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4 A brief history of scientific research of the shelf seas to 1960 ................................................................................... While the scientific study of the deep ocean is generally considered to have started with the Challenger expedition in 1872–1876, the systematic investigation of the shallow seas did not develop until some time later. Some important early observations were made at coasts, notably of the tides which were first accurately recorded at the port of Brest in 1679.

2 Sensors for biogeochemistry and beyond The basic physical measurements of pressure, temperature and electrical conductivity are, in principle, straightforward; the challenge lies largely with achieving the accuracy needed to quantify the small changes in density that drive mean flows in the ocean. When we want to make measurements of biogeochemical or ecological parameters, the challenge becomes far more extreme. There are still many measurements that require water to be collected and analysed using laboratory equipment on the ship, or even back ashore.

2009). The measurements of the sea surface elevation by microwave sensors (altimeters) on satellites have provided pictures of geostrophic currents and the mesoscale circulation in the deep ocean but works less well in shallow seas because of the large spatial scale of the ‘footprint’ of the microwave beam and interference from land at the coastal boundary. A more useful microwave technique for shelf seas is Synthetic Aperture Radar (SAR) which detects changes in surface roughness and thereby, in favourable conditions, allows the detection of internal wave motions.