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This paper reviews the historical development of concepts and practices in the science of ocean predictions. It begins with meteorology, which conducted the first forecasting experiment in 1950, followed by wind waves, and continuing with tidal and storm surge predictions to arrive at the first successful ocean mesoscale forecast in 1983. The work of Professor A. R. Robinson of Harvard University, who produced the first mesoscale ocean predictions for the deep ocean regions is documented for the first time. The scientific and technological developments that made accurate ocean predictions possible are linked with the gradual understanding of the importance of the oceanic mesoscales and their inclusion in the numerical models. Ocean forecasting developed first at the regional level, due to the relatively low computational requirements, but by the end of the 1990s, it was possible to produce global ocean uncoupled forecasts and coupled ocean-atmosphere seasonal forecasts.

We review mechanisms and studies of exchange between the north-east Atlantic and the adjacent shelf sea. Mechanisms include: well-developed summer upwelling and associated filaments off Portugal and north-west Spain giving exchange O(3 m**2/s per unit length of shelf); prevailing westerly winds further north driving exchange O(1 m**2/s); poleward flow along most of the upper slope with associated secondary circulation O(1 m**2/s); meanders and eddies in this poleward flow; eddies shed from slope waters into the Bay of Biscay; local exchanges at shelf spurs and depressions or canyons (e.g. dense-water cascading of order 1 m**2/s). Tidal transports are larger; their reversal every six hours makes exchange largely ineffective except where internal tides are large and non-linear, as in the Celtic Sea where solitons carry water with exchange O(1 m**2/s). These various physical exchanges amount to an estimated 2-3 m**2/s per unit length of shelf, between ocean and shelf; a numerical model estimate is comparable: 2.5 x 106 m**3/s onto and off the shelf from Brittany to Norway. Mixing controls the seasonal thermocline, affecting primary production and hence fluxes and fate of organic matter. Specifically, CO2 take-up by primary production, settling below the thermocline before respiration, and then off-shelf transport, make an effective shelf-sea “pump” (for CO2 from the atmosphere to the deep ocean). However, knowledge of biogeochemical fluxes is generally sparse; there is scope for more measurements, model validation and estimates from models.

Images from acoustic reflections in the water column were obtained during the EU funded GO experiment in the Gulf of Cadiz, and oceanographic data at the same place and time were also collected. The experiment(www.dur.ac.uk/eu.go/) focused on a section across the Mediterranean Water flow against and down the continental slope. The present analysis concerns the data on the continental slope at one end of the seismic section. XBT, XCTD and CTD sections were taken on the slope to analyze the properties of the water column. The XBT provide fine resolution in space and time, and are analyzed to estimate diffusivity and mixing parameters. This is also related with the local circulation and internal wave contributions using data from ADCPs and moored temperature loggers. The finer resolution of the XBT and seismic data gives a new view on the mixing. Different ways to compare seismic and oceanographic data will be discussed.

The GO project (European Union-NEST-Adventure funding; www.durac.uk/eu.go) aims to assess the potential of seismic imaging of the water column. a dedicated experiment (April-May 2007, gulf of Cadiz) looked at varying Mediterranean Outflow water (MOW) flow along and down the continental slope. Distinctive MOW properties provide strong reflection from seismic sounding. We aim to relate water properties to mixing and hence (e.g.) tides, internal waves, eddies. Physical oceanography results derive from 500 XBT casts, typical spacing 2km, and moorings: three ACDPs, three temperature strings and near-sea-bed turbulence in line on the north-eastern margin of Portimao Canyon (water depths 740-980m); a fourth ADCP-6 km along-slope in 1015 m depth. CTD and LADCP profiling on an IFM-Geomar research cruise, closely following the seismic sections, supplemented the GO measurements. We examine the structures observed on the principal line through the moorings (five surveys,) and compare with the contemporary seismic data that further constrain observed boundaries. The mooring data and profiles are analysed for tides and internal wave spectra, small-scale structure and turbulence to estimate diffusivity and mixing.

On the shelf slope north of Scotland the rate of turbulent kinetic energy (TKE) dissipation,calculated from density overturns, is 6±1×10-7 Wkg-1. Using a standard mixing efficiency, this dissipation rate is equivalent to a diapycnal diffusivity of 10-3 m2s-1, two orders of magnitude larger than typical open ocean background levels. The rate of TKE dissipation cannot be fully explained by local shear and strain measurements so we invoke a far-field source of energy, supplied in the form of internal waves, to drive mixing over the slope. The across-slope internal wave energy flux is 130 Wm-1 at semi-diurnal frequencies with 103±20 Wm-1 contained in the pycnocline. This can be reconciled with the TKE dissipation rate by assuming all the internal wave energy is dissipated in the ~4.5 km that the pycnocline intersects the slope. The rate of TKE dissipation inferred from this assumption is between 3 and 6×10-7 Wkg-1, comparable to the dissipation rate calculated from density overturns, and emphasizes the role of internal waves in the transfer of tidal energy, not just into the abyssal ocean, but around complex topography.

The Faroe-Shetland Channel is an important passageway for watermass exchange between the North Atlantic and the Arctic Oceans, being the primary route of overflow waters from the Nordic Seas entering the Iceland Basin. The hydrography of the Channel is dominated by a permanent pycnocline that separates high salinity North Atlantic Water, flowing northward against the West Shetland slope in a barotropic slope current, and typically southward flowing intermediate and deep waters that originate in the Arctic basin. Mixing in the pycnocline may be enhanced by turbulent instabilities resulting from the shear flow or by internal waves generated along the West Shetland slope and over the Wyville-Thompson Ridge. During F. S. Poseidon cruise 328 in September 2005, three CTD/LADCP sections across the Faroe-Shetland Channel were completed and a station over the West Shetland slope occupied for 24 hours with a cast every hour. Two methods of calculating diapycnal eddy diffusivity (κρ) from the cast data are used, scaling of density overturns [e.g., Thorpe, 1977], and comparison of the vertical shear spectrum with the Garrett and Munk model of the background internal wave field [Garrett and Munk, 1975] following the method of Naveira Garabato et al. [2004]. In the permanent pycnocline κρ is found to be ≥ 10-3 m2 s-1, an order of magnitude larger than in the regions of weak stratification. Over the Faroe slope, mixing is enhanced through out the watercolumn with κρ approaching 10-2 m2 s-1. Mixing is also enhanced where the pycnocline meets the West Shetland slope with a semi-diurnal cycle apparent in both the depth of the pycnocline and the strength of the mixing. In the slope current at the shelf edge κρ is less, of the order 10-3.5 m2 s-1. There is good agreement between the methods in the regions of stratification, although where N2 < 10-5 s-2 Thorpe scaling estimates κρ an order of magnitude larger than the vertical shear spectrum method.

The Faroe-Shetland channel is a major pathway for the thermohaline circulation in the North Atlantic. Cold deep water from the Nordic Seas flows to the southwest whilst above warm North Atlantic water flows to the northeast. The boundary between these two water bodies creates a strong impedance contrast that is imaged on seismic reflection data, and can be traced across the channel to where it interacts with the continental slope. In the contexts of mixing and representativeness of hydrographic observations, an important issue is how internal waves populating a water mass boundary like this one evolve over short time periods. The seismic method acquires a sequence of snapshots of the boundary as the acquisition system is towed through the water layer. These snapshots can be reconstructed to show how the shape of the boundary changes and, for the Faroe-Shetland channel, these reconstructions show that the internal wavefield is ergodic. That is, the statistical properties of a series of measurements at one location are the same as the properties of a single measurement at many locations. Further, their spectra show a reduction in amplitude with decreasing wavelength as predicted by the Garrett-Munk spectrum. These reconstructions also show that the longer wavelength features are stationary or very slow moving with respect to the seismic acquisition vessel, so that stacking does not damage the large-scale geometry. In these data a second boundary can be mapped at the bottom of the channel. We interpret this as being caused by the strong currents in the channel mobilising sediments in the bottom nepheloid layers. Although the sediment concentrations are small the fact that these bodies form reflections reinforces the interpretation based on forward models that, typically, the bottom has little reflectivity rather than a signal-to-noise imaging problem.

This pioneering project is the first dedicated EU project to address this novel research area that will ultimately bring the spatial resolution of the sub-surface seismic image, as used by the hydrocarbons industry, to address problems in oceanography. The project places demands on both sides: for the geophysicists, proving how the observed reflections are linked to boundaries in the water column; for the oceanographer, being able to build models and interpret data on the 10 m scale rather than the 1 km scale; and together, understanding how a 2-D snapshot of the 3-D ocean structure can be interpreted and translated into understanding of the dynamics of heat and mass transfer. A major goal will be providing the confidence to use legacy seismic data collected for academic research and hydrocarbon exploitation for understanding ocean processes. The project will: 1.produce a joint interpretation from a combined calibration experiment with the simultaneous collection of both seismic and oceanographic data in the Gulf of Cadiz; 2.build models based on oceanographic research and compute synthetic seismic data to test strategies; 3.explore novel methods to use seismic data to understand processes involved in ocean mixing including internal waves and interaction with continental slopes; 4.provide new data for research into oceanic mixing processes; 5.establish research expertise in the EU at centres of excellence that can be used for training and exploitation of this new opportunity and that can compete with non-EU laboratories; 6.provide new tools to aid monitoring ocean circulation and heat transport which are important to climate change and its implications for weather patterns in Europe, and in controlling the marine ecosystem.

Very recent measurements made on the eastern flank of the Faroe-Shetland Channel have revealed intense and prolonged periods of highly non-linear internal wave activity at the intersection of the interface between Arctic and Atlantic origin waters with the continental slope at a depth of 600m. An array of 10 moorings was deployed between 7th and 21st September 2005 in a "cross" formation of dimension 5km oriented along the slope, centred on 60.2N 4.7W in a water depth of 600m. At this location the Scotland-Faroes branch of the North Atlantic inflow to the Arctic Mediterranean flows north-eastward as a slope current above modified North Atlantic water masses recirculating in the channel and above the south-westward flowing Arctic origin water masses. Repeated, lowered ADCP casts revealed intensified tidal currents below the main thermocline; with rising bands of maximum shear at the dominant M2 tidal period coincident with the region of maximum stratification. Moored ADCP and temperature records show many cases when near-bed temperature and velocity exhibit sharp changes followed by packets of solitons of elevation propagating up-slope. For 8 consecutive tidal cycles, the soliton packets appeared to be quasi-phase locked to the semi-diurnal frequency. Frequently the solitons were not rank ordered, indicative of intense dissipation of the leading wave. In some instances soliton-induced non-hydrostatic pressure changes were measured. In this paper we describe in detail the cross-slope propagation and along-slope variation of these deep tidal bores and solitons of elevation as they pass through the mooring array antenna: we also discuss their generation mechanism and energetics of mixing and energy loss.

The hydrochemical and physical functioning of UK river basins, estuaries and coastal waters through to the open sea are outlined in relation to British environmental research over the last ten or more years. An overview of a considerable body of published work is presented in the context of current findings and future research challenges. This is linked to this special issue of Science of the Total Environment ‘Land Ocean Interaction: processes, functioning and environmental management: a UK perspective’ for which this contribution provides a conclusion.