Sea Level Time Series Research Articles

Recent and future manifestations of a contingent global mean sea level acceleration

Abstract We analyzed globally averaged satellite altimetry mean sea level time series during 1993 – 2018 and their future manifestations for the following 25 years using a kinematic model, which consists of a trend, a contingent uniform acceleration, and a random error model. The analysis of variance results shows that the model explains 71.7% of the total variation in global mean sea level for which 70.6% is by the secular trend, and 1.07% is due to a contingent uniform acceleration. The remaining 28.3% unexplained variation is due to the random errors, which are dominated by a first order autoregressive process driven mostly by oceanic and atmospheric variations over time. These numbers indicate more bumps and jumps for the future manifestations of the global mean sea level anomalies as illustrated using a one-step ahead predictor in this study. Our findings suggest preponderant random errors are poised to further confound and negatively impact the certitude of published estimates of the uniform global sea level acceleration as well as its prediction under an increasingly warmer Earth.

VALIDACIÓN E IMPLEMENTACIÓN DE UNA HERRAMIENTA OPERACIONAL PARA EL PRONÓSTICO DE MAREAS EN EL PACÍFICO COLOMBIANO (CASO DE ESTUDIO ISLA GORGONA)

Las mareas son los procesos más regulares que se presentan en los océanos, producto del movimiento periódico de ascenso y descenso del nivel del mar. Esta clase de proceso hidrodinámico a escala local en zonas costeras e insulares es de gran importancia, debido a que las islas pequeñas juegan un papel muy importante para la pesca, el turismo y actividades socioeconómicas en general. En La isla Gorgona situada en el Pacífico Colombiano, es de gran importancia comprender la dinámica mareal, ya que sus alteraciones a nivel regional y local controlan en gran medida los atributos particulares de la biota de Gorgona, la cual tiene un impacto en los procesos ecológicos que moldean la diversidad marina del parque, afectando las actividades socioeconómicas de la isla. Es por esto, que el presente trabajo tiene como objetivo determinar el régimen mareal en la Isla Gorgona (Cauca), identificando las principales componentes armónicas que ejercen mayor influencia en la zona; y el régimen medio del nivel del mar, a partir de modelación numérica y datos medidos in-situ.

Assessment of Tide Gauge Biases and Precision by the Combination of Multiple Collocated Time Series

AbstractThis study proposes a method for the cross calibration of tide gauges. Based on the combination of at least three collocated sea level time series, it takes advantage of the least squares variance component estimation (LS-VCE) method to assess both sea level biases and uncertainties in real conditions. The method was applied to a multi-instrument experiment carried out on Aix Island, France, in 2016. Six tide gauges were deployed to carry out simultaneous sea level recordings for 11 h. The best results were obtained with an electrical contact probe, which reaches a 3-mm uncertainty. The method allows us to assess both the biases and the precision—that is, the full accuracy—for each instrument. The results obtained with the proposed combination method have been compared to that of a buddy-checking method. It showed that the combination of all the time series also provides more precise bias estimates.

Temporal Modeling of Anomalous Coastal Sea Level Values Using Synoptic Climatological Patterns

AbstractShort‐term changes in sea level can have substantial impacts on coastlines, and increases in coastal flooding have been observed as the mean sea level continues to climb. While extreme events such as hurricanes have been well studied in terms of their impacts on anomalous sea level values, anomalous sea levels due to less extreme atmospheric events have been less well studied, despite the increases in nuisance flood events that have occurred. In this study, we assess the relationship between short‐term atmospheric circulation patterns and anomalous coastal sea level values for all oceanic tidal gauges in the conterminous United States for the period 1979–2016. Atmospheric patterns are depicted using self‐organizing maps for four variables: sea level pressure, 10‐m wind, 850‐mb temperature, and 700‐mb geopotential height. We then reconstruct the time series of anomalous sea level through nonlinear autoregressive models with exogenous input (NARX models), an artificial neural network‐based time series model. Results show that these four atmospheric variables can successfully model sea level, with a correlation between model and observation using a closed‐loop (open‐loop) architecture of 0.83 (0.64), with a median absolute error of 3.34 (4.90) cm. The model generally performs better in winter than summer, and along the Pacific Coast than the Atlantic and Gulf Coasts. By using the NARX methodology, we intend to next assess its utility as a forecasting tool.

ДОЛГОВРЕМЕННАЯ ИЗМЕНЧИВОСТЬ ТЕЧЕНИЙ В ЗОНЕ СУБАРКТИЧЕСКОГО ФРОНТА АТЛАНТИЧЕСКОГО ОКЕАНА

Based on time series of near-bottom current velocities and temperatures obtained in the period June, 2016 to July, 2017, at three points in the Atlantic Subarctic Front, along with the use of multi-year (since 1993 up to now) satellite ocean surface sounding data, multi-scale fluctuations of ocean surface and near-bottom flows over the western and eastern flanks of the Reykjanes ridge, as well as near Hatton Rise, on the Rokoll plateau, are studied. Hydrological profiles were carried out from the ocean surface to the bottom with readings every 10 m, when setting and retrieving the buoy stations. Using data from the Bank of hydrological stations (WOD13), SST satellite arrays (Pathfinder), long-term sea level and geostrophic velocities time series (AVISO), and bottom topography (model ETOPO-1), features of longterm cyclical fluctuations of SST, sea level, geostrophic currents on the ocean surface were defined in the sub-polar North Atlantic. It is shown that, in accordance with the large-scale thermohaline structure of the Subarctic front, two branches of the North Atlantic Current are detected on the ocean surface.One is directed from the Hatton towards the Icelandic-Faroese Rise, and the other – alomg the western flank of the Reykjanes Ridge toward Iceland. For the first branch, which is the main continuation of the North Atlantic Current, the average (for 25 years) water drift at a speed of 9.1±0.1 cm/s is determined to the northeast. The second branch, which forms the eastern part of the Subarctic cyclonic gyre, has the average water drift at a speed of 4.0±0.1 cm/s is directed north-northeast, along the western flank of the Reykjanes Ridge. In the intermediate waters of the frontal zone, an average water flow is observed at a speed of 2.7±0.1 cm/s to the north-northeast, along the eastern slope of the Reykjanes ridge.Due to the multy-scale components of the total variability, the average kinetic energy densities(KED) of total currents (109, 45, 97, (±3) erg/cm3, at station points from east to west) are much greater than the mean drift KED. The near-bottom flows on the Reykjanes ridge flanks are opposite to the direction of the North Atlantic Current. Outside the Subarctic gyre, the direction of average transport is maintained from the ocean surface to the bottom. The average (per year) KED of near-bottom currents are 31, 143, 27 (±3 erg/cm3), for three stations from east to west, respectively. In the intermediate waters of the frontal zone, above the eastern slope of the Reykjanes Ridge, there is a powerful reverse (relative to the North Atlantic Current) near-bottom water flow to the south-west, with a high average speed of ~ 15 cm/s. The KED of the currents during the year varies widely from zero to ~ 600 erg/cm3. The overall variability is due to cyclical variations and intermittency (“flashes”) of currents. Perennial cycles, seasonal variations, synoptic fluctuations with periods in the range of 30–300 days, as well as inertial oscillations and semi-diurnal tidal waves are distinguished. The intermittency of oscillations is partly due to changes in low-frequency flows, which can lead to a dopler frequency shift in the cyclic components of the spectrum. The amplitude of temperature fluctuations in the bottom layer for the year was (0.07–0.10) ± 0.01°C by the standard deviation. The seasonal changes of the bottom temperature are not detected. However, a linear trend with a warming of ~ (0.10–0.15) ± 0.01°С per year is noticeable.

Sea Level Variation around Australia and Its Relation to Climate Indices

This study aims at investigating the intradecadal and decadal signals of the sea level using 25 years of altimetry data around Australia. We have used the multivariable spectral analysis to extract six periodic signals at the 95% confidence level from altimetry-derived sea-level time series in the study area. They are signals with periods of 1, 1.5, 3, 4.3, 5.7 and 11.17 years, which can also be detected in the estimated power spectra from climate indices of the Interdecadal Pacific Oscillation, Multivariate ENSO Index, and Pacific Decadal Oscillation. A parametric model including the detected periodic signals is used to estimate sea-level trends. The determined trends in the area are in a good agreement with recent studies that consider effects of climate indices through a multivariate regression model. The advantage of our model is to present more descriptive explanation of the sea level signals around Australia in terms of periodicity and spatial variability.

Evaluation and combination of quad-constellation multi-GNSS multipath reflectometry applied to sea level retrieval

The satellites of the Global Navigation Satellite System (GNSS) continuously broadcast L-band signals at about a 20-cm wavelength. Some signal-to-noise ratio (SNR) data received by off-shelf geodetic antennas contain the multipath information of the sea, and they have been demonstrated for use in retrieving sea levels; however, compared with conventional tide gauges, this GNSS multipath reflectometry (GNSS-MR) technique is limited in terms of both precision and sampling rate. The simplest measure to increase the sampling rate of retrievals is to use SNR data from more satellite tracks at more satellite constellations. This study estimated the sea level of station BRST belonging to the Multi-GNSS Experiment (MGEX) using SNR data of four constellations (GPS, GLONASS, Galileo, and BeiDou) of the GNSS. It was found that the S5X/S2X, S2P/S2C, S5X, and S7I SNR types had optimal precisions for the GPS, GLONASS, Galileo, and BeiDou, respectively. In addition, we developed a multi-GNSS combination algorithm to formulate a 10-min sea level time series based on a state transition equation set and a robust regression solution strategy. The combined sea level retrieval time series had an approximately 40%–75% accuracy improvement compared to individual signal sea level retrievals; with a constant sampling interval in the 10 min window, the combined method presented here is beneficial for both the precision and sampling rate. This approach is novel and advanced in two key ways, in that we use data from four constellations simultaneously and through the regression strategy, which is applied to synthesize all data into a time series at regular 10-min intervals. This technique could be applied to other sites and is therefore beneficial for the GNSS-MR community.

Chaotic Analysis for Malaysian West Coast Sea Level: a Case Study of Kukup, Johor

Sea level prediction is an important task for navigation, coastal engineering, geodetic application and recreational activities. Predicting the behavior of future sea level is necessary for protection of coastal as well as for monitoring and forecasting of changes in fishery and marine ecosystems. This study is focused on the analysis and prediction of hourly sea level time series data at the benchmark station located in Kukup, Johor by using chaotic approach. The aim of this study was to detect the presence of chaotic behavior by the phase space reconstruction and Cao methods, and also a local linear approximation method is employed for prediction purposes. The results revealed that the value of correlation coefficient between the observed and predicted time series is 0.879 which is near to one. This indicates that the local linear approximation method can be used to predict the sea level time series in Malaysia. Indeed, the result of this study is expected to help stakeholder such as Department of Survey and Mapping Malaysia (JUPEM) in having a better sea level management.

Altimetry-based sea level trends along the coasts of Western Africa

We present results of contemporary coastal sea level changes along the coasts of Western Africa, obtained from a dedicated reprocessing of satellite altimetry data done in the context of the ESA ‘Climate Change Initiative’ sea level project. High sampling rate (20 Hz) sea level data from the Jason-1 and Jason-2 missions over a 14-year-long time span (July 2002 to June 2016) are considered. The data were first retracked using the ALES adaptative leading edge subwaveform retracker. The X-TRACK processing system developed to optimize the completeness and accuracy of the corrected sea level time series in coastal ocean areas was then applied. From the 14-year long sea level time series finally obtained, we estimate sea level trends along the Jason-1 & 2 tracks covering the study region. We analyze regional variations in sea level trends, with a focus on the changes observed between the open ocean to the coastal zone. Compared to the conventional 1 Hz sea level products dedicated to open ocean applications, the retracked 20 Hz measurements used in this study allow us to retrieve valid sea level information much closer to the coast (less than 3–4 km to the coast, depending on the satellite track location). The main objective of this study is twofold: (1) provide sea level products in the coastal areas from reprocessed altimetry data and (2) check whether sea level changes at the coast differ from that reported in the open ocean with conventional altimetry products. In the selected region, results show that over the study period, sea level trends observed near the coast of Western Africa are significantly different than offshore trends. In order to assess the robustness of the results, detailed analyses are performed at several locations to discriminate between possible drifts in the geophysical corrections and physical processes potentially able to explain the sea level changes observed close to the coast.

Assessment of Sea Level Rise at West Coast of Portugal Mainland and Its Projection for the 21st Century

Based on the updated relative sea level rise rates, 21st-century projections are made for the west coast of Portugal Mainland. The mean sea level from Cascais tide gauge and North Atlantic satellite altimetry data have been analyzed. Through bootstrapping linear regression and polynomial adjustments, mean sea level time series were used to calculate different empirical projections for sea level rise, by estimating the initial velocity and its corresponding acceleration. The results are consistent with an accelerated sea level rise, showing evidence of a faster rise than previous century estimates. Based on different numerical methods of second order polynomial fitting, it is possible to build a set of projection models of relative sea level rise. Applying the same methods to regional sea level anomaly from satellite altimetry, additional projections are also built with good consistency. Both data sets, tide gauge and satellite altimetry data, enabled the development of an ensemble of projection models. The relative sea level rise projections are crucial for national coastal planning and management since extreme sea level scenarios can potentially cause erosion and flooding. Based on absolute vertical velocities obtained by integrating global sea level models, neo-tectonic studies, and permanent Global Positioning System (GPS) station time series, it is possible to transform relative into absolute sea level rise scenarios, and vice-versa, allowing the generation of absolute sea level rise projection curves and its comparison with already established global projections. The sea level rise observed at the Cascais tide gauge has always shown a significant correlation with global sea level rise observations, evidencing relatively low rates of vertical land velocity and residual synoptic regional dynamic effects. An ensemble of sea level projection models for the 21st century is proposed with its corresponding probability density function, both for relative and absolute sea level rise for the west coast of Portugal Mainland. A mean sea level rise of 1.14 m was obtained for the epoch of 2100, with a likely range of 95% of probability between 0.39 m and 1.89 m.

Application of GNSS interferometric reflectometry for detecting storm surges

A single geodetic GNSS station placed at the coast has the capability of a traditional tide gauge for sea-level measurements, with the additional advantage of simultaneously obtaining vertical land motions. The sea-level measurements are obtained using GNSS signals that have reflected off the water, using analysis of the signal-to-noise ratio (SNR) data. For the first time, we apply this technique to detect extreme weather-induced sea-level fluctuations, i.e., storm surges. We first derive 1-year sea-level measurements under normal weather conditions, for a GNSS station located in Hong Kong, and compare them with traditional tide-gauge data to validate its performance. Our results show that the RMS difference between the individual GNSS sea-level measurements and tide-gauge records is about 12.6 cm. Second, we focus on the two recent extreme events, Typhoon Hato of 2017 and Typhoon Mangkhut of 2018, that are ranked the third and second most powerful typhoons hitting Hong Kong since 1954 in terms of maximum sea level. We use GNSS SNR data from two coastal stations to produce sea-level measurements during the two typhoon events. Referenced to predicted astronomical tides, the storm surges caused by the two events are evident in the sea-level time series generated from the SNR data, and the results also agree with tide-gauge records. Our results demonstrate that this technique has the potential to provide a new approach to monitor storm surges that complement existing tide-gauge networks.

Rescue of the 1873–1922 high and low waters of the Porto Corsini/Marina di Ravenna (northern Adriatic, Italy) tide gauge

The historical data corresponding to the period 1873–1922 of the Porto Corsini (northern Adriatic, Italy) tide gauge have been retrieved from the archive of the Italian Istituto Geografico Militare, in Florence ( http://www.igmi.org ). The data consist of daily high and low waters, which were recorded in six handwritten volumes. The 1873–1896 observations were, until now, totally unknown since they were never published, while, for the remaining years, only monthly mean values were available. We digitized and quality controlled the rescued data. Searching in different archives, we also found detailed information on the three sites occupied by the tide gauge within the Porto Corsini/Marina di Ravenna harbor. In addition, the rescue of the leveling data and of the datum definition made it possible to realize a homogeneous time series of monthly mean sea-level values, which now spans 144 years. Sea-level time series exceeding a century are rare, and they are most important because they provide key information for studying climate change-related processes. The Porto Corsini/Marina di Ravenna area is affected by natural subsidence, much enhanced by anthropogenic activities during the period 1940–1980, in particular. Using leveling, GPS and InSAR data we have modeled the subsidence behavior over the 1873–2016 period. After removing the subsidence from the series of monthly mean values, we estimated a long-period linear sea-level rise of + 1.25 ± 0.16 mm/year.

Optimal mathematical and statistical models to estimate vertical crustal movements using satellite altimetry and tide gauge data

AbstractKnowledge of vertical crustal movement is fundamental to quantify absolute sea level changes at tide gauge locations as well as for satellite altimetry calibration validations. While GPS measurements at collocated tide gauge stations fulfill this need, currently only few hundred tide gauge stations are equipped with GPS, and their measurements do not span a long period of time. In the past, several studies addressed this problem by calculating relative and geocentric trends from the tide gauge and satellite altimetry measurements respectively, and then difference the two trends to calculate the rate of changes at the tide gauge stations. However, this approach is suboptimal. This study offers an optimal statistical protocol based on themethod of condition equations with unknown parameters. An example solution demonstrates the proposed mathematical and statistical models’ optimality in estimating vertical crustal movement and its standard error by comparing them with the results of current methods. The proposed model accounts for the effect of autocorrelations in observed tide gauge and satellite altimetry sea level time series, adjusts observed corrections such as inverted barometer effects, and constraints tide gauge and satellite altimeter measurement to close. The new model can accommodate estimating other systematic effects such as pole tides that are not eliminated by differencing.

Determinación de la cota máxima de inundación en la frontera colombo-ecuatoriana aplicando modelación numérica.

En el presente estudio, se determinó la Línea de Más Alta Marea para el área comprendida entre las poblaciones de Candelillas de la Mar y Salahondita, ubicada sobre el Litoral Pacífico Colombiano (LPC), Pacífico Sudeste. Se efectuó un análisis armónico a las series de tiempo de nivel del mar medidas in situ, y a las que se generaron a partir de modelamiento numérico (considerando la escasa información disponible del nivel de mar en esta área). La marea meteorológica fue simulada empleando técnicas estadísticas de Montecarlo; considerando la naturaleza estocástica de esta variable. El comportamiento descrito por las series medidas in situ y modeladas, se analizó a partir del Test de normalidad (test de Kolmogorov-Smirnov y Shapiro-Wilk). Posteriormente, estas fueron correlacionadas por medio del método de correlación de Spearman, donde los cambios en la morfología de la costa y la ausencia de información batimétrica de algunas áreas, condicionó el comportamiento de los coeficientes obtenidos. Para el cálculo de los regímenes medio y extremal, se aplicaron las metodologías establecidas, tomando como base los coeficientes obtenidos en estudios anteriores (Otero, 2005). A partir de los resultados obtenidos, se determinaron las cotas máximas de inundación para cada uno de los puntos de estudio, que sirvieron como base para el trazado de la Línea de Más Alta Marea en el área de estudio.

Merged envisat and jason satellite altimeters using crossovers adjustment to determine sea level variability

It is considered that climate change has been increasing the global air temperature and rising sea level. Thus, the monitoring of sea level is necessary to mitigate the hazard risk. For estimating sea level change from various altimetric missions, attention must be taken to determine the bias of measurements between altimetric different missions. The aim of this study is to merge both of Jason series and Envisat satellite altimeters for estimating sea level variability around the Indonesian Seas. To create sea level time series, two adjustment methods are employed: tandem mission data and sea level anomaly differences at crossovers. The adjustment using tandem mission between Jason-1 and Jason-2 obtained a relative difference of 32.8 ± 5.4 mm. The adjustment method at crossovers is applied for combining Envisat and Jason series which is already intercalibrated. The mean crossovers differences between Envisat and reference missions are less than 2.5 cm. By using merged datasets from all missions, it is discovered that the trend in the Indonesian seas for a period of 10 years is 11.9 mm years−1. The map of sea level trends from all satellites data for that period is performed in 1° × 1° regular grids.

The evolution of edge waves propagated over a variable slope-shelf topography

A discussion is presented of the propagation of trapped waves over continental shelves having the idealized and realistic topography. The emphasis is made on the investigation of influence of the shelf shape and width on the lower modes edge wave parameters. The conclusions were based on the solution of the complete boundary-value problem using the difference approximation algorithms. A three-dimensional model was used to reproduce waves generated on the Turkish coast of Black Sea caused by the climatological wind. The model, simulated sea-level time-series, was subjected to Fast Fourier Transform to compute the power spectral density of water oscillations. It is found that the absolute maximum of the first mode wave takes place near the shore and over the edge of the shelf. Increasing the width of the continental slope leads to slower attenuation of the wave towards the open sea. The most resistant wave processes were computed on the Cape Inceburun.

Tidal and subtidal oscillations in a shallow water system in southern Brazil

ABSTRACT Sea level oscillations in time scales between hours and days have a great vertical amplitude regarding the low lying coastal gradient of the beaches in the Rio Grande do Sul coast. However, the mechanism of oscillations is poorly understood since the scarcity of observational data makes it impossible to determine the forces that control sea level oscillations. Therefore, hourly sea level and wind time series with a time period of 650 days were examined. It has been found that the mean tidal and subtidal amplitudes were very similar to each other and that a considerable portion of the energy from sea level oscillations was due to astronomical forces. A new perspective was introduced when high and low frequencies were compared, leading to the comprehension that astronomical tides should be considered in coastal studies in southern Brazil. The sea level time series analyzed in this study showed that the maximum amplitude of the high spring tide was 0.53m, and that the subtidal rise caused by the wind reached up to 0.66m. In general, when large tidal and subtidal amplitudes are added, it can generate extreme events of sea level rise on the coast, which constitute a direct threat to coastal communities and habitats.

A New Centennial Sea‐Level Record for Antalya, Eastern Mediterranean

AbstractQuantitative estimates of sea‐level rise in the Mediterranean Basin become increasingly accurate thanks to detailed satellite monitoring. However, such measuring campaigns cover several years to decades, while longer‐term sea‐level records are rare for the Mediterranean. We used a data archeological approach to reanalyze monthly mean sea‐level data of the Antalya‐I (1935–1977) tide gauge to fill this gap. We checked the accuracy and reliability of these data before merging them with the more recent records of the Antalya‐II (1985–2009) tide gauge, accounting for an eight‐year hiatus. We obtain a composite time series of monthly and annual mean sea levels spanning some 75 years, providing the longest record for the eastern Mediterranean Basin, and thus an essential tool for studying the region's recent sea‐level trends. We estimate a relative mean sea‐level rise of 2.2 ± 0.5 mm/year between 1935 and 2008, with an annual variability (expressed here as the standard deviation of the residuals, σresiduals = 41.4 mm) above that at the closest tide gauges (e.g., Thessaloniki, Greece, σresiduals = 29.0 mm). Relative sea‐level rise accelerated to 6.0 ± 1.5 mm/year at Antalya‐II; we attribute roughly half of this rate (~3.6 mm/year) to tectonic crustal motion and anthropogenic land subsidence. Our study highlights the value of data archeology for recovering and integrating historic tide gauge data for long‐term sea‐level and climate studies.

A continuous simulation approach for the estimation of extreme flood inundation in coastal river reaches affected by meso- and macrotides

Considering the joint probability of occurrence of high sea levels and river discharges, as well as the interactions between these sources of flooding, is of major importance to produce realistic inundation maps in river reaches affected by the sea level. In this paper, we propose a continuous simulation method for the estimation of extreme inundation in coastal river reaches. The methodology combines the generation of synthetic long-term daily time series of river discharge and sea level, the downscaling of daily values to a time resolution of a few minutes, the computation of inundation levels with an unsteady high-resolution two-dimensional model and the use of interpolation techniques to reconstruct long-term time series of water surface from a limited number of characteristic cases. The method is especially suitable for small catchments with times of concentration of a few hours, since it considers the intradiurnal variation of river discharge and sea level. The methodology was applied to the coastal town of Betanzos (NW of Spain), located at a river confluence strongly affected by the sea level. Depending on the return period and on the control point considered, the results obtained with the proposed methodology show differences up to 50 cm when compared with the standard methodology used in this region for the elaboration of flood hazard maps in accordance with the requirements of the European Directives. These results indicate the need for adaption of the standard methodology in order to produce more realistic results and a more efficient evaluation of flood hazard mitigation measures.

Non-seasonal sea level variations in the Korea Strait and regional atmospheric conditions

Kim, J.-K.; Choi, B.-J., and Lee S.-H., 2018. Non-seasonal sea level variations in the Korea Strait and regional atmospheric conditions. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 581–585. Coconut Creek (Florida), ISSN 0749-0208.To investigate dominant sea level variations in the Korea Strait (KS) and to find their responsible factors, Empirical Orthogonal Function (EOF) analysis was performed on the non-seasonal components of sea level, wind, and sea level pressure data from 1993 to 2014. The non-seasonal sea level variation accounts for 20% of the total sea level variations in the KS. The first EOF mode of the sea level explains 63.8% of the total variance and represents strait-wide simultaneous sea level oscillations. EOF analysis on the surface wind data over the KS and the East China Sea was performed and the first EOF of winds, explaining 49.5% of the total variance, represents the strength of the northeasterly wind. The amplitude time series of the first EOFs from wind and sea level data has correlation coefficients (r) of 0.48. The sea level and wind data have common spectral peaks at periods of 5.1 and 10.2 months. Variance and the first EOF of the steric height in the KS are relatively high around Jeju Island while they are small near the south coast of Korea. Correlation between the amplitude time series of sea level and steric height first modes is low (r = 0.20). The basin-wide simultaneous sea level variations with intra-seasonal and interannual periods in the KS are found to be modulated by variations in the regional surface winds and sea level pressure patterns over the East China Sea and the KS rather than by changes in local steric height.