The strengthening East Australian Current, its eddies and biological effects — an introduction and overview     

Iain M. Suthers  Jock W. YoungMark E. Baird  Moninya RoughanJason D. Everett  Gary B. BrassingtonMaria Byrne  Scott A. CondieJason R. Hartog  Christel S. HasslerAlistair J. Hobday  Neil J. HolbrookHamish A. Malcolm  Peter R. OkePeter A. Thompson  Ken Ridgway 《Deep Sea Research Part II: Topical Studies in Oceanography》2011,58(5):538-546

The poleward flowing East Australian Current (EAC) is characterised by its separation from the coast, 100-200 nautical miles north of Sydney, to form the eastward flowing Tasman Front and a southward flowing eddy field. The separation zone greatly influences coastal ecosystems for the relatively narrow continental shelf (only 15-50 km wide), particularly between 32-34°S. In this region the continental shelf has a marked shift in the seasonal temperature-salinity relationship and elevated surface nitrate concentrations. This current parallels the portion of the coast where Australia’s population is concentrated and has a long history of scientific research. However, understanding of physical and biological processes driven by the EAC, particularly in linking circulation to ecosystems, is limited. In this special issue of 16 papers on the EAC, we examine the effects of climatic wind-stress forced ocean dynamics on EAC transport variability and coastal sea level, from ENSO to multi-decadal time scales; eddy formation and structure; fine scale connectivity and larval retention. Comparisons with the poleward-flowing Leeuwin Current on Australia’s west coast show differences in ecosystem productivity that can be attributed to the underlying physics in each region. On average there is double the chlorophyll a concentration on the east coast than the west. In comparison to the Leeuwin, the EAC may have less local retention of larvae and act as a partial barrier to onshore transport, which may also be related to the local spawning and early life history of small pelagic fish on each coast. Inter-annual variations in the EAC transport produce a detectable sea-level signal in Sydney Harbour, which could provide a useful fisheries index as does the Fremantle sea level and Leeuwin Current relationship. The EAC’s eddy structure and formation by the EAC are examined. A particular cold-core eddy is shown to have a “tilt” towards the coast, and that during a rotation the flow of particles may rise up to the euphotic zone and then down beneath. In a warm-core eddy, surface flooding is shown to produce a new shallower surface mixed layer and promote algal growth. An assessment of plankton data from 1938-1942 showed that the local, synoptic conditions had to be incorporated before any comparison with the present. There are useful relationships of water mass characteristics in the Tasman Sea and separation zone with larval fish diversity and abundance, as well as with long-line fisheries. These fisheries-pelagic habitat relationships are invaluable for fisheries management, as well as for climate change assessments.There is further need to examine the EAC influence on rainfall, storm activity, dust deposition, and on the movements by fish, sharks and whales. The Australian Integrated Marine Observing System (IMOS) has provided new infrastructure to determine the changing behaviour of the EAC and its bio-physical interaction with the coasts and estuaries. The forecasting and hindcasting capability developed under the Bluelink project has provided a new tool for data synthesis and dynamical analysis. The impact of a strengthening EAC and how it influences the livelihoods of over half the Australian population, from Brisbane to Sydney, Hobart and Melbourne, is just being realised.  相似文献   

Mean sea level trends around the English Channel over the 20th century and their wider context     

Ivan Haigh  Robert Nicholls  Neil Wells 《Continental Shelf Research》2009

This paper provides estimates of rates of change in mean sea level around the English Channel, based on an extensive new hourly sea level data set for the south coast of the UK, derived from data archaeology. Mean sea level trends are found to vary by between 0.8 and 2.3 mm/yr around the Channel. The rates of mean sea level change are calculated by removing the coherent part of the sea level variability from the time series of annual mean sea level before fitting linear trends. The improvement in accuracy gained by using this approach is assessed by comparing trends with those calculated using the more traditional method, in which linear trends are fitted directly to the original records. Removal of the coherent part of the sea level variability allows more precise trends to be calculated from records spanning 30 years. With the traditional approach 50 years is required to obtain the same level of accuracy. Rates of vertical land movement are approximated by subtracting the mean sea level trends from the most recent regional estimate of change in sea level due to oceanographic processes only. These estimated rates are compared to measurements from geological data and advanced geodetic techniques. There is good agreement around most of the UK. However, the rates estimated from the sea level records imply that the geological data suggest too much submergence along the western and central parts of the UK south coast. Lastly, the paper evaluates whether the high rates of mean sea level rise of the last decade are unusual compared to trends observed at other periods in the historical record and finds that they are not.  相似文献   

The view from out West: embeddedness, inter-personal relations and the development of an indigenous film industry in Vancouver   总被引：1，自引：0，他引：1  

Neil M. Coe   《Geoforum》2000,31(4):391-407

This paper considers the development of a particular cultural industry, the indigenous film and television production sector, in a specific locality, Vancouver (British Columbia, Canada). Vancouver’s film and television industry exhibits a high level of dependency on the location shooting of US funded productions, a relatively mobile form of foreign investment capital. As such, the development of locally developed and funded projects is crucial to the long-term sustainability of the industry. The key facilitators of growth in the indigenous sector are a small group of independent producers that are attempting to develop their own projects within a whole series of constraints apparently operating at the local, national and international levels. At the international level, they are situated within a North American cultural industry where the funding, production, distribution and exhibition of projects is dominated by US multinationals. At the national level, both government funding schemes and broadcaster purchasing patterns favour the larger production companies of central Canada. At the local level, producers have to compete with the demands of US productions for crew, locations and equipment. I frame my analysis within notions of the embeddedness or embodiment of social and economic relations, and suggest that the material realities of processes operating at the three inter-linked scales, are effectively embodied in a small group of individual producers and their inter-personal networks.  相似文献   

Late Quaternary solifluction sheets in the British uplands     

Stephan Harrison  Leanne Hughes  Neil Glasser  Oliver Kuras 《第四纪科学杂志》2021,36(7):1162-1173

Solifluction sheets are large-scale and extensive valley-floor and valley-side landforms developed widely in the British Isles from mass-wasting of glacial and periglacial sediments during late-glacial times. We describe their geographical distribution and review the processes that have led to their development. We use data from the Cheviot Hills, the one site in the British Isles where sedimentology and optically stimulated luminescence dating have been combined, to assess their age and nature of deposition. We also present data from central Wales where a new mapping and resistivity survey has reconstructed the nature of valley-side solifluction sheets. We explore the relative lack of recent research on these landforms and argue that solifluction sheets represent a clear example of how upland geomorphological systems have responded to late-glacial climate change. We end by identifying a number of areas where research on these enigmatic features could be focussed, including better understanding of their distribution, sedimentology and age.  相似文献   

Magnetic spherules in coastal plain sediments,Sullivan's Island,South Carolina,USA     

Pamela L. Taylor  Robert L. Nusbaum  A. Kem Fronabarger  Michael P. Katuna  Neil Summer 《Meteoritics & planetary science》1996,31(1):77-80

Abstract— We extracted black, magnetic spherules from well cuttings of Oligocene sediments in the coastal plain of South Carolina, USA. Three possible origins were considered: industrial, volcanic, and extraterrestrial. An extraterrestrial origin by ablation of parent meteoroid material is proposed, based on the spherule morphologies, the presence of metallic Fe cores in many of the spherules, and the detection of wüstite in some of the oxide rims. Low Ni contents are problematic but may be attributed to the ablation of a low-Ni parental body, such as hexahedrite. The presence of spherules in somewhat clay-like, sandy sediments is unusual, as most magnetic spherules are found in abyssal muds. Based on benthic foraminiferal assemblages and sediment distribution above, within, and below the beds containing spherules, it is unlikely that the spherules were transported from a deep-sea environment.  相似文献   

Propagation Modelling Based On Wavefield Factorization and Invariant Imbedding     

John Mccoy  L. Neil Frazer 《Geophysical Journal International》1986,86(3):703-717

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The relationship between the magnitude and direction of the geomagnetic field during the Late Tertiary in Eastern Iceland     

Neil Roberts  John Shaw 《Geophysical Journal International》1984,76(3):637-651

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Canonical planetary perturbation equations for velocity-dependent forces,and the Lense-Thirring precession     

Neil Ashby  Timothy Allison 《Celestial Mechanics and Dynamical Astronomy》1993,57(4):537-585

A form of planetary perturbation theory based on canonical equations of motion, rather than on the use of osculating orbital elements, is developed and applied to several problems of interest. It is proved that, with appropriately selected initial conditions on the orbital elements, the two forms of perturbation theory give rise to identical predictions for the observable coordinates and velocities, while the orbital elements themselves may be strikingly different. Differences between the canonical form of perturbation theory and the classical Lagrange planetary perturbation equations are discussed. The canonical form of perturbation theory in some cases has advantages when the perturbing forces are velocity-dependent, but the two forms of perturbation theory are equivalent if the perturbing forces are dependent only on position and not on velocity. The canonical form of the planetary perturbation equations are derived and applied to the Lense Thirring precession of a test body in a Keplerian orbit around a rotating mass source.  相似文献   

Speleothem stable isotope records interpreted within a multi-proxy framework and implications for New Zealand palaeoclimate reconstruction   总被引：1，自引：0，他引：1  

Andrew Lorrey  Paul Williams  Jim Salinger  Tim Martin  Jonathan Palmer  Anthony Fowler  Jian-xin Zhao  Helen Neil 《Quaternary International》2008,187(1):52

A primary step in the interpretation of speleothem stable isotope records (¹⁸O/¹⁶O and ¹³C/¹²C) is to conduct a comparison with other local palaeoclimate proxies. Here, two new master speleothem δ¹⁸O and δ¹³C records (one from eastern North Island, and the other from western/southern South Island, New Zealand) are evaluated against independent precipitation and temperature proxy information to assess their palaeoclimate reconstruction potential. This comparison also resulted in a serendipitous opportunity to reconstruct past circulation using climate regime classification [Lorrey, A.M., Fowler, A.M., Salinger, J., 2007a. Regional climate regime classification as a qualitative tool for interpreting multi-proxy palaeoclimate data spatial patterns: a New Zealand case study. Palaeo-3, in press], specifically because these two regional climate districts are hyper-sensitive to westerly circulation changes, and in many cases, exhibit contrasting climate character in response to circulation anomalies.For both the western South Island and the eastern North Island master speleothem δ¹³C records, variations tracked changes in relative regional precipitation. The δ¹⁸O master speleothem record for both regions varied with temperature change. Both records contain strong regional climate signals that suggest they have good value for palaeoclimate reconstruction. The ensuing attempt at a multi-proxy reconstruction of regional climate regimes from the compiled proxies indicates past circulation in the New Zealand sector has varied considerably during the past four millennia. Centennial-scale circulation changes for the past 4000 years are evident, and are analogous to modern Blocking, Zonal and Trough regime types [Kidson J. W., 2000. An analysis of New Zealand synoptic types and their use in defining weather regimes. International Journal of Climatology 20, 299–316] that characterise changes in present-day (prevailing) westerly circulation. This palaeoclimate reconstruction indicates modern regional climate regime classification can be extended at least as far back as the temporal coverage of the records presented here, and it can likely be improved on with better dating control and the addition of new records with higher resolution. It is also anticipated that future work will expand to include more proxy data from across New Zealand to improve the clarity of past climate regime occurrence for the Late Holocene.  相似文献   

Inversion of sonic waveforms with unknown source and receiver functions     

L. Neil Frazer  Xinhua Sun  Roy H. Wilkens 《Geophysical Journal International》1997,129(3):579-586

A seismogram that is several times the length of the source-receiver wavelet is windowed into two parts—these may overlap—to obtain two seismograms with approximately the same source function but different Green's functions. A similarly windowed synthetic seismogram gives two corresponding synthetic seismograms. The spectral product of the window 1 data with the window 2 synthetic is equal to the spectral product of the window 1 synthetic with the window 2 data only if the correct earth model is used to compute the synthetic. This partition principle is applied to well-log sonic waveform data from Ocean Drilling Project hole 806B, a slow formation, and used there to estimate Poisson's ratio from a single seismogram whose transmitter and receiver functions are unknown. A multichannel extension of the algorithm gives even better results. The effective borehole radius R _b, was included in the inversion procedure, because of waveform sensitivity to R _b. Inversion results for R _b agreed with the sonic caliper, but not the mechanical caliper; thus if R _b is not included in the inversion its value should be taken from the sonic caliper.  相似文献