient and contemporary observations of change through modeling. A follow-up to the 2nd International Conference on Arctic Research Planning,19-21 November 2007, Potsdam, Germany

The Arctic Ocean is the missing piece for any global model. Records of processes at both long and short timescales will be necessary to predict the future evolution of the Arctic Ocean through what appears to be a period of rapid climate change. Ocean monitoring is impoverished without the long-timescale records available from paleoceanography and the boundary conditions that can be obtained from marine geology and geophysics. The past and the present are the key to our ability to predict the future