Using continuous GPS and absolute gravity to separate vertical land movements and changes in sea-level at tide-gauges in the UK

Researchers investigating climate change have used historical tide-gauge measurements from all over the world to investigate the changes in sea-level that have occurred over the last century or so. However, such estimates are a combination of any true sea-level variations and any vertical movements of the land at the specific tide-gauge. For a tide- gauge record to be used to determine the climate related component of changes in sea-level, it is therefore necessary to correct for the vertical land movement component of the observed change in sea-level. In 1990, the Institute of Engineering Surveying and Space Geodesy and Proudman Oceanographic Laboratory started developing techniques based on the Global Positioning System (GPS) for measuring vertical land movements (VLM) at tide-gauges in the UK. This paper provides brief details of these early developments and shows how they led to the establishment of continuous GPS (CGPS) stations at a number of tide-gauges. The paper then goes on to discuss the use of absolute gravity (AG), as an independent technique for measuring VLM at tide-gauges. The most recent results, from CGPS time-series dating back to 1997 and AG time-series dating back to 1995/1996, are then used to demonstrate the complementarity of these two techniques and their potential for providing site-specific estimates of VLM at tide-gauges in the UK.

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Recent sea level rise on Ireland's east coast based on multiple tide gauge analysis

10.5194/os-2020-81 ◽

2020 ◽

Author(s):

Amin Shoari Nejad ◽

Andrew C. Parnell ◽

Alice Greene ◽

Brian P. Kelleher ◽

Gerard McCarthy

Keyword(s):

Time Series ◽

Sea Level Rise ◽

Sea Level ◽

Continuous Time ◽

East Coast ◽

Tide Gauge ◽

Tide Gauges ◽

Missing Value ◽

Global Average ◽

Good Agreement

Abstract. We analysed multiple tide gauges from the east coast of Ireland over the period 1938–2018. We validated the different time series against each other and performed a missing value imputation exercise, which enabled us to produce a homogenised record. The recordings of all tide gauges were found to be in good agreement between 2003–2015, though this was markedly less so from 2016 to the present. We estimate the sea level rise in Dublin port for this period at 10 mm yr−1. The rate over the longer period of 1938–2015 was 1.67 mm yr−1 which is in good agreement with the global average. We found that the rate of sea level rise in the longer term record is cyclic with some extreme upward and downward trends. However, starting around 1980, Dublin has seen significantly higher rates that have been always positive since 1996, and this is mirrored in the surrounding gauges. Furthermore, our analysis indicates an increase in sea level variability since 1980. Both decadal rates and continuous time rates are calculated and provided with uncertainties in this paper.

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Review and Assessment of gap-filling methods from tide-gauges: Maxima missing at the Esbjerg, Denmark station, before 1910.

10.5194/egusphere-egu2020-4487 ◽

2020 ◽

Author(s):

Peter Thejll

Keyword(s):

Sea Level ◽

Tide Gauge ◽

Model Fit ◽

Tide Gauges ◽

Harmonic Model ◽

Gap Filling ◽

Tide Gauge Data ◽

Tide Gauge Record ◽

Long Baseline ◽

Gauge Data

Information on extremes of the sea-level is obtained from tide-gauge records. &#160;Such records may have gaps.Estimates of potential changes in the size and/or frequency of sea-level extremes are hampered by long gaps, or when just the high extremes are missing due, e.g. to equipment failure.Methods used for filling such gaps can be based on having multiple records from gauges near each other; but what to do if there is only one record? This problem can typically occur when old tide-gauge records are used -- the use of multiple recorders at the same place is more wide-spread today. However, especially older and therefore longer records hold the key to obtaining long-baseline insights into the temporal evolution of extreme tides and thus impacts of e.g. climate change.In this work, we review and assess methods for gap filling. We asses using the 'known truth' method, i.e. by applying realistic gaps to complete gauge records and reconstructing and then comparing errors calculated as the diffrence between modelled and actual values. &#160;We compare a simple harmonic model fit method to various spline methods as well as Neural network and deep learning approches. &#160;We also test a hybrid method which uses not just tide-gauge data but also air pressure readings from a meteorological station near the tide-gauge.We then attempt to fill in the missing maxima of the Esbjerg, Denmark hourly tide-gauge record since 1889. Particularly, before 1910 the maxima above 300 cm are missing (Bijl, et al., 1999), and we try to fill these in.

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Two-dimensional reconstruction of past sea level (1950–2003) from tide gauge data and an Ocean General Circulation Model

Climate of the Past ◽

10.5194/cp-5-217-2009 ◽

2009 ◽

Vol 5 (2) ◽

pp. 217-227 ◽

Cited By ~ 37

Author(s):

W. Llovel ◽

A. Cazenave ◽

P. Rogel ◽

A. Lombard ◽

M. B. Nguyen

Keyword(s):

Time Series ◽

Sea Level ◽

General Circulation ◽

Tide Gauge ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Two Dimensional ◽

Tide Gauges ◽

Dimensional Reconstruction ◽

Ocean General Circulation

Abstract. A two-dimensional reconstruction of past sea level is proposed at yearly interval over the period 1950–2003 using tide gauge records from 99 selected sites and 44-year long (1960–2003) 2°×2° sea level grids from the OPA/NEMO ocean general circulation model with data assimilation. We focus on the regional variability and do not attempt to compute the global mean trend. An Empirical Orthogonal Function decomposition of the reconstructed sea level grids over 1950–2003 displays leading modes that reflect two main components: (1) a long-term (multi-decadal), regionally variable signal and (2) an interannual, regionally variable signal dominated by the signature of El Nino-Southern Oscillation. Tests show that spatial trend patterns of the 54-year long reconstructed sea level significantly depend on the temporal length of the two-dimensional sea level signal used for the reconstruction (i.e., the length of the gridded OPA/NEMO sea level time series). On the other hand, interannual variability is well reconstructed, even when only ~10-years of model grids are used. The robustness of the results is assessed, leaving out successively each of the 99 tide gauges used for the reconstruction and comparing observed and reconstructed time series at the non considered tide gauge site. The reconstruction performs well at most tide gauges, especially at interannual frequency.

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

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-18-0235.1 ◽

2019 ◽

Vol 36 (10) ◽

pp. 1983-1996 ◽

Cited By ~ 2

Author(s):

Kevin Gobron ◽

Olivier de Viron ◽

Guy Wöppelmann ◽

Étienne Poirier ◽

Valérie Ballu ◽

...

Keyword(s):

Time Series ◽

Sea Level ◽

Variance Component ◽

Tide Gauge ◽

Electrical Contact ◽

Combination Method ◽

Tide Gauges ◽

Contact Probe ◽

Component Estimation ◽

Cross Calibration

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.

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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

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Sea Surface Height Predictions from the Global Navy Coastal Ocean Model during 1998–2001*

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-1680.1 ◽

2004 ◽

Vol 21 (12) ◽

pp. 1876-1893 ◽

Cited By ~ 47

Author(s):

Charlie N. Barron ◽

A. Birol Kara ◽

Harley E. Hurlburt ◽

C. Rowley ◽

Lucy F. Smedstad

Keyword(s):

Time Series ◽

Sea Level ◽

Tide Gauge ◽

Ocean Model ◽

Sea Surface ◽

Tide Gauges ◽

Model Data ◽

Free Running ◽

R Value ◽

Coastal Ocean Model

Abstract A ⅛° global version of the Navy Coastal Ocean Model (NCOM), operational at the Naval Oceanographic Office (NAVOCEANO), is used for prediction of sea surface height (SSH) on daily and monthly time scales during 1998–2001. Model simulations that use 3-hourly wind and thermal forcing obtained from the Navy Operational Global Atmospheric Prediction System (NOGAPS) are performed with/without data assimilation to examine indirect/direct effects of atmospheric forcing in predicting SSH. Model–data evaluations are performed using the extensive database of daily averaged SSH values from tide gauges in the Atlantic, Pacific, and Indian Oceans obtained from the Joint Archive for Sea Level (JASL) center during 1998–2001. Model–data comparisons are based on observations from 282 tide gauge locations. An inverse barometer correction was applied to SSH time series from tide gauges for model–data comparisons, and a sensitivity study is undertaken to assess the impact of the inverse barometer correction on the SSH validation. A set of statistical metrics that includes conditional bias (Bcond), root-mean-square (rms) difference, correlation coefficient (R), and nondimensional skill score (SS) is used to evaluate the model performance. It is shown that global NCOM has skill in representing SSH even in a free-running simulation, with general improvement when SSH from satellite altimetry and sea surface temperature (SST) from satellite IR are assimilated via synthetic temperature and salinity profiles derived from climatological correlations. When the model was run from 1998 to 2001 with NOGAPS forcing, daily model SSH comparisons from 612 yearlong daily tide gauge time series gave a median rms difference of 5.98 cm (5.77 cm), an R value of 0.72 (0.76), and an SS value of 0.45 (0.51) for the ⅛° free-running (assimilative) NCOM. Similarly, error statistics based on the 30-day running averages of SSH time series for 591 yearlong daily tide gauge time series over the time frame 1998–2001 give a median rms difference of 3.63 cm (3.36 cm), an R value of 0.83 (0.85), and an SS value of 0.60 (0.64) for the ⅛° free-running (assimilated) NCOM. Model– data comparisons show that skill in 30-day running average SSH time series is as much as 30% higher than skill for daily SSH. Finally, SSH predictions from the free-running and assimilative ⅛° NCOM simulations are validated against sea level data from the tide gauges in two different ways: 1) using original detided sea level time series from tide gauges and 2) using the detided data with an inverse barometer correction derived using daily mean sea level pressure extracted from NOGAPS at each location. Based on comparisons with 612 yearlong daily tide gauge time series during 1998–2001, the inverse barometer correction lowered the median rms difference by about 1 cm (15%–20%). Results presented in this paper reveal that NCOM is able to predict SSH with reasonable accuracies, as evidenced by model simulations performed during 1998–2001. In an extension of the validation over broader ocean regions, the authors find good agreement in amplitude and distribution of SSH variability between NCOM and other operational model products.

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2-D reconstruction of past sea level (1950–2003) using tide gauge records and spatial patterns from a general ocean circulation model

Climate of the Past Discussions ◽

10.5194/cpd-5-1109-2009 ◽

2009 ◽

Vol 5 (2) ◽

pp. 1109-1132 ◽

Cited By ~ 6

Author(s):

W. Llovel ◽

A. Cazenave ◽

P. Rogel ◽

A. Lombard ◽

M. Bergé-Nguyen

Keyword(s):

Time Series ◽

Sea Level ◽

Ocean Circulation ◽

Tide Gauge ◽

Circulation Model ◽

Global Ocean ◽

Tide Gauges ◽

Ocean Circulation Model ◽

Tide Gauge Records ◽

Function Decomposition

Abstract. A two-dimensional reconstruction of past sea level is proposed at yearly interval over the period 1950–2003 using tide gauge records at 99 selected sites and 44-year long (1960–2003) 2°×2° gridded dynamic heights from the OPA/NEMO global ocean circulation model with data assimilation. An Empirical Orthogonal Function decomposition of the reconstructed sea level over 1950–2003 displays leading modes that reflect two main components: a long-term (multi-decadal) but regionally variable signal and interannual fluctuations dominated by the signature of El Nino-Southern Oscillation. Tests show that spatial trend patterns of the 54-year long reconstructed sea level (1950–2003) significantly depend on the length of the gridded OPA/NEMO time series used to compute spatial covariance signal used for the reconstruction (i.e., the length of the gridded OPA/NEMO time series). On the other hand, the interannual variability is well reconstructed, even with ~10-year long of the OPA/NEMO model or satellite altimetry-based sea level grids. The robustness of the results is assessed, leaving out successively each of the 99 tide gauges when reconstructing the sea level signal and then comparing observed and reconstructed time series at the non contributing tide gauge site. The reconstruction performs well at most tide gauges, especially at interannual frequency.

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Variability of Winter Storminess in the Eastern United States during the Twentieth Century from Tide Gauges

Journal of Climate ◽

10.1175/jcli-d-12-00561.1 ◽

2013 ◽

Vol 26 (23) ◽

pp. 9713-9726 ◽

Cited By ~ 25

Author(s):

Philip R. Thompson ◽

Gary T. Mitchum ◽

Cedric Vonesch ◽

Jianke Li

Keyword(s):

United States ◽

Twentieth Century ◽

North America ◽

Sea Level ◽

Large Scale ◽

Tide Gauge ◽

Storm Track ◽

Eastern United States ◽

Tide Gauges ◽

Tide Gauge Record

Interannual to multidecadal variability of winter storminess in the eastern United States was studied using water level measurements from coastal tide gauges. The proximity to the coast of the primary winter storm track in the region allows the use of tide gauges to study temporal modulations in the frequency of these storms. Storms were identified in high-passed, detided sea level anomalies in 20 gauges from all coasts of North America to assess variability in winter storminess along particular storm tracks. The primary result is a significant multidecadal increase in the number of storms affecting the southeastern United States from the early to late twentieth century. The authors propose that this change is due to an increased tendency for the jet stream to meander south over the eastern United States since the 1950s. This mechanism is supported by long-term changes in the large-scale sea level pressure pattern over North America. The nature of the multidecadal change in storm frequency is unclear, because limited tide gauge record lengths prevent distinguishing between a trend and an oscillation.

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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.

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Monitoring the Vertical Land Motion of Tide Gauges and Its Impact on Relative Sea Level Changes in Korean Peninsula Using Sequential SBAS-InSAR Time-Series Analysis

Remote Sensing ◽

10.3390/rs13010018 ◽

2020 ◽

Vol 13 (1) ◽

pp. 18

Author(s):

Suresh Krishnan Palanisamy Vadivel ◽

Duk-jin Kim ◽

Jungkyo Jung ◽

Yang-Ki Cho ◽

Ki-Jong Han

Keyword(s):

Time Series ◽

Synthetic Aperture Radar ◽

Sea Level ◽

Korean Peninsula ◽

Tide Gauge ◽

Synthetic Aperture ◽

Tide Gauges ◽

Sea Level Changes ◽

Vertical Land Motion

The relative sea-level changes from tide gauges in the Korean peninsula provide essential information to understand the regional and global mean sea-level changes. Several corrections to raw tide gauge records are required to account for coastal vertical land motion (VLM), regional and local coastal variability. However, due to the lack of in-situ measurements such as leveling data and the Global Navigation Satellite System (GNSS), making precise assessments of VLM at the tide gauges is still challenging. This study aims to address the above limitation to assess the VLM in the Korean tide gauges using the time-series Interferometric Synthetic Aperture Radar (InSAR) technique. For 10 tide gauges selected in the Korean peninsula, we applied the Stanford Method for Persistent Scatterers (StaMPS)—Small Baseline Subset (SBAS) method to C-band Sentinel-1 A/B Synthetic Aperture Radar (SAR) data acquired during 2014/10–2020/05, with the novel sequential interferograms pair selection approach to increase the slowly decorrelating filtered phase (SDFP) pixels density near the tide gauges. Our findings show that overall the tide gauges in the Korean peninsula are stable, besides the largest VLM observed at Pohang tide gauge station (East Sea) of about −26.02 mm/year; also, higher rates of uplift (>1 mm/year) were observed along the coast of Yellow Sea (Incheon TG and Boryeong TG) and higher rates of subsidence (<−2 mm/year) were observed at Jeju TG and Seogwipo TG. Our approach estimates the rate of VLM at selected tide gauges with an unprecedented spatial and temporal resolution and is applicable when the in-situ and GNSS observations are not available.

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