ISSN:0197-9337    

DOI:10.1002/esp.3290200102

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractGlobal mean sea level is a potentially sensitive indicator of climate change. Global warming will contribute to worldwide sea‐level rise (SLR) from thermal expansion of ocean water, melting of mountain glaciers and polar ice sheets. A number of studies, mostly using tide‐gauge data from the Permanent Service for Mean Sea Level, Bidston Observatory, England, have obtained rates of global SLR within the last 100 years that range between 0·3 and 3 mm yr−1, with most values concentrated between 1 and 2 mm yr−1. However, the reliability of these results has been questioned because of problems with data quality and physical processes that introduce a high level of spatial and temporal variability. Sources of uncertainty in the sea‐level data include variations in winds, ocean currents, river runoff, vertical earth movements, and geographically uneven distribution of long‐term records. Crustal motions introduce a major source of error. To a large extent, these can be filtered by employing palaeo‐sea‐level proxies, and geophysical modelling to remove glacio‐isostatic changes. Ultimately, satellite geodesy will help resolve the inherent ambiguity between the land and ocean level changes recorded by tide gauges.Future sea level is expected to rise by ∼ 1 m, with a ‘best‐guess’ value of 48 cm by the year 2100. Such rates represent an acceleration of four to seven times over present rates. Local land subsidence could substantially increase the apparent SLR. For example, Louisiana is currently experiencing SLR trends nearly 10 times the global mean rate.These recently reduced SLR estimates are based on climate models that predict a zero to negative contribution to SLR from Antarctica. Most global climate models (GCMs) indicate an ice accumulation over Antarctica, because in a warmer world, precipitation will exceed ablation/snow‐melt. However, the impacts of attritional processes, such as thinning of the ice shelves, have been downplayed according to some experts. Furthermore, not all climate models are in agreement. Opposite conclusions may be drawn from the results of other GCMs. In addition, the West Antarctic Ice Sheet is potentially subject to dynamic and volcanic instabilities that are difficult to predict. Because of the great uncertainty in SLR projections, careful monitoring of future sea‐level trends by upgraded tide‐gauge networks and satellite geodesy will become essential.Finally, because of the high spatial variability in crustal subsidence rates, wave climates and tidal regimes, it will be the set of local conditions (especially therelativesea‐level rise), rather than a single global mean sea‐level trend, that will determine each lo

ISSN:0197-9337    

DOI:10.1002/esp.3290200103

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractSea‐level rise (SLR) is considered to be important for barrier behaviour when barriers are swash‐aligned and single‐crested, which is typical of only one part of a barrier's lifeterm. Under such conditions gravel‐barrier retreat rate correlates with mesoscale (sub‐decadal:102a) SLR rate is the critical control on barrier retreat, as mesoscale SLR variation in combination with surge potential is able to raise water level to the elevation threshold sufficient for barrier overwash and hence drive ba

ISSN:0197-9337    

DOI:10.1002/esp.3290200104

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIn order to maintain an elevation in the intertidal zone at which marsh vegetation can survive, vertical accretion of the marsh surface must take place at a rate at least equal to the rate of relative sea‐level rise. Net vertical accretion of coastal marshes is a result of interactions between tidal imports, vegetation and depositional processes. All of these factors are affected, directly or indirectly, by alterations in marsh hydrology which might occur as a result of sea‐level rise. The overall response of coastal marshes to relative sea‐level rise depends upon the relative importance of the inorganic and organic components of the marsh soil and the impact of increased hydroperiod on net accumulation. The varied combination of factors contributing to sediment supply, and their complexity at the scale of individual marshes, means that predicting the response of suspended sediment concentration in marsh floodwater to any changes which may occur as a result of sea‐level rise, at anything other than the local scale is unlikely to be accurate. The impact of sea‐level rise on net below‐ground production is also complex. The sensitivity of certain species to waterlogging and soil chemical changes could result in a change in species composition or the migration of vegetation zones. Consequently, predicting the net impact of sea‐level rise on organic matter accumulation is fraught with difficulties and requires improved understanding of interactions between vegetation, soil and hydrolo

ISSN:0197-9337    

DOI:10.1002/esp.3290200105

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractCoral islands formed of largely unconsolidated sands only a few metres above sea level are thought to be particularly vulnerable to sea‐level rise consequent upon global warming. However, scenarios which predict catastrophic flooding and loss of island area need reassessment, particularly in the light of the continued downwards revision of projected rates of future sea‐level rise. Revised questions concern the interactions between reef growth and sea‐level change, biophysical constraints on coral growth, and the importance to reef systems of potential changes in the magnitude, frequency and location of tropical cyclones and hurricanes. It is clear that most reefs have the growth potential to meet even the highest of future sea‐level rise scenarios, but too little is known about physiological and physical constraints to reef growth to adequately evaluate the importance of these two factors in constraining this potential at the present time. Future sea‐level rise in the tropical oceans, and coral reef responses, will take place against a backdrop of inter‐regional differences in Holocene sea levels, resulting from the varying interaction of eustatic and hydro‐isostatic processes. These differences have generated varying constraints on the development of modern reefs and varying inherited topographies upon which future sea‐level changes will be superimposed. These controls are particularly important in assessing differences in vulnerability to future sea‐level rise for reef islands in the Pacific Ocean and

ISSN:0197-9337    

DOI:10.1002/esp.3290200106

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe exact response of mangrove shorelines to anticipated sea‐level rise will depend upon the balance between sedimentation and sea‐level change. Within the Top End of the Northern Territory of Australia there are extensive, relatively unmodified, tide‐dominated mangrove forests, where tidal processes redistribute sediment. Harbours, such as Darwin Harbour, and tidal rivers, such as the South Alligator River with its associated coastal and estuarine plains, represent opposite extremes in terms of Holocene sedimentary infill, and will respond differently to sea‐level rise. In Darwin Harbour, mangrove assemblages can be recognized in geomorphologically defined habitats. Similar topography within and between creeks implies morphodynamic equilibrium with tidal processes. Tidal reworking of sediment may maintain an equilibrial profile under gradually rising sea level, with resuspension of lower intertidal and subtidal muds and their redeposition within upper intertidal mangrove habitats. In contrast, the plains along the coast and tidal rivers draining into van Diemen Gulf developed during the post‐glacial marine transgression, and since sea level stabilized, around 6000 years ago, coastal plains have prograded. These broad plains are presently not extensively influenced by salt water, but are often at elevations close to, or even below, modern high‐tide levels. They may, therefore, revert to saline conditions particularly rapidly if the sea rises. The pattern of change may not be directly analogous to marine incursion experienced in the early Holocene, because broad plains have been able to prograde during the last 6000 years of relatively stabl

ISSN:0197-9337    

DOI:10.1002/esp.3290200107

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractAlthough a traditional geological survey of terraced coastal slopes is an essential part of studies aimed to reconstruct relative sea‐level changes, the stratigraphic and chronological data so obtained frequently prove inadequate to completely unravel the sometimes very complex history of sea‐level fluctuation, especially where erosion has prevailed over deposition and/or deposits are difficult to date.On the basis of our experience we think that much additional information can be gained through geomorphological interpretation of the profiles of those slopes. In order to facilitate such interpretation, a computer simulation model is developed that is able to predict the morphogenic response to a variety of possible relative‐sea‐level histories. The results can be used to envisage some new interpretation keys for the analysis of real situations and, hopefully, as bases for the conception of general models of coastal slope evolution under the action of a variable sea level.Though preliminary, the results so far obtained permit identification of the geomorphological consequences (in terms of resulting slope profile) of ordered successions of transgressions and regressions of different amplitude, rate, order and style. Moreover they provide interesting insights into the role that different styles of tectonic uplift may play in the phenomenon of multiple terracing of coastal

ISSN:0197-9337    

DOI:10.1002/esp.3290200108

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0197-9337    

DOI:10.1002/esp.3290200109

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY