Erosion and Flooding—Threats to Coastal Infrastructure in the Arctic: A Case Study from Herschel Island,Yukon Territory,Canada     

Boris Radosavljevic  Hugues Lantuit  Wayne Pollard  Paul Overduin  Nicole Couture  Torsten Sachs  Veit Helm  Michael Fritz 《Estuaries and Coasts》2016,39(4):900-915

Arctic coastal infrastructure and cultural and archeological sites are increasingly vulnerable to erosion and flooding due to amplified warming of the Arctic, sea level rise, lengthening of open water periods, and a predicted increase in frequency of major storms. Mitigating these hazards necessitates decision-making tools at an appropriate scale. The objectives of this paper are to provide such a tool by assessing potential erosion and flood hazards at Herschel Island, a UNESCO World Heritage candidate site. This study focused on Simpson Point and the adjacent coastal sections because of their archeological, historical, and cultural significance. Shoreline movement was analyzed using the Digital Shoreline Analysis System (DSAS) after digitizing shorelines from 1952, 1970, 2000, and 2011. For purposes of this analysis, the coast was divided in seven coastal reaches (CRs) reflecting different morphologies and/or exposures. Using linear regression rates obtained from these data, projections of shoreline position were made for 20 and 50 years into the future. Flood hazard was assessed using a least cost path analysis based on a high-resolution light detection and ranging (LiDAR) dataset and current Intergovernmental Panel on Climate Change sea level estimates. Widespread erosion characterizes the study area. The rate of shoreline movement in different periods of the study ranges from ?5.5 to 2.7 m·a^?1 (mean ?0.6 m·a^?1). Mean coastal retreat decreased from ?0.6 m·a^?1 to ?0.5 m·a^?1, for 1952–1970 and 1970–2000, respectively, and increased to ?1.3 m·a^?1 in the period 2000–2011. Ice-rich coastal sections most exposed to wave attack exhibited the highest rates of coastal retreat. The geohazard map combines shoreline projections and flood hazard analyses to show that most of the spit area has extreme or very high flood hazard potential, and some buildings are vulnerable to coastal erosion. This study demonstrates that transgressive forcing may provide ample sediment for the expansion of depositional landforms, while growing more susceptible to overwash and flooding.  相似文献   

Sediment Nitrogen Fixation: a Call for Re-evaluating Coastal N Budgets     

Silvia E. Newell  Mark J. McCarthy  Wayne S. Gardner  Robinson W. Fulweiler 《Estuaries and Coasts》2016,39(6):1626-1638

Coastal ocean primary productivity is often limited by nitrogen (N) availability, which is determined by the balance between N sources (e.g., N-fixation, groundwater, river inputs, etc.) and sinks (e.g., denitrification, sediment burial, etc.). Historically, heterotrophic N-fixation in sediments was excluded as a significant source of N in estuarine budgets, based on low, indirectly measured rates (e.g., acetylene reduction assay) and because it was unnecessary to achieve mass balance. Many recent studies using net N₂ flux measurements have shown that sediment N-fixation can equal or exceed N₂ loss. In an effort to quantify N₂ production and consumption simultaneously, we measured N-fixation and denitrification directly in sediment cores from a temperate estuary (Waquoit Bay, MA). N-fixation, dissimilatory nitrate reduction to ammonium, and denitrification occurred simultaneously, and the net N₂ flux shifted from uptake (N-fixation) to efflux (denitrification) over the 120-h incubation. Evidence for N-fixation included net ²⁸N₂ and ³⁰N₂ uptake, ¹⁵NH₄ ⁺ production from ³⁰N₂ additions, ¹⁵N_{organic matter} production, and nifH expression. N-fixation from ³⁰N₂ was up to eight times higher than potential denitrification. However, N-fixation calculated from ¹⁵NO₃ ^? was one half of the measured fixation from ³⁰N₂, indicating that ¹⁵NO₃-isotope labeling calculations may underestimate N-fixation. These results highlight the dynamic nature of sediment N cycling and suggest that quantifying individual processes allows a greater understanding of what net N₂ fluxes signify and how that balance varies over time.  相似文献   

A geochemical reconstruction of oil generation in the Barrow Sub-basin of Western Australia     

John K. Volkman  Robert Alexander  Robert Ian Kagi  Rohinton A. Noble  Carry Wayne Woodhouse 《Geochimica et cosmochimica acta》1983,47(12):2091-2105

A suite of crude oils and petroleum source rock extracts from the Barrow Sub-basin of Western Australia have been analysed for biological marker compounds by capillary GC-MS, and for volatile hydrocarbons by whole oil capillary GC. These analyses were used to calculate values for twenty-three biomarker parameters in order to assess aspects of source type, maturity, migration and biodegradation of the hydrocarbons.The crude oils had a source in the Upper Jurassic Dingo Claystone formation. These hydrocarbons accumulated in the reservoir sands and in some cases were biodegraded. Several accumulation and biodegradation episodes have been recognised while the basin continued to subside, which resulted in a suite of oils showing marked differences in composition.  相似文献   

Comparison of Michigan Basin crude oils (reply to comments by Illich and Grizzle and by Pruitt)     

Philip A. Meyers  Wayne E. Moore 《Geochimica et cosmochimica acta》1983,47(6):1161-1162

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Diurnal variations of winds over an upwelling region off Oregon     

Wayne Burt  Henry Crew  Noel Plutchak  Jozef Dumon 《Boundary-Layer Meteorology》1974,6(1-2):35-45

The diurnal variation of surface winds off the coast of Oregon is described and compared with a recent analysis of winds off the coast of Peru. The Oregon wind speeds have a distinct 24-h periodicity, while the Peru wind speeds were reported to have an irregular 12-h variation. The long-and trans-shore components of both winds exhibit 24-h periodicities; the ratio of the long-shore to trans-shore diurnal amplitudes off Oregon is 2.8, twice the ratio found off Peru. Although meteorological conditions off Oregon were quasi-stationary during the period investigated, there were considerable day-to-day variations in diurnal amplitudes and phases. Diurnal amplitudes were found to be correlated with the daily mean long-shore winds.  相似文献   

Chloride Contamination in Alum Creek, Central Ohio     

Wayne A. Pettyjohn 《Ground water》1975,13(4):332-339

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Developing a Partnership with Your Consultant     

Wayne A. Hamilton 《Ground Water Monitoring & Remediation》1991,11(2):56-59

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The effects of sea salts on the forms of nitrogen released from estuarine and freshwater sediments: Does ion pairing affect ammonium flux?     

Wayne S. Gardner  Sybil P. Seitzinger  John M. Malczyk 《Estuaries and Coasts》1991,14(2):157-166

In sediments with oxidized surface layers, the percentage of mineralized nitrogen that is nitrified/denitrified, compared with that released directly as ammonium, appears to be affected by the presence of sea salts. In estuarine systems, a significant portion of the nitrogen is released as ammonium, whereas in freshwater systems, most of the mineralized nitrogen is often released from the sediments as nitrogen gas. We hypothesized that this discrepancy is caused by differential competition between physical diffusion and nitrification/denitrification in the two systems. The vertical migration (by Fickian diffusion) of ammonium out of the oxic layer may be hindered by cation exchange (or sorption) interactions with sediment particles to a greater extent in fresh water than in estuarine systems. The resulting relatively long residence time, and potentially high levels of particle-bound ammonium in the freshwater sediments, would favor nitrification as the major ammonium removal process. By contrast, ion pair formation of ammonium with seawater anions and blockage of sediment cation exchange sites with seawater cations may allow a sizable fraction of the ammonium to diffuse out of estuarine sediments before it is nitrified. A salt effect, consistent with this hypothesis, has been demonstrated in experimental systems by changing the ionic composition of water flowing above intact cores of freshwater and estuarine sediments. Steady-state ammonium release from Lake Michigan sediments was substantially enhanced in the presence of 30% seawater over that in the presence of lake water alone. Likewise, steady-state ammonium release, from Ochlockonee River and Bay sediments (Florida) and from Toms River and Barnegat Bay sediments (New Jersey), was usually higher in the presence of diluted synthetic seawater than it was in the presence of fresh water.  相似文献   

Impacts of summer warming on the energy and water balance of wetland tundra     

Wayne R. Rouse  Derek W. Carlson  E. J. Weick 《Climatic change》1992,22(4):305-326

Measurements, made at a high subarctic, maritime, wetland tundra site, are presented for three different growing seasons. These are divided into hot-dry, normal-dry and normal-wet years and the behaviour of their surface energy and water balances is examined within the framework of a combination model. For periods of comparable energy availability, evapotranspiration during hot-dry conditions can be larger than during cooler and wetter periods. This results from small stomatal resistance in the sparse canopy of well-rooted sedges, and from the ability of peat soils to supply water under conditions of large atmospheric demand. This demand is expressed in terms of the vapour pressure deficit and it counteracts the large surface resistances which develop during dry periods. In many respects, the energy balance of a subarctic wetland tundra is comparable to observations and models for temperate agricultural and forest lands, in spite of the fact that the soils are organic, the vegetation canopy is sparse and there is continuous permafrost. A dry year promotes deeper thaw depths in the permafrost soils, during the growing season, than does a wet one. This is due to larger ground heat fluxes and larger soil thermal diffusivities. We concluded that maritime, wetland tundra, growing on peat soils, displays feedback mechanisms, which can offset the effects of moisture stress, caused by summer climate warming of a similar magnitude to that simulated by General Circulation Models for a 2 × CO₂ scenario.  相似文献   

Laboratory spectroscopic studies of atmospherically important radicals using fourier transform spectroscopy     

P. T. Wassell  R. P. Wayne  Ballard  W. B. Johnston 《Journal of Atmospheric Chemistry》1989,8(1):63-85

This paper describes laboratory experiments designed to obtain the infrared spectra of some atmospherically important radical species and related compounds. A Fourier transform spectrometer was used that was capable of yielding resolutions as great as 0.0024 cm^-1, and optical paths of up to 512 m were employed. The objective of the experiments was to obtain the spectra for subsequent application to remote sounding measurements in the atmosphere.Radicals were generated by a variety of chemical reactions involving atoms or other highly reactive precursors. Spectra of the ₃ band of NO₃, at ca. 1500 cm^-1, were obtained with up to 0.005 cm^-1 resolution using the reaction between NO₂ and O₃ to produce the radical. The most satisfactory source of ClO was found to be the reaction between Cl and O₃, and the (1-0) vibration-rotation band in the region 829–880 cm^-1 was recorded at a resolution of 0.02 cm^-1. We were unable to observe infrared absorption of HO₂ with any of the radical sources that we tested. High-resolution survey spectra were obtained of compounds used as reactants, or formed as side-products in the radical-generating processes. These compounds included N₂O₅, HNO₃, ClONO₂, FNO₂, Cl₂O, HO₂NO₂, and probably FO₂.The ability to monitor concentrations of the NO₃ radical in the visible region of the spectrum as well as the concentrations of reactants and other products in the infrared region allowed us to undertake a study of the time-dependent interactions occurring when NO₂ reacts with O₃. The results indicate the importance of heterogeneous processes, especially when traces of water are present, and lend credence to suggestions that heterogeneous mechanisms in the NO₃–N₂O₅–H₂O system might be a viable source of HNO₃ in the atmosphere.  相似文献