Diver-operated piston corer for nearshore use

A diver-operated piston corer suitable for collecting cores of >3 m length from fine-grained nearshore sediment has been developed. The corer uses a platform that rests on the sediment surface supporting both the operators and a derrick that maintains the piston at the sediment-water interface. The core is insected into and recovered from the sediment manually. The technique offers several advantages; low cost, minimal disruption of the sediment-water interface, little compaction of the sediment, the ability to collect longer length cores than is possible with gravity corers, and the ability to be deployed from relatively small boats. Dissolved ammonium and inorganic carbon data are presented from a 3.3-m core collected by this technique from Tomales Bay, California.     

Rock-magnetic proxies of climate change in the loess-palaeosol sequences of the western Loess Plateau of China

Results of the first detailed study of the climate proxy record in the loess-palaeosol sequence at Xining-one of the few palaeoclimate sites in the currently arid western Loess Plateau of China-illustrate the importance of making many types of rock-magnetic measurements other than susceptibility. A multiparameter approach yielded confirmation that here, as elsewhere in the Loess Plateau, the susceptibility enhancement in palaeosols was caused primarily by ultrafine magnetite and maghaemite. Nevertheless, magnetic enhancement was caused not exclusively by changes in relative grain size, but also by variations in concentration and mineralogy of the magnetic fraction.
The effects of concentration variations were removed through normalization of susceptibility and anhysteretic remanence with saturation magnetization and saturation remanence, respectively. the resulting signal was ascribed more confidently to variation in magnetic grain size, which in turn was interpreted as a better proxy of pedogenesis than simple susceptibility. Variations in magnetic mineralogy were also determined to constrain interpretations further. the data were then used to discuss climate history at Xining. Finally, results from Xining were compared with other western sites and contrasted with eastern sites.
In summary: (1) data is presented from a new Loess Plateau site which also appears to yield a global climate signal; (2) a demonstration is made of a more rock-magnetically robust way to separate concentration, composition and grain-size controls on susceptibility and other magnetic parameters; and (3) models are provided for inter-regional comparisons of palaeoclimate proxy records.     

Producer Services Research in the United Kingdom

This paper reviews recent research in the United Kingdom on producer services and suggests directions for further research. A recurrent theme in UK-based geographic research into producer services is the role of service activities, establishments, and trade in uneven development of the UK space economy, a role manifested in uneven provision and quality of services in peripheral regions. During the 1980s, overall growth in demand for producer services and the rapid rise in metropolitan London real estate costs reduced London's dominance, but these trends moderated by the end of the decade. In the absence of adequate government statistics, regular and standardized surveys are needed to compile a time series of service change in the United Kingdom. Directions for continued empirical research include the role of producer services in innovation and technology transfer, the implications of information technology for the location of employment in the sector, and the impacts of productivity increases on employment and wages.     

The effect of horizontal resolution on ocean surface heat fluxes in the ECMWF model

Annual mean ocean surface heat fluxes have been studied as a function of horizontal resolution in the ECMWF model (cycle 33) and compared with Oberhuber's COADS (1959–1979) based empirical estimates. The model has been run at resolutions of T21, T42, T63 and T106 for 15 months with prescribed monthly varying climatological SST and sea ice. The T42 simulation was extended to 2 years, which enabled us to determine that many differences between the resolution runs were significant and could not be explained by the fact that individual realizations of an ensemble of years can be expected to give different estimates of the annual mean climate state. In addition to systematic differences between the modeled and the observed fluxes, the simulated fields of surface shortwave and longwave radiation showed much more spatial variability than the observed estimates. In the case of the longwave radiation this may be attributable more to deficiencies in the observations than to errors in the model. The modeled latent and sensible heat fields were in better agreement with observations. The primary conclusion concerning the dependence of ocean surface fluxes on resolution is that the T21 simulation differed significantly from the higher resolution runs, especially in the tropics. Although the differences among the three higher resolution simulations were generally small over most of the world ocean, there were local areas with large differences. It appears, therefore, that in relation to ocean surface heat fluxes, a resolution greater than T42 may not be justified for climate model simulations, although the locally large differences found between the higher resolution runs suggest that convergence has not been achieved everywhere even at T106.     

Climate and chronic respiratory disease in Sydney - The case of asthma

Asthma remains a major health concern for many Australians. Currently mortality and morbidity rates are very high and have increased substantially over the last 10 years. Within Sydney there is a distinctive pattern of asthma risk with both inner-city and outer western suburbs figuring prominently.This paper looks at asthma within the Sydney metropolitan area. It pays particular attention to the direct and indirect effects of weather and climate on the disease, as well as the interplay between a number of biophysical and socio-economic factors and the role played by outdoor and indoor air pollution. In particular it discusses the relationship between topography, meteorology, air pollution and asthma in Sydney. Finally, it argues that climate change will greatly influence the prevalence and distribution of the disease.     

Responses of marsh fishes and breeding wading birds to low temperatures: A possible behavioral link between predator and prey

In the Everglades of southern Florida, several species of spring- and winter-nesting wading birds (Ciconiiformes) often abandon their nests in response to periods of cold or wet and windy weather. Using stepwise logistic regression of a variety of hydrologic and meteorologic variables on the probability of great egret nest failure, we found that cold temperatures and high wind speeds were most closely associated with nest failure in the Everglades. Water level fluctuation was not a significant correlate of failure. Quantitative visual surveys in the field showed that even moderate cooling events (15°C minimum daily temperature) dramatically altered the observed densities of marsh fishes. In controlled conditions in the laboratory, we observed centrarchid, poeciliid, and cyprinodontid fishes during normal high (19–23°C) and simulated cold snap (8–11°C) temperatures. At low temperatures, the fishes exhibited reduced activity, sought refuge by hiding in vegetation and/or substrate, and fled our approach to the tank at much greater distances. Threshold temperatures for these behaviors varied considerably between the laboratory (9–11°C) and field (15–20°C), and may be explained by differences in the previous thermal experience of the two groups of fishes. We hypothesize that the temperature-induced scarcity of fishes during spring cold snaps is an important cause of disruption of nesting for several species of wading birds in the Everglades.     

Flood control failures in a Third World City: Benin City,Nigeria — some environmental factors and policy issues

GeoJournal - Inspite of step-up efforts at controlling flood hazards in Third World cities, the frequency and magnitude of the flood problem have more than doubled in recent years. A survey of the...