1,720,983 research outputs found
Multisensor monitoring of plume dynamics in the north-western Mediterranean
No full textWe used data from various space-borne sensors to monitor the marine ecosystem in the northwestern Mediterranean Sea, at the Costa Dorada, between the City of Barcelona and the estuary of the river Ebro. The aim of this study was to demonstrate that the combination of different remote sensing data (acquired at different electromagnetic frequencies) allows for an improved monitoring system, in particular for a better monitoring of the marine ecosystem and, hence, a better coastal zone management. We present remote sensing data acquired by the Synthetic Aperture Radar (SAR) and the Along-Track Scanning Radiometer (ATSR) aboard the Second European Remote Sensing Satellite (ERS-2), and by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) on the SeaStar satellite. By combining the different data we are able to overcome specific drawbacks of the single sensors, like an insufficient temporal coverage, or a strong dependence on weather and daylight conditions. Within the study area two main features have been selected as examples, which are well visible on many of the analysed images. The first one exhibits a higher load of chlorophyll-a and surface-active compounds and a lower sea surface temperature (SST), which is likely to be caused by the plume of the river Llobregat, southwest of Barcelona. It can clearly be seen from the imagery how the river plume is driven along the coast by the local currents. The second feature can be related to cooling water being released from a nuclear power plant and causing turbulence in the water body, which in turn gives rise to signatures visible on the ERS-SAR imagery
A freshwater jet on the east Greenland shelf (abstract of paper presented at ASLO/AGU Ocean Sciences Meeting, Honolulu, HI, 11-15 Feb 2002)
No full textValidating SMOS ocean surface salinity in the Atlantic with Argo and operational ocean model data
No full textThis paper provides an assessment of synoptic measurements of sea surface salinity (SSS) from the European Space Agency Soil Moisture and Ocean Salinity (SMOS) satellite. Due to the complex nature of the response of L-band signals to SSS, SMOS provides three values of SSS at each grid point from three different forward models. To meet oceanographic requirements for SSS retrieval accuracy, SMOS Level 2 SSS products are averaged over time and space. This paper reports on validation studies in the Atlantic based on monthly Level 3 products on a grid for September 2010. Outside coastal regions, large-scale SSS patterns from SMOS are in general agreement with climatology, Argo, and ocean model output. During September 2010, SSS from descending passes provides reasonable quantitative estimates, while SSS from ascending passes overestimates SSS by over 1 practical salinity unit (psu). The daily mean difference in SSS between ascending and descending passes varies during August–December 2010, reaching a maximum in September. Differences in SMOS SSS from the three models are an order of magnitude smaller than differences between ascending and descending passes. Gridded SMOS SSS data are compared against output from the U.K. Met Office Forecasting Ocean Assimilation Model (FOAM)-Nucleus for European Modelling of the Ocean (NEMO). Basic checks confirm that SSS from FOAM-NEMO is unbiased against Argo and that FOAM-NEMO SSS is a useful independent data source to validate and rapidly identify departures in SMOS SSS. Over the whole Atlantic, SMOS SSS variability against FOAM-NEMO is around 0.9 psu, decreasing to 0.5 psu over the subtropical North Atlantic
Coupled Ocean Atmosphere Processes and European Climate (COAPEC): improved understanding of the coupled climate system
Full text linkCOAPEC (http://coapec.nerc.ac.uk/) is a five-year Directed Science Programme funded by the Natural Environment Research Council (NERC). COAPEC is providing advances in understanding the mechanisms by which the ocean and atmosphere interact, how these processes are represented in state-of-the-art numerical climate models and how they determine the predictability of the climate system over seasonal-decadal timescales. Processes studied include the generation and propagation of salinity and heat anomalies in the North Atlantic, the influence of the thermohaline circulation and the role of storm tracks on European Climate. The influence of remote processes, including ocean-atmosphere coupling in tropical Atlantic warm events and Southern Ocean circulation are also being investigated.
As part of the programme, new coupled models are being developed, including: a coupled hybrid isopycnic coordinate model; fast models for multi-ensemble runs to investigate model parameters space, using both high performance machines and spare home PC resources; a QG model to investigate high resolution ocean processes in coupled systems and validated ice models for coupled modelling. Underpinning research into improving the observational datasets, such as the SOC flux climatology, and into the influence of sea-ice observations in General Circulation Models is also being carried out as part of the programme.
To place these advances into a socially relevant context, COAPEC is also investigating the methods for using, and economic benefits of, climate forecasts at seasonal timescales for the UK health sector and the UK energy industry
Observations of atmosphere-ocean freshwater input with in situ and satellite measurements of surface salinity and rain
No full textOcean feature detection using altimetry backscatter: the Gulf Stream
No full textThis study presents a basic analysis of ERS-1 altimeter data, from its 3-day repeat track periods taken over a section of the Gulf Stream. Along track variations of radar backscatter (σ0) have been compared with positions of the Gulf Stream derived from the composite maps of sea surface temperature from ship and satellite-sensor observations, produced by NOAA. Variations in σ0 , indicating potential interaction with the Gulf Stream, are found at both high and low wind speed conditions. At high wind speeds, comparison with model wind data indicates that peaks in altimeter-derived wind speeds along the path of the North Wall of the Gulf Stream may be related to real increases in wind speed. A possible reason may be a tendency for winter storm tracks to follow the same path as sections of the Gulf Stream. At low wind speeds, minima in altimeter derived winds are associated with sections of the path of the Gulf Stream but there were no comparable occurrences of low wind speeds in model wind fields, with implied consequences for winds derived from satellite sensor data. Although, for low wind speeds, the cause of these 'anomalously high' backscatter regions is unknown, such associated relatively 'calmer' waters have been previously noted as the result either of a tendency for surface slicks to be confined to the shears associated with local current systems or by wave-current interaction mechanisms causing a local reduction in the sea surface roughness
Monitoring the eastern Alboran Sea using combined altimetry and in situ data
No full textAs part of the Observations and Modelling of Eddy-scale Geostrophic and Ageostrophic circulation project, a cruise to the Almeria-Oran front in the Eastern Alboràn (Western Mediterranean) was carried out from November 1996 to January 1997. During the cruise, a fine-scale survey, designed to be oriented along European Remote-sensing Satellite ground tracks, was repeated several times. Hydrographic and current profile data were collected continuously using an undulating, towed conductivity-temperature-depth sensor and an acoustic Doppler current profiler. The in situ data have been processed to give profiles of the absolute surface current at several locations across the front. Estimates of the absolute current profile have been made from repeated tracks in order to understand some of the sources of error. These 'one-time' calculations of absolute profiles have been merged with several years worth of altimeter data to monitor the flow across the Almeria-Oran front. At times the front appears to move to the south, apparently when the eastern Alboràn gyre collapses, as has been observed in previous studies
A freshwater jet on the east Greenland Shelf
No full textIn August 1997, RRS Discovery cruise 230 (World Ocean Circulation Experiment (WOCE) section A25) ran a hydrographic section into Cape Farewell on the southern tip of Greenland. The closest approach to the shore was 2 nm in a water depth of 160 m over the east Greenland shelf. Analysis of the hydrographic data (conductivity-temperature-depth (CTD), vessel-mounted acoustic Doppler current profiler, and thermosalinograph) has revealed a current flowing southwestward, ~15 km wide, 100 m deep, and centered ~10 km offshore. We believe it to be driven by meltwater runoff from Greenland. This feature, which we call the East Greenland Coastal Current (EGCC), carries a little less than 1 Sv (106 m3 s-1) with peak current speeds of ~1 m s-1 at the surface. The center of the EGCC lies on a salinity front with maximum salinity contrast ~4 practical salinity units (psu) between coast and shelf break and between surface and bottom. A spot value of freshwater transport is 0.06 Sv (1800 km3 yr-1), which is equivalent to ~30% of the Arctic freshwater gain. The presence of the EGCC and its continuity up the east Greenland coast as far as Denmark Strait is confirmed in satellite sea surface temperature images and surface drifter tracks. We estimate the sensitivity of its freshwater flux to changes in melt season mean surface air temperature to be >25% per 1°C
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