NORTH ATLANTIC OSCILLATION SIGNATURES IN WESTERN IBERIAN TREE-RINGS

Exactly dated ring-width chronologies derived from Pyrenean oak and sweet chestnut trees growing in northern Extremadura, Spain, were evaluated for their potential as proxies for regional precipitation and North Atlantic Oscillation variability. The relationships among tree-rings, instrumental climatic records, and three versions of the NAO index were computed for different time subperiods over the last century. The results indicate that tree-ring records reflect, with variable intensity, both short-term and long-term variations in climate. Multiple correlation and regression analysis revealed that summer precipitation appeared to be the major factor affecting tree growth at inter-annual timescales. Moreover, since fluctuations in accumulated variability in annual rainfall over southwest Iberia are controlled by winter precipitation, the accumulated rainfall (August of the year n -1 to July of year n ) and winter NAO indices are also strongly correlated with tree-ring records at interdecadal timescales. This relationship appears to be especially strong during the second half of the 20th century, which is consistent with an increase of the NAO signal in the annual precipitation during the later part of the century. These results indicate that tree-rings from western Iberia are potential proxies of the NAO variability, useful to be included in palaeoclimatic model studies.     

CHANGING CONCEPTIONS OF SUSTAINABILITY IN BARCELONA'S PUBLIC PARKS*

ABSTRACT. In this article we explore the relationships between public parks and a broad interpretation of sustainability, taking as a case study the city of Barcelona, Spain. Recent official discourses in Barcelona insist on sustainability as one of the fundamental assets of public parks. Yet whether these urban artifacts actually contribute to sustainability objectives in environmental and social terms remains to be examined. We compare two public parks in Barcelona‐the Parc Joan Miró (1983), and the Parc de Diagonal Mar (2002)–and show how, in the former, the integration of the social, political, and environmental dimensions of sustainability was largely achieved, whereas in the latter, only the environmental dimension appears to have been considered.     

EVIDENCE FOR EXPANDED MIDDLE AND LATE PLEISTOCENE GLACIER EXTENT IN NORTHWEST NELSON,NEW ZEALAND

The extent of Late Quaternary glaciation in the northwest Nelson region of New Zealand has traditionally been regarded as minor, with small‐scale valley glaciation in confined upland reaches. New geomorphological evidence, including moraines, kame terraces, till‐mantled bedrock and outwash terraces, indicate that greatly expanded valley glaciers flowed into the lowland valley system at the mouths of the Cobb‐Takaka and Anatoki drainages. The timing for this ice advance into lowland valleys is constrained by lowland landform characteristics and a single cosmogenic exposure age, suggesting Late and Middle Pleistocene ice expansion, respectively. Evidence for expanded upland ice on the Mount Arthur Tableland and adjacent areas includes trimlines, boulder trains and roche moutonées. Two cosmogenic exposure ages on upland bedrock surfaces suggest that major ice expansion occurred during MIS 3 and/or 4, while previously published exposure dating from Cobb Valley suggests large MIS 2 ice expansion as well. The inferred, markedly expanded ice left little or no clear geomorphic imprint on the Cobb–Takaka Gorge, and required temperature depression of 4–6°C with near‐modern precipitation levels.     

WIDESPREAD EFFECTS OF CLIMATIC WARMING ON FRESHWATER ECOSYSTEMS IN NORTH AMERICA

Freshwaters in different regions show many similarities and differences in their responses to climatic warming. Bases for comparison include reports from regional committees, long-term records for several sites where climate has warmed in the past two decades and other human alterations to freshwaters that simulate some of the expected results of climatic warming, such as reservoir construction. Palaeoecological studies of freshwaters under climatic warming and differences in communities under different climatic regimes are also considered. Major changes in the physical, chemical and biological characteristics of lakes occur. Many of the changes to lakes and streams are the result of strong effects of climatic warming on terrestrial catchments. Inputs from catchments can be either dampened or amplified by in-lake processes, in some cases causing counter-intuitive responses, such as the acidification of streams but alkalinization of lakes in areas where supplies of base cations are limited. Consideration of land–water interactions and interactions between climatic warming and other human stresses are important for the accurate prediction of the effects of climatic change. © 1997 John Wiley & Sons, Ltd.     

Chronology of Murrumbidgee River palaeochannels on the Riverine Plain,southeastern Australia

Four major periods of palaeochannel activity have been identified on the Murrumbidgee sector of the Riverine Plain of southeastern Australia. On the basis of stratigraphic information the channels reveal a picture of changing flow conditions during the last full glacial cycle. The ages of the periods were determined from nearly 40 thermoluminescence dates on surficial fluvial and aeolian sediments. These are named the Coleambally phase, which occurred from 105 to 80 ka (the mid- to latter part of Oxygen Isotope Stage 5), the Kerarbury phase from 55 to 35 ka (Stage 3), the Gum Creek phase from 35 to 25 ka (late Stage 3 to early Stage 2) and the Yanco phase from 20 to 13 ka (late Stage 2). The present flow regime was established by about 12 ka (Stage 1). The first two phases correlate with episodes of enhanced fluvial activity in northern and central Australia and with reduced dust activity globally. The phases in Stage 2 appear to be associated with seasonal snow melt and increased peak flows in periods flanking the Last Glacial Maximum. Source-bordering aeolian dunes associated with the Coleambally, Kerarbury and Yanco phases were found, however, the TL dates show that some have undergone aeolian reworking. Thermoluminescence dating and fluvial stratigraphy have revealed a detailed picture of Late Quaternary climate and flow regime changes that has the potential to extend to identified deposits stratigraphically older than those described here.     

Developers in the public interest? The role of urban development corporations in the Anglophone Caribbean

Urban centres in the Caribbean face a wide variety of infrastructural and planning challenges. One of the key strategies that has been adopted by national governments to address these challenges is the formation of urban development corporations. These are governmental agencies with powers to facilitate urban regeneration in specific areas. This paper examines the history, role and function of urban development corporations in Jamaica, Antigua and Barbuda, and Trinidad and Tobago. The Urban Development Corporation (UDC) was formed in Jamaica in 1968, the St John's Development Company (SJDC) in Antigua and Barbuda was created in 1986, and the Urban Development Corporation of Trinidad and Tobago (UDeCOTT) was established in 1994. These bodies share the characteristic of having far-reaching planning and development powers within specific areas. For example, the SJDC is able 'to acquire, manage, or dispose of lands and to lay out, construct, and maintain roads, buildings, public parks, piers, car parks, and other public amenities' within specified designated areas, whilst Jamaica's UDC is empowered 'to carry out and/or secure the laying out and development of "designated areas". These three urban development corporations can be seen to act as developers in the public interest, as agents of modernisation, and as responses to neoliberalisation. However, whilst they have succeeded in effecting large-scale transformations to the urban landscape, this has often been achieved through a top-down development process with exemption from planning regulations and little accountability to the residents of the cities.     

Bedform climbing in theory and nature

Where bedforms migrate during deposition, they move upward (climb) with respect to the generalized sediment surface. Sediment deposited on each lee slope and not eroded during the passage of a following trough is left behind as a cross-stratified bed. Because sediment is thus transferred from bedforms to underlying strata, bedforms must decrease in cross-sectional area or in number, or both, unless sediment lost from bedforms during deposition is replaced with sediment transported from outside the depositional area. Where sediment is transported solely by downcurrent migration of two-dimensional bedforms, the mean thickness of cross-stratified beds is equal to the decrease in bedform cross-sectional area divided by the migration distance over which that size decrease occurs; where bedforms migrate more than one spacing while depositing cross-strata, bed thickness is only a fraction of bedform height. Equations that describe this depositional process explain the downcurrent decrease in size of tidal sand waves in St Andrew Bay, Florida, and the downwind decrease in size of transverse aeolian dunes on the Oregon coast. Using the same concepts, dunes that deposited the Navajo, De Chelly, and Entrada Sandstones are calculated to have had mean heights between several tens and several hundreds of metres.     

THE DENDROCLIMATOLOGICAL POTENTIAL OF AN ALPINE SHRUB,CASSIOPE MERTENSIANA,FROM MOUNT RAINIER,WA, USA

The application of dendrochronological techniques to shrubs found in arctic and alpine plant communities is opening previously untapped regions to the exploration of plant‐climate ecological relationships and climate reconstruction. In this pilot study, we present growth (1963–2004), reproduction (1963–2004), and stable carbon isotope ratio (1975–2004) chronologies for Cassiope mertensiana from a subalpine site in Mount Rainier National Park, Washington, USA. Based on simple linear correlation analysis, positive correlations characterize plant growth and previous year mean maximum temperature in April and June, suggesting the influence of temperature on snowpack and, in turn, on growing season length, plant and soil insulation, and nutrient and moisture availability. Plant growth and reproduction are significantly correlated with current year July mean maximum temperature and total precipitation, indicating the importance of a warm and extended growing season for optimal plant development. Using step‐wise multiple linear regression analysis, we developed a preliminary calibration model for July mean maximum temperature (R = 0.63), extending over the 1974–2004 time period. This archive has the potential to elucidate multi‐scale, spatially‐explicit, ecological and climatic information for alpine ecosystems situated along a north‐south transect from the southern Yukon to the Pacific Northwest of the United States.