scholarly journals Studying the Sensitivity of Satellite Altimetry, Tide Gauge and GNSS Observations to Changes in Vertical Displacements

2021 ◽  
Vol 15 (4) ◽  
pp. 45-58
Author(s):  
Katarzyna Pajak ◽  
Kamil Kowalczyk ◽  
Jānis Kaminskis ◽  
Magdalena Idzikowska
Keyword(s):  
Sea Level ◽  
Satellite Altimetry ◽  
Adriatic Sea ◽  
Tide Gauge ◽  
Vertical Motion ◽  
Crustal Movement ◽  
Vertical Crustal Movement ◽  
Vertical Land Motion ◽  
Vertical Displacements ◽  
Sea Coast

Tide gauge observations provide sea level relative to the Earth’s crust, while satellite altimetry measures sea level variations relative to the centre of the Earth’s mass. Local vertical land motion can be a significant contribution to the measured sea level change.Satellite altimetry was traditionally used to study the open ocean, but this technology is now being used over inland seas too.The difference of both observations can be used to estimate vertical crustal movement velocities along the sea coast. In this paper, vertical crustal movement velocities were investigated at tide gauge sites along the Adriatic Sea coast by analyzing differences between Tide Gauge (TG) and Satellite Altimetry (SA) observations. Furthermore, the estimated vertical motion rates were compared with those from nearby GNSS measurements.The study determines the practical relationships between these vertical crustal movements and those determined from unrelated data acquired from the neighbouring GNSS stations. The results show general consistence with the present geodynamics in the Adriatic Sea coastal zone.

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

2019 ◽  
Vol 9 (1) ◽  
pp. 144-153
Author(s):  
H. Bâki Iz ◽  
T. Y. Yang ◽  
C. K. Shum ◽  
C. Y. Kuo
Keyword(s):  
Sea Level ◽  
Statistical Models ◽  
Satellite Altimetry ◽  
Tide Gauge ◽  
Crustal Movement ◽  
Sea Level Changes ◽  
Unknown Parameters ◽  
Vertical Crustal Movement ◽  
Proposed Model ◽  
Systematic Effects

Abstract Knowledge 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 the method 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.

scholarly journals Revisiting Vertical Land Motion and Sea Level Trends in the Northeastern Adriatic Sea Using Satellite Altimetry and Tide Gauge Data

2020 ◽  
Vol 8 (11) ◽  
pp. 949 ◽  
Author(s):  
Francesco De Biasio ◽  
Giorgio Baldin ◽  
Stefano Vignudelli
Keyword(s):  
Inverse Problem ◽  
Time Series ◽  
Sea Level ◽  
Satellite Altimetry ◽  
Adriatic Sea ◽  
Tide Gauge ◽  
Sea Level Change ◽  
Linear Inverse Problem ◽  
Level Change ◽  
Vertical Land Motion

We propose a revisited approach to estimating sea level change trends based on the integration of two measuring systems: satellite altimetry and tide gauge (TG) time series of absolute and relative sea level height. Quantitative information on vertical crustal motion trends at six TG stations of the Adriatic Sea are derived by solving a constrained linear inverse problem. The results are verified against Global Positioning System (GPS) estimates at some locations. Constraints on the linear problem are represented by estimates of relative vertical land motion between TG couples. The solution of the linear inverse problem is valid as long as the same rates of absolute sea level rise are observed at the TG stations used to constrain the system. This requirement limits the applicability of the method with variable absolute sea level trends. The novelty of this study is that we tried to overcome such limitations, subtracting the absolute sea level change estimates observed by the altimeter from all relevant time series, but retaining the original short-term variability and associated errors. The vertical land motion (VLM) solution is compared to GPS estimates at three of the six TGs. The results show that there is reasonable agreement between the VLM rates derived from altimetry and TGs, and from GPS, considering the different periods used for the processing of VLM estimates from GPS. The solution found for the VLM rates is optimal in the least square sense, and no longer depends on the altimetric absolute sea level trend at the TGs. Values for the six TGs’ location in the Adriatic Sea during the period 1993–2018 vary from −1.41 ± 0.47 mm y−1 (National Research Council offshore oceanographic tower in Venice) to 0.93 ± 0.37 mm y−1 (Rovinj), while GPS solutions range from −1.59 ± 0.65 (Venice) to 0.10 ± 0.64 (Split) mm y−1. The absolute sea level rise, calculated as the sum of relative sea level change rate at the TGs and the VLM values estimated in this study, has a mean of 2.43 mm y−1 in the period 1974–2018 across the six TGs, a mean standard error of 0.80 mm y−1, and a sample dispersion of 0.18 mm y−1.

Validation of sea surface heights from satellite altimetry along the Indian coast

2021 ◽  
Author(s):  
Milaa Murshan ◽  
Balaji Devaraju ◽  
Nagarajan Balasubramanian ◽  
Onkar Dikshit
Keyword(s):  
Time Series ◽  
Sea Level ◽  
Satellite Altimetry ◽  
Tide Gauge ◽  
Atmospheric Correction ◽  
North Indian Ocean ◽  
Sea Surface ◽  
Indian Coast ◽  
Vertical Land Motion ◽  
And Performance

<p>Satellite altimetry provides measurements of sea surface height of centimeter-level accuracy over open oceans. However, its accuracy reduces when approaching the coastal areas and over land regions. Despite this downside, altimetric measurements are still applied successfully in these areas through altimeter retracking processes. This study aims to calibrate and validate retracted sea level data of Envisat, ERS-2, Topex/Poseidon, Jason-1, 2, SARAL/AltiKa, Cryosat-2 altimetric missions near the Indian coastline. We assessed the reliability, quality, and performance of these missions by comparing eight tide gauge (TG) stations along the Indian coast. These are Okha, Mumbai, Karwar, and Cochin stations in the Arabian Sea, and Nagapattinam, Chennai, Visakhapatnam, and Paradip in the Bay of Bengal. To compare the satellite altimetry and TG sea level time series, both datasets are transformed to the same reference datum. Before the calculation of the bias between the altimetry and TG sea level time series, TG data are corrected for Inverted Barometer (IB) and Dynamic Atmospheric Correction (DAC). Since there are no prior VLM measurements in our study area, VLM is calculated from TG records using the same procedure as in the Technical Report NOS organization CO-OPS 065. </p><p>Keywords— Tide gauge, Sea level, North Indian ocean, satellite altimetry, Vertical land motion</p>

Estimation of Vertical Land Motion at the Tide Gauges in Turkey

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

<p>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.</p><p> </p><p><strong>Keywords: Vertical land motion, Sea Level Changes, Tide gauge, Satellite altimetry, GPS, CGPS </strong></p>

scholarly journals INVESTIGATON OF SEA LEVEL CHANGE ALONG THE BLACK SEA COAST FROM TIDE GAUGE AND SATELLITE ALTIMETRY

2015 ◽  
Vol XL-1-W5 ◽  
pp. 67-71 ◽  
Author(s):  
N. B. Avsar ◽  
S. H. Kutoglu ◽  
S. Jin ◽  
B. Erol
Keyword(s):  
Sea Level ◽  
Black Sea ◽  
Satellite Altimetry ◽  
Tide Gauge ◽  
The Black Sea ◽  
Level Change ◽  
Black Sea Coast ◽  
Grid Points ◽  
Sea Coast

In this study, we focus on sea level changes along the Black Sea coast. For this purpose, at same observation period the linear trends and the components of seasonal variations of sea level change are estimated at 12 tide gauge sites (Amasra, Igneada, Trabzon-II, Sinop, Sile, Poti, Batumi, Sevastopol, Tuapse, Varna, Bourgas, and Constantza) located along the Black Sea coast and available altimetric grid points closest to the tide gauge locations. The consistency of the results derived from both observations are investigated and interpreted. Furthermore, in order to compare the trends at the same location, it is interpolated from the trends obtained at the altimetric grid points in the defined neighbouring area with a diameter of 0.125° using a weighted average interpolation algorithm at each tide gauge site. For some tide gauges such as Sevastopol, Varna, and Bourgas, it is very likely that the trend estimates are not reliable because the time-spans overlapping the altimeter period are too short. At Sile, the long-term change for the time series of both data types do not give statistically significant linear rates. However, when the sites have long-term records, a general agreement between the satellite altimetry and tide gauge time series is observed at Poti (~20 years) and Tuapse (~18 years). On the other hand, the difference of annual phase between satellite altimetry and tide gauge results is from 1.32° to 71.48°.

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

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.

Reassessing sea level change rates in the Mediterranean Sea in the age of altimetry

2021 ◽  
Author(s):  
Francesco De Biasio ◽  
Stefano Vignudelli
Keyword(s):  
Mediterranean Sea ◽  
Sea Level ◽  
Satellite Altimetry ◽  
Adriatic Sea ◽  
Tide Gauge ◽  
Sea Level Change ◽  
Data Sets ◽  
Level Change ◽  
The Mediterranean

<p>Consistent long-term satellite-based data-sets of sea surface elevation exist nowadays to study sea level variability, globally and at regional scales. Two of them are suitable for climate-related studies: one produced in the framework of the European Space Agency (ESA)-funded Sea Level Climate Change Initiative (SL_CCI); the other offered by the European Copernicus Climate Change Service (C3S). Both data-sets cover the global ocean since 1993 to 2015 (SL_CCI) and to present (C3S) at spatial resolution of 0.25 x 0.25 degrees. The first is obtained by merging data from all the available satellite altimetry missions. The second one relies only on a couple of simultaneous altimetry missions at a time to provide stable long-term variability estimates of sea level, is constantly updated and has resolution 0.125 x 0.125 degrees in the Mediterranean Sea.<br>Previous studies have investigated the relationship between satellite-derived absolute sea level change rates and tide gauge observations of relative sea level change in littoral zones of the Mediterranean basin [Fenoglio-Mark, L., 2002; Fenoglio-Mark et al., 2012]. Other studies made use also of global positioning system measurements of vertical land motion in addition to tide gauge and satellite altimetry data [Rocco F.V., 2015; Zerbini et al., 2017]. Vignudelli et al., [2018] highlighted the difficulty of deriving spatially-consistent information on the sea level rates at regional scale in the Adriatic Sea. Other studies have claimed the possibility to merge locally isolated information into a coherent regional picture using a linear inverse problem approach [Wöppelmann and Marcos, 2012]: such approach has been successfully applied to a number of tide gauges in the Adriatic Sea [De Biasio et al., 2020]. The approach tested in the Adriatic Sea is going to be extended to the Mediterranean and major findings will be presented at conference.<br>The motivation of this study is that industrial areas are widely spread along the littoral zone of the southern Europe, and residential settlements are densely scattered along the coasts of the Mediterranean Sea. Not least, a strongly rooted seaside tourism is one of the main economic resources of the region, which is particularly exposed to the sea level variability of both natural and anthropogenic origin. A well known example of such a exposition is Venice (northern Italy) which has been recently hit by the second-highest tide in recorded history (November 2019), and is being protected against storm surges by the MOSE barrier since October 2020. Therefore, a re-analyses of the actual sea level rates with novel methodologies that take into account a better usage of all available observations is key to understand the future coastal sea level changes and their relative importance.</p><p>Fenoglio-Marc, L. 2002. DOI: 10.1016/S1474-7065(02)00084-0</p><p>Fenoglio-Marc, L.; Braitenberg, C.; Tunini, L. 2012. DOI: 10.1016/j.pce.2011.05.014</p><p>Rocco, F.V. Ph.D. Thesis, 2015. URI: https://amslaurea.unibo.it/id/eprint/10172</p><p>Zerbini, S.; Raicich, F.; Prati, C.M.; Bruni, S.; Conte, S.D.; Errico, M.; Santi, E. 2017. DOI: 10.1016/j.earscirev.2017.02.009</p><p>Vignudelli, S., De Biasio, F., Scozzari, A. Zecchetto, S., and Papa, A. 2019. DOI:10.1007/1345_2018_51</p><p>Wöppelmann, G. and Marcos, M. 2012. DOI: 10.1029/2011JC007469</p><p>De Biasio, F., Baldin, G. and Vignudelli, S. 2020. DOI:10.3390/jmse8110949</p>

scholarly journals An Attempt to Observe Vertical Land Motion along the Norwegian Coast by CryoSat-2 and Tide Gauges

2019 ◽  
Vol 11 (7) ◽  
pp. 744 ◽  
Author(s):  
Martina Idžanović ◽  
Christian Gerlach ◽  
Kristian Breili ◽  
Ole Andersen
Keyword(s):  
Sea Level ◽  
High Frequency ◽  
Satellite Altimetry ◽  
Tide Gauge ◽  
Ice Sheets ◽  
Tide Gauges ◽  
Tide Gauge Data ◽  
Norwegian Coast ◽  
Vertical Land Motion ◽  
Gauge Data

Present-day climate-change-related ice-melting induces elastic glacial isostatic adjustment (GIA) effects, while paleo-GIA effects describe the ongoing viscous response to the melting of late-Pleistocene ice sheets. The unloading initiated an uplift of the crust close to the centers of former ice sheets. Today, vertical land motion (VLM) rates in Fennoscandia reach values up to around 10 mm/year and are dominated by GIA. Uplift signals from GIA can be computed by solving the sea-level equation (SLE), S ˙ = N ˙ − U ˙ . All three quantities can also be determined from geodetic observations: relative sea-level variations ( S ˙ ) are observed by means of tide gauges, while rates of absolute sea-level change ( N ˙ ) can be observed by satellite altimetry; rates of VLM ( U ˙ ) can be determined by GPS (Global Positioning System). Based on the SLE, U ˙ can be derived by combining sea-surface measurements from satellite altimetry and relative sea-level records from tide gauges. In the present study, we have combined 7.5 years of CryoSat-2 satellite altimetry and tide-gauge data to estimate linear VLM rates at 20 tide gauges along the Norwegian coast. Thereby, we made use of monthly averaged tide-gauge data from PSMSL (Permanent Service for Mean Sea Level) and a high-frequency tide-gauge data set with 10-min sampling rate from NMA (Norwegian Mapping Authority). To validate our VLM estimates, we have compared them with the independent semi-empirical land-uplift model NKG2016LU_abs for the Nordic-Baltic region, which is based on GPS, levelling, and geodynamical modeling. Estimated VLM rates from 1 Hz CryoSat-2 and high-frequency tide-gauge data reflect well the amplitude of coastal VLM as provided by NKG2016LU_abs. We find a coastal average of 2.4 mm/year (average over all tide gauges), while NKG2016LU_abs suggests 2.8 mm/year; the spatial correlation is 0.58.

scholarly journals TIDE GAUGE AND SATELLITE ALTIMETRY DATA FOR POSSIBLE VERTICAL LAND MOTION DETECTION IN SOUTH EAST BOHOL TRENCH AND FAULT

2019 ◽  
Vol XLII-4/W19 ◽  
pp. 369-376
Author(s):  
R. Reyes ◽  
D. Noveloso ◽  
A. Rediang ◽  
M. Passaro ◽  
D. Bringas ◽  
...  
Keyword(s):  
Sea Level ◽  
Land Subsidence ◽  
Satellite Altimetry ◽  
Tide Gauge ◽  
Satellite Altimeter ◽  
Land Uplift ◽  
In Situ Data ◽  
Vertical Land Motion ◽  
The Difference ◽  
Gnss Measurements

Abstract. Coupled with the occurrence of regional/local sea level rise on urbanized coastal cities is the possibility of land subsidence that contaminates the measurement by the tide gauge (TG) sensors. Another technology that could possibly check the in-situ data from tide gauge is satellite altimetry. The sea surface height (SSH) measured from satellite altimeter is compared with the observed tide gauge sea level (TGSL) to detect vertical land motion (VLM). This study used satellite altimeter retracked products near the TG Stations in Tagbilaran, Bohol; Dumaguete, Negros Oriental; and Mambajao, Camiguin located in the vicinity of the South East Bohol Trench and Fault (SEBTF).Based on the results, the TG site in Tagbilaran is undergoing land subsidence. The rate of VLM is around 5 mm/year from 2009 to 2017. The same trend was manifested in the GNSS observed data in the PHIVOLCS monitoring station in Tagbilaran and the geodetic levelling done in the area. After the October 15, 2013 earthquake in Bohol, downward trends of around 27 mm/year and 17 mm/year were observed from GNSS measurements and SSH-TGSL difference respectively. These different rates may be due to the distance between the two sensors. The comparison between SSH and TGSL in Dumaguete showed small difference with a VLM rate of 1.8 mm/year. The difference in SSH-TGSL in Mambajao is quite large with a downward rate of 9.4 mm/year. This result needs to be further investigated for TG or TGBM instability or monitored for a possibility of land uplift.

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