Disentangling vertical land motion and waves from coastal sea level altimetry and tide gauges

Vertical land motion at tide gauges influences sea level rise acceleration; this must be addressed for interpreting reliable sea level projections. In recent years, tide gauge records for the Eastern coast of Korea have revealed rapid increases in sea level rise compared with the global mean. Pohang Tide Gauge Station has shown a +3.1 cm/year sea level rise since 2013. This study aims to estimate the vertical land motion that influences relative sea level rise observations at Pohang by applying a multi-track Persistent Scatter Interferometric Synthetic Aperture Radar (PS-InSAR) time-series analysis to Sentinel-1 SAR data acquired during 2015–2017. The results, which were obtained at a high spatial resolution (10 m), indicate vertical ground motion of −2.55 cm/year at the Pohang Tide Gauge Station; this was validated by data from a collocated global positioning system (GPS) station. The subtraction of InSAR-derived subsidence rates from sea level rise at the Pohang Tide Gauge Station is 6 mm/year; thus, vertical land motion significantly dominates the sea level acceleration. Natural hazards related to the sea level rise are primarily assessed by relative sea level changes obtained from tide gauges; therefore, tide gauge records should be reviewed for rapid vertical land motion along the vulnerable coastal areas.

Download Full-text

The zone of influence: matching sea level variability from coastal altimetry and tide gauges for vertical land motion estimation

Ocean Science ◽

10.5194/os-17-35-2021 ◽

2021 ◽

Vol 17 (1) ◽

pp. 35-57

Author(s):

Julius Oelsmann ◽

Marcello Passaro ◽

Denise Dettmering ◽

Christian Schwatke ◽

Laura Sánchez ◽

...

Keyword(s):

Sea Level ◽

Spatial Scales ◽

Tide Gauges ◽

Sea Level Changes ◽

Relative Sea Level ◽

Sea Level Variability ◽

Vertical Land Motion ◽

Spatial Coverage ◽

Coupling Procedure ◽

Zone Of Influence

Abstract. Vertical land motion (VLM) at the coast is a substantial contributor to relative sea level change. In this work, we present a refined method for its determination, which is based on the combination of absolute satellite altimetry (SAT) sea level measurements and relative sea level changes recorded by tide gauges (TGs). These measurements complement VLM estimates from the GNSS (Global Navigation Satellite System) by increasing their spatial coverage. Trend estimates from the SAT and TG combination are particularly sensitive to the quality and resolution of applied altimetry data as well as to the coupling procedure of altimetry and TGs. Hence, a multi-mission, dedicated coastal along-track altimetry dataset is coupled with high-frequency TG measurements at 58 stations. To improve the coupling procedure, a so-called “zone of influence” (ZOI) is defined, which confines coherent zones of sea level variability on the basis of relative levels of comparability between TG and altimetry observations. Selecting 20 % of the most representative absolute sea level observations in a 300 km radius around the TGs results in the best VLM estimates in terms of accuracy and uncertainty. At this threshold, VLMSAT-TG estimates have median formal uncertainties of 0.58 mm yr−1. Validation against GNSS VLM estimates yields a root mean square (rmsΔVLM) of VLMSAT-TG and VLMGNSS differences of 1.28 mm yr−1, demonstrating the level of accuracy of our approach. Compared to a reference 250 km radius selection, the 300 km zone of influence improves trend accuracies by 15 % and uncertainties by 35 %. With increasing record lengths, the spatial scales of the coherency in coastal sea level trends increase. Therefore, the relevance of the ZOI for improving VLMSAT-TG accuracy decreases. Further individual zone of influence adaptations offer the prospect of bringing the accuracy of the estimates below 1 mm yr−1.

Download Full-text

Integrating Non-Tidal Sea Level data from altimetry and tide gauges for coastal sea level prediction

Advances in Space Research ◽

10.1016/j.asr.2011.11.016 ◽

2012 ◽

Vol 50 (8) ◽

pp. 1099-1106 ◽

Cited By ~ 14

Author(s):

Yongcun Cheng ◽

Ole Baltazar Andersen ◽

Per Knudsen

Keyword(s):

Sea Level ◽

Tide Gauges ◽

Level Data ◽

Coastal Sea

Download Full-text

River-discharge effects on United States Atlantic and Gulf coast sea-level changes

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1805428115 ◽

2018 ◽

Vol 115 (30) ◽

pp. 7729-7734 ◽

Cited By ~ 29

Author(s):

Christopher G. Piecuch ◽

Klaus Bittermann ◽

Andrew C. Kemp ◽

Rui M. Ponte ◽

Christopher M. Little ◽

...

Keyword(s):

United States ◽

Sea Level ◽

River Discharge ◽

Sea Level Change ◽

The United States ◽

Ocean Dynamics ◽

Sea Level Changes ◽

Level Change ◽

Vertical Land Motion ◽

Coastal Sea

Identifying physical processes responsible for historical coastal sea-level changes is important for anticipating future impacts. Recent studies sought to understand the drivers of interannual to multidecadal sea-level changes on the United States Atlantic and Gulf coasts. Ocean dynamics, terrestrial water storage, vertical land motion, and melting of land ice were highlighted as important mechanisms of sea-level change along this densely populated coast on these time scales. While known to exert an important control on coastal ocean circulation, variable river discharge has been absent from recent discussions of drivers of sea-level change. We update calculations from the 1970s, comparing annual river-discharge and coastal sea-level data along the Gulf of Maine, Mid-Atlantic Bight, South Atlantic Bight, and Gulf of Mexico during 1910–2017. We show that river-discharge and sea-level changes are significantly correlated (p<0.01), such that sea level rises between 0.01 and 0.08 cm for a 1 km3 annual river-discharge increase, depending on region. We formulate a theory that describes the relation between river-discharge and halosteric sea-level changes (i.e., changes in sea level related to salinity) as a function of river discharge, Earth’s rotation, and density stratification. This theory correctly predicts the order of observed increment sea-level change per unit river-discharge anomaly, suggesting a causal relation. Our results have implications for remote sensing, climate modeling, interpreting Common Era proxy sea-level reconstructions, and projecting coastal flood risk.

Download Full-text

Estimation of Vertical Land Motion at the Tide Gauges in Turkey

10.5194/egusphere-egu2020-7110 ◽

2020 ◽

Author(s):

Muharrem Hilmi Erkoç ◽

Uğur Doğan ◽

Seda Özarpacı ◽

Hasan Yildiz ◽

Erdinç Sezen

Keyword(s):

Time Series ◽

Sea Level ◽

Satellite Altimetry ◽

Tide Gauge ◽

Marmara Sea ◽

Tide Gauges ◽

Sea Level Changes ◽

Coordinate Time ◽

Coordinate Time Series ◽

Vertical Land Motion

This study aims to estimate vertical land motion (VLM) at tide gauges (TG), located in the Mediterranean, Aegean and the Marmara Sea coasts of Turkey, from differences of multimission satellite altimetry and TG sea level time series. Initially, relative sea level trends are estimated at 7 tide gauges stations operated by the Turkish General Directorate of Mapping over the period 2001-2019. Subsequently, absolute sea level trends independent from VLM are computed from multimission satellite altimetry data over the same period. We have computed estimates of linear trends of difference time series between altimetry and tide gauge sea level after removing seasonal signals by harmonic analysis from each time series to estimate the vertical land motion (VLM) at tide gauges. Traditional way of VLM determination at tide gauges is to use GPS@TG or preferably CGPS@TG data. We therefore, processed these GPS data, collected over the years by several TG-GPS campaigns and by continuous GPS stations close to the TG processed by GAMIT/GLOBK software. Subsequently, the GPS and CGPS vertical coordinate time series are used to estimate VLM. These two different VLM estimates, one from GPS and CGPS coordinate time series and other from altimetry-TG sea level time series differences are compared.&#160;Keywords: Vertical land motion, Sea Level Changes, Tide gauge, Satellite altimetry, GPS, CGPS

Download Full-text

THE VERTICAL LAND MOTION OF TIDE GAUGE AND ABSOLUTE SEA LEVEL RISE IN BOHAI SEA

ISPRS Annals of Photogrammetry Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-annals-iv-2-w5-601-2019 ◽

2019 ◽

Vol IV-2/W5 ◽

pp. 601-606

Author(s):

D. Zhou ◽

W. Sun ◽

Y. Fu ◽

X. Zhou

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Bohai Sea ◽

Tide Gauge ◽

Sea Level Change ◽

Tide Gauges ◽

Sea Level Changes ◽

The Bohai Sea ◽

Level Change ◽

Vertical Land Motion

Abstract. The ground vertical movement of the tide gauges around the Bohai sea was firstly analyzed by using the observation data from 2009 to 2017 of the nine co-located GNSS stations. It was found that the change rate of ground vertical motion of four stations was in the same order of magnitude as the sea level change. In particular, the land subsidence rate of BTGU station reaches 11.47&thinsp;mm/yr, which should be paid special attention to in the analysis of sea level change. Then combined with long-term tide gauges and the satellite altimetry results, the sea level changes in the Bohai sea and adjacent waters from 1993 to 2012 were analyzed. The relative and absolute sea level rise rates of the sea area are 3.81&thinsp;mm/yr and 3.61&thinsp;mm/yr, respectively, both are higher than the global average rate of change. At the same time, it is found that the vertical land motion of tide gauge stations is the main factor causing regional differences in relative sea level changes.

Download Full-text

Validation of the ALES Coastal Altimetry Dataset against the Norwegian Tide Gauges

10.5194/egusphere-egu21-14596 ◽

2021 ◽

Author(s):

Fabio Mangini ◽

Antonio Bonaduce ◽

Léon Chafik ◽

Laurent Bertino

Keyword(s):

Sea Level ◽

Satellite Altimetry ◽

Tide Gauge ◽

Linear Trend ◽

Tide Gauges ◽

Sea Level Variability ◽

Preliminary Results ◽

In Situ Data ◽

Coastal Sea

Satellite altimetry measurements, complemented by in-situ records, have made a fundamental contribution to the understanding of global sea level variability for almost 30 years. Due to land contamination, it performs best over the open ocean. However, over the years, there has been a significant effort to improve the altimetry products in coastal regions. Indeed, altimetry observations could be fruitfully used in the coastal zone to complement the existing tide gauge network which, despite its relevance, does not represent the entire coast.&#160;Given the important role of coastal altimetry in oceanography, we have recently decided to check the quality of a new coastal altimetry dataset, ALES, along the coast of Norway. The Norwegian coast is well covered by tide gauges and, therefore, particularly suitable to validate a coastal altimetry dataset. Preliminary results show a good agreement between in-situ and remote sensing sea-level signals in terms of linear trend, seasonal cycle and inter-annual variability. For example, the linear correlation coefficient between the inter-annual sea level variability from altimetry and tide gauges exceeds 0.8. Likewise, the root mean square difference between the two is less than 2 cm at most tide gauge locations. A comparison with Breili et al. (2017) shows that ALES performs better than the standard satellite altimetry products at estimating sea level trends along the coast of Norway. Notably, in the Lofoten region, the difference between the sea level trends computed using ALES and the tide gauges range between 0.0 to 0.7 mm/year, compared to circa 1 to 3 mm/year found by Breili et al. (2017). These preliminary results go in the direction of obtaining an accurate characterization of coastal sea-level at the high latitudes based on coastal altimetry records, which can represent a valuable source of information to reconstruct coastal sea-level signals in areas where in-situ data are missing or inaccurate.

Download Full-text

Sea level changes and vertical land motion from altimetry and tide gauges in the Southern Levantine Basin

Journal of Geodynamics ◽

10.1016/j.jog.2019.05.007 ◽

2019 ◽

Vol 128 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Bayoumy Mohamed ◽

Abdallah Mohamed ◽

Khaled Alam El-Din ◽

Hazem Nagy ◽

Ahmed Elsherbiny

Keyword(s):

Sea Level ◽

Tide Gauges ◽

Sea Level Changes ◽

Vertical Land Motion ◽

Levantine Basin

Download Full-text

Annual cycle in coastal sea level from tide gauges and altimetry

Journal of Geophysical Research Atmospheres ◽

10.1029/2009jc005767 ◽

2010 ◽

Vol 115 (C4) ◽

Cited By ~ 20

Author(s):

Sergey V. Vinogradov ◽

Rui M. Ponte

Keyword(s):

Sea Level ◽

Annual Cycle ◽

Tide Gauges ◽

Coastal Sea

Download Full-text

Vertical land motion in the Iberian Atlantic coast and its implications for sea level change evaluation

Journal of Applied Geodesy ◽

10.1515/jag-2020-0012 ◽

2020 ◽

Vol 14 (3) ◽

pp. 361-378

Author(s):

V. B. Mendes ◽

S. M. Barbosa ◽

D. Carinhas

Keyword(s):

Time Series ◽

Sea Level ◽

Satellite Altimetry ◽

Tide Gauge ◽

Atlantic Coast ◽

Sea Level Change ◽

Tide Gauges ◽

Tide Gauge Records ◽

Level Change ◽

Vertical Land Motion

AbstractIn this study, we estimate vertical land motion for 35 stations primarily located along the coastline of Portugal and Spain, using GPS time series with at least eight years of observations. Based on this set of GPS stations, our results show that vertical land motion along the Iberian coastline is characterized, in general, by a low to moderate subsidence, ranging from −2.2 mm yr−1 to 0.4 mm yr−1, partially explained by the glacial isostatic adjustment geophysical signal. The estimates of vertical land motion are subsequently applied in the analysis of tide gauge records and compared with geocentric estimates of sea level change. Geocentric sea level for the Iberian Atlantic coast determined from satellite altimetry for the last three decades has a mean of 2.5 ± 0.6 mm yr−1, with a significant range, as seen for a subset of grid points located in the vicinity of tide gauge stations, which present trends varying from 1.5 mm yr−1 to 3.2 mm yr−1. Relative sea level determined from tide gauges for this region shows a high degree of spatial variability, that can be partially explained not only by the difference in length and quality of the time series, but also for possible undocumented datum shifts, turning some trends unreliable. In general, tide gauges corrected for vertical land motion produce smaller trends than satellite altimetry. Tide gauge trends for the last three decades not corrected for vertical land motion range from 0.3 mm yr−1 to 5.0 mm yr−1 with a mean of 2.6 ± 1.4 mm yr−1, similar to that obtained from satellite altimetry. When corrected for vertical land motion, we observe a reduction of the mean to ∼1.9 ± 1.4 mm yr−1. Actions to improve our knowledge of vertical land motion using space geodesy, such as establishing stations in co-location with tide gauges, will contribute to better evaluate sea level change and its impacts on coastal regions.

Download Full-text