Search results for "Ocean"
showing 10 items of 2919 documents
Controls on strontium and barium incorporation into freshwater bivalve shells ( Corbicula fluminea )
2017
Abstract Trace elements of bivalve shells can potentially serve as proxies of environmental change. However, to reconstruct past environments using the geochemical properties of the shells and determine the degree to which the element levels are biologically influenced, it is essential to experimentally determine the relationship between environmental variables and the element composition of the shells. To disentangle possible controls on the incorporation of strontium and barium into freshwater bivalve shells, we conducted controlled laboratory experiments using the extremely salinity and temperature tolerant Asian clam, Corbicula fluminea as a model species. Bivalves were reared for five …
Recent advances in space-time statistics with applications to environmental data: An overview
2003
[1] This paper introduces a special section based on general environmental scientific problems, with a particular focus on using atmospheric data. All the papers and authors provide the methodology to study, analyze, predict, and evaluate the spatial-temporal behavior and the complicated spatial-temporal structure of the data. The overall aim is to present up-to-date developments in spatial and spatiotemporal statistics in the field of the atmosphere, to present on-going research, and to discuss important problems to be addressed in the near future.
Growth patterns of the topshell Phorcus lineatus (da Costa, 1778) in northern Iberia deduced from shell sclerochronology
2019
Combined shell growth pattern and oxygen isotope analysis has become a powerful approach in palaeoclimate and archaeological studies for reconstructing palaeoclimate conditions and littoral exploitation patterns, respectively. Recent investigations have shown that the gastropod Phorcus lineatus (da Costa, 1778) forms its shell in conditions of near equilibrium with the oxygen isotope signature of the seawater environment, demonstrating the utility of this species for reconstruction of sea surface temperature and determination of the season of harvest in archaeological studies. In contrast, the shell growth patterns of this species have received virtually no attention despite providing infor…
Oceanographic control on shell growth of Arctica islandica (Bivalvia) in surface waters of Northeast Iceland — Implications for paleoclimate reconstr…
2015
Absolutely dated, annually resolved sea surface temperature records from middle to higher latitudes covering long time intervals are crucial to better understand the climate system. Such data can potentially be obtained from variations in shell growth of long-lived bivalves such as Arctica islandica. This study presents the first statistically robust 178-yr long composite chronology (covering 1835–2012) based on sixteen live-collected and subfossil specimens of A. islandica from unpolluted, shallow waters of Northeast Iceland. Between 1875 and 1996, up to 43% of the variation in annual shell growth was explained by SST during February to September. Faster growth occurred when temperatures w…
Climatic and oceanographic changes in the Azores region during the last 74.7 Ka
2018
In this study, we reconstruct the complex palaeoclimatic and palaeohydrographic history of the North Atlantic Ocean during the Upper Pleistocene-Holocene, through a high-resolution Globigerinoides ruber - Globigerinoides elongatus plexus study. The studied core (ATA13-OF-KT1) was collected southwest of the Azores islands near the present-day boundary of the Subtropical Gyre/Azores Front Current System (STG/AFCS). Quantitative and stable isotope data of the G. ruber - G. elongatus plexus chromotypes and selected morphotypes showed cyclic oscillations of the STG/AFCS boundary linked to climatic variability at orbital and millennial scales, during the last 74.7 ka.
Radiative and dynamic effects of absorbing aerosol particles over the Pearl River Delta, China
2008
Abstract Results are reported from a ground-based measurement campaign conducted in a highly polluted region in southeast of China in October–November 2004. The experiment focused on absorbing aerosol particles and their effects on the solar radiation field and local meteorology. A Raman lidar in conjunction with Sun photometer data measured profiles of particle extinction; ground-based in situ data of aerosol optical properties were collected by nephelometer and absorption photometer. Exceptionally high values of aerosol optical depth of up to 1.5 were observed. The measurements were input to a radiative transfer model, which simulated high solar radiative forcing values for the aerosol pa…
Retrieval of oceanic chlorophyll concentration with relevance vector machines
2006
Abstract In this communication, we evaluate the performance of the relevance vector machine (RVM) for the estimation of biophysical parameters from remote sensing data. For illustration purposes, we focus on the estimation of chlorophyll-a concentrations from remote sensing reflectance just above the ocean surface. A variety of bio-optical algorithms have been developed to relate measurements of ocean radiance to in situ concentrations of phytoplankton pigments, and ultimately most of these algorithms demonstrate the potential of quantifying chlorophyll-a concentrations accurately from multispectral satellite ocean color data. Both satellite-derived data and in situ measurements are subject…
Land surface processes: description, theoretical approaches, and physical laws underlying their measurements
1991
For more than a decade, evidence has accumulated from climate model experiments that the exchanges of momentum, heat, and moisture at the surface are phenomena that strongly influence the dynamics and thermodynamics of the atmosphere.
Multiscale analyses and characterizations of surface topographies
2018
International audience; This work studies multiscale analyses and characterizations of surface topographies from the engineering and scientific literature with an emphasis on production engineering research and design. It highlights methods that provide strong correlations between topographies and performance or topographies and processes, and methods that can confidently discriminate topographies that were processed or that perform differently. These methods have commonalities in geometric characterizations at certain scales, which are observable with statistics and measurements. It also develops a semantic and theoretical framework and proposes a new system for organizing and designating …
Parametric Design of Sailing Hull Shapes
2006
The author presents an original algorithm aimed at automatically generating the hull shape of a sailing yacht starting from an initial set of parameters. The procedure consists of two steps. First one keel line and a Designed Water Line (DWL in the following) are faired according to a set of parameters, say length of water line, canoe body draft, stem angle and some adimensional coefficients. This information is then used to fair the hull surface, which must in turn fulfil more prerequisites (parameters like displaty cement, floatation area and related coefficients). The hull is defined by means of a B-spline surface, the fairing of which is ensured by allowing for all the imposed objective…