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1.
Pipia L. Fabregas X. Aguasca A. Lopez-Martinez C. 《Geoscience and Remote Sensing Letters, IEEE》2008,5(1):88-92
In this letter, a coherence-based technique for atmospheric artifact removal in ground-based (GB) zero-baseline synthetic aperture radar (SAR) acquisitions is proposed. For this purpose, polarimetric measurements acquired using the GB-SAR sensor developed at the Universitat Politecnica de Catalunya are employed. The heterogeneous environment of Collserola Park in the outskirts of Barcelona, Spain, was selected as the test area. Data sets were acquired at X-band during one week in June 2005. The effects of the atmosphere variations between successive zero-baseline SAR polarimetric acquisitions are treated here in detail. The need to compensate for the resulting phase-difference errors when retrieving interferometric information is put forward. A compensation technique is then proposed and evaluated using the control points placed inside the observed scene. 相似文献
2.
Ocean Dynamics - Coastal waters are globally challenging areas to monitor not only because of the high resolution needed to resolve the scales at stake but also because most satellites are not yet... 相似文献
3.
Molcard Anne Gramoullé Anthony Mazoyer Camille Bourg Natacha Ourmières Yann 《Ocean Dynamics》2021,71(10):993-1009
Ocean Dynamics - Coastal regions are vulnerable areas with often high population density, as well as tourism and maritime activities that may have negative impact on the environment. From a... 相似文献
4.
Mihale Matobola Joel Tungaraza Clavery Baeyens Willy Brion Natacha 《Ocean Science Journal》2021,56(3):241-255
Ocean Science Journal - Elemental (C, N) and isotopic (δ13C, δ15N) signatures were used as proxies to identify seasonal changes in proportions of sedimentary organic matter (OM) in the... 相似文献
5.
Natacha Pasche Georges Alunga Keely Mills Fabrice Muvundja David B. Ryves Michael Schurter Bernhard Wehrli Martin Schmid 《Journal of Paleolimnology》2010,44(4):931-946
This study interprets the recent history of Lake Kivu, a tropical lake in the East African Rift Valley. The current gross
sedimentation was characterized from a moored sediment trap array deployed over 2 years. The past net sedimentation was investigated
with three short cores from two different basins. Diatom assemblages from cores were interpreted as reflecting changes in
mixing depth, surface salinity and nutrient availability. The contemporary sediment trap data indicate seasonal variability,
governed by diatom blooms during the annual mixing in the dry season, similar to Lakes Malawi and Tanganyika. The ratio of
settling fluxes to net sediment accumulation rates implies mineralization rates of 80–90% at the sediment-water interface.
The sediment cores revealed an abrupt change ~40 years ago, when carbonate precipitation started. Since the 1960s, deep-water
methane concentrations, nutrient fluxes and soil mineral inputs have increased considerably and diatom assemblages have altered.
These modifications probably resulted from a combination of three factors, commonly altering lake systems: the introduction
of a non-native fish species, eutrophication, and hydrological changes inducing greater upwelling. Both the fish introduction
and increased rainfall occurred at the time when the onset of carbonate precipitation was observed, whereas catchment population
growth accompanied by intensified land use increased the flux of soil minerals already since the early twentieth century due
to more intense erosion. 相似文献
6.
We studied zooplankton contribution to the total particulate phosphatase activity, the kinetics of this activity, the relation to the different taxonomic groups and the role of particle-bound bacteria. The activity of total particulate material collected from a liter of seawater was more elevated in May, June and August than during the rest of the year. These high activities resulted from a high contribution of the >90 microm fraction which account then for more than 60% of the total particulate activity. Two Michaelian processes with high and low V(max) were disclosed on this fraction. The high V(max) component was responsible for the high summer activities. During these periods, high densities of cirriped Cypris were found which were statistically correlated with this high V(max) component as with its specific activity. Moreover, the contribution of attached bacteria to these high activities was low. In return, this contribution was predominant during the periods of low activity. A simple method was developed to characterise this bacterial activity. 相似文献
7.
Audrey Recouvreur Natacha Fabregas Thierry Mulder Vincent Hanquiez Kelly Fauquembergue Elsa Tournadour Herv Gillet Jean Borgomano Emmanuelle Poli Jean‐Baptiste Kucharski Stanislas Wilk 《Sedimentology》2021,68(1):266-293
The large acoustic data set acquired during the Carambar cruises is composed of high resolution bathymetry, backscatter data and very‐high resolution seismic lines which allow for an overview of the morphology and sediment transfer processes from the shallow upper slope to the abyssal plain of a modern carbonate system: the north‐eastern slope of the Little Bahama Bank. Surficial distribution of the acoustic facies and echofacies reflects a wide variety of sedimentary processes along and across the slope. The western sector of the Little Bahama Bank is dominated by depositional processes whereas its eastern sector, which is incised in the lower slope by giant canyons, is affected by erosion and bypass processes. Datasets suggest that currents play an important role both in along‐slope sedimentary processes and in the abyssal plain. The Antilles Current appears to affect a large part of the middle and lower slopes. The absence of sizeable present‐day channel/levée complexes or lobes at the mouth of the canyon – revealed by the bathymetric map – indicates that the southward flowing Deep Western Boundary Current influences modern abyssal sediment deposition. Based on depositional processes and indicators of canyon maturity observed in facies distribution, the current study proposes that differential subsidence affects the eastern versus western part of the bank. The morphology of the Great Abaco Canyon and Little Abaco Canyon, which extend parallel to the platform, and the Little Bahama Bank slope appears to be related to the Great Abaco Fracture Zone. 相似文献
8.
With the long-term goal of developing an operational forecast system for total water level, we conduct a hindcast study of global storm surges for Fall 2014 using a baroclinic ocean model based on the NEMO framework. The model has 19 vertical levels, a horizontal resolution of 1/12°, and is forced by hourly forecasts of atmospheric wind and air pressure. Our first objective is to evaluate the model’s ability to predict hourly sea levels recorded by a global array of 257 tide gauges. It is shown that the model can provide reasonable predictions of surges for the whole test period at tide gauges with relatively large tidal residuals (i.e., gauges where the standard deviation of observed sea level, after removal of the tide, exceeds 5 cm). Our second objective is to quantify the effect of density stratification on the prediction of global surges. It is found that the inclusion of density stratification increases the overall predictive skill at almost all tide gauges. The increase in skill for the instantaneous peak surge is smaller. The location for which the increase in overall skill is largest (east coast of South Africa) is discussed in detail and physical reasons for the improvement are given. 相似文献
9.
Paquin Jean-Philippe Lu Youyu Taylor Stephanne Blanken Hauke Marcotte Guillaume Hu Xianmin Zhai Li Higginson Simon Nudds Shannon Chanut Jérôme Smith Gregory C. Bernier Natacha Dupont Frédéric 《Ocean Dynamics》2020,70(3):365-385
Ocean Dynamics - In the context of Canada’s Ocean Protection Plan (OPP), improved coastal and near-shore modelling is needed to enhance marine safety and emergency response capacity in the... 相似文献
10.
Natacha Jean Grard Bog Jean-Louis Jamet Dominique Jamet Simone Richard 《Estuarine, Coastal and Shelf Science》2009,81(4):470-480
We report here dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) levels as a function of plankton communities and abiotic factors over a 12-month cycle in the Mediterranean oligotrophic coastal and shallow ecosystem of Niel Bay (N.W. Mediterranean Sea, France). Total particulate DMSP (DMSPp) and DMS concentrations were highly seasonal, peaking during a spring (April) bloom at 8.9 nM and 73.9 nM, respectively. Significant positive correlations were found between total DMSPp concentration and the abundance or biomass of the dinoflagellate Prorocentrum compressum (Spearman's rank correlation test: r = 0.704; p = 0.011). Similarly, DMS concentrations peaked during the development of blooms of P. compressum and Gymnodinium sp. There seemed to be a positive relationship between the chlorophyll a to pheopigment ratio and DMS concentrations, suggesting that DMS was released during phytoplankton growth. High DMS levels recorded in the shallow Niel Bay may also result from the activity of benthic macroalgae, and/or macrophytes such as Posidonia spp., or the resuspension of sulfur species accumulating in sediments. The fractionation of particulate DMSP into three size classes (>90 μm, 5–90 μm and 0.2–5 μm) revealed that 5–90 μm DMSP-containing particles made the greatest contribution to the total DMSPp pool (annual mean contribution = 62%), with a maximal contribution in April (96%). This size class consisted mainly of dinoflagellates (annual mean contribution = 68%), with P. compressum and Gymnodinium sp. the predominant species, together accounting for up to 44% of the phytoplankton present. The positive correlation between DMSP concentration in the 5–90 μm size class and the abundance of P. compressum (Spearman's rank correlation test: r = 0.648; p = 0.023) suggests that this phytoplankton species would be the major DMSP producer in Niel Bay. The DMSP collected in the >90 μm fraction was principally associated with zooplankton organisms, dominated by copepods (nauplii and copepodites). DMSP>90, not due to a specific zooplankton production, resulted from the phytoplankton cells ingested during grazing. The concomitant peaks of DMS concentration and zooplankton abundance suggest that zooplankton may play a role in releasing DMSP and/or DMS through sloppy feeding. 相似文献