Multi-decadal coastal change in New Zealand: Evidence, mechanisms and implications     

Karin R. Bryan  Paul S. Kench  Deirdre E. Hart 《New Zealand geographer》2008,64(2):117-128

Abstract:   Coastal research and monitoring on New Zealand beaches have typically examined seasonal and event-driven (storms) changes in the coast. However, historical records are now of sufficient length to indicate that change occurs at longer timescales. This paper presents examples of multi-decadal change at three case-study locations around New Zealand. Results show that morphological adjustment of the coast occurs at multi-decadal scales and is much larger than short-term dynamics. Physical mechanisms driving changes are ill defined but may be associated with El Niños and La Niña episodes which modulate waves and sea level, as well as changes in sediment supply.  相似文献   

The role of biomorphodynamics in estuarine evolution in New Zealand     

Barend Van Maanen  Giovanni Coco  rew Swales  Karin R. Bryan 《New Zealand geographer》2008,64(2):162-164

Abstract:   Biomorphodynamic interactions, the feedback loops that operate between physical processes, biology and morphology, affect the long-term evolution of estuaries. This paper outlines how consideration of such interactions and implementation through innovative modelling techniques can become the next crucial step needed to advance understanding of estuarine evolution.  相似文献   

New Zealand coastal system boundaries, connections and management   总被引：1，自引：1，他引：0  

Deirdre E. Hart  Karin R. Bryan 《New Zealand geographer》2008,64(2):129-143

Abstract:    Understanding coastal boundaries, connections and drivers of landscape change is integral to effective coastal planning and management. This concept is explored here through case studies representing two very different New Zealand systems: embayed sand beaches in eastern and western open-coast settings; and mixed sand and gravel coast river-mouth lagoons. When framed within a resource and environmental management context these studies indicate that national recognition of the dynamic and interactive nature of coastal environments is a relatively new and amorphous phenomenon in New Zealand and, as such, has been ineffective in driving integrated regional management practices and sustainable coastal outcomes.  相似文献   

Impacts of a bivalve mass mortality event on an estuarine food web and bivalve grazing pressure     

Hannah F. E. Jones  Conrad A. Pilditch  David P. Hamilton  Karin R. Bryan 《新西兰海洋与淡水研究杂志》2013,47(3):370-392

Declines in bivalve populations have been quite common worldwide, often associated with coastal development, pollution and climate change. In addition to the impacts of these chronic stressors, occasional mass mortality events may have severe consequences on ecosystem services and biodiversity. In this study, we examined the impact of a mass mortality event of the clam (Austrovenus stutchburyi) on an estuarine food web and the grazing pressure exerted by the bivalve population. In February 2009, c. 60% of the clam population died in Whangateau Harbour, New Zealand. Population clearance rate calculations suggest that the clam population do not exert significant top-down control on phytoplankton biomass in the estuary, and thus the impact of the mortality event on bivalve grazing pressure was less severe than the reduction in abundance would suggest. A trophic model shows that phytoplankton play a limited role in the estuary food web, which is instead dominated by microphytobenthos and clams. This study highlights the importance of microphytobenthos in shallow estuaries, and the application of the trophic model is a useful tool that can identify key components of the ecosystem and could help inform monitoring programmes.  相似文献   

A relationship between liquid water content and chemical composition in clouds     

Detlev Mller  Karin Acker  Wolfgang Wieprecht 《Atmospheric Research》1996,41(3-4)

In this paper we present two-year results from the Cloud Chemistry Measurements Programme, carried out at Mt. Brocken/Hart (Germany) to assess the influence of cloud physical parameters on the chemical composition of clouds. There are large variations in the chemical composition of cloud water. We found that the liquid water content of clouds predominantly determines the ionic content. The relationship is best approximated by a power function, nearly identical for all chemical species. We identified deviations of data points from the general relationship accompanying events with different air pollution situations. An important conclusion is that cloud chemistry monitoring in the sense of air pollution studies is meaningless without measurement of cloud physical parameters. These are liquid water content, cloud base altitudes, and to some extent, droplet size distribution.  相似文献   

9000 years of geochemical evolution of lithogenic major and trace elements in the sediment of an alpine lake – the role of climate, vegetation, and land-use history     

Karin A. Koinig  William Shotyk  André F. Lotter  Christian Ohlendorf  Michael Sturm 《Journal of Paleolimnology》2003,30(3):307-320

A 9000cal. year record of geochemistry was analysed in a sediment core obtained from a Swiss alpine hard-water lake (1937 ma.s.l.) that is located at the present-day tree-line. Geochemical stratigraphies are compared to changes in mineralogy, grain-size, pollen, and macrofossil records. This allows the reconstruction of the effects of changes in vegetation and of 3500 years of land-use in the catchment area on sediment geochemistry. Using principal component analysis, two major geochemical groups are distinguished: (i) Changes in concentrations of Rb, Ti, Zr, Fe, As, and Pb are closely related to corresponding changes in the concentrations of quartz and clay. They are thus considered to represent the silicate fraction which shows an increase from the oldest to the youngest core section. (ii) In contrast, Ca and Sr concentrations are positively correlated with changes in silt, sand, and calcite. They are therefore considered to represent the carbonate fraction which gradually decreased. Based on constrained cluster analysis, the core is divided into two major zones. The oldest zone (A; 9000–6400 cal.BP) is characterised by high concentrations of detrital carbonates. The more open catchment vegetation at that time promoted the physical weathering of these carbonates. The second major zone (B, 6400 cal.BP–1996 AD) is divided into four subsections with boundaries at ca. 3500, 2400, and 160cal. BP. The lower part of this zone, B1, is characterized by a gradual decrease in the carbonate-silt fraction and a pronounced increase in the silicate-clay fraction. This is concurrent with the expansion of Picea in the catchment area, which probably stabilized the soil. The middle part, B2 and B3 (3500–160cal. BP), comprises pronounced fluctuations in all elements, especially Ca, Sr, Mn, and Rb, but also in clay and silt. These changes are related to varying intensities of alpine farming. In the same section, Mn/Fe ratios are highly variable, suggesting changes in the mixing regime of the lake with phases of anoxic bottom water. The uppermost section, B4 (since 160cal. BP), is characterized by a steep decline in the silicate fraction and an increase in Ca and Sr. Despite the decrease in the silicate fraction, Pb increases, due to elevated atmospheric input resulting from early metal pollution, are masked by the high natural variability. Generally, changes in vegetation, which correspond to climate changes in the early Holocene and to human activities since ca. 3700cal. BP, are the controlling factor for variations in the geochemical composition of the sediment of Sägistalsee.  相似文献   

Limnological conditions in a subarctic lake (northern Québec, Canada) during the late Holocene: analyses based on fossil diatoms     

Karin Ponader  Reinhard Pienitz  Warwick Vincent  Konrad Gajewski 《Journal of Paleolimnology》2002,27(3):353-366

A fossil diatom record covering the past 3000 cal. years BP wasanalyzed from a small lake in northwestern Québec near the northernlimit of present-day tree-line. Fragilaria virescens var.exigua Grunow in Van Heurck was the dominant speciesthroughout the core with abundances ranging between 13–35% of thetotal valve count. There was a replacement of alkaliphilous taxa byacidophilous taxa beginning ca. 1300 cal. yr ago, probably reflectinglong-term, natural acidification processes. A diatom-based transfer functionwas used to provide quantitative estimates of variations in lakewater dissolvedorganic carbon (DOC). These inferred values showed that DOC concentrations haveremained stable over the past 3000 years (mean ± S.D. = 5 ± 0.43 mg C l^–1), suggesting relatively constant allochthonouscarbon inputs and underwater light conditions during the late Holocene. Thereconstructed DOC data were compared to the palynological record from the samelake. Our study indicates that, in contrast to paleolimnological records fromlakes in central and western Canada, climatic variations and associatedvegetational shifts have been too subtle to cause pronounced variations in DOCin this northern Québec site.  相似文献   

Analysis of magnetic data over part of the Younger Granite Province of Nigeria     

Charles O. Ofoegbu  Karin Hein 《Pure and Applied Geophysics》1991,136(2-3):173-189

The results of a magnetic study of part of the Younger Granite Province of Nigeria are presented here. Spectral analysis of the magnetic anomalies over the area has been carried out in an effort to estimate the depth to magnetic sources. Average magnetic source depth of 286 m has been obtained for the area and this is thought to be related to the depth to the top of the main anomalous structures in the area. Observed magnetic anomaly profiels taken across the area have been interpreted in terms of arbitrarily shaped bodies—whose existence was confirmed by 3-D Hilbert transformation-using nonlinear optimization techniques. The modelled bodies occur at depths of 200–760 m and have magnetizations of 0.29–0.47 A/m. The results from the analysis of the magnetic field are discussed in relation to the results from previous gravity studies over the area and the mode of emplacement of the Younger Granites.  相似文献   

Die kurzwellige Strahlung von Sonne und Himmel auf einen nach Süden orientierten Würfel     

Karin Schram  J. C. Thams 《Pure and Applied Geophysics》1967,66(1):183-200

Zusammenfassung In Locarno-Monti am Alpensüdfuss wurde von Juni 1961 bis Dezember 1964 die kurzwellige Strahlung von Sonne und Himmel (Globalstrahlung) auf die Flächen eines nach Süden orientierten Würfels registriert. An Hand dieses Materials konnten mittlere Tages- und Jahresgänge der Globalstrahlung für extreme und mittlere Strahlungsbedingungen gewonnen werden. Der Anteil der Strahlungsenergie, die auf eine senkrechte Fläche fällt, an der gesamten Strahlung auf den Würfel, wird von der Orientierung der Wand und der relativen Sonnenscheindauer beeinflusst. Es wurde die Abhängigkeit des Strahlungsgenusses der verschieden orientierten Wände von der relativen Sonnenscheindauer untersucht. Mit Hilfe dieser Zusammenhänge wurden klimatologische Mittelwerte der Globalstrahlung aus langjährigen Mittelwerten der relativen Sonnenscheindauer in Locarno-Monti abgeleitet. Um auch für Stationen, an denen die Globalstrahlung nur auf die horizontale Fläche gemessen wird, jene auf senkrechte Flächen berechnen zu können, werden die Verhältnisse der Strahlung von Sonne und Himmel auf eine Wand zu der auf die horizontale Fläche angegeben.

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Summary Measurements of the short wave radiation of sund and sky (global radiation) on surfaces of a cube orientated to the south have been carried out at Locarno-Monti (Switzerland) from June 1961 to December 1964. These data were used for deducing the annual and daily variations of the global radiation under extreme and average conditions. The percentage of the radiation energy on a vertical surface on the entire radiation on the cube depends on the orientation of the surface and on the relative duration of sunshine. Further researches involve the dependence of the radiation on vertical walls of different orientation on the duration of sunshine. With the aid of these relations and the climatological means of the relative duration of sunshine at Locarno-Monti average values of the global radiation could be determined. In order to calculate the radiation on vertical surfaces for those stations, for which only measurements of the global radiation on a horizontal surface are available, the relations between the radiation on a wall to that on a horizontal surface must be known.

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Résumé De juin 1961 à décembre 1964, le rayonnement de courtes longueurs d'onde du soleil et du ciel (rayonnement global) a été enregistré à Locarno-Monti, au pied sud des Alpes, au moyen de surfaces réceptrices disposées suivant les faces d'un cube orienté vers le sud. Le matériel de mesure recueilli permet d'établir les variations journalières et saisonnières moyennes du rayonnement global lors de conditions extrêmes et moyennes de rayonnement. Rapportée à l'énergie rayonnante totale interceptée par le cube, la fraction de rayonnement reçue par une certaine face verticale dépend de l'orientation de cette face et de la durée relative d'insolation. On étudie l'influence de cette dernière sur l'éclairement dont jouissent les différentes faces du cube. A l'aide des relations trouvées, on calcule des moyennes climatologiques du rayonnement global à partir de moyennes tirées des longues séries d'enregistrements de la durée relative d'insolation à Locarno-Monti. En donnant encore le rapport des rayonnements du soleil et du ciel reçus respectivement par une surface verticale et par l'horizontale, on rend possible l'évaluation du rayonnement global tombant sur une paroi verticale aux stations où seuls des récepteurs horizontaux sont mis en uvre.

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Riassunto A Locarno-Monti, al piede meridionale delle Alpi, fu registrata dal giugno 1961 al dicembre 1964 la radiazione a onde corte del sole e cielo (radiazione globale) sulle superficie di un cubo orientato verso sud. Partendo da questo materiale poterono essere ricavati gli andamenti medi giornalieri e annuali della radiazione globale per condizioni di radiazione estreme e media. La parte di energia della radiazione, che cade su una superficie verticale, rispetto all'energia totale sul cubo è influenzata dall'orientamento della superficie e dalla durata relative dell'insolazione. È stata studiata la dipendenza tra la radiazione ricevuta dalle superficie diversamente orientate e la durata relativa dell'insolazione. Con l'ausilio di queste relazioni furono calcolati valori medi climatologici della radiazione globale dai valori medi pluriannuali della durata dell'insolazione a Locarno-Monti. Per poter calcolare anche per le stazioni, per le quali la radiazione globale fu misurata solo su una superficie orizzontale, quella su superficie verticali, vengono comunicati i rapporti tra la radiazione sole e cielo su una superficie verticale e la radiazione sulla superficie orizzontale.

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Thermal Equilibrium States of Europa's Ice Shell: Implications for Internal Ocean Thickness and Surface Heat Flow     

Hauke HussmannTilman Spohn  Karin Wieczerkowski 《Icarus》2002,156(1):143-151

Ice-shell thickness and ocean depth are calculated for steady state models of tidal dissipation in Europa's ice shell using the present-day values of the orbital elements. The tidal dissipation rate is obtained using a viscoelastic Maxwell rheology for the ice, the viscosity of which has been varied over a wide range, and is found to strongly increase if an (inviscid) internal ocean is present. To determine steady state values, the tidal dissipation rate is equated to the heat-transfer rate through the ice shell calculated from a parameterized model of convective heat transfer or from a thermal conduction model, if the ice layer is found to be stable against convection. Although high dissipation rates and heat fluxes of up to 300 mWm⁻² are, in principle, possible for Europa, these values are unrealistic because the states for which they are obtained are thermodynamically unstable. Equilibrium models have surface heat flows around 20 mWm⁻² and ice-layer thicknesses around 30 km, which is significantly less than the total thickness of the H₂O-layer. These results support models of Europa with ice shells a few tens of kilometers thick and around 100-km-thick subsurface oceans.  相似文献