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

Pająk Katarzyna, Kowalczyk Kamil, Kaminskis Jānis, Idzikowska Magdalena

Geomatics and Environmental Engineering

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2021

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Vol. 15, no. 4

45--58

EN

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.

2

Sea level prediction using climatic variables: a comparative study of SVM and hybrid wavelet SVM approaches

Sithara S., Pramada S. K., Thampi Santosh G.

Acta Geophysica

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2020

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Vol. 68, no. 6

1779--1790

EN

Climate change is expected to adversely afect the coastal ecosystem in many ways. One of the major consequences of climate change in coastal areas is sea level rise. In order to manage this problem efciently, it is essential to obtain reasonably accurate estimates of future sea level. This study focuses essentially on the identifcation of climatic variables infuencing sea level and sea level prediction. Correlation analysis and wavelet coherence diagrams were used for identifying the infuencing variables, and support vector machine (SVM) and hybrid wavelet support vector machine (WSVM) techniques were used for sea level prediction. Sea surface temperature, sea surface salinity, and mean sea level pressure were observed to be the major local climatic variables infuencing sea level. Halosteric efect is found to have a major impact on the sea level. The variables identifed were subsequently used as predictors in both SVM and WSVM. WSVM employs discrete wavelet transform to decompose the variables before being input to the SVM model. The performance of both the models was compared using statistical measures such as root mean square error (RMSE), correlation coefcient (r), coefcient of determination (r 2 ), average squared error, Nash–Sutclife efciency, and percentage bias along with graphical indicators such as Taylor diagrams and regression error characteristic curves. Results indicate that the WSVM model predicted sea level with an RMSE of 0.029 m during the training and 0.040 m during the testing phases. The corresponding values for SVM are 0.043 m and 0.069 m, respectively. Also, the other statistical measures and graphical indicators suggest that WSVM technique outperforms the SVM approach in the prediction of sea level.

3

A unique fossil record from neptunian sills: the world's most extreme example of stratigraphic condensation (Jurassic, western Sicily)

Wendt J.

Acta Geologica Polonica

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2017

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Vol. 67, no. 2

163--199, [6]

EN

Neptunian sills at Rocca Busambra, a fragment of the Trapanese/Saccense Domain in western Sicily, host the most abundant ammonite and gastropod fauna which has ever been recorded from the Jurassic of the western Tethys. The fauna is dominated by parautochthonous organisms which were swept into the sills by gentle transport. Ammonites are characterized by perfect preservation and small size, a feature which is due to the predominance of microconchs but also of stunting. The most complete sill is 0.7 m thick and could be separated into 17 levels which range in age from the early Toarcian into the late Kimmeridgian, thus representing the most extreme case of palaeontologically and depositionally documented stratigraphic condensation in Earth history. The unique feature of the Rocca Busambra sills is due to the interaction of three processes: extreme stratigraphic condensation on the sea floor, weak tectonic fracturing of the host rock and repeated reopening on top of already existing sills. Contrasting percentages of gastropods in individual levels reflect sea-level oscillations which correspond to long known low- and highstands during the Jurassic of the western Tethys. Comparisons with other ammonite-bearing sill faunas reveal several similarities, but represent only short-timed phases of tectonic pulses and deposition.

4

Corretions to sea level anomalies data due to geocenter motion

Kosek W., Wnęk A., Zbylut-Górska M.

Geomatics, Landmanagement and Landscape

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2015

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no. 2

33--44

EN

The objective of this paper is computation of the corrections to sea level anomaly data due to center of Earth mass variations. The geocenter motion model was computed from the center of mass coordinates data determined from observations of space geodetic techniques such as Satellite Laser Ranging (SLR), Global Navigation Satellite System (GNSS) and Doppler Orbitography and Radiopositionig Integrated on Satellite (DORIS). In order to compute the geocenter motion model the center of mass coordinates data were filtered using wavelet based semblance filtering which allows computing a common signal in two time series. Based on determined geocenter motion model a correction to sea level anomalies (SLA) data due to geocenter motion was determined. This kind of correction to sea level anomaly data is of the order of few millimetres and should be applied to altimetric measurements to refer them to the International Terrestrial Reference Frame (ITRF) Origin considered as the center of figure.

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Litostratygrafia dolnego syluru w odsłonięciu Bardo Stawy (południowa część Gór Świętokrzyskich) - związek ze zmianami poziomu morza i cyrkulacją oceaniczną

Trela W., Salwa S.

Przegląd Geologiczny

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2007

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Vol. 55, nr 11

971-978

EN

The lower Llandovery black radiolarian cherts and shales of the Bardo Formation are interpreted as transgressive to highstand deposits produced by the marine flooding initiated in latest Ordovician time (persculptus graptolite zone). This formation was divided into the Rembów radiolarian chert Member and Zbrza shale Member. The sedimentary record of the Rembów Member was folded due to the late Caledonian tectonic activity. The accumulation of the radiolarian cherts was influenced by an upwelling system generated by the SE trade winds, which were active along the southern margin of the southern Holy Cross Mountains.