scholarly journals Validation of Copernicus Sea Level Altimetry Products in the Baltic Sea and Estonian Lakes

2020 ◽  
Vol 12 (24) ◽  
pp. 4062
Author(s):  
Aive Liibusk ◽  
Tarmo Kall ◽  
Sander Rikka ◽  
Rivo Uiboupin ◽  
Ülo Suursaar ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Sea Level ◽  
Tide Gauge ◽  
Tide Gauges ◽  
The Baltic Sea ◽  
Geoid Model ◽  
Temporal Sampling ◽  
Level 3 ◽  
The Baltic ◽  
Level 2

Multi-mission satellite altimetry (e.g., ERS, Envisat, TOPEX/Poseidon, Jason) data have enabled a synoptic-scale view of ocean variations in past decades. Since 2016, the Sentinel-3 mission has provided better spatial and temporal sampling compared to its predecessors. The Sentinel-3 Ku/C Radar Altimeter (SRAL) is one of the synthetic aperture radar altimeters (SAR Altimeter) which is more precise for coastal and lake observations. The article studies the performance of the Sentinel-3 Level-2 sea level altimetry products in the coastal areas of the Baltic Sea and on two lakes of Estonia. The Sentinel-3 data were compared with (i) collocated Global Navigation Satellite System (GNSS) ship measurements, (ii) the Estonian geoid model (EST-GEOID2017) together with sea-level anomaly corrections from the tide gauges, and (iii) collocated buoy measurements. The comparisons were carried out along seven Sentinel-3A/B tracks across the Baltic Sea and Estonian lakes in 2019. In addition, the Copernicus Marine Environment Monitoring Service (CMEMS) Level-3 sea-level products and the Nucleus for European Modelling of the Ocean (NEMO) reanalysis outcomes were compared with measurements from Estonia’s 21 tide gauges and the buoy deployed offshore. Our results showed that the uncertainty of the Sentinel-3 Level-2 altimetry product was below decimetre level for the seacoast and the selected lakes of Estonia. Results from CMEMS Level-3 altimetry products showed a correlation of 0.83 (RMSE 0.18 m) and 0.91 (RMSE 0.27 m) when compared against the tide gauge measurements and the NEMO model, respectively. The overall performance of the altimetry products was very good, except in the immediate vicinity of the coastline and for the lakes, where the accuracy was nearly three times lower than for the open sea, but still acceptably good.

scholarly journals Validation of Sentinel-3 SAR Level-2 and Level-3 Products in the Baltic Sea and Estonian lakes

2020 ◽  
Author(s):  
Aive Liibusk ◽  
Tarmo Kall ◽  
Sander Rikka ◽  
Rivo Uiboupin ◽  
Ülo Suursaar ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Sea Level ◽  
Tide Gauge ◽  
Radar Altimeter ◽  
Geoid Model ◽  
Sea Level Anomaly ◽  
Temporal Sampling ◽  
Level 3 ◽  
The Baltic ◽  
Level 2

Multimission satellite altimetry (e.g. ERS, Envisat, TOPEX/Poseidon, Jason) data have enabled a synoptic view of ocean variations in the past decades, including sea-level rise and mesoscale circulations. Since 2016, the Sentinel-3 mission has provided better spatial and temporal sampling compared with its predecessors. The Sentinel-3 Ku/C Radar Altimeter (SRAL) is one of the synthetic aperture radar altimeters (SAR Altimeter) which is more precise in coastal and lake observations. In this study, we validate Sentinel-3 Level-2 products in Baltic Sea coastal areas and two lakes in Estonia. Moreover, the Copernicus Marine Environment Monitoring Service (CMEMS) Level-3 sea-level anomaly data and the Nucleus for European Modelling of the Ocean (NEMO) reanalysis model outcomes are compared with measurements from a tide gauge network. A dense in situ water level network deployed along the coast for geodetic observation was utilised to provide ground truths for validating altimetry results. Three validation methods were used for Level-2 data: (i) collocated Sentinel-3 and GNSS ship measurements; (ii) a national geoid model (EST-GEOID2017) with sea-level anomaly correction; (iii) collocated Sentinel-3 and buoy measurements. The validations were carried out in seven Sentinel-3A/B overpasses in 2019. Our results show that the uncertainty of the Sentinel-3 Level-2 altimetry product is below decimetre level on the Estonian coast and the targeted lakes. Results from CMEMS Level-3 showed a correlation of 0.8 (RMSE 0.19 m) and 0.91 (RMSE 0.27 m) when compared against tide gauge measurements and NEMO model, respectively.

scholarly journals Spatial sea-level reconstruction in the Baltic Sea and in the Pacific Ocean from tide gauges observations

2016 ◽  
Vol 59 (3) ◽  
Author(s):  
Marco Olivieri ◽  
Giorgio Spada
Keyword(s):  
Pacific Ocean ◽  
Baltic Sea ◽  
Sea Level ◽  
Tide Gauge ◽  
Tide Gauges ◽  
The Baltic Sea ◽  
Data Set ◽  
The Pacific ◽  
The Pacific Ocean ◽  
The Baltic

<p>Exploiting the Delaunay interpolation, we present a newly implemented 2-D sea-level reconstruction from coastal sea-level observations to open seas, with the aim of characterizing the spatial variability of the rate of sea-level change. To test the strengths and weaknesses of this method and to determine its usefulness in sea-level interpolation, we consider the case studies of the Baltic Sea and of the Pacific Ocean. In the Baltic Sea, a small basin well sampled by tide gauges, our reconstructions are successfully compared with absolute sea-level observations from altimetry during 1993-2011. The regional variability of absolute sea level observed across the Pacific Ocean, however, cannot be reproduced. We interpret this result as the effect of the uneven and sparse tide gauge data set and of the composite vertical land movements in and around the region. Useful considerations arise that can serve as a basis for developing sophisticated approaches.</p>

Sea level variations in the coastal region from altimetry – Using optimal interpolation in the Baltic Sea for 3-day mean sea level from altimetry, tide gauge and model data

2021 ◽  
Author(s):  
Ida Margrethe Ringgaard ◽  
Jacob L. Høyer ◽  
Kristine S. Madsen ◽  
Adili Abulaitijiang ◽  
Ole B. Andersen
Keyword(s):  
Baltic Sea ◽  
Sea Level ◽  
Temporal Resolution ◽  
Satellite Altimetry ◽  
Tide Gauge ◽  
Coastal Region ◽  
Optimal Interpolation ◽  
The Baltic Sea ◽  
Spatial Coverage ◽  
The Baltic

&lt;p&gt;The rise and fall of the sea surface in the coastal region is observed closely by two different sources: tide gauges measure the relative sea level anomaly at the coast at high temporal resolution (minutes or hours) and satellite altimeters measure the absolute sea surface height of the open ocean along tracks multiple times a day. However, these daily tracks are scattered across the Baltic Sea with each track being repeated at a lower temporal resolution (days). Due to the inverse relationship between spatial and temporal coverage of the satellite altimetry data, gridded satellite altimetry products often prioritize spatial coverage over temporal resolution, thus filtering out the high sea level variability. In other words, the satellite data, and especially averaged products, often miss the daily sea level variability, such as storm surges, which is most important for all societies in the coastal region. To compensate for the sparse spatial coverage from satellite altimetry, we here present an experimental product developed as part of the ESA project Baltic+SEAL: &amp;#160;on a 3-day scale, the DMI Optimal Interpolation (DMI-OI) method is combined with error statistics from a storm surge model as well as 3-day averages from both tide gauge observations and satellite altimetry tracks to generate a gridded sea level anomaly product for the Baltic Sea for year 2017. The product captures the overall temporal evolution of the sea level changes well for most areas with an average RMSE wrt. tide gauge observations of 17.2 cm and a maximum of 34.2 cm. Thus, the 3-day mean gridded product shows potential as an alternative to monthly altimetry products, although further work is needed.&lt;/p&gt;

scholarly journals Geodetic SAR for Height System Unification and Sea Level Research—Observation Concept and Preliminary Results in the Baltic Sea

2020 ◽  
Vol 12 (22) ◽  
pp. 3747
Author(s):  
Thomas Gruber ◽  
Jonas Ågren ◽  
Detlef Angermann ◽  
Artu Ellmann ◽  
Andreas Engfeldt ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Sea Level ◽  
Tide Gauge ◽  
The Baltic Sea ◽  
Early Results ◽  
Height System ◽  
First Results ◽  
The Baltic ◽  
Sea Area ◽  
The Impact

Traditionally, sea level is observed at tide gauge stations, which usually also serve as height reference stations for national leveling networks and therefore define a height system of a country. One of the main deficiencies to use tide gauge data for geodetic sea level research and height systems unification is that only a few stations are connected to the geometric network of a country by operating permanent GNSS receivers next to the tide gauge. As a new observation technique, absolute positioning by SAR using active transponders on ground can fill this gap by systematically observing time series of geometric heights at tide gauge stations. By additionally knowing the tide gauge geoid heights in a global height reference frame, one can finally obtain absolute sea level heights at each tide gauge. With this information the impact of climate change on the sea level can be quantified in an absolute manner and height systems can be connected across the oceans. First results from applying this technique at selected tide gauges at the Baltic coasts are promising but also exhibit some problems related to the new technique. The paper presents the concept of using the new observation type in an integrated sea level observing system and provides some early results for SAR positioning in the Baltic sea area.

scholarly journals SEA LEVEL VARIATIONS IN THE GULF OF BOTHNIA

1973 ◽  
Vol 4 (1) ◽  
pp. 41-53 ◽  
Author(s):  
EUGENIE LISITZIN
Keyword(s):  
Baltic Sea ◽  
Sea Level ◽  
Water Volume ◽  
Tide Gauges ◽  
The Baltic Sea ◽  
Land Uplift ◽  
Gulf Of Bothnia ◽  
Sea Level Variations ◽  
The Baltic

An attempt is made to compute the sea level variations in the Gulf of Bothnia, which is isolated by islands and thresholds from the Baltic Sea proper. Observations from tide gauges during the 30-year period 1931–1960 were used. The effect of land uplift was taken into consideration. The maximum annual deviation in water volume from the long-term mean corresponded to 20.74 km3..

scholarly journals Anomalous secular sea-level acceleration in the Baltic Sea caused by isostatic adjustment

2014 ◽  
Vol 57 (4) ◽  
Author(s):  
Giorgio Spada ◽  
Marco Olivieri ◽  
Gaia Galassi
Keyword(s):  
Baltic Sea ◽  
Sea Level ◽  
Ocean Circulation ◽  
Tide Gauge ◽  
Average Rate ◽  
The Baltic Sea ◽  
Tide Gauge Records ◽  
Sea Level Acceleration ◽  
Global Sea Level ◽  
The Baltic

<p>Observations from the global array of tide gauges show that global sea-level has been rising at an average rate of 1.5-2 mm/yr during the last ~150 years [Douglas 1991, Spada and Galassi 2012]. Although a global sea-level acceleration was initially ruled out [Douglas 1992], subsequent studies [Douglas 1997, Church and White 2006, Jevrejeva et al. 2008, Church and White 2011] have coherently proposed values of ~1 mm/year/century [Olivieri and Spada 2013]. More complex non-linear trends and abrupt sea-level variations have now also been recognized. Globally, these could manifest a regime shift between the late Holocene and the current rhythms of sea-level rise [Gehrels and Woodworth 2013], while locally they result from ocean circulation anomalies, steric effects and wind stress [Bromirski et al. 2011, Merrifield 2011]. Although isostatic readjustment affects the local rates of secular sea-level change [Milne and Mitrovica 1998, Peltier 2004], a possible impact on regional acceleration has been so far discounted [Douglas 1992, Jevrejeva et al. 2008, Woodworth et al. 2009] since the process evolves on a millennium time scale [Turcotte and Schubert 2002]. Here we report a previously unnoticed anomaly in the long-term sea-level acceleration of the Baltic Sea tide gauge records, and we explain it by the classical post-glacial rebound theory and numerical modeling of glacial isostasy. Contrary to previous assumptions, our findings demonstrate that isostatic compensation plays a role in the regional secular sea-level acceleration.</p>

scholarly journals Multidecadal Sea Level Variability in the Baltic Sea and Its Impact on Acceleration Estimations

2021 ◽  
Vol 8 ◽  
Author(s):  
Armin Agha Karimi ◽  
Mohammad Bagherbandi ◽  
Milan Horemuz
Keyword(s):  
Baltic Sea ◽  
Sea Level Rise ◽  
Sea Level ◽  
Tide Gauge ◽  
Linear Trend ◽  
The Baltic Sea ◽  
Warming Hiatus ◽  
The Baltic

Multidecadal sea level variation in the Baltic Sea is investigated from 1900 to 2020 deploying satellite and in situ datasets. As a part of this investigation, nearly 30 years of satellite altimetry data are used to compare with tide gauge data in terms of linear trend. This, in turn, leads to validation of the regional uplift model developed for the Fennoscandia. The role of North Atlantic Oscillation (NAO) in multidecadal variations of the Baltic Sea is also analyzed. Although NAO impacts the Baltic Sea level on seasonal to decadal time scales according to previous studies, it is not a pronounced factor in the multidecadal variations. The acceleration in the sea level rise of the basin is reported as statistically insignificant in recent studies or even decelerating in an investigation of the early 1990s. It is shown that the reason for these results relates to the global warming hiatus in the 1950s−1970s, which can be seen in all eight tide gauges used for this study. To account for the slowdown period, the acceleration in the basin is investigated by fitting linear trends to time spans of six to seven decades, which include the hiatus. These results imply that the sea level rise is accelerated in the Baltic Sea during the period 1900–2020.

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