Geochemistry of groundwater in front of a warm‐based glacier in Southeast Greenland     

Søren Munch Kristiansen  Jacob Clement Yde  Teresa Gómez Bárcena  Bjarne Holm Jakobsen  Jesper Olsen  Niels Tvis Knudsen 《Geografiska Annaler: Series A, Physical Geography》2013,95(2):97-108

Groundwater in front of warm‐based glaciers is likely to become a more integrated part of the future proglacial hydrological system at high latitudes due to global warming. Here, we present the first monitoring results of shallow groundwater chemistry and geochemical fingerprinting of glacier meltwater in front of a warm‐based glacier in Southeast Greenland (Mittivakkat Gletscher, 65° 41′ N, 37° 48′ W). The groundwater temperature, electrical conductivity and pressure head were monitored from August 2009 to August 2011, and water samples were collected in 2009 and analyzed for major ions and water isotopes (δD, δ¹⁸O). The 2 yrs of monitoring revealed that major outbursts of glacier water during the ablation season flushed the proglacial aquifer and determined the groundwater quality for the next 2–8 weeks until stable chemical conditions were reached again. Water isotope composition shows that isotopic fractionation occurs in both groundwater and glacier meltwater, but fractionation due to evaporation from near‐surface soil moisture prior to infiltration has the most significant effect. This study shows that groundwater in Low Arctic Greenland is likely to possess a combined geochemical and isotopic composition, which is distinguishable from other water sources in the proglacial environment. However, the shallow groundwater composition at a given time is highly dependent on major outbursts of glacier water in the previous months.  相似文献   

Numerical Modeling of Atoll Island Hydrogeology   总被引：3，自引：0，他引：3  

by R.T. Bailey  J.W. Jenson  and A.E. Olsen 《Ground water》2009,47(2):184-196

We implemented Ayers and Vachers' (1986) inclusive conceptual model for atoll island aquifers in a comprehensive numerical modeling study to evaluate the response of the fresh water lens to selected controlling climatic and geologic variables. Climatic factors include both constant and time-varying recharge rates, with particular attention paid to the effects of El Niño and the associated drought it brings to the western Pacific. Geologic factors include island width; hydraulic conductivity of the uppermost Holocene-age aquifer, which contains the fresh water lens; the depth to the contact with the underlying, and much more conductive, Pleistocene karst aquifer, which transmits tidal signals to the base of the lens; and the presence or absence of a semiconfining reef flat plate on the ocean side. Sensitivity analyses of steady-steady simulations show that lens thickness is most strongly sensitive to the depth to the Holocene-Pleistocene contact and to the hydraulic conductivity of the Holocene aquifer, respectively. Comparisons between modeling results and published observations of atoll island lens thicknesses suggest a hydraulic conductivity of approximately 50 m/d for leeward islands and approximately 400 m/d for windward islands. Results of transient simulations show that lens thickness fluctuations during average seasonal conditions and El Niño events are quite sensitive to island width, recharge rate, and hydraulic conductivity of the Holocene aquifer. In general, the depletion of the lens during drought conditions is most drastic for small, windward islands. Simulation results suggest that recovery from a 6-month drought requires about 1.5 years.  相似文献   

Coastal erosion vs riverine sediment discharge in the Arctic Shelf seas   总被引：8，自引：0，他引：8  

Volker Rachold  Mikhail N. Grigoriev  Felix E. Are  Steve Solomon  Erk Reimnitz  Heidemarie Kassens  Martin Antonow 《International Journal of Earth Sciences》2000,89(3):450-460

This article presents a comparison of sediment input by rivers and by coastal erosion into both the Laptev Sea and the Canadian Beaufort Sea (CBS). New data on coastal erosion in the Laptev Sea, which are based on field measurements and remote sensing information, and existing data on coastal erosion in the CBS as well as riverine sediment discharge into both the Laptev Sea and the CBS are included. Strong regional differences in the percentages of coastal erosion and riverine sediment supply are observed. The CBS is dominated by the riverine sediment discharge (64.45᎒⁶ t a^-1) mainly of the Mackenzie River, which is the largest single source of sediments in the Arctic. Riverine sediment discharge into the Laptev Sea amounts to 24.10᎒⁶ t a^-1, more than 70% of which are related to the Lena River. In comparison with the CBS, the Laptev Sea coast on average delivers approximately twice as much sediment mass per kilometer, a result of higher erosion rates due to higher cliffs and seasonal ice melting. In the Laptev Sea sediment input by coastal erosion (58.4᎒⁶ t a^-1) is therefore more important than in the CBS and the ratio between riverine and coastal sediment input amounts to 0.4. Coastal erosion supplying 5.6᎒⁶ t a^-1 is less significant for the sediment budget of the CBS where riverine sediment discharge exceeds coastal sediment input by a factor of ca. 10.  相似文献   

Watson: A new link in the HE iron chain     

Edward Olsen  Andrew Davis  Roy S. Clarke  Ludolf Schultz  Hartwig W. Weber  Robert Clayton  Toshiko Mayeda  Eugene Jarosewich  Paul Sylvester  Lawrence Grossman  Ming-Sheng Wang  Michael E. Lipschutz  Ian M. Steele  James Schwade 《Meteoritics & planetary science》1994,29(2):200-213

Abstract— Watson, which was found in 1972 in South Australia, contains the largest single silicate rock mass seen in any known iron meteorite. A comprehensive study has been completed on this unusual meteorite: petrography, metallography, analyses of the silicate inclusion (whole rock chemical analysis, INAA, RNAA, noble gases, and oxygen isotope analysis) and mineral compositions (by electron microprobe and ion microprobe). The whole rock has a composition of an H-chondrite minus the normal H-group metal and troilite content. The oxygen isotope composition is that of the silicates in the HE iron meteorites and lies along an oxygen isotope fractionation line with the H-group chondrites. Trace elements in the metal confirm Watson is a new HE iron. Whole rock Watson silicate shows an enrichment in K and P (each ～2X H-chondrites). The silicate inclusion has a highly equilibrated igneous (peridotite-like) texture with olivine largely poikilitic within low-Ca pyroxene: olivine (Fa₂₀), opx (Fs₁₇Wo₃), capx (Fs₉Wo₄₁) (with very fine exsolution lamellae), antiperthite feldspar (An_1–Or₅) with <1 μm exsolution lamellae (An_1–3Or_>40), shocked feldspar with altered stoichiometry, minor whitlockite (also a poorly characterized interstitial phosphate-rich phase) and chromite, and only traces of metal and troilite. The individual silicate minerals have normal chondritic REE patterns, but whitlockite has a remarkable REE pattern. It is very enriched in light REE (La is 720X C1, and Lu is 90X C1, as opposed to usual chonditic values of ～300X and 100–150X, respectively) with a negative Eu anomaly. The enrichment of whole rock K is expressed both in an unusually high mean modal Or content of the feldspar, Or₁₃, and in the presence of antiperthite. Whole rock trace element data for the silicate mass support the petrography. Watson silicate was an H-chondrite engulfed by metal and melted at > 1550 °C. A flat refractory lithophile and flat REE pattern (at ～1x average H-chondrites) indicate that melting took place in a relatively closed system. Immiscible metal and sulfide were occluded into the surrounding metal host. Below 1100 °C, the average cooling rate is estimated to have been ～1000 °C/Ma; Widmanstätten structure formed, any igneous zoning in the silicates was equilibrated, and feldspar and pyroxene exsolution took place. Cooling to below 300 °C was completed by 3.5 Ga B. P. At 8 Ma, a shock event took place causing some severe metal deformation and forming local melt pockets of schreibersite/metal. This event likely caused the release of Watson into interplanetary space. The time of this event, 8Ma, corresponds to the peak frequency of exposure ages of the H-chondrites. This further confirms the link between HE irons and the H-chondrites, a relationship already indicated by their common oxygen isotope source. Watson metal structures are very similar to those in Kodaikanal. Watson, Kodaikanal and Netschaëvo form the young group of HE meteorites (ages 3.7 ± 0.2 Ga). They appear to represent steps in a chain of events that must have taken place repeatedly on the HE parent body or bodies from which they came: chondrite engulfed in metal (Netschaëvo); chondrite melted within metal (Watson); and finally melted silicate undergoing strong fractionation with the fractionated material emplaced as globules within metal (Kodaikanal). Watson fills an important gap in understanding the sequence of events that took place in the evolution of the IIE-H parent body(ies). This association of H-chondrite with HE metal suggests a surface, or near surface process-a suggestion made by several other researchers.  相似文献   

Proceedings of the Pro Mare Symposium on Polar Marine Ecology, Trondheim, Norway, 12-16 May 1990     

Egil Sakshaug  Christopher C.E. Hopkins  Nils Are Øritsland 《Polar research》1991,10(1):1-4

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Barringer Medal Citation for William A. Cassidy     

Edward J. Olsen 《Meteoritics & planetary science》1996,31(4):431-432

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Sediment accumulation rates in Conowingo reservoir as determined by man-made and natural radionuclides     

R. I. McLean  J. K. Summers  C. R. Olsen  S. L. Domotor  I. L. Larsen  H. Wilson 《Estuaries and Coasts》1991,14(2):148-156

The Susquehanna River is the major contributor to sediment loadings in the Chesapeake Bay. Because many environmental contaminants are associated with suspended particulates, the degree of particle retention within the reservoirs of the lower Susquehanna River is an important consideration in evaluating contaminant loadings to the Chesapeake Bay. Profiles of weapons-test Cs-137, nuclear power plant-related Cs-134 and Cs-137, and naturally-derived Pb-120 were used to estimate rates of sediment accretion in the conowingo Reservioir, an impoundment of the Susquehanna River along the Maryland-Pennsylvania border. Net accretion rates ranged from about 2 cm yr^?1 downstream of a nuclear power plant cooling discharge to a high of about 7 cm yr^?1 at the mount of an incoming creek. Slight, but consistent, increases in the annual rate of accretion since the creation of the reservoir in 1928 are apparent. The current net average annual sediment load reatined by the reservoir is estimated to be 0.4×10⁶ to 1.5 × 10⁶ metric tons yr^?1. The retained sediment load represents about 8–23% of the long-time average sediment input to the reservoir.  相似文献   

Using thermoterrace dimensions to calculate the coastal erosion rate     

F. E. Are  M. N. Grigoriev  H.-W. Hubberten  V. Rachold 《Geo-Marine Letters》2005,25(2-3):121-126

Thermoterraces in syngenetic ice complexes are widespread along the erosion dominated Yakutia Arctic coast. Thermoterraces progressively record quantitative information about their existence, which may be used to determine the mean shore retreat rate during the time they are present. Initial measurements of four thermoterraces on the south coast of the Dmitry Laptev Strait were carried out by the authors in 2002 and shore retreat rates were calculated. Comparison of erosion rates obtained using thermoterrace dimensions and geodetic survey results with those determined using aerial photographs showed that erosion rate values obtained in these two ways are approximately of the same order.  相似文献   

Pollutant—particle associations and dynamics in coastal marine environments: a review     

C. R. Olsen  N. H. Cutshall  I. L. Larsen 《Marine Chemistry》1982,11(6):501-533

A wide variety of substances, including known or potential pollutants, become associated with particles in coastal marine environments. This association may result from: (1) ion exchange, precipitation, or hydrophobic interactions with the particle surface, (2) co-precipitation with iron and manganese hydrous oxide coatings, (3) complexation with organic substances bound or aggregated with particles, (4) incorporation into mineral lattices, organisms or fecal material, or (5) flocculation of colloidal organic and inorganic matter during river and sea water mixing. The transport, accumulation and fate of such chemically-reactive pollutants in coastal marine environments are governed to a great extent by particle dynamics. Understanding of the mechanisms and processes affecting pollutant-particle associations and dynamics allows the prediction of the fate of a wide variety of pollutants in estuarine, coastal and marine environments.  相似文献   

Cellular energy allocation in the Arctic sea ice amphipod Gammarus wilkitzkii exposed to the water soluble fractions of oil     

Olsen GH  Carroll J  Sva E  Camus L 《Marine environmental research》2008,66(1):213-214

Increasing offshore oil and gas activities in the European Arctic has raised concerns of the potential anthropogenic impact of oil-related compounds on the polar marine ecosystem. We measured cellular energy allocation (CEA) in the sea ice amphipod Gammarus wilkitzkii after exposure for one month to the water soluble fraction (WSF) of oil. The CEA biomarker measures the energy budget of organisms by biochemically assessing changes in carbohydrates, protein and lipid content as well as the electron transport system activity. A significantly higher protein content was observed in the medium dose compared to controls, while the total energy budget was not affected in G. wilkitzkii. This indicates that parts of the energy budget of G. wilkitzkii, which is a key species in the Arctic ecosystem, is affected by a WSF of oil.  相似文献