Hazards and risks in the marine environment

Context

Earth observation data from the ERS satellite is helpful in the assessment and/or forewarning of a range of environmental risks and hazards in the marine environment, whether natural or manmade. Warning or forecasting systems may cover: risk assessment and management, hazard monitoring and forecasting, warning formulation, transmission and dissemination of warnings, and response mechanisms.

The emphasis of the use of spaceborne SAR data for monitoring sea ice and illegal oil spills is in complementing existing data sources, and optimising conventional monitoring and response mechanisms. This is due to the temporal and spatial coverage characteristic of satellites. ERS-2 Low Bit Rate data however, which is acquired more or less continuously, can provide the primary data source for certain marine services, where data collected from in-situ measurement techniques such as buoys do not exist.

Contents

The risks and hazards covered here encompass two main areas which threaten activities in the marine environment:

• Forecasting and nowcasting of winds and waves
• The climatology of winds and waves
• Sea ice navigation and monitoring

Oil spills, whether accidental or deliberate are another significant hazard in the marine environment. More information can be found in Coastal Zone Monitoring and Management, which includes other oceanographic applications : bathymetric mapping in shallow water, and ship detection. Natural disasters on land (flooding, earthquakes) and the risks thereof are covered in Natural Disasters - Assessment and Response.

Forecasting sea state for offshore operations and marine engineering

Illustration: A trawler in high waves

Marine conditions change very rapidly and can vary considerably between locations only a few kilometres apart. Errors in the planning of marine operations dependent on favorable conditions can be economically damaging, and in extreme cases even cost human lives. Consequently, weather and sea-state forecasts are critical to activities such as ship routing, fishing, management of offshore operations and coordinating rescue services, all of which require accurate and reliable information within a few hours of observation. To serve this marine market, the ERS Low Bit Rate fast delivery data stream, the development of appropriate ocean and weather forecasting models and data assimilation schemes, and an operational mobile communications infrastructure are all essential components.

The use of fast-delivery products from the ERS series radar altimeter, scatterometer, SAR and ATSR instruments can improves the accuracy and coverage of weather and sea-state forecast services. ERS offers consistent and geographically homogeneous data, for monitoring and forecasting of frontier areas where such a service did not previously exist, due to lack of sufficient coverage by ships of opportunity.

The climatology of marine areas for offshore operations

Illustration: Deploying an offshore oil rig (courtesy Shell UK Exploration & Production)

Information on the local climatology of waves is important in minimizing risks for a wide range of marine activities, such as locating offshore installations, planning offshore operations, for coastal defence planning and for the planning of naval exercises and other major ship routing operations.

Time series of sea state information are being developed as a basis for predicting conditions. For information on wave height, there exists presently ten years worth of data available from the Geosat, Topex-Poseidon altimeters as well as the ERS series. As this time series lengthens, the value of the information increases in terms of the ability to estimate seasonal climatologies, and predict extreme wave parameters such as the 50 year return waveheight. Information on the climatology of wave period and direction can also be derived from ERS instruments, useful modelling oscillations in coupled structures such as when fixing a riser pipe to an oil rig.

Sea ice monitoring and navigation for Arctic operators

Illustration: The MV Arctic, owned and operated by Canarctic Shipping (Courtesy GEC-Marconi Ltd. and Canarctic Shipping)

Daily sea-ice information is required for navigation during winter throughout the northern Baltic, around Svalbard, the Greenland Sea, along the east coasts of Canada and northern USA, the Great Lakes, and during summer in the European, Russian and Canadian Arctic. Three to seven day forecasts are also needed for strategic planning. The type of information required includes location of the ice edge, estimates of ice type and it's concentration. Also important is measurement of ice drift and speed.

The efficacy of Fast Delivery ERS SAR data has been demonstrated within well-established national sea-ice services. This use is based mainly upon manual interpretation, and is used as a complementary data source to traditional satellite sources such as Passive Microwave Radiometry, and low resolution optical data. In parallel, value-adding companies within Europe are developing the next generation of workstation which incorporate new techniques from the science community in order to automate feature interpretation and tracking. Additionally, demonstrations are being made of the use of ERS SAR data for shipping and offshore activities close to the ice edge.

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry