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Storm surges are responsible for great damage to coastal property and loss of life every year. Coastal management and adaptation practices are essential to reduce such damage. Numerical models provide a useful tool for informing these practices as they simulate sea level with high spatial resolution. Here we investigate the ability of a barotropic version of the HAMSOM model to simulate sea level extremes of meteorological origin in the Mediterranean Sea, including those caused by explosive cyclones. For this purpose, the output of the model is compared to hourly sea level observations from six tide gauge records (Valencia, Barcelona, Marseille, Civitavecchia, Trieste, and Antalya). It is found that the model underestimates the positive extremes significantly at all stations, in some cases by up to 65%. At Trieste, the model can also sometimes overestimate the extremes significantly. The differences between the model and the residuals are not constant for extremes of a given height, which limits the applicability of the numerical model for storm surge forecasting because calibration is difficult. The 50 and 10 year return levels are reasonably well captured by the model at all stations except Barcelona and Marseille, where they are underestimated by over 30%. The number of exceedances of the 99.9th and 99.95% percentiles over a period of 25 years is severely underestimated by the model at all stations. The skill of the model for predicting the timing and value of the storm surges seems to be higher for the events associated with explosive cyclones at all stations.

We investigate how well methods based on empirical orthogonal functions (EOFs) can reconstruct global mean sea level (GMSL). We first explore the analytical solution of the method and then perform a series of numerical experiments using modelled data. In addition, we present a new GMSL reconstruction for the period 1900-2011 computed both with and without a spatially uniform EOF (EOF0). The method without the EOF0 uses global information, which leads to a better reconstruction of the variability, though with some underestimation. The trend, however, is not captured, which motivates the use of the EOF0. When the EOF0 is used the method reduces to the generalized weighted mean with regularization of altimetry records at tide gauge locations, and thus it uses no global information. This results in a poor reconstruction of the variability. Although the trend is better captured (biases smaller than ±25%) with the EOF0, using the covariance matrix of deseasonalized monthly time series as the basis for determining the contribution of each tide gauge to the trend is dubious because it assumes that the inter-annual variability and the trend are driven by the same mechanisms. A significant fraction of the inter-annual to decadal variability (~4mm peak-to-peak and ~2mm standard error) in the new GMSL reconstruction without the EOF0 is consistent with land hydrology changes associated with the El Niño-Southern Oscillation (ENSO). When the EOF0 is used, we find no correlation with either the ENSO or land hydrology changes, and decadal fluctuations are ~5 times greater.

Large waves pose risks to ships, offshore structures, coastal infrastructure and ecosystems. This paper analyses 10 years of in-situ measurements of significant wave height (Hs) and maximum wave height (Hmax) from the ocean weather ship Polarfront in the Norwegian Sea. During the period 2000 to 2009, surface elevation was recorded every 0.59 s during sampling periods of 30 min. The Hmax observations scale linearly with Hs on average. A widely-used empirical Weibull distribution is found to estimate average values of Hmax/Hs and Hmax better than a Rayleigh distribution, but tends to underestimate both for all but the smallest waves. In this paper we propose a modified Rayleigh distribution which compensates for the heterogeneity of the observed dataset: the distribution is fitted to the whole dataset and improves the estimate of the largest waves. Over the 10-year period, the Weibull distribution approximates the observed Hs and Hmax well, and an exponential function can be used to predict the probability distribution function of the ratio Hmax/Hs. However, the Weibull distribution tends to underestimate the occurrence of extremely large values of Hs and Hmax. The persistence of Hs and Hmax in winter is also examined. Wave fields with Hs>12 m and Hmax>16 m do not last longer than 3 h. Low-to-moderate wave heights that persist for more than 12 h dominate the relationship of the wave field with the winter NAO index over 2000–2009. In contrast, the inter-annual variability of wave fields with Hs>5.5 m or Hmax>8.5 m and wave fields persisting over ~2.5 days is not associated with the winter NAO index.

This paper analyses 10 years of in-situ measurements of significant wave height (Hs) and maximum wave height (Hmax) from the ocean weather ship Polarfront in the Norwegian Sea. The 30-minute ship-borne wave recorder measurements of Hmax and Hs are shown to be consistent with theoretical wave distributions. The linear regression between Hmax and Hs has a slope of 1.53. Neither Hs nor Hmax show a significant trend in the period 2000–2009. These data are combined with earlier observations. The long-term trend over the period 1980–2009 in annual Hs is 2.72 ± 0.88 cm/year. Mean Hs and Hmax are both correlated with the North Atlantic Oscillation (NAO) index during winter. The correlation with the NAO index is highest for the more frequently encountered (75th percentile) wave heights. The wave field variability associated with the NAO index is reconstructed using a 500-year NAO index record. Hs and Hmax are found to vary by up to 1.42 m and 3.10 m respectively over the 500-year period. Trends in all 30-year segments of the reconstructed wave field are lower than the trend in the observations during 1980–2009. The NAO index does not change significantly in 21st century projections from CMIP5 climate models under scenario RCP85, and thus no NAO-related changes are expected in the mean and extreme wave fields of the Norwegian Sea.

Sea level in the Mediterranean Sea over the period 1993–2011 is studied on the basis of altimetry, temperature, and salinity data and gravity measurements from Gravity Recovery and Climate Experiment (GRACE) (2002–2010). An observed increase in sea level corresponds to a linear sea level trend of 3.0 ± 0.5 mm/yr dominated by the increase in the oceanic mass in the basin. The increase in sea level does not, however, take place linearly but over two 2–3 year periods, each contributing 2–3 cm of sea level. Variability in the basin sea level and its mass component is dominated by the winter North Atlantic Oscillation (NAO). The NAO influence on sea level is primarily linked with atmospheric pressure changes and local wind field changes. However, neither the inverse barometer correction nor a barotropic sea level model forced by atmospheric pressure and wind can remove fully the NAO influence on the basin sea level. Thus, a third contributing mechanism linked with the NAO is suggested. During winter 2010, a low NAO index caused a basin sea level increase of 12 cm which was almost wholly due to mass changes and is evidenced by GRACE. About 8 cm of the observed sea level change can be accounted for as due to atmospheric pressure and wind changes. The residual 4 cm of sea level change is caused by the newly identified contribution. The physical mechanisms that may be responsible for this additional contribution are discussed.

Decadal sea level variations from tide gauge records along the western European coast and in the Mediterranean Sea commencing in the late 19th and early 20th centuries are examined relative to large-scale atmospheric forcing. Recent studies have provided evidence for a link between sea level in the eastern North Atlantic and atmospheric forcing, however the nature of this relationship is still unclear. Here the outputs of a regional barotropic model and a nearly global baroclinic model are used in conjunction with wind stress and heat flux data to explore the physical mechanisms responsible for the observed sea level variability. All tide gauge records show significant decadal variability (up to 15 cm) and are highly correlated with the NAO and among themselves at decadal periods. There is a coherent sea level signal that affects the eastern boundary of the North Atlantic northward of 25°N and is limited to a narrow band of the order of a few hundred kilometers along the coast. This band tends to become narrower towards higher latitudes. We find that longshore wind and wave propagation along the boundary are the major contributors to coastal sea level variability but no significant contribution from mass redistribution linked to changes in the strength of the subtropical gyre is observed. The mass component dominates sea level in the Mediterranean and is mainly driven by mass exchanges with the Atlantic, which explains the correlation between both regions. Southward of 25°N, sea level changes are mainly driven by heat advection through Ekman fluxes.

Sea level observations from tide-gauge records located at the Adriatic coasts are analysed. The estimated sea level trends show variability in time and space. Spatial variability is assessed by estimating the differential trends by reference to Trieste. For many of the stations the differential trends become smaller than the corresponding error bars. This indicates that the land, atmospheric and oceanic contributors to sea level change are, at long scales, uniform in the basin. Observed trends in the longer records differ significantly for the periods before 1960 and after 1960. Atmospheric forcing has been a significant contribution in sea level variability for the period 1960 onwards. The atmospheric trends account for −0.8 mm/year for the period 1960–2000. No significant atmospheric trends appear to be present at the period 1900–1960. Changes in the atmospheric forcing alone are not capable of explaining fully the difference in the sea level trends for the periods before and after 1960. Steric trends for the period 1960–2000 have also been identified. Their magnitude depends on the depth used for their estimation. Steric trends range between −0.4 mm/year for the upper 100 m to −2.4 mm/year for the whole water column. The residual sea level after the removal of atmospheric and steric effects ranges between 2 and 3.4 mm/year at various stations with an associated error bar of 1 mm/year. This residual must be accounted for by land movements and incoming signals through the strait of Otranto. The coherence of high frequency sea level signals in the north part of the Adriatic Sea is also analysed for the period 2002–2005 using eight tide gauges. The first empirical orthogonal function contains 71% of the variability indicating that the known coherency at inter-annual and inter-decadal scales extends partly to the higher frequency too.

The nodal modulation of the diurnal (K1 and O1) and semi-diurnal (M2, and K2) tidal constituents at the coasts of the Mediterranean Sea and the eastern Atlantic is estimated and its spatial variability mapped. Fourteen hourly tide gauge records each spanning more than 18 years are considered in this analysis. Ten tide gauges are located in the Mediterranean Sea and four in the Bay of Biscay. The nodal modulation of the most energetic tidal constituent (M2) reaches up to 5 cm at the eastern Atlantic coasts, while within the Mediterranean Sea its modulation is in general less than 1.2 cm. The largest K2 nodal modulation found is 3.7 cm in the eastern Atlantic coasts. In the Mediterranean Sea, smaller modulation amplitudes, ranging between 0.4 and 1.4 cm are found. The K1 tide constituent has the largest amplitude nodal modulation within the Mediterranean Sea of 1.9 cm in the north Adriatic Sea, which is also larger than the modulation of this constituent at the eastern Atlantic coasts. The O1 tide constituent has the highest amplitude nodal modulation (1.4 cm) at the eastern Atlantic coasts. In the Mediterranean Sea the maximum value is 1 cm in the north Adriatic Sea. The derived nodal modulations of the diurnal and semi-diurnal constituents follow, in general, the equilibrium tidal theory. The tidal amplitudes for all four components do not indicate significant secular trends for most tide gauges. The tidal phases indicate significant negative trends for all four tidal constituents within the central and eastern Mediterranean Sea.

Estimates of extreme sea levels and return periods have been based mainly on hourly sampling rates. Technological development has enabled the sampling rates to increase and sampling rates of 5–10 min are becoming increasingly common. In this paper we explore the relationship between extreme sea levels and estimated return periods based on hourly and shorter sampling periods in three tide-gauges one at the Atlantic coasts of Spain (Coruña), one in the western Mediterranean (Malaga) and one in the N. Adriatic (Trieste). Significant differences of several centimetres are found in the hourly and 5 min extremes. These reflect in significant underestimation of the 50-year return levels which in Trieste reach 38 cm. A theoretical relationship between the high and the low sampling rate of extremes is also tested. Thus updated 50-year return levels for the Mediterranean and the coasts of the Iberian peninsula are produced assuming that the differences identified in the various stations generalise to other tide-gauge (hourly) records for which hourly values have been analysed earlier.

The temporal and spatial variability of the seasonal signals in the Mediterranean Sea and the Atlantic Iberian coast is explored on the basis of tide gauge data. Mean amplitudes range in the various stations between 3 and 7 cm for the mean annual component and between 1 and 3 cm for the semiannual component. On average, seasonal signals account for approximately 20% of the total variance of monthly records. The seasonal cycle is unsteady in time, with large variations in amplitudes and phases in some stations reaching up to 8 cm and 40 d, respectively. The contribution of the direct atmospheric effects to the seasonal cycle has been estimated by means of the output of a barotropic model forced with wind and atmospheric pressure. This contribution is regionally coherent, albeit variable in time. The annual cycle of the residuals (observations minus atmospherically induced sea level) is larger than that of the observations by about 2–3 cm. The residual semiannual cycle is smaller than that of the observations by about 25%. The temporal variability of the seasonal cycle of the residual series is also explored. Changes in water temperatures at the upper layers is the only parameter that appears connected with the observed variations.

Sea level trends derived from North Atlantic and the Mediterranean Sea tide gauges have been re-evaluated with a common reference period (1960–2000) and with the atmospheric component of the observed sea level variability quantified and removed by means of regional barotropic ocean models forced by wind and atmospheric pressure. The atmospherically forced trends are important and have values of −0.2 ± 0.1 mm/yr in the North Atlantic (west coast), −0.2 ± 0.2 mm/yr in the NE Atlantic, 0.3 ± 0.4 mm/yr in North Sea and −0.7 ± 0.1 mm/yr in the Mediterranean. The residual sea level trends corrected for post-glacial rebound processes are 0.9 ± 0.4 mm/yr in the Mediterranean, 1.1 ± 0.6 mm/yr in the NW Atlantic, 1.3 ± 1.0 mm/yr in the NE Atlantic and 1.3 ± 0.8 mm/yr in the North Sea. Atmospheric forcing is partly responsible for the observed patterns of sea level rise and for part of the observed sea level acceleration during the 1990s. The residual trends have further been corrected for the influence of the steric effects. In the Mediterranean removing the steric component increases the trends by 40% and makes them consistent with the Atlantic trends. The remaining sea level rise rates are due to mass addition and their spatial pattern in the region can be related to Greenland ice-melting rates.

Precipitation is a parameter that varies on many different spatial and temporal scales. Here we look at interannual variations associated with the North Atlantic Oscillation (NAO) and the Southern Oscillation (SO), comparing the spatial and temporal changes as shown by three data sets. The Global Precipitation Climatology Project (GPCP) product is based upon satellite data, whereas both the National Centers for Environmental Prediction (NCEP) and European Centre for Medium-Range Weather Forecasts (ECMWF) climatologies are produced through reanalysis of atmospheric circulation models. All three products show a consistent response to the NAO in the North Atlantic region, with negative states of the NAO corresponding to increases in precipitation over Greenland and southern Europe, but to a decrease over northern Europe. None of the climatologies display any net change in total rainfall as a result of the NAO, but rather a redistribution of precipitation patterns. However, this redistribution of rain is important because of its potential effect on oceanic overturning circulation. Similarly, all three data sets concur that the SO has a major effect on precipitation in certain tropical regions; however, there is some disagreement amongst the data sets as to the regional sensitivity, with NCEP showing a much weaker response than GPCP and ECMWF over Indonesia. The GPCP and NCEP climatologies show that the various phases of El Niño and La Niña act to redistribute, rather than enhance, the freshwater cycle. Given that the models incorporate no actual observations of rain, and are known to be imperfect, it is surprising how well they represent these interannual phenomena.

Coastal sea level measured from tide gauges exhibits coherent variability at interannual and decadal scales. We investigate sea-level variability of large geographic areas using annual mean sea-level values obtained from the longest available records of coastal observations. Eight sea-level regional indices are constructed for the Atlantic and the Pacific Ocean basins. High coherency of sea-level variability at the decadal timescales between different oceanic regions is observed. The role of large-scale atmospheric forcing is then examined by comparison with the El Niño–Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). Strong correlation between the NAO and the second empirical orthogonal function (EOF) of the northwest Atlantic data set was observed. The second EOF is also significantly correlated with the latitudinal position of Gulf Stream and the Arctic Oscillation (AO). Sea-level changes in the northeast Atlantic are driven by the NAO. Correlation with the AO was also observed. In the Pacific Ocean, ENSO dominates sea-level variability along the eastern and southwest sides of the basin. ENSO signatures appear also in the southwest Atlantic, indicating teleconnection patterns. It is proposed that ENSO-related variability in this region is forced through the Pacific–South American teleconnection mechanism. The correlation between southwest Atlantic sea level and ENSO increased after 1980. Sea-level variability on decadal scales in the northwest Pacific region is influenced by the Pacific Decadal Oscillation.

Sea level values from a two-dimensional model of the Mediterranean Sea forced by atmospheric pressure and wind are used to estimate the barotropic flow through the Strait of Gibraltar for the period 1958–2001. The Mediterranean mean sea level derived from the model ranges between ±20 cm with a standard deviation of 5.5 cm and is correlated to the North Atlantic Oscillation (NAO) index. Thus NAO historical data and reconstructions are used to derive the Mediterranean Sea level variability from 1659 until 2001. The accuracy of the reconstruction is estimated in 2.7 cm for monthly mean values, 0.41 cm for annual mean values, and 0.22 cm for decadal mean values (0.48 cm for decadal winter mean sea level). The barotropic flow through the strait is computed from the model output as the time derivative of the total volume of the basin. During the period 1958–2001 the estimated daily flow ranges between ±2.7 Sv, with a standard deviation of 0.56 Sv. The dominant periodicities are in between 1 and 2 weeks. At these scales the model successfully reproduces previously published flow estimates based on current meter observations, which confirms that atmospheric pressure and wind dominate the intraseasonal variability of the flow. For the annual cycle the variability of the atmospherically induced flow is similar to the variability of the flow induced by the evaporation-precipitation (E-P) budget (±0.025 Sv), though absolute values of the first are about a third of the latter. At longer timescales the atmospheric contribution is much smaller than the E-P induced flow.

The 9 longest tide-gauge records in the Mediterranean Sea are compared with the output of a barotropic model forced by atmospheric pressure and wind. Between 1958 and 2001 the tide-gauges indicate sea level trends of −0.4 to 0.7 mm/yr. During the same period the model shows sea level reduction of −0.4 to −0.7 mm/yr linked with the North Atlantic Oscillation (NAO). After the removal of the meteorological influence from the sea level records the resulting trends are ~0.3 ± 0.4 mm/yr at the western Mediterranean and ~1.3 ± 0.4 mm/yr at the eastern Mediterranean. The eastern basin is strongly affected by rapid sea level rise in the period 1993–2001 with rates of 5–10 mm/yr which are probably related to the Eastern Mediterranean Transient (EMT).

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 10–20cm. 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 (<4cm) 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

The thermosteric contribution of the North Atlantic Oscillation (NAO) to the North Sea sea level for the winter period is investigated. Satellite sea surface temperature as well as in situ measurements are used to define the sensitivity of winter water temperature to the NAO as well as to determine the trends in temperature. The sea surface temperature sensitivity to the NAO is about 0.85˚ C per unit NAO which results in thermosteric sea level changes of about 1- 2 cm per unit NAO. The sensitivity of SST to the NAO is strongly time dependent. Model data from a 2d hydrodynamic tide + surge model are used in combination with the estimated thermosteric anomalies to explain the observed sea level changes and in particular the sensitivity of the datasets to the NAO variability. The agreement between the model and the observed data is improved by the inclusion of the thermosteric effect.

Forcing mechanisms for sea level variability in the Black Sea are investigated in the context of an observed increase in the sea level of this basin by 2.5 mm/yr over the last 60 years. Temperature and salinity variations computed from the Mediterranean Data Archeology and Rescue (MEDAR) data set exhibit significant interdecadal variability. However, the corresponding steric height variation does not show a long-term increase and thus cannot account for the observed change in sea level. The impact of surface freshwater flux (P-E) changes is also investigated using two independent data sets. The first data set, which is based on measurements collected in the basin, can explain most of the sea level variability, with only 0.8 mm/yr remaining unexplained. The second data set, output from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis, is unable to explain any of the observed trend. Potential contributions from changes in river runoff and surface pressure are quantified but found to be minor terms. By comparing the observed salinity changes with the sea level rise and the P-E variability in the first data set, we infer that the P-E variations are the primary cause for the observed sea level rise, while land movements are likely to partly contribute, too. The relationship of Black Sea temperature and salinity variability with corresponding variability in the connected Aegean Sea has also been explored. A significant correlation is found between the salinity of the upper water of the Aegean Sea and the layer between 50 and 300 m in the Black Sea, indicating that the latter layer is a product of the Mediterranean inflow.

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 pres- sure 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(35) 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). 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 (350 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.

The historical database (Published by IFREMER/DITI/IDT on behalf of the MEDATLAS consortium under contract MAS2-CT93-0074, 1997) is analysed on a seasonal basis for trends in the surface and intermediate water masses of the Mediterranean Sea. Significant trends are found in both the East and West Mediterranean but often to differing degrees. The upper waters of the entire Eastern Mediterranean Basin have been undergoing a sustained period of cooling throughout all seasons since about 1950. Salinities have also been found to be increasing over the same period with the strongest trends often being found at the shallowest horizontal levels examined. The Western Mediterranean Basin exhibits the same salinification throughout the upper waters as seen in the Eastern Mediterranean but the temperature trends are more varied and a basin wide cooling is not evident. The origin of these trends is most likely related to changes in the large-scale meteorological forcing of the Mediterranean region. The magnitude of changes to Levantine Intermediate Water (LIW) are in fact smaller than previously suggested thus indicating that the transfer of properties from the East to West Mediterranean via the LIW is not the major contributor to changes in the deep water characteristics of the Western Mediterranean.

An acoustic doppler current profiler (ADCP) is used to measure the currents and estimate the transports over the Camarinal Sill at the Strait of Gibraltar. The deepest measurements of the ADCP compare well with an underlying conventional current meter. The exchange interface between the Atlantic and the Mediterranean water is defined as the depth of the maximum vertical shear. The mean depth of the shear interface is 147 m. The time series of the depth of the interface and the currents are used to estimate the transports across the Strait. The resulting values are 0.78 Sv for the Atlantic inflow and −0.67 Sv for the Mediterranean outflow. The time series of the shear interface include fortnightly oscillations of 19 m. The time series of the transports are compared with the pressure and sea level difference records across the Strait. Linear multiple regression is used to estimate the (statistical) contribution of each parameter on the variation of transports. The cross strait sea level difference is well correlated with the Atlantic inflow and accounts for 57% of the variability of the transport records which improves to 78% when the fortnightly and monthly cycles are included in the linear regression. The Mediterranean outflow is best correlated with the along strait sea level difference which accounts for only 10% of the variability of the transport record. Again the addition of the Msf and the MM cycles improves the percentage of the variance accounted for to 37%. The local, along strait wind component is significantly correlated with, both the Atlantic inflow and the across strait sea level difference.