scholarly journals Estimating Vertical Land Motion from Remote Sensing and In-Situ Observations in the Dubrovnik Area (Croatia): A Multi-Method Case Study

2020 ◽  
Vol 12 (21) ◽  
pp. 3543
Author(s):  
Marijan Grgić ◽  
Josip Bender ◽  
Tomislav Bašić
Keyword(s):  
Sea Level ◽  
Tide Gauge ◽  
Single Point ◽  
Altimeter Data ◽  
Satellite Altimeter ◽  
Vertical Land Motion ◽  
Observation Methods ◽  
Tide Gauge Measurements ◽  
Gnss Observations

Different space-borne geodetic observation methods combined with in-situ measurements enable resolving the single-point vertical land motion (VLM) and/or the VLM of an area. Continuous Global Navigation Satellite System (GNSS) measurements can solely provide very precise VLM trends at specific sites. VLM area monitoring can be performed by Interferometric Synthetic Aperture Radar (InSAR) technology in combination with the GNSS in-situ data. In coastal zones, an effective VLM estimation at tide gauge sites can additionally be derived by comparing the relative sea-level trends computed from tide gauge measurements that are related to the land to which the tide gauges are attached, and absolute trends derived from the radar satellite altimeter data that are independent of the VLM. This study presents the conjoint analysis of VLM of the Dubrovnik area (Croatia) derived from the European Space Agency’s Sentinel-1 InSAR data available from 2014 onwards, continuous GNSS observations at Dubrovnik site obtained from 2000, and differences of the sea-level change obtained from all available satellite altimeter missions for the Dubrovnik area and tide gauge measurements in Dubrovnik from 1992 onwards. The computed VLM estimates for the overlapping period of three observation methods, i.e., from GNSS observations, sea-level differences, and Sentinel-1 InSAR data, are −1.93±0.38 mm/yr, −2.04±0.22 mm/yr, and −2.24±0.46 mm/yr, respectively.

Observing Sea Level Changes Using Satellite Altimetry and In Situ Data

2020 ◽  
Author(s):  
Nikos Flokos ◽  
Maria Tsakiri
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Zone ◽  
Satellite Altimetry ◽  
Tide Gauge ◽  
Altimeter Data ◽  
Atmospheric Effects ◽  
Data Sets ◽  
Altimetry Data

<p>corresponding author: N.Flokos</p><p>[email protected]</p><p>ABSTRACT</p><p>Sea level change is one of the key indicators of climate change with numerous effects such as flooding, erosion of beaches, salt intrusion.  The detailed global picture of sea level and the monitoring of its spatial-temporal changes is performed by Satellite Altimetry (SA). Nowadays, SA data compare well with measurements from the global tide gauge network, but the aim of 0.3 mm/year accuracy in the altimeter derived rate of global mean sea level rise is still not fully met. </p><p>Whilst the precise determination of global and regional sea level rise from SA data is promising, there is however an observational gap in our knowledge regarding the coastal zone. While Tide Gauges (TG) are usually located at the coast, therefore providing coastal sea level measurements, altimeters have difficulties there. Filling this gap becomes important when considering that the impact of sea level rise can be devastating on the coast with effects on society and ecosystems. This makes it even more significant knowing that there are many stretches of the world’s coast that still do not possess in situ level measuring devices.  </p><p>This work aims to discuss the available data and methods that link the SA measurements of sea level rise with TG measurements. Whilst there is rich literature on relevant applications, it is important to have a clear and concise methodology on this.</p><p>Tide gauge data</p><p>Several post processing steps need to be applied to the raw TG data to enrich the raw Sea Surface Heights (SSH) values and make them comparable with SA data. There are several geophysical corrections, such as pressure and wind effects, which can be applied to TG data in order to deduce  Sea Level (SL) and be consistent with altimeter data. High frequency atmospheric effects on TG data are corrected using the Dynamic Atmospheric Correction (DAC) provided by AVISO. One other large uncertainty is the vertical stability of the TG benchmark over time. TG data must be corrected for the Vertical Land Motion (VLM) to enable the comparison of two sea level measurements (TG and SA) and their later integration within the surfaces of the absolute sea heights. The main VLM dataset can be obtained from SONEL database (SONEL 2016) which provides crustal velocities from the continuous GNSS measurements at sites collocated to the TG.</p><p>Satellite altimetry data</p><p>Whilst Satellite Altimetry over the open ocean is a mature discipline, global altimetry data collected over the coastal ocean remain still largely unexploited. This is because of intrinsic difficulties in the corrections and issues of land contamination in the footprint that have so far resulted in systematic flagging and rejection of these data. In this work, the relevant methodology to overcome these problems and extend the capabilities of current and future altimeters to the coastal zone (coastal altimetry) will be discussed and a number of coastal altimetry data sets will be used (eg SARvatore, X-TRACK, RADS etc). Finally, a practical example using real data sets over the Aegean Sea will be presented. </p><p> </p><p> </p>

scholarly journals 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

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.

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.

scholarly journals New Methods Measure How Vertical Land Motion Affects Sea Level

Eos ◽  
2016 ◽  
Vol 97 ◽  
Author(s):  
Lily Strelich
Keyword(s):  
Sea Level ◽  
Satellite Data ◽  
Tide Gauge ◽  
Vertical Motion ◽  
Sea Levels ◽  
New Methods ◽  
Vertical Land Motion ◽  
Tide Gauge Measurements ◽  
Rising Sea Levels

Researchers demonstrate the value of combining GPS and satellite data on vertical motion of the Earth's surface with tide gauge measurements to track rising sea levels.

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

&lt;p&gt;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.&amp;#160;&lt;/p&gt;&lt;p&gt;Keywords&amp;#8212; Tide gauge, Sea level, North Indian ocean, satellite altimetry, Vertical land motion&lt;/p&gt;

scholarly journals Interpreting and analyzing King Tide in Tuvalu

2014 ◽  
Vol 14 (2) ◽  
pp. 209-217 ◽  
Author(s):  
C.-C. Lin ◽  
C.-R. Ho ◽  
Y.-H. Cheng
Keyword(s):  
Tide Gauge ◽  
Spring Tide ◽  
Temporal Distribution ◽  
Warm Water ◽  
Altimeter Data ◽  
Spatial And Temporal Distribution ◽  
Water Effect ◽  
Satellite Altimeter ◽  
Loss Of Life ◽  
Satellite Altimeter Data

Abstract. The spatial and temporal distribution of sea-level rise has the potential to cause regional flooding in certain areas, and low-lying island countries are severely at risk. Tuvalu, an atoll country located in the southwest Pacific Ocean, has been inundated by this regional flooding for decades. Tuvaluans call this regional flooding phenomenon King Tide, a term not clearly defined, blaming it for loss of life and property in announcing their intention to migrate. In this study, we clarified and interpreted King Tide, and analyzed the factors of King Tide in Tuvalu. Using tide gauge and topographical data, we estimated that 3.2 m could be considered the threshold of King Tide, which implied half of the island of Tuvalu was flooded with seawater. This threshold is consistent with the finding of the National Oceanic and Atmospheric Administration that King Tide events occur once or twice a year. We surveyed 28 King Tide events to analyze the factors of regional flooding. Tide gauge and satellite altimeter data from 1993 to 2012 were cross-validated and indicated that the King Tide phenomenon is significantly related to the warm-water effect. Warm water contributed to the King Tide phenomenon by an average of 5.1% and a maximum of 7.8%. The height of King Tide is affected by the combined factors of spring tide, storm surge, climate variability, and, significantly, by the warm-water effect.

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