Accelerated relative sea-level rise and rapid coastal erosion:: testing a causal relationship for the Louisiana barrier islands

The role of relative sea-level rise as a cause for the rapid erosion of Louisiana's barrier island coast is investigated through a numerical implementation of a modified Bruun rule that accounts for the low percentage of sand-sized sediment in the eroding Louisiana shoreface. Shore-normal profiles from 150 km of coastline west of the Mississippi delta are derived from bathymetric surveys conducted during the 1880s, 1930s and 1980s. An RMS difference criterion is employed to test whether an equilibrium profile form is maintained between survey years. Only about half the studied profiles meet the equilibrium criterion; this represents a significant limitation on the potential applicability of the Bruun rule. The profiles meeting the equilibrium criterion, along with measured rates of relative sea-level rise, are used to hindcast shoreline retreat rates at 37 locations within the study area. Modeled and observed shoreline retreat rates show no significant correlation. Thus, in terms of the Bruun approach, relative sea-level rise has no power for hindcasting (and presumably forecasting) rates of coastal erosion for the Louisiana barrier islands.     

Formation and distribution of manganese nodule deposit in the northwestern margin of Clarion-Clipperton fracture zones,northeast equatorial Pacific

In the northwestern margin of the Clarion and Clipperton fracture zones, manganese nodules are latitudinally variable in character, resulting from the progressive (re)generation of nodules since the Oligocene as the Pacific Plate migrates northwestward beneath the equatorial production zone. Complemented by the surface water productivity, bottom current activities have concentrated nodules in the Oligocene to Miocene siliceous clay. Resedimentation processes on nodules form three types of nodules with concentric structures and 10 Å-manganaterich bottoms, by periodically causing the diagenetic growth of nodules within the topmost sediment layer.     

Wave climate in a groin field

Wave records at seven different locations within a groin field have been analysed by both statistical and spectral approaches to study the general wave climate. The wave heights and periods from the wave records were obtained by both upcross and downcross methods for the statistical approach. The variation of different wave height and wave period parameters with respect to the time of measurement at a particular location and its variation at different locations within the groin field at a particular instant of time are presented and discussed in detail in this paper. It is generally found that the wave heights follow the Weibull distribution.     

Plate boundaries and evolution of the Solomon Sea region

The Solomon Sea Plate was widely developed during late Oligocene, separating the proto-West Melanesian Arc from the proto-Trobriand Arc. Spreading in the Bismarck Sea and in the Woodlark Basin resulted from interaction between the Pacific and Australian Plates, specifically from the collision of the proto-West Melanesian Arc with north New Guinea, which occurred after arc reversal. This model explains the extensive Miocene, Pliocene, and Quaternary volcanism of the Papua New Guinea mainland as it related to southward subduction of the Trobriand Trough. Our interpreted plate motions are concordant with the geological evidence onshore and also with complex tectonic features in the Solomon Sea Basin Region.     

Benthic Metabolism and Standing Stock in the Central and Northern Deep Red Sea

Abstract. Benthic metabolism and standing stocks were investigated in the deep Red Sea between 21^o and 27^oN, Activity was assessed by the determination of respiration rates with a shipboard method and by calculating oxygen consumption from the activity in the electron transport system. We attempted to compare results from different latitudes within the warm Red Sea and with data from cold Atlantic environments. Our investigations were part of an environmental risk assessment to evaluate future mining of metalliferous sediments from the Atlantis II Deep.