First results are presented for ocean surface wind speed retrieval from reflected GPS signals measured by the low Earth orbiting UK TechDemoSat‐1 satellite (TDS‐1). Launched in July 2014, TDS‐1 provides the first new spaceborne Global Navigation Satellite System‐Reflectometry (GNSS‐R) data since the pioneering UK‐Disaster Monitoring Mission (UK‐DMC) experiment in 2003. Examples of onboard‐processed delay‐Doppler maps reveal excellent data quality for winds up to 27.9 m/s. Collocated Advanced Scatterometer (ASCAT) winds are used to develop and evaluate a wind speed algorithm based on signal‐to‐noise ratio (SNR) and the bistatic radar equation. For SNRs greater than 3 dB, wind speed is retrieved without bias and a precision around 2.2 m/s between 3 and 18 m/s even without calibration. Exploiting lower SNR signals, however, requires good knowledge of the antenna beam, platform attitude, and instrument gain setting. This study demonstrates the capabilities of low‐cost, low‐mass, and low‐power GNSS‐R receivers ahead of their launch on the NASA Cyclone GNSS (CYGNSS) constellation in 2016.

Satellite altimeter (Topex/Poseidon, 1992–2001) and tide-gauge measurements are used to explore the relationship of the sea level of the North Atlantic and neighbouring seas and coastlines to the North Atlantic Oscillation (NAO). Altimeter measurements suggest significant gyre-scale influence of the NAO in the North Atlantic, but also stronger influences on the continental shelf and inland seas of Europe. A north–south dipole in sea-level anomaly consistent with a hydrostatic response to the NAO sea-level pressure dipole is evident, but there are also large non-hydrostatic effects. The strongest response on the European Shelf is in the southeastern part of the North Sea where sea level is positively correlated to NAO Index. The sea level in two semi-enclosed seas, the Baltic Sea positively and the Mediterranean Sea negatively, is also strongly influenced by the NAO. A weak negative correlation is apparent around the northeastern coastline of North America. These features are confirmed by contemporary coastal tide-gauge data, but the tide-gauge data also show that the influence of the NAO was weaker early in the Twentieth Century (20C) on parts of the Northwest European coastline. Inter-annual sea-level variability associated with fluctuations in the NAO are generally much larger than those associated with secular trends. Inferred multi-decadal fluctuations associated with the NAO are very substantial compared to the 15(±5) cm estimated for 20C global sea-level rise (Church, J.A., Gregory, J.M., Huybrechts, P., Kuhn, M., Lambeck, K., Nhuan, M.T., Qin, D. and Woodworth, P.L. ( 2001 Church J.A. Gregory J.M. Huybrechts P. Kuhn M. Lambeck K. Nhuan M.T. Qin D. Woodworth P.L. 2001 Changes in sea level. Chapter 11 of the Intergovernmental Panel on Climate Change Third Assessment Report pp. 639–694 Cambridge University Press Cambridge [Google Scholar] ). Changes in sea level. Chapter 11 of the Intergovernmental Panel on Climate Change Third Assessment Report, pp. 639–694. Cambridge University Press, Cambridge.) and scenario forecasts for the 21C (˜50 cm). Therefore, the behaviour of the NAO in the next few decades will be a major regional factor in sea-level rise and coastal vulnerability in some European regions.

Within the framework of a Tyndall Centre research project, sea level and wave changes around the UK and in the North Sea have been analysed. This paper integrates the results of this project. Many aspects of the contribution of the North Atlantic Oscillation (NAO) to sea level and wave height have been resolved. The NAO is a major forcing parameter for sea-level variability. Strong positive response to increasing NAO was observed in the shallow parts of the North Sea, while slightly negative response was found in the southwest part of the UK. The cause of the strong positive response is mainly the increased westerly winds. The NAO increase during the last decades has affected both the mean sea level and the extreme sea levels in the North Sea. The derived spatial distribution of the NAO-related variability of sea level allows the development of scenarios for future sea level and wave height in the region. Because the response of sea level to the NAO is found to be variable in time across all frequency bands, there is some inherent uncertainty in the use of the empirical relationships to develop scenarios of future sea level. Nevertheless, as it remains uncertain whether the multi-decadal NAO variability is related to climate change, the use of the empirical relationships in developing scenarios is justified. The resulting scenarios demonstrate: (i) that the use of regional estimates of sea level increase the projected range of sea-level change by 50% and (ii) that the contribution of the NAO to winter sea-level variability increases the range of uncertainty by a further 10–20 cm. On the assumption that the general circulation models have some skill in simulating the future NAO change, then the NAO contribution to sea-level change around the UK is expected to be very small (<4 cm) by 2080. Wave heights are also sensitive to the NAO changes, especially in the western coasts of the UK. Under the same scenarios for future NAO changes, the projected significant wave-height changes in the northeast Atlantic will exceed 0.4 m. In addition, wave-direction changes of around 20° per unit NAO index have been documented for one location. Such changes raise the possibility of consequential alteration of coastal erosion.

Hourly sea level data from tide gauges and a barotropic model are used to explore the spatial and temporal variability of sea level extremes in the Mediterranean Sea and the Atlantic coasts of the Iberian peninsula on seasonal time scales. Significant spatial variability is identified in the observations in all seasons. The Atlantic stations show larger extreme values than the Mediterranean Sea primarily due to the tidal signal. When the tidal signal is removed most stations have maximum values of less than 90 cm occurring in winter or autumn. The maxima in spring and summer are less than 60 cm in most stations. The wind and atmospheric forcing contributes about 50 cm in the winter and between 20–40 cm in the other seasons. In the western Mediterranean the observed extreme values are less than 50 cm, except near the Strait of Gibraltar. Direct atmospheric forcing contributes significantly to sea level extremes. Maximum sea level values due to atmospheric forcing reach in some stations 45 cm during the winter. During the summer the contribution of the direct atmospheric forcing is between 10–20 cm. The Adriatic Sea shows a resonant behaviour with maximum extreme observed sea level values around 200 cm found at the northern part. Trends in the 99.9% percentiles are present in several areas, however most of them are removed when the 50% percentile is subtracted indicating that changes in the extremes are in line with mean sea level change. The North Atlantic Oscillation and the Mediterranean Oscillation Index are well correlated with the changes in the 99.9% winter values in the Atlantic, western Mediterranean and the Adriatic stations. The correlation of the NAO and the MOI indices in the Atlantic and western Mediterranean is significant in the autumn too. The correlations between the NAO and MOI index and the changes in the sea level extremes become insignificant when the 50% percentile is removed indicating again that changes in extremes have been dominated by changes in the mean sea level.