Long-term Sea Level Variability Research Articles

Analysis of the Shoreline Changes using Geoinformatics in Ghoramara Island of Hugli Estuary, West Bengal in India

Conceptual FrameworkCoastal decrepitude is the loss of topographical resources along the coast as a result of silt, temperature fluctuations, tidal shifts, and wave breaking. Hydraulic activity, scraping, abrasion, and erosion are the major causes of erosion; other factors that affect it include the condition of the shore, rocks, joints, fissures, marine chemical reactions, and wave force. ObjectivesThe primary objectives of this study are to analyze the coastline changes between 1972 and 2022 utilizing remote sensing and GIS data and forecast the changes in the shoreline in 2032. MethodsThe study examined coastal areas from 1972 to 2022 using multi-temporal satellite data from Landsat TM and Landsat OLI/TIRS. Shoreline change and the calculations related to it were examined using the Digital Shoreline Analysis System using near-infrared bands and tasseled cap transformation, to determine the rate of change in the shoreline, the study also employed Shoreline Change Envelope and End Point Rate techniques. ResultsCoastal erosion caused substantial damage to the island between 1972 and 2022. The northern, southeastern, and western regions of the coast are seeing the highest levels of coastal erosion. The south coast experiences considerable erosion, whereas the west and southeast coasts experience the least. The EPR of Ghoramara Island has mean, minimum, and maximum changes of -10.59, -4.13, and -35.93, respectively. A notable inshore shift has occurred in the northern portion of Ghoramara, extending from 676 meters to 855 meters. The study also uses tidal gauge records and Revised Local Reference data from the Haldia Gauge Station to track long-term sea level variations. According to the study, Ghoramara Island's shoreline will change by 2032, with the greatest negative changes expected to occur around the island's western and southern borders. ConclusionThe study shows a significant decrease in Ghoramara's shoreline regions between 1972 and 2022, with a 3,000-population shifted from the place in 2016 due to Lohachara's submergence. Changes in the island's morphology and human activities have reduced cultivation. The study suggests increasing mangrove vegetation to combat coastal erosion and prevent further displacement of people to neighboring islands.

Long-term sea-level variability along the coast of Japan during the 20th century revealed by a 1/10$$^{\circ }$$ OGCM

Long-term sea-level variability along the coast of Japan during the 20th century revealed by a 1/10$$^{\circ }$$ OGCM

Seasonal and long-term sea-level variations and their forcing factors in the northern Bay of Bengal: A statistical analysis of temperature, salinity, wind stress curl, and regional climate index data

In the northern Bay of Bengal, mechanisms of seasonal sea-level variation have not previously been examined, and the understanding of longer-term inter-annual sea-level variation is also not concrete. These parameters are addressed in this study utilizing available tide gauge and satellite altimetry data. The contribution of steric sea level to seasonal and longer-term inter-annual sea-level variations is quantified, and statistical analysis is performed to determine the correlations of various atmospheric and oceanic factors with sea level. This study suggests that the trend of sea-level rise in this bay (4 ± 1.33 mm/year) is higher than the global average (3.32 ± 0.46 mm/year) for the studied period 1993 to 2018. The rate of sea-level rise is higher along the coast than in the offshore area and the highest in the central part of the coast. Sea level shows a strong seasonal variation: sea level is the lowest in the winter but the highest in autumn. The contribution from the thermosteric sea level is higher to the observed sea level from winter to early summer, whereas contributions from the halosteric sea level and wind stress curl are higher during autumn. Long-term variations in sea level show strong positive correlations with thermosteric sea level, indicating that temperature is a major local controlling factor for sea-level change. In addition to local factors, long-term sea level also varies by remote forcing (equatorial zonal wind stress), which explains approximately 36 % of the sea-level variation in this bay. Sea level is low during the combined events of positive Indian Ocean dipole (IOD) and El Niño, whereas the sea level is high during the combined events of negative IOD and La Niña. This study provides an improved understanding of seasonal and longer-term inter-annual variations of sea level and the necessary groundworks for a dedicated model study to further quantify all the components of the sea-level budget in the study areas.

ИЗМЕНЧИВОСТЬ УРОВНЯ ОХОТСКОГО МОРЯ У ЕГО ПОБЕРЕЖИЙ В НАЧАЛЕ XXI ВЕКА И ЕЁ ОТОБРАЖЕНИЕ В ГЛОБАЛЬНЫХ РЕАНАЛИЗАХ

The paper aims to investigate basic features of modern long-term variations of the Okhotsk Sea level in its coastal areas and establish feasibility of certain retrospective analysis databases usage for determination of mean rates of the above processes. The reanalysis databases considered include Global Ocean Physics Reanalysis GLORYS12v.1 by the Copernicus Marine Environment Monitoring Service and ICDC-reanalysis supported by the Integrated Climate Data Center, which provide coverage of the sea in question. The raised problem is of significant interest for physiographers, oceanographers and involved in coastal shipping and marine safety in the Sea of Okhotsk. Long-term sea level variations are most accurately monitored by tide gauge stations, which, however, are scarce along the coast of the sea in question. Less accurate and not uniformly available through easier to use and collect data is the satellite monitoring by radar altimeters. Global retrospective analyses based on mathematical modelling are considered to be an effective instrument to assess sea levels at any given time at any point.

Satellite Altimetry and Tide Gauge Observed Teleconnections between Long-Term Sea Level Variability in the U.S. East Coast and the North Atlantic Ocean

Rising sea levels amplify the threat and magnitude of storm surges in coastal areas. The U.S. east coast region north of Cape Hatteras has shown a significant sea level rise acceleration and is believed to be a “hot-spot” for accelerating tidal flooding. To better understand the forcing mechanism of long-term regional sea level change, in order to more efficiently implement local sea level rise adaptation and mitigation measures, this work investigated the teleconnections between low-frequency sea level variability in the coastal region north of Cape Hatteras and the subpolar/tropical North Atlantic Ocean by using tide gauge measurements, satellite altimetry data and a sea level reconstruction dataset. The correlation analysis demonstrates that the tide-gauge measured sea level variability in the area north of Cape Hatteras is highly and positively correlated with that observed by satellite altimetry in the subpolar and tropical North Atlantic between 1993 and 2002. Over the following decade (2003–2012), the phase of the teleconnection in the subpolar region was reversed and the spatio-temporal correlation in the tropical North Atlantic was enhanced. Furthermore, the positive correlation in the region north of Cape Hatteras’s near shore area is strengthened, while the negative correlation in the Gulf Stream front region is weakened. The North Atlantic Oscillation and Atlantic Multidecadal Oscillation, which affect variations of the Atlantic Meridional Overturning Circulation and Gulf Stream, were shown to have significant impacts on the decadal changes of the teleconnections. Coherent with satellite altimetry data, the reconstructed sea level dataset in the 20th century exhibits similar spatial correlation patterns with the Atlantic Meridional Overturning Circulation, North Atlantic Oscillation and Atlantic Multidecadal Oscillation indices.

The interplay of dynamic topography and eustasy on continental flooding in the late Paleozoic

Global sea level change can be inferred from sequence stratigraphic and continental flooding data. These methods reconstruct sea level from peri-cratonic and cratonic basins that are assumed to be tectonically stable and sometimes called reference districts, and from spatio-temporal correlations across basins. However, it has been understood that long-wavelength (typically hundreds of km) and low-amplitude (<2 km) vertical displacements of the Earth's surface due to mantle flow, namely dynamic topography, can occur in the absence of crustal deformation. Dynamic topography can drive marine inundation or regional emergence of continents and must be taken into consideration for eustasy estimates. Our analysis indicates that the long-term trend in global-scale maximum flooding over the late Paleozoic generally correlates with global sea level curves. The first-order flooding history of North America correlates with some estimates of eustasy. The Paleozoic inundation of South America does not follow long-term sea level variations. The flooding lows during the Early Carboniferous and high during the Late Carboniferous are at odds with estimates of eustasy and can be explained by dynamic uplift and subsidence, respectively. Our dynamic topography models indicate that the Yangtze Platform of South China experienced significant dynamic subsidence during the transition from Permian to Triassic largely due to proto-Pacific subduction and its northward motion to collide with North China. The reference districts – Western New York, Oklahoma and Kansas, and West Texas in North America – were to some degree affected by dynamic uplift and subsidence associated with long-lived Panthalassa subduction zones, closure of the Rheic Ocean and large-scale upwelling above the African deep-mantle structure during late Paleozoic times. This indicates that some published global sea level curves may include non-eustatic signals such as dynamic uplift or subsidence. The interpretation of stratigraphic data gathered from these reference districts should be treated with caution to estimate global sea level variations.

THE DYNAMICS OF STORM SURGE AND MEAN SEA LEVEL VARIABILITY IN THE NORTHEASTERN CASPIAN SEA

Storm surge is a major natural hazard to the construction and operation of infrastructure projects in shallow and gently sloping coastal areas such as the northeastern part of the Caspian Sea. Up-surge events cause significant coastal flooding, while down-surge events disrupt marine transportation by constraining safe navigable water depths. Coastal developments therefore have to achieve a judicious balance of these conflicting constraints. Further, the unpredictability of long-term and intra-annual Mean Sea Level (MSL) variability as well as periodic freeze-up and break-up due to ice formation in this part of the Caspian Sea complicate a robust and unequivocal basis for defining storm surge hazards.

Long-term Caspian Sea level variations based on the ERA-interim model and rivers discharge

ABSTRACTIn this research, precipitation-evaporation is studied based on the ERA-Interim model of ECMWF in order to estimate changes in the Caspian Sea (CS) level and the validity of the results is evaluated in a period between 1980 to the end of 2015. Recorded data about the rivers entering the CS were also studied for better prediction of changes in water level. According to satellite images and software analyses, in average, evaporation has increased with a rate of 0.89 km3/year, while precipitation and rivers discharge have decreased by the rates of 1.09 and 1.41 km3/year, respectively during the 36 years. The standard deviation of the sea level changes caused by Volga discharge (normally entering 249.13 km3/year into the sea alone) is closer to the recorded standard deviation obtained from the change of the CS level than the other two factors. Also, the lowest and the highest correlation coefficients relative to the recorded sea level changes were calculated considering the simultaneous effect of precipitation-evaporation and simultaneous effect of all parameters, respectively. As a conclusion, it can be said that the main reason for decreasing the CS level during recent years could be attributed to the rise of evaporation in comparison to precipitation and inlet rivers’ discharges.

A direct scaling analysis for the sea level rise

The estimation of long-term sea level variability is of primary importance for a climate change assessment. Despite the value of the subject, no scientific consensus has yet been reached on the existing acceleration in observed values. The existence of this acceleration is crucial for coastal protection planning purposes. The absence of the acceleration would enhance the debate on the general validity of current future projections. Methodologically, the evaluation of the acceleration is a controversial and still open discussion, reported in a number of review articles, which illustrate the state-of-art in the field of sea level research. In the present paper, the well-proven direct scaling analysis approach is proposed in order to describe the long-term sea level variability at 12 worldwide-selected tide gauge stations. For each of the stations, it has been shown that the long-term sea level variability exhibits a trimodal scaling behaviour, which can be modelled by a power law with three different pairs of shape and scale parameters. Compared to alternative methods in literature, which take into account multiple correlated factors, this simple method allows to reduce the uncertainties on the sea level rise parameters estimation.

Interannual and long-term sea level variability in the eastern Indian Ocean and South China Sea

Sea level anomalies (SLAs) derived from satellite observations (over a period of 22 years) and tide gauge data compiled from 66 stations from the eastern Indian Ocean and South China Sea (SCS) and western Pacific Ocean have been analyzed to study the interannual to long term variation of SLAs in the eastern Indian Ocean and SCS. Spatial patterns of sea level variability on the eastern boundary of the Indian Ocean exhibit non-coherent variability with SCS but show coherent variability with western Pacific Ocean. We find coherent variability in interannual SLAs in the Bay of Bengal, Andaman Sea, Malacca Strait and Java Strait. A large fraction of interannual SLA variations in the eastern SCS and interior SCS is linked to El Nino-Southern Oscillation (ENSO) and rest of the region is characterized by small scale interannual variations. The interannual SLAs in the SCS show seasonality with pronounced variation during winter and fall seasons. Interannual surface wind anomalies associated with Indian Ocean Dipole (IOD) and ENSO explain sea level interannual variability in the eastern Indian Ocean and SCS. The decadal sea level variability associated with Pacific Decadal Oscillation (PDO) and decadal ENSO are observed in the SCS.

Observing water-level variations from space-borne high-resolution Synthetic Aperture Radar (SAR) image correlation

The potential of correlating high-resolution Synthetic Aperture Radar images to estimate local water-level variations is analysed based on observing the motions of floating structures. By computing range and azimuth offsets on a COSMO-SkyMed multi-temporal data-set in an area of the French Atlantic Coast, displacement signatures were detected in several harbours of the region. They can be associated with specific floating structures, whose vertical motion is mostly driven by tides. Although the image resolution is not the best achievable for the COSMO-SkyMed sensor, comparison with ground-based tide information revealed that the obtained space-borne measurements are consistent with the tide gauges to a decimetric accuracy. Even if the requirements for traditional users of tidal data are not met by the current revisit time of the COSMO-SkyMed constellation, the method proposed here provides complementary measures, which are already well aligned to requirements of users concerned with long-term sea-level variation and river or lake water stocks.

A study of sea level variability and its long-term trend in the South China Sea

On the basis of the satellite maps of sea level anomaly (MSLA) data and in situ tidal gauge sea level data, correlation analysis and empirical mode decomposition (EMD) are employed to investigate the applicability of MSLA data, sea level correlation, long-term sea level variability (SLV) trend, sea level rise (SLR) rate and its geographic distribution in the South China Sea (SCS). The findings show that for Dongfang Station, Haikou Station, Shanwei Station and Zhapo Station, the minimum correlation coefficient between the closest MSLA grid point and tidal station is 0.61. This suggests that the satellite altimeter MSLA data are effective to observe the coastal SLV in the SCS. On the monthly scale, coastal SLV in the western and northern part of SCS are highly associated with coastal currents. On the seasonal scale, SLV of the coastal area in the western part of the SCS is still strongly influenced by the coastal current system in summer and winter. The Pacific change can affect the SCS mainly in winter rather than summer and the affected area mostly concentrated in the northeastern and eastern parts of the SCS. Overall, the average SLR in the SCS is 90.8 mm with a rising rate of (5.0±0.4) mm/a during 1993–2010. The SLR rate from the southern Luzon Strait through the Huangyan Seamount area to the Xisha Islands area is higher than that of other areas of the SCS.

Sea Level Acceleration in the China Seas

While global mean sea level rise (SLR) and acceleration (SLA) are indicators of climate change and are informative regarding the current state of the climate, assessments of regional and local SLR are essential for policy makers responding to, and preparing for, changes in sea level. In this work, three acceleration detection techniques are used to demonstrate the robust SLA in the China Seas. Interannual to multidecadal sea level variations (periods &gt;2 years), which are mainly related to natural internal climate variability and significantly affect estimation of sea level acceleration, are removed with empirical mode decomposition (EMD) analysis prior to the acceleration determination. Consistent SLAs of 0.085 ± 0.020 mm·yr−2 (1950–2013) and 0.074 ± 0.032 mm·yr−2 (1959–2013) in regional tide gauge records are shown to result from the three applied approaches in the Bohai Sea (BS) and East China Sea (ECS), respectively. The SLAs can be detected in records as short as 20 years if long-term sea level variability is adequately removed. The spatial distribution of SLA derived from a sea level reconstruction shows significant SLA in the BS, Yellow Sea (YS) and Yangtze River Estuary.

Can the Gulf Stream induce coherent short-term fluctuations in sea level along the US East Coast? A modeling study

Much attention has been given in recent years to observations and models that show that variations in the transport of the Atlantic Meridional Overturning Circulation (AMOC) and in the Gulf Stream (GS) can contribute to interannual, decadal, and multi-decadal variations in coastal sea level (CSL) along the US East Coast. However, less is known about the impact of short-term (time scales of days to weeks) fluctuations in the GS and their impact on CSL anomalies. Some observations suggest that these anomalies can cause unpredictable minor tidal flooding in low-lying areas when the GS suddenly weakens. Can these short-term CSL variations be attributed to changes in the transport of the GS? An idealized numerical model of the GS has been set up to test this proposition. The regional model uses a 1/12° grid with a simplified coastline to eliminate impacts from estuaries and small-scale coastal features and thus isolate the GS impact. The GS in the model is driven by inflows/outflows, representing the Florida Current (FC), the Slope Current (SC), and the Sargasso Sea (SS) flows. Forcing the model with an oscillatory FC transport with a period of 2, 5, and 10 days produced coherent CSL variations from Florida to the Gulf of Maine with similar periods. However, when imposing variations in the transports of the SC or the SS, they induce CSL variations only north of Cape Hatteras. The suggested mechanism is that variations in GS transport produce variations in sea level gradient across the entire GS length and this large-scale signal is then transmitted into the shelf by the generation of coastal-trapped waves (CTW). In this idealized model, the CSL variations induced by variations of ∼10 Sv in the transport of the GS are found to resemble CSL variations induced by ∼5 m s−1 zonal wind fluctuations, though the mechanisms of wind-driven and GS-driven sea level are quite different. Better understanding of the relation between variations in offshore currents and CSL will help to improve the prediction of both short-term water level anomalies that cause flooding, as well as spatial variations in long-term sea level variability and coastal sea level rise.

A study of long-term sea level variability in the East China Sea

From the analyses of the satellite altimeter Maps of Sea Level Anomaly (MSLA) data, tidal gauge sea level data and historical sea level data, this paper investigates the long-term sea level variability in the East China Sea (ECS). Based on the correlation analysis, we calculate the correlation coefficient between tidal gauge and the closest MSLA grid point, then generate the map of correlation coefficient of the entire ECS. The results show that the satellite altimeter MSLA data is effective to observe coastal sea level variability. An important finding is that from map of correlation coefficient we can identify the Kuroshio. The existence of Kuroshio decreases the correlation between coastal and the Pacific sea level. Kurishio likes a barrier or a wall, which blocks the effect of the Pacific and the global change. Moreover, coastal sea level in the ECS is mainly associated with local systems rather than global change. In order to calculate the long-term sea level variability trend, the empirical mode decomposition (EMD) method is applied to derive the trend on each MSLA grid point in the entire ECS. According to the 2-D distribution of the trend and rising rate, the sea level on the right side of the axis of Kuroshio rise faster than in its left side. This result supports the barrier effect of Kuroshio in the ECS. For the entire ECS, the average sea level rose 45.0 mm between 1993 and 2010, with a rising rate of (2.5±0.4) mm/a which is slower than global average. The relatively slower sea level rising rate further proves that sea level rise in the ECS has less response to global change due to its own local system effect.

Effects of the North Atlantic Oscillation and wind waves on salt marsh dynamics in the Danish Wadden Sea: a quantitative model as proof of concept

Long-term eustatic sea-level variation has been recognized as a primary factor affecting the hydrological and geomorphic dynamics of salt marshes. However, recent studies suggest that wind waves influenced by atmospheric oscillations also may play an important role in many coastal areas. Although this notion has been conceptually introduced for the Wadden Sea, no modeling attempts have been made yet. As a proof of concept, this study developed a simulation model using the commercially available STELLA® software, based on long-term data on water level and sedimentation collected at a back-barrier marsh on the Skallingen peninsula in Denmark. In the model, the frequency (number year–1) of wind-driven extreme high water level (HWL) events (>130 cm Danish Ordnance Zero) was simulated in terms of the North Atlantic Oscillation (NAO) index. Then, surface accretion (cm year–1) and submergence duration (h year–1) were simulated for the period 1933–2007. The model showed good performances: simulated rates of surface accretion and simulated durations of submergence decreased from 1950 to 1980, the point at which the NAO shifted from its negative to its positive phase, and increased thereafter. Despite continuous increases in surface elevation, increases in simulated submergence duration were apparently due to wind-driven HWL events, which generally increased in frequency after 1980. These findings for the Danish Wadden Sea add to the growing body of evidence that the role of atmospheric oscillations—e.g., the NAO—as drivers of wind-generated water level variations merits more attention in assessing the impact of climate change on coastal marshes.

Decadal and long-term sea level variability in the tropical Indo-Pacific Ocean

In this study, we analysed decadal and long-term steric sea level variations over 1966–2007 period in the Indo-Pacific sector, using an ocean general circulation model forced by reanalysis winds. The simulated steric sea level compares favourably with sea level from satellite altimetry and tide gauges at interannual and decadal timescales. The amplitude of decadal sea level variability (up to ~5 cm standard deviation) is typically nearly half of the interannual variations (up to ~10 cm) and two to three times larger than long-term sea level variations (up to 2 cm). Zonal wind stress varies at decadal timescales in the western Pacific and in the southern Indian Ocean, with coherent signals in ERA-40 (from which the model forcing is derived), NCEP, twentieth century and WASWind products. Contrary to the variability at interannual timescale, for which there is a tendency of El Nino and Indian Ocean Dipole events to co-occur, decadal wind stress variations are relatively independent in the two basins. In the Pacific, those wind stress variations drive Ekman pumping on either side of the equator, and induce low frequency sea level variations in the western Pacific through planetary wave propagation. The equatorial signal from the western Pacific travels southward to the west Australian coast through equatorial and coastal wave guides. In the Indian Ocean, decadal zonal wind stress variations induce sea level fluctuations in the eastern equatorial Indian Ocean and the Bay of Bengal, through equatorial and coastal wave-guides. Wind stress curl in the southern Indian Ocean drives decadal variability in the south-western Indian Ocean through planetary waves. Decadal sea level variations in the south–western Indian Ocean, in the eastern equatorial Indian Ocean and in the Bay of Bengal are weakly correlated to variability in the Pacific Ocean. Even though the wind variability is coherent among various wind products at decadal timescales, they show a large contrast in long-term wind stress changes, suggesting that long-term sea level changes from forced ocean models need to be interpreted with caution.

Comparison of Mediterranean sea level variability as given by three baroclinic models

We compare the results of three baroclinic models with the aim of evaluating their skills in reproducing Mediterranean long‐term sea level variability. The models are an ocean‐ice coupled forced global model (ORCA), a regional forced ocean model (OM8) and a regional coupled atmosphere‐ocean model (MITgcm). Model results are compared for the period 1961–2000 against hydrographic observations for water mass properties and steric sea level, and against satellite altimetry data and a reconstruction for sea level. All models represent the temperature variability of the upper layers reasonably well, but exhibit a considerable positive drift in the temperature of the deep layers due to an imbalance between the surface heat flux and the heat flux through Gibraltar. OM8 and MITgcm simulate the process of dense water formation better than ORCA thanks to their higher resolution in the model grid and in the atmospheric forcings. Concerning sea level variability, MITgcm is the only model that simulates well the inter‐annual sea level variability associated with the Eastern Mediterranean Transient. However, none of the models is able to reproduce other features that have clear signatures on sea level. The inter‐annual variability of Mediterranean mean sea level is better reproduced by the ORCA model because it is the only one considering the mass contribution from the Atlantic. The lack of that component in the regional models is a major shortcoming to reproduce Mediterranean sea level variability. Finally, mean sea level trends are overestimated by all models due to the spurious warming drift in the deep layers.

Reconstruction of a continuous high-resolution CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; record over the past 20 million years

Abstract. The gradual cooling of the climate during the Cenozoic has generally been attributed to a decrease in CO2 concentration in the atmosphere. The lack of transient climate models and, in particular, the lack of high-resolution proxy records of CO2, beyond the ice-core record prohibit, however, a full understanding of, for example, the inception of the Northern Hemisphere glaciation and mid-Pleistocene transition. Here we elaborate on an inverse modelling technique to reconstruct a continuous CO2 series over the past 20 million year (Myr), by decomposing the global deep-sea benthic δ18O record into a mutually consistent temperature and sea level record, using a set of 1-D models of the major Northern and Southern Hemisphere ice sheets. We subsequently compared the modelled temperature record with ice core and proxy-derived CO2 data to create a continuous CO2 reconstruction over the past 20 Myr. Results show a gradual decline from 450 ppmv around 15 Myr ago to 225 ppmv for mean conditions of the glacial-interglacial cycles of the last 1 Myr, coinciding with a gradual cooling of the global surface temperature of 10 K. Between 13 to 3 Myr ago there is no long-term sea level variation caused by ice-volume changes. We find no evidence of change in the long-term relation between temperature change and CO2, other than the effect following the saturation of the absorption bands for CO2. The reconstructed CO2 record shows that the Northern Hemisphere glaciation starts once the long-term average CO2 concentration drops below 265 ppmv after a period of strong decrease in CO2. Finally, only a small long-term decline of 23 ppmv is found during the mid-Pleistocene transition, constraining theories on this major transition in the climate system. The approach is not accurate enough to revise current ideas about climate sensitivity.

Wind effects on estimates of sea level rise

[1] Variability in sea level at the longest periods observable in modern records has recently been found to be well correlated with local atmospheric pressure. At shorter periods, however, longshore winds are known to be one of the primary mechanisms for forcing sea level variability on the eastern margins of the ocean. There is a remarkable ∼80 mm drop in mean sea level on both the eastern North Pacific and North Atlantic coasts between the late 1800s and early 1900s; it is found here to be in agreement with longshore wind forcing from the equator up to the latitude of the observed tide stations. Better-resolved data beginning in 1960 show that the delay near the annual period between wind forcing and sea level is approximately 1 month. The relative high in sea level in the late 1800s on the west coast of Europe appears to have propagated westward across the Atlantic as a long Rossby wave and then to have been seen on the east coast of the United States. Because many features in long-term sea level variability are correlated with wind forcing on time scales from annual to decades, it will be prudent to base conclusions about long-term sea level rise on the longest records available. The results here are based on forcing by longshore winds; the related issue of the extent to which open ocean wind curl may also be responsible is not addressed here, nor the extent to which coastal sea level observations are representative of the open ocean.