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Extreme sea levels along the densely monitored coasts of the North Atlantic Ocean and the Gulf of Mexico have been investigated using high‐frequency tide gauge measurements in the GESLA‐2 data set (www.gesla.org). Our results, based on nontidal residuals and skew surges in records since 1960, confirm that mean sea level (MSL) is a major, but not a unique, driver of extremes. Regionally coherent linear trends and correlations with large‐scale climate patterns are found in extreme events, even after the removal of MSL. A similar conclusion, that MSL is a major but not the only driver of extremes, comes from a small number of long records starting in the mid‐19th century. The records show slight increases in the intensity of extreme episodes at centennial time scales, together with multidecadal variability unrelated to MSL. Objective statistical criteria have been used to investigate whether extreme sea level distributions are stationary or not, resulting in nonstationarity being favored in many records, with or without accounting for changes in MSL. Extremes have been found to favor a non‐Gumbel behavior at many locations, with implications for the accuracy of return levels for coastal engineering. Extreme sea level changes since 1960 are regionally coherentSkew surges and nontidal sea level residuals are consistent in terms of long‐term trends and variabilityMean sea level is a major but not the only driver of extreme sea levels

A review is conducted on the status of sea-level monitoring in the British Overseas Territories (BOTs), showing where measurements have been made in the last two decades by various groups and thereby indicating where investments in future recording are needed. The sea level has risen in every territory since the early 1990s, and is predicted to increase by approximately 0.25–1.0 m by the end of the twenty-first century, depending on the emissions scenario. As a result, it is maintained that sea-level monitoring is needed in all BOTs, both for local coastal applications and as British contributions to the worldwide sea-level monitoring programme.

Using a suite of ocean model simulations and a set of dedicated twin experiments, we show that the exchange flow between the Mediterranean and the North Atlantic leads to a drop in time mean European coastal sea level along the Atlantic coast north of Gibraltar. The drop is about 7 cm along the Portuguese coast and remains apparent (though reduced) as far north as the Norwegian coast. We also show that Mediterranean time and spatial mean sea level is about 9 cm lower than it would be without the exchange flow (but assuming a small supply from the Atlantic to balance evaporation). Each of these relationships makes possible an estimate of the magnitude of the exchange flow based on sea level measurements, and estimates of 0.8 and 0.91 sverdrups are made consistent with previous determinations based mainly on current measurements in the Strait of Gibraltar. Mediterranean‐Atlantic exchange flow lowers European coastal sea levelSea level can be used to measure Mediterranean‐Atlantic exchangesProcesses in the Strait of Gibraltar strongly influence European mean sea level

The variability in mean sea level (MSL) during 1950–2009 along the northeast American Atlantic coast north of Cape Hatteras has been studied, using data from tide gauges and satellite altimetry and information from the Liverpool/Hadley Centre (LHC) ocean model, thereby providing new insights into the spatial and temporal scales of the variability. Although a relationship between sea level and the overturning circulation can be identified (an increase of approximately 1.5 cm in MSL for a decrease of 1 Sv in overturning transport), it is the effect of the nearshore wind forcing on the shelf that is found to dominate the interannual sea‐level variability. In particular, winds are found to be capable of producing low‐frequency changes in MSL (“accelerations”) in a narrow coastal band, comparable to those observed by the tide gauges. Evidence is presented supporting the idea of a “'common mode” of spatially coherent low‐frequency MSL variability, both to the north and south of Cape Hatteras and throughout the northwest Atlantic, which is associated with large spatial‐scale density changes from year to year. MSL variability along the N American coast is highly coherentThis MSL variability is forced to a great extent by the windThe MOC plays only a small part in this variability

The authors present the development and implementation of a ‘tsunami enabled’ tidegauge which allows real time data to be returned from almost anywhere on Earth. At itscentre is a low power, embedded Linux platform, which performs the data logging andcommunications. This is attached to a radar and pressure sensors that are queried overa serial interface. Telemetry is through the Inmarsat Broadband Global Area Network(BGAN) system which allows a bi-directional broadband connection over Ethernet,permitting remote reconfiguration when required, and faster, more frequent tide gaugedata. Data transmission is over an internet connection with files containing one minutevalues from three sensors returned every five minutes

This paper gives an overview of several important issues concerned with the measurement and understanding of long-term sea level change, which is one of the most important topics in sea level science. The issues discussed span science, technology and our ability to fund and operate the national and global observation networks required for a proper understanding of long-term change and its impacts. Many of these topics were explored at a ‘Celebration of UK sea level science’ at the Royal Society on 16–17 February 2004, and are discussed further in a number of papers in this volume.

Global sea level rise will present a major scientific, environmental and socio-economic challenge during the 21st century. This paper reviews the main oceanographic and geophysical processes which contribute to sea level change, with particular emphasis on the ability of space gravity missions to contribute to an enhancement of our understanding of the various processes, and ultimately to a better understanding of sea level change itself. Of special importance is the need to understand better the ocean circulation, and the contribution of ocean thermal expansion to sea level change.

The pathophysiology of seroma formation has yet to be determined. Therefore, the present study was undertaken to calculate the incidence of postoperative seromas after definitive breast cancer operations utilizing electrocautery dissection. Additionally, we attempted to identify risk factors associated with seroma development and to examine seroma formation in relation to operative procedure. A retrospective review of 252 breast cancer operations was undertaken. Patients were subdivided by operative procedure: modified radical mastectomy (MRM; n = 148), breast preservation with axillary node dissection (n = 64), or MRM with immediate reconstruction (n = 40). Electrocautery was used in development of skin flaps. Seromas developed in 39 of the 252 operations for an incidence of 15.5 per cent. Seroma formation was significantly lower in those patients receiving MRM with immediate reconstruction than in those receiving MRM (2.5% vs19.6%; P= 0.009) and tended to be lower than for patients receiving breast preservation with axillary node dissection (14.06%; P= 0.052). Neoadjuvant chemotherapy was performed in 18 patients, of whom 6 developed seromas (P= 0.030). The incidence of postoperative seromas was low despite the use of electrocautery. An association of postoperative seromas with neoadjuvant chemotherapy was noted. Additionally, it appears that immediate reconstruction may reduce the incidence of postoperative seromas, presumably by filling the dead space in the chest wall.

We document an exceptional large‐spatial scale case of changes in tidal range in the North Sea, featuring pronounced trends between −2.3 mm/yr at tide gauges in the United Kingdom and up to 7 mm/yr in the German Bight between 1958 and 2014. These changes are spatially heterogeneous and driven by a superposition of local and large‐scale processes within the basin. We use principal component analysis to separate large‐scale signals appearing coherently over multiple stations from rather localized changes. We identify two leading principal components (PCs) that explain about 69% of tidal range changes in the entire North Sea including the divergent trend pattern along United Kingdom and German coastlines that reflects movement of the region’s semidiurnal amphidromic areas. By applying numerical and statistical analyses, we can assign a baroclinic (PC1) and a barotropic large‐scale signal (PC2), explaining a large part of the overall variance. A comparison between PC2 and tide gauge records along the European Atlantic coast, Iceland, and Canada shows significant correlations on time scales of less than 2 years, which points to an external and basin‐wide forcing mechanism. By contrast, PC1 dominates in the southern North Sea and originates, at least in part, from stratification changes in nearby shallow waters. In particular, from an analysis of observed density profiles, we suggest that an increased strength and duration of the summer pycnocline has stabilized the water column against turbulent dissipation and allowed for higher tidal elevations at the coast. Tide gauges in the German Bight show large increases in the tidal range (e.g., difference between tidal high and tidal low waters) since the mid‐1950s, but the causes remain largely unknown. Here we show that the trends in the tidal range have opposite signs in the southwest and the southeast of the North Sea, indicating that different causes may be present. Using various analytical methods and numerical modeling, we show that the changes in the southwest are primarily externally driven by appearing coherently at many sites in the Atlantic Ocean. In contrast, tidal range variability in the German Bight seems to be associated with changes in the vertical density structure of the North Sea. 70 North Sea tide gauges evince contrasting trends in tidal range between the United Kingdom (−1.0 mm/yr) and the German Bight (3.3 mm/yr) since 1958We use principal component analysis (PCA) to separate local (e.g., building measures) from large‐scale effects of oceanographic originThe first PC explains 77% of variance in the German Bight and is linked to stability changes in shallow, seasonally stratified waters 70 North Sea tide gauges evince contrasting trends in tidal range between the United Kingdom (−1.0 mm/yr) and the German Bight (3.3 mm/yr) since 1958 We use principal component analysis (PCA) to separate local (e.g., building measures) from large‐scale effects of oceanographic origin The first PC explains 77% of variance in the German Bight and is linked to stability changes in shallow, seasonally stratified waters

Scientists and engineers have observed for some time that tidal amplitudes at many locations are shifting considerably due to nonastronomical factors. Here we review comprehensively these important changes in tidal properties, many of which remain poorly understood. Over long geological time scales, tectonic processes drive variations in basin size, depth, and shape and hence the resonant properties of ocean basins. On shorter geological time scales, changes in oceanic tidal properties are dominated by variations in water depth. A growing number of studies have identified widespread, sometimes regionally coherent, positive, and negative trends in tidal constituents and levels during the 19th, 20th, and early 21st centuries. Determining the causes is challenging because a tide measured at a coastal gauge integrates the effects of local, regional, and oceanic changes. Here, we highlight six main factors that can cause changes in measured tidal statistics on local scales and a further eight possible regional/global driving mechanisms. Since only a few studies have combined observations and models, or modeled at a temporal/spatial resolution capable of resolving both ultralocal and large‐scale global changes, the individual contributions from local and regional mechanisms remain uncertain. Nonetheless, modeling studies project that sea level rise and climate change will continue to alter tides over the next several centuries, with regionally coherent modes of change caused by alterations to coastal morphology and ice sheet extent. Hence, a better understanding of the causes and consequences of tidal variations is needed to help assess the implications for coastal defense, risk assessment, and ecological change. Tides are one of the most persistent and dominant forces that shape our planet. The regular and predictable daily, fortnightly, monthly, annual, interannual, and longer‐term changes in tides, driven by astronomical forces, are well understood. However, scientists and engineers have observed for some time that tides at many locations are shifting considerably due to nonastronomical factors. Here, we carry out a review of these important changes in tides, many of which remain poorly understood. We highlight that over long geological time scales, changes in tides are driven by tectonic processes, which alter the size, depth, and shape of the ocean. Over shorter geological time scales, changes in tides are mainly driven by changes in water depth. In recent decades, a growing number of studies have identified widespread, and sometimes regionally coherent, changes in tides during the last 150 years. However, determining exactly what has caused these more recent changes in tides has proven difficult. We discuss the local and regional/global mechanisms that might be responsible for the observed changes. Modeling studies predict that sea level rise and climate change will continue to alter tides over the next several centuries. Therefore, a better understanding of what is causing changes in tides is needed. Tidal properties have changed, and continue to evolve, due to nonastronomical factorsAttributing causation remains challengingRegionally coherent increases/decreases in tidal properties are likely to occur over the next centuries

Measurements have been made of the astronomical tide in Loch Ness, Scotland, which is not directly connected to marine tides. Our measurements of the loch tide are, so far as we know, the first in a European lake where the tide originates primarily from ocean tide loading. Loch Ness is a readily accessible lake and is in a region for which the neighboring ocean tides are large and described well by modern global ocean tide models. The principal tidal constituent, M2,was observed to have an amplitude of approximately 1.5 mm, and to be in antiphase, at each end of the loch. These values are in close agreement with the theoretical combined effects of the direct gravitational tide (body tide) and the tilt effects due to ocean tide loading, computed using Green's functions based on conventional elastic‐Earth models. By analyzing over long periods for coherent tidal signals, we are able to significantly improve the signal‐to‐noise ratio in the tilt values compared with values obtained by direct level differencing. Our tilt accuracy of better than 10−8, measured over 35 km, demonstrates Loch Ness as one the world's longest and most accurate tiltmeters. Despite this unprecedented accuracy, Earth tidal models are still at least as accurate as our ability to measure them. First tide measurements in a European lake due to ocean tide loadingResolution of reported interpretations of reasons for certain lake tidesDemonstration of the accuracy of lake tide measurements compared to GPS

A quasi‐global sea level data set from tide gauges has been used to investigate extreme sea level events and their spatial and temporal variabilities. Modern methods based on a nonstationary extreme value analysis have been applied to the maxima of the total elevations and surges for the period of 1970 and onward. A subset of the data was used to study changes over the 20th century. The analyses demonstrate the magnitude and timing of the seasonal cycle of extreme sea level occurrence, the magnitude of long‐term trends in extreme sea levels, the evidence for perigean and nodal astronomical tidal components in the extremes, and the relationship of the interannual variability in high water levels to other ocean and atmosphere variations as represented by climate indices. The subtraction from the extreme sea levels of the corresponding annual median sea level results in a reduction in the magnitude of trends at most stations, leading to the conclusion that much of the change in the extremes is due to change in the mean values.