Limnology of Two Antarctic Epishelf Lakes and their Potential to Record Periods of Ice Shelf Loss   总被引：1，自引：0，他引：1  

James A. Smith  Dominic A. Hodgson  Michael J. Bentley  Elie Verleyen  Melanie J. Leng  Steven J. Roberts 《Journal of Paleolimnology》2006,35(2):373-394

George VI Ice Shelf is the largest ice shelf on the western side of the Antarctic Peninsula and its northern margin marks the southern most latitudinal limit of recent ice shelf retreat. As part of a project to reconstruct the long-term (Holocene) history of George VI Ice Shelf we studied two epishelf lakes impounded by the ice shelf at Ablation Point, on the east coast of Alexander Island. These lakes, Moutonnée and Ablation, are stratified water bodies with a lower marine layer and an upper freshwater layer. To determine if their sediment records could be used to detect past changes in the presence or absence of the ice shelf it was necessary to describe their present-day limnology and sedimentology. We measured water column chemistry and sampled the water column and sediments of the lakes along vertical and horizontal transects. We analysed these samples for diatoms, stable isotopes (δ¹⁸O, δ²H, δ¹³C_DIC, δ¹³C_org), geochemistry (TOC, TN, C/N ratios) and physical sedimentology (grain-size). This was supplemented by chemical and biological reference data from the catchments. Results showed that the water columns of both lakes are nutrient limited and deficient in phytoplankton. Benthic productivity is low and decreases with depth. Comparison of water column chemistry with an earlier survey shows a net increase in the thickness of the freshwater layer in Moutonnée Lake between 1973 and 2001, which could indicate that George VI Ice Shelf has thinned during this period. However, a similar trend was not observed in Ablation Lake (5 km to the north) and an alternative explanation is that the changes are a seasonal phenomena. Data from the surface sediment transects identified a number of proxies that respond to the present day stratification of the water column including diatom species composition, stable isotopes and geochemistry, particularly in Moutonnée Lake. Collectively these data have been used to develop a conceptual model for determining past ice shelf configuration in epishelf lakes. Specifically, periods of past ice shelf loss, and the removal of the ice dam, would see the present stratified epishelf lake replaced by a marine embayment. It is suggested that this change would leave a clear signature in the lake sediment record, notably the deposition of an exclusively marine biological assemblage, increased ice rafted debris and δ¹³C_org values that are indicative of marine derived organic matter. These authors contributed equally to this work  相似文献   

J. Wainwright and M. Mulligan (eds), Environmental modelling: finding the simplicity in complexity     

Dominic R. Kniveton 《Journal of Paleolimnology》2006,36(4):433-434

  相似文献   

Indicator Geostatistical Analysis of Sand Interconnections Within a Till   总被引：1，自引：0，他引：1  

Joel R. Sminchak  David F. Dominic  Robert W. Ritzi  Jr. 《Ground water》1996,34(6):1125-1131

  相似文献   

The Neupert effect: What can it tell us about the impulsive and gradual phases of solar flares?     

Brian R. Dennis  Dominic M. Zarro 《Solar physics》1993,146(1):177-190

The Neupert effect is the name given to the correlation observed in many flares between the time-integrated microwave and hard X-ray emissions and the soft X-ray emission light curve. We have used hard X-ray data from the Hard X-Ray Burst Spectrometer (HXRBS) on the Solar Maximum Mission (SMM) and soft X-ray data from the detector on GOES to determine what fraction of all events show this correlation and how the correlation changes from the impulsive to the gradual phase. We have found that of 66 HXRBS events observed in 1980 with a peak rate of > 1000 counts s^-1, 58 (80%) showed good correlations with peaks in the GOES time derivative plot corresponding to peaks in the hard X-ray (HXR) plots to within ±20 s. In 20 of these good-correlation cases (30%), the soft X-ray (SXR) time derivative stays high after the HXR emission has decreased suggesting that the later emissions result from energy release in a loop already affected by the initial energy release. In 8 of the 13 flares that showed poor correlation, the SXR time derivative shows no peak corresponding to the initial HXR impulsive peak that has structure on a time scale of 1 s. This suggests that in these events the initial impulsive energy release results primarily in electron acceleration, and that the secondary plasma heating from the accelerated electrons contributes relatively little compared to the more gradual plasma heating already taking place at the same time. The more gradually varying events, commonly referred to as type C flares, tend to show poorer correlation between the SXR time derivative and the HXR time profile. Of 26 GOES X1 or greater flares recorded between 1980 and 1989 with HXR peaks lasting over 10 rain, 13 (50%) showed poor correlation with the gradual HXR peaks either not registering at all in the SXR time derivative plots or showing up as very broad peaks. In one case, on 1981 April 26, the SXR time derivative peak was delayed by 13 rain. Only 17 (65%) of the 26 X-flares had an earlier, impulsive component and of those, 12 (71%) showed good correlation between the impulsive peaks.  相似文献   

Origin and significance of 13-hydroxychlorophyll derivatives in sediments     

J Stuart Walker  Angela H Squier  Dominic A Hodgson  Brendan J Keely   《Organic Geochemistry》2002,33(12)

The authenticity of hydroxychlorophyll derivatives in sediments has been verified by subjecting pure chlorophyll preparations to the extraction method used for sediments. Model studies of chlorophyll autoxidation reveal hydroxychlorophyll as the major product formed in the presence of hydrogen peroxide. Its stability to further oxidation implies that hydroxychlorophyll derivatives are not precursors of aetioporphyrins and are more likely to produce cycloalkanoporphyrins via the processes of diagenesis. The occurrence of 13²-hydroxyphaeophytin a throughout a sediment core from Loch Ness confirms it to be a widespread chlorophyll oxidation product formed during early diagenesis. Profiles of hydroxychlorophyll derivatives in a sediment core from an Antarctic lake demonstrate their potential for use as markers of oxidation processes in palaeoenvironmental assessment.  相似文献   

Fractal interrelationships between topography and structure     

Thomas H. Wilson  Jovita Dominic 《地球表面变化过程与地形》1998,23(6):509-525

Factal interrelationships between topography and structure are investigated in two areas of the North American central Appalachian Mountains: one in the intensely deformed Valley and Ridge province and the other in the relatively undeformed foreland area of the Appalachian Plateau province. In the Valley and Ridge province the fractal dimensions of topographic and structural relief vary systematically along the strike of major folds following a second-order polynominal trend. Cross-correlation of the fractal dimensions of topography to structure indicates that there is a significant positive correlation between the two. Fractal analysis of topography in the relatively undeformed foreland area of the Appalachian Plateau revealed no significant variation in the fractal characteristics of topography across the study area, consistent with the lack of near-surface structure. However, fractal analysis of deeper structures beneath the Plateau area undertaken using reflection seismic data revealed step-wise increases in fractal dimension from the deeply buried Precambrian basement to the near-surface. These vertical changes in fractal dimension can be related to the tectonic history of the area. Taken together, these studies indicate that fractal analysis provides a means to quantify and compare the influence of near-surface structure on topographic development and lateral and vertical structural variability. Fractal analysis provides a means to characterize the systematic changes in the complex patterns formed by topography and structure and the interrelationships between them. Similarity in their fractal characteristics implies similarity in the relative amplitude and abundance of different wavelength features in the topographic or structural profile. © 1998 John Wiley & Sons, Ltd.  相似文献   

Long-term morphodynamic evolution of estuaries: An inverse problem     

Harshinie Karunarathna  Dominic Reeve  Mark Spivack 《Estuarine, Coastal and Shelf Science》2008

A new technique for predicting long-term variations in estuary morphology is developed using a morphological evolution equation that isolates diffusive and non-diffusive processes in estuaries. The contribution from non-diffusive processes to the morphological changes of the estuary is incorporated in the governing equation by a source function. The source function is derived by solving an inverse problem using historic survey data of the Humber estuary, UK covering a period of 150 years.  相似文献   

Exploring former subglacial Hodgson Lake,Antarctica Paper I: site description,geomorphology and limnology     

Dominic A. Hodgson  Stephen J. Roberts  Michael J. Bentley  James A. Smith  Joanne S. Johnson  Elie Verleyen  Wim Vyverman  Andy J. Hodson  Melanie J. Leng  Andreas Cziferszky  Adrian J. Fox  David C.W. Sanderson 《Quaternary Science Reviews》2009,28(23-24):2295-2309

  相似文献   

Linear free energy relationships for metal-ligand complexation: Monodentate binding to negatively-charged oxygen donor atoms     

Richard F. Carbonaro  Dominic M. Di Toro 《Geochimica et cosmochimica acta》2007,71(16):3958-3968

The analysis presented below suggests that the following equation models monodentate binding to negatively-charged oxygen donor atoms with no distinction between phenolic, carboxylic or inorganic hydroxide functional groups: log K_ML = α_O log K_HL + β_O; where K_ML is the metal-ligand formation constant, K_HL is the corresponding proton-ligand formation constant, and α_O and β_O are termed the Irving-Rossotti slope and intercept, respectively. Linear free energy relationships (LFERs) of this type are presented for 24 different metal ions complexing to negatively-charged oxygen donor atoms. Ligands selected for use in LFERs meet the following criteria: (i) they contain negatively-charged oxygen donor atoms (e.g., carboxylic acids and phenols), (ii) they are capable of only monodentate binding to metal ions, (iii) steric hindrances are not expected to influence the extent of metal-ligand binding, and (iv) the negatively-charged oxygen donor atom is the only functional group that imparts charge. The intercept of all LFERs was nearly zero for all metal ions investigated (β_O ≈ 0). The magnitude of α_O indicates the relative preference of metal binding to negatively-charged oxygen donor atoms and to the proton. Values of α_O can be used in QSARs (quantitative structure activity relationships) to estimate metal-NOM (natural organic matter) binding constants employed in the Windermere Humic Aqueous Model (WHAM) version V.  相似文献   

Greenhouse gas intensity of three main crops and implications for low-carbon agriculture in China     

Wen Wang  Liping Guo  Yingchun Li  Man Su  Yuebin Lin  Christian de Perthuis  Xiaotang Ju  Erda Lin  Dominic Moran 《Climatic change》2015,128(1-2):57-70

  相似文献