Steve Groom

The Portugal coastal counter current off NW Spain: new insights on its biogeochemical variability

Abstract Time series of wind-stress data, AVHRR and SeaWiFS satellite images, and in situ data from seven cruises are used to assemble a coherent picture of the hydrographic variability of the seas off the Northwest Iberian Peninsula from the onset (September–October) to the cessation (February–May) of the Portugal coastal counter current (PCCC). During this period the chemistry and the biology of the shelf, slope and ocean waters between 40° and 43°N have previously been undersampled. Novel information extracted from these observations relate to: 1. The most frequent modes of variability of the alongshore coastal winds, covering event, seasonal and long-term scales; 2. The conspicuous cycling between stratification and homogenisation observed in PCCC waters, which has key implications for the chemistry and biology of these waters; 3. The seasonal evolution of nitrite profiles in PCCC waters in relation to the stratification cycle; 4. The Redfield stoichiometry of the remineralisation of organic matter in Eastern North Atlantic Central Water (ENACW)—the water mass being transported by the PCCC; 5. The separation of coastal (mesotrophic) from PCCC (oligotrophic) planktonic populations by a downwelling front along the shelf, which oscillates to and fro across the shelf as a function of coastal wind intensity and continental runoff; and 6. The photosynthetic responses of the PCCC and coastal plankton populations to the changing stratification and light conditions from the onset to the cessation of the PCCC.

New production of the NW Iberian shelf during the upwelling season over the period 1982–1999

New production (NP) is calculated for NW Iberian shelf waters from 421 to 431N (3500 km 2 ), at the fortnight, upwelling-season (March–October) and inter-annual time-scales. The time series used are (1) upwelling rates (daily values of offshore Ekman transport from 1982 to 1999), (2) bottom shelf temperatures (twice a week values from 1987 to 1999), and (3) the nutrient–temperature relationships ofupwelled Eastern North Atlantic Central Water (ENACW) obtained during 14 hydrographic cruises to the study area (between 1977 and 1998). Marked inter-annual variability is observed, both at the fortnight and the seasonal time-scales. Average NP over the upwelling-season ranged from 330 to 815 mg C m � 2 d � 1 (mean, 4907145 mg C m � 2 d � 1 ) in the 1982–1999 period. Large inter-annual changes ofupwelling rates are the reason behind the NP fluctuations: 83% ofthe variability ofNP can be explained by the offshore Ekman Transport ð� QX Þ: NP is compared with satellite-derived net microbial community production (NCP) during the 1998– 1999 upwelling seasons, when SeaWiFS images are available. An average upwelling-season NP/NCP ratio of0.33 was obtained, indicating that 67% of NCP is respired in situ and 33% is exported off-shelf to the surrounding oligotrophic ocean.

Remote sensing of sea surface temperature and chlorophyll during Lagrangian experiments at the Iberian margin

Satellite derived sea surface temperature (SST) and chlorophyll data are used to characterise the period of upwelling during a cruise on which two Lagrangian drift experiments were conducted off the Iberian Atlantic coast in August 1998. During the cruise there was a prolonged period of equator-ward winds which favour upwelling; three distinct maxima were observed in the meteorological data interspersed with periods of relaxation. The SST and chlorophyll imagery show upwelling to be active with distinct offshore filaments that are cooler and of higher chlorophyll concentration than the surrounding oceanic water; these filaments represent an important cross-shelf transport mechanism. A front detection methodology has been applied to satellite images and suggests that these filaments are distinct, long-lived features, characterised by enhanced primary production.

SeaWiFS discrimination of harmful algal bloom evolution

The discrimination of harmful algal blooms (HABs) from space would benefit both the capability of early warning systems and the study of environmental factors affecting the initiation of blooms. Unfortunately, there are no published techniques using global monitoring satellite sensors to distinguish the resulting subtle changes in ocean colour, so in situ sampling is needed to identify the species in any observed bloom. This paper investigates multivariate classification as an objective means to discriminate harmful and harmless algae and monitor their dynamics using ocean colour data derived from satellite sensors. The classifier is trained and tested using Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) data, though the method is designed to be generic for other sensors. Time‐series results are presented using the new HAB likelihood index and suggest that SeaWiFS has some capability for observing the dynamic evolution of harmful blooms of Karenia mikimotoi, Chattonella verruculosa and cyanobacteria. Further, a multi‐band spatial subtraction algorithm is described to automate the identification of bloom regions and improve the accuracy in discriminating HABs.

Traceable radiometry underpinning terrestrial- and helio-studies (TRUTHS)

The Traceable Radiometry Underpinning Terrestrial- and Helio- Studies (TRUTHS) mission offers a novel approach to the provision of key scientific data with unprecedented radiometric accuracy for Earth Observation (EO) and solar studies, which will also establish well-calibrated reference targets/standards to support other EO missions. This paper presents the TRUTHS mission and its objectives. TRUTHS will be the first satellite mission to calibrate its EO instrumentation directly to SI in orbit, overcoming the usual uncertainties associated with drifts of sensor gain and spectral shape by using an electrical rather than an optical standard as the basis of its calibration. The range of instruments flown as part of the payload will also provide accurate input data to improve atmospheric radiative transfer codes by anchoring boundary conditions, through simultaneous measurements of aerosols, particulates and radiances at various heights. Therefore, TRUTHS will significantly improve the performance and accuracy of EO missions with broad global or operational aims, as well as more dedicated missions. The provision of reference standards will also improve synergy between missions by reducing errors due to different calibration biases and offer cost reductions for future missions by reducing the demands for on-board calibration systems. Such improvements are important for the future success of strategies such as Global Monitoring for Environment and Security (GMES) and the implementation and monitoring of international treaties such as the Kyoto Protocol. TRUTHS will achieve these aims by measuring the geophysical variables of solar and lunar irradiance, together with both polarised and unpolarised spectral radiance of the Moon, Earth and its atmosphere. Published by Elsevier Ltd on behalf of COSPAR.

WPS orchestration using the Taverna workbench: The eScience approach

eScience is an umbrella concept which covers internet technologies, such as web service orchestration that involves manipulation and processing of high volumes of data, using simple and efficient methodologies. This concept is normally associated with bioinformatics, but nothing prevents the use of an identical approach for geoinfomatics and OGC (Open Geospatial Consortium) web services like WPS (Web Processing Service). In this paper we present an extended WPS implementation based on the PyWPS framework using an automatically generated WSDL (Web Service Description Language) XML document that replicates the WPS input/output document structure used during an Execute request to a server. Services are accessed using a modified SOAP (Simple Object Access Protocol) interface provided by PyWPS, that uses service and input/outputs identifiers as element names. The WSDL XML document is dynamically generated by applying XSLT (Extensible Stylesheet Language Transformation) to the getCapabilities XML document that is generated by PyWPS. The availability of the SOAP interface and WSDL description allows WPS instances to be accessible to workflow development software like Taverna, enabling users to build complex workflows using web services represented by interconnecting graphics. Taverna will transform the visual representation of the workflow into a SCUFL (Simple Conceptual Unified Flow Language) based XML document that can be run internally or sent to a Taverna orchestration server. SCUFL uses a dataflow-centric orchestration model as opposed to the more commonly used orchestration language BPEL (Business Process Execution Language) which is process-centric.

The SeaWiFS Automatic data Processing System (SeaAPS)

The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) was designed to measure ocean colour, the spectral variation of water-leaving radiance that can be related to the concentrations of phytoplankton pigments, coloured dissolved organic material and suspended particulate matter. The Dundee Satellite Receiving Station records and archives 1-km imagery covering the European shelf-seas, north-east Atlantic Ocean and Mediterranean Sea, which is subsequently processed in near-real time by Plymouth Marine Laboratory using SeaWiFS Automatic Processing System (SeaAPS). SeaWiFS imagery is combined with contemporary Advanced Very High Resolution Radiometer (AVHRR) sea surface temperature data to provide products, supplied via the World Wide Web, that are used within many areas of oceanographic research.

Developments in Earth observation for the assessment and monitoring of inland, transitional, coastal and shelf-sea waters

The Earths surface waters are a fundamental resource and encompass a broad range of ecosystems that are core to global biogeochemical cycling and food and energy production. Despite this, the Earths surface waters are impacted by multiple natural and anthropogenic pressures and drivers of environmental change. The complex interaction between physical, chemical and biological processes in surface waters poses significant challenges for in situ monitoring and assessment and often limits our ability to adequately capture the dynamics of aquatic systems and our understanding of their status, functioning and response to pressures. Here we explore the opportunities that Earth observation (EO) has to offer to basin-scale monitoring of water quality over the surface water continuum comprising inland, transition and coastal water bodies, with a particular focus on the Danube and Black Sea region. This review summarises the technological advances in EO and the opportunities that the next generation satellites offer for water quality monitoring. We provide an overview of algorithms for the retrieval of water quality parameters and demonstrate how such models have been used for the assessment and monitoring of inland, transitional, coastal and shelf-sea systems. Further, we argue that very few studies have investigated the connectivity between these systems especially in large river-sea systems such as the Danube-Black Sea. Subsequently, we describe current capability in operational processing of archive and near real-time satellite data. We conclude that while the operational use of satellites for the assessment and monitoring of surface waters is still developing for inland and coastal waters and more work is required on the development and validation of remote sensing algorithms for these optically complex waters, the potential that these data streams offer for developing an improved, potentially paradigm-shifting understanding of physical and biogeochemical processes across large scale river-sea systems including the Danube-Black Sea is considerable.

A near‐real time automatic MODIS data processing system

The Moderate Resolution Imaging Spectroradiometer (MODIS) on‐board the Aqua and Terra platforms was designed to improve understanding of global dynamics and processes occurring on the land, in the oceans, and in the lower atmosphere. The UK Dundee Satellite Receiving Station has two X‐band receiving systems capable of capturing direct broadcast data from these spacecraft with a range covering the European shelf‐areas, north‐east Atlantic ocean and the western Mediterranean Sea. Raw data are transferred to the Plymouth Marine Laboratory (PML) and processed in near‐real time into ocean colour and sea‐surface temperature products for the academic community. Data can be used operationally and are made available through the web within 1.5 hours of the satellite overpass time. To our knowledge this is the only such developed system in Europe producing near‐real time MODIS ocean colour products.

The detection and mapping of algal blooms from space

Algal blooms change the colour of water through absorption by pigments and scattering by cells and associated detrital material. This paper gives a brief introduction, primarily using ocean colour imagery, to the use of satellite Earth observation measurements in detecting and mapping algal blooms. Two examples, using Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) imagery, show blooms within northern European waters.