Mapping and valuation of ecosystems and economic activities along the coast of Cameroon: implications of future sea level rise.

The vulnerability of the coastal zone of Cameroon to flooding from sea level rise (SLR) was quantified using Geographic Information System (GIS) flooding analysis. The main economic activities and ecosystems along this area were iden tified using secondary data. Valuations of non- market values of ecosystems were based on the ecosystem service product method. The low-lying coastal areas were found to be physically and socio-economically susceptible to impacts of SLR due to their high ecological and economic value. A digitised land use/land cover (LULC) classification was produced from low resolution topographic maps and Google Earth images of the area. The digital elevation model (DEM) used was acquired by the shuttle radar topography mission. Evaluation of potential land loss due to inundation was based on empirical approaches using minimum and maximum scenarios of 2 and 10 m flooding. These were estimated considering the best available SLR data for the area, mean high water levels and wave heights during storms. The estimated SLR range from 2.3 m to 9.2 m for the low and high scenarios, respectively, by 2050 and from 2.6 m to 9.7 m for the low and high scenarios, respectively, by the year 2100. Results indicate that 112 km 2 (1.2 %) and 1,216 km 2 (12.6 %) of the coastal area will be lost from a 2 m (equivalent to a low scenario by 2050) and 10 m (equivalent to a high scenario by 2100) flooding, respectively. 0.3 % to 6.3 % of ecosystems worth US$ 12.13 billion/yr could be at risk of flooding by the years 2050 and 2100. The areas under a serious threat cont ain mangroves, sea and airport, residential and industrial areas of Douala. Main plantation crops of banana and palms will be slightly affected. The identification of the soci o-economic impacts of projected SLR on vulnerable coastlines and populations is important for timely actions to be taken in mitigating the effects of natural disasters in the coastal zone

Holocene relative sea-level changes in northwest Ireland: An empirical test for glacial isostatic adjustment models

The late-Quaternary relative sea-level (RSL) history of Ireland is complex, positioned at the margins of the former British-Irish Ice Sheet, and subject to the influence of ice unloading and forebulge collapse. Geophysical models of post-glacial isostatic adjustment (GIA) provide estimates of the pattern of RSL change since deglaciation which may be tested and validated with empirical data from proxy records. For the region of northwest Ireland, there is a paucity of high-quality RSL data and, therefore, equivocal evidence to support the GIA models that predict a mid to Late-Holocene RSL highstand of between +0.5 and +2 m above present. This study aims to investigate this model-data discrepancy by reconstructing RSL change from a near continuous salt-marsh sequence at Bracky Bridge, Donegal, spanning the last ca. 2500 years. We develop a transfer function model to reconstruct the vertical position of sea level using a regional diatom training set to quantify the indicative meaning and predict the palaeomarsh elevation of the core samples. A chronology is provided by a combination of 14 C and 210 Pb data, with sample specific ages derived from an age-depth model using a Bayesian framework. Our reconstruction shows ca. 2 m of relative sea-level rise in the past 2500 years. This is not compatible with some previously published sea-level index points from the region, which we re-interpret as freshwater/terrestrial limiting data. These results do not provide any evidence to support a Mid-Holocene RSL highstand above present sea level. Whilst none of the available GIA models replicate the timing and magnitude of the Late-Holocene RSL rise in our reconstruction, those which incorporate a thick and extensive British-Irish Sea Ice Sheet provide the best fit

Nonlinear landscape and cultural response to sea-level rise

Rising sea levels have been associated with human migration and behavioral shifts throughout prehistory, often with an emphasis on landscape submergence and consequent societal collapse. However, the assumption that future sea-level rise will drive similar adaptive responses is overly simplistic. While the change from land to sea represents a dramatic and permanent shift for preexisting human populations, the process of change is driven by a complex set of physical and cultural processes with long transitional phases of landscape and socioeconomic change. Here, we use reconstructions of prehistoric sea-level rise, paleogeographies, terrestrial landscape change, and human population dynamics to show how the gradual inundation of an island archipelago resulted in decidedly nonlinear landscape and cultural responses to rising sea levels. Interpretation of past and future responses to sea-level change requires a better understanding of local physical and societal contexts to assess plausible human response patterns in the future

Late Holocene sea-level changes and vertical land movements in New Zealand

Coasts in tectonically active regions face varying threat levels as land subsides or uplifts relative to rising sea levels. We review the processes influencing relative sea-level change in New Zealand, and the geological context behind ongoing land movements, focussing on major population centres. Whilst Holocene sea levels have been reconstructed using a variety of techniques, recent work uses salt-marsh microfossil assemblages to reconstruct relative sea-level changes over the past few centuries. For the twentieth century, these proxy-based studies often show enhanced rates of sea-level rise relative to tide-gauge observations. The effects of tectonic subsidence must be considered, alongside vertical and dating uncertainties in the sea-level reconstructions. Global Positioning Systems (GPS) observations for the past few decades show that vertical land movement (VLM) may be influencing rates of relative sea-level rise. However, the short period of GPS observations, during which trends and rates have varied at some localities, raises questions over the longer-term contribution of VLM to sea-level change over the past few centuries and for future projections. We argue that high-resolution palaeo-sea-level reconstructions from salt-marsh sedimentary sequences can help to answer these questions regarding the interplay between sea-level change and VLM at key locations

Spectral quantification of nonlinear behaviour of the nearshore seabed and correlations with potential forcings at Duck, N.C., U.S.A

Local bathymetric quasi-periodic patterns of oscillation are identified from monthly profile surveys taken at two shore-perpendicular transects at the USACE field research facility in Duck, North Carolina, USA, spanning 24.5 years and covering the swash and surf zones. The chosen transects are the two furthest (north and south) from the pier located at the study site. Research at Duck has traditionally focused on one or more of these transects as the effects of the pier are least at these locations. The patterns are identified using singular spectrum analysis (SSA). Possible correlations with potential forcing mechanisms are discussed by 1) doing an SSA with same parameter settings to independently identify the quasi-periodic cycles embedded within three potentially linked sequences: monthly wave heights (MWH), monthly mean water levels (MWL) and the large scale atmospheric index known as the North Atlantic Oscillation (NAO) and 2) comparing the patterns within MWH, MWL and NAO to the local bathymetric patterns. The results agree well with previous patterns identified using wavelets and confirm the highly nonstationary behaviour of beach levels at Duck; the discussion of potential correlations with hydrodynamic and atmospheric phenomena is a new contribution. The study is then extended to all measured bathymetric profiles, covering an area of 1100m (alongshore) by 440m (cross-shore), to 1) analyse linear correlations between the bathymetry and the potential forcings using multivariate empirical orthogonal functions (MEOF) and linear correlation analysis and 2) identify which collective quasi-periodic bathymetric patterns are correlated with those within MWH, MWL or NAO, based on a (nonlinear) multichannel singular spectrum analysis (MSSA). (...continued in submitted paper)Comment: 50 pages, 3 tables, 8 figure

Testing the Mid-Holocene Relative Sea-Level Highstand Hypothesis in North Wales, United Kingdom

Accurate Holocene relative sea-level curves are vital for modelling future sea-level changes, particularly in regions where relative sea-level changes are dominated by isostatically induced vertical land movements. In North Wales, various glacial isostatic adjustment (GIA) models predict a mid-Holocene relative sea-level highstand between 4 and 6 ka, which is unsubstantiated by any geological sea-level data but affects the ability of geophysical models to model accurately past and future sea levels. Here, we use a newly developed foraminifera-based sea-level transfer function to produce a 3300-year-long late-Holocene relative sea-level reconstruction from a salt marsh in the Malltraeth estuary on the south Anglesey coast in North Wales. This is the longest continuous late-Holocene relative sea-level reconstruction in Northwest Europe. We combine this record with two new late-Holocene sea-level index points (SLIPs) obtained from a freshwater marsh at Rhoscolyn, Anglesey, and with previously published regional SLIPs, to produce a relative sea-level record for North Wales that spans from ca. 13,000 BP to the present. This record leaves no room for a mid-Holocene relative sea-level highstand in the region. We conclude that GIA models that include a mid-Holocene sea-level highstand for North Wales need revision before they are used in the modelling of past and future relative sea-level changes around the British Isles

The Evolution of Compact Binary Star Systems

We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and BHs are thought to be the primary astrophysical sources of gravitational waves (GWs) within the frequency band of ground-based detectors, while compact binaries of WDs are important sources of GWs at lower frequencies to be covered by space interferometers (LISA). Major uncertainties in the current understanding of properties of NSs and BHs most relevant to the GW studies are discussed, including the treatment of the natal kicks which compact stellar remnants acquire during the core collapse of massive stars and the common envelope phase of binary evolution. We discuss the coalescence rates of binary NSs and BHs and prospects for their detections, the formation and evolution of binary WDs and their observational manifestations. Special attention is given to AM CVn-stars -- compact binaries in which the Roche lobe is filled by another WD or a low-mass partially degenerate helium-star, as these stars are thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure

How many is enough? Determining optimal count totals for ecological and palaeoecological studies of testate amoebae

Testate amoebae are increasingly used in ecological and palaeoecological studies of wetlands. To characterise the amoeba community a certain number of individuals need to be counted under the microscope. To date, most studies have aimed for 150 individuals, but that sample size is not based on adequate evidence. When testate amoeba concentrations are low, it can be difficult or impossible to reach this total. The impacts of lower count totals have never been seriously scrutinised. We investigated the impact of count size on number of taxa identified, quantitative inferences of environmental variables and the strength of the links between amoebae and environmental data in the context of predicting depth to water table. Low counts were simulated by random selection of individuals from four existing datasets. Results show progressively diminishing returns by all criteria as count size increases from low numbers to counts of 150. A higher count is required to identify all taxa than to adequately characterise the community for transfer function inference. We suggest that in most cases, it will be a more efficient use of time to count a greater number of samples to a lower count. While a count of 50 individuals may be sufficient for some samples from some sites we recommend that counts of 100 individuals should be sufficient for most samples. Counts need only be increased to 150 or more where the aim is to identify relatively minor, but still potentially ecologically relevant community changes. This approach will help reduce lack of replication and low resolution, which are common limitations in testate amoeba-based palaeoecological and ecological studies

Tephrochronology

Tephrochronology is the use of primary, characterized tephras or cryptotephras as chronostratigraphic marker beds to connect and synchronize geological, paleoenvironmental, or archaeological sequences or events, or soils/paleosols, and, uniquely, to transfer relative or numerical ages or dates to them using stratigraphic and age information together with mineralogical and geochemical compositional data, especially from individual glass-shard analyses, obtained for the tephra/cryptotephra deposits. To function as an age-equivalent correlation and chronostratigraphic dating tool, tephrochronology may be undertaken in three steps: (i) mapping and describing tephras and determining their stratigraphic relationships, (ii) characterizing tephras or cryptotephras in the laboratory, and (iii) dating them using a wide range of geochronological methods. Tephrochronology is also an important tool in volcanology, informing studies on volcanic petrology, volcano eruption histories and hazards, and volcano-climate forcing. Although limitations and challenges remain, multidisciplinary applications of tephrochronology continue to grow markedly

Revised Lithostratigraphy of the Sonsela Member (Chinle Formation, Upper Triassic) in the Southern Part of Petrified Forest National Park, Arizona

BACKGROUND: Recent revisions to the Sonsela Member of the Chinle Formation in Petrified Forest National Park have presented a three-part lithostratigraphic model based on unconventional correlations of sandstone beds. As a vertebrate faunal transition is recorded within this stratigraphic interval, these correlations, and the purported existence of a depositional hiatus (the Tr-4 unconformity) at about the same level, must be carefully re-examined. METHODOLOGY/PRINCIPAL FINDINGS: Our investigations demonstrate the neglected necessity of walking out contacts and mapping when constructing lithostratigraphic models, and providing UTM coordinates and labeled photographs for all measured sections. We correct correlation errors within the Sonsela Member, demonstrate that there are multiple Flattops One sandstones, all of which are higher than the traditional Sonsela sandstone bed, that the Sonsela sandstone bed and Rainbow Forest Bed are equivalent, that the Rainbow Forest Bed is higher than the sandstones at the base of Blue Mesa and Agate Mesa, that strata formerly assigned to the Jim Camp Wash beds occur at two stratigraphic levels, and that there are multiple persistent silcrete horizons within the Sonsela Member. CONCLUSIONS/SIGNIFICANCE: We present a revised five-part model for the Sonsela Member. The units from lowest to highest are: the Camp Butte beds, Lot's Wife beds, Jasper Forest bed (the Sonsela sandstone)/Rainbow Forest Bed, Jim Camp Wash beds, and Martha's Butte beds (including the Flattops One sandstones). Although there are numerous degradational/aggradational cycles within the Chinle Formation, a single unconformable horizon within or at the base of the Sonsela Member that can be traced across the entire western United States (the "Tr-4 unconformity") probably does not exist. The shift from relatively humid and poorly-drained to arid and well-drained climatic conditions began during deposition of the Sonsela Member (low in the Jim Camp Wash beds), well after the Carnian-Norian transition