Mapping Sea Surface Height Using New Concepts of Kinematic GNSS Instruments

For over 25 years, satellite altimetry observations have provided invaluable information about sea-level variations, from Global Mean Sea-Level to regional meso-scale variability. However, this information remains difficult to extract in coastal areas, where the proximity to land and complex dynamics create complications that are not sufficiently accounted for in current models. Detailed knowledge of local hydrodynamics, as well as reliable sea-surface height measurements, is required to improve and validate altimetry measurements. New kinematic systems based on Global Navigation Satellite Systems (GNSS) have been developed to map the sea surface height in motion. We demonstrate the capacity of two of these systems, designed to measure the height at a centimetric level: (1) A GNSS floating carpet towed by boat (named CalNaGeo); and (2) a combination of GNSS antenna and acoustic altimeter (named Cyclopée) mounted on an unmanned surface vehicle (USV). We show that, at a fixed point, these instruments provide comparable accuracy to the best available tide gauge systems. When moving at up to 7 knots, the instrument velocity does not affect the sea surface height accuracy, and the two instruments agree at a cm-level.

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Performance Assessment of GNSS-R Polarimetric Observations for Sea Level Monitoring

10.5194/egusphere-egu21-12709 ◽

2021 ◽

Author(s):

Mahmoud Rajabi ◽

Mstafa Hoseini ◽

Hossein Nahavandchi ◽

Maximilian Semmling ◽

Markus Ramatschi ◽

...

Keyword(s):

Time Series ◽

Circular Polarization ◽

Sea Level ◽

Tide Gauge ◽

Satellite System ◽

Sea Surface ◽

Analysis Tool ◽

Lower Accuracy ◽

Coastal Sea ◽

Global Navigation Satellite

Determination and monitoring of the mean sea level especially in the coastal areas are essential, environmentally, and as a vertical datum. Ground-based Global Navigation Satellite System Reflectometry (GNSS-R) is an innovative way which is becoming a reliable alternative for coastal sea-level altimetry. Comparing to traditional tide gauges, GNSS-R can offer different parameters of sea surface, one of which is the sea level. The measurements derived from this technique can cover wider areas of the sea surface in contrast to point-wise observations of a tide gauge. &#160;We use long-term ground-based GNSS-R observations to estimate sea level. The dataset includes one-year data from January to December 2016. The data was collected by a coastal GNSS-R experiment at the Onsala space observatory in Sweden. The experiment utilizes three antennas with different polarization designs and orientations. The setup has one up-looking, and two sea-looking antennas at about 3 meters above the sea surface level. The up-looking antenna is Right-Handed Circular Polarization (RHCP). The sea-looking antennas with RHCP and Left-Handed Circular Polarization (LHCP) are used for capturing sea reflected Global Positioning System (GPS) signals. A dedicated reflectometry receiver (GORS type) provides In-phase and Quadrature (I/Q) correlation sums for each antenna based on the captured interferometric signal. The generated time series of I/Q samples from different satellites are analyzed using the Least Squares Harmonic Estimation (LSHE) method. This method is a multivariate analysis tool which can flexibly retrieve the frequencies of a time series regardless of possible gaps or unevenly spaced sampling. The interferometric frequency, which is related to the reflection geometry and sea level, is obtained by LSHE with a temporal resolution of 15&#160;minutes. The sea level is calculated based on this frequency in six modes from the three antennas in GPS L1 and L2 signals.Our investigation shows that the sea-looking antennas perform better compared to the up-looking antenna. The highest accuracy is achieved using the sea-looking LHCP antenna and GPS L1 signal. The annual Root Mean Square Error (RMSE) of 15-min GNSS-R water level time series compared to tide gauge observations is 3.7 (L1) and 5.2 (L2) cm for sea-looking LHCP, 5.8 (L1) and 9.1 (L2) cm for sea-looking RHCP, 6.2 (L1) and 8.5 (L2) cm for up-looking RHCP. It is worth noting that the GPS IIR block satellites show lower accuracy due to the lack of L2C code. Therefore, the L2 observations from this block are eliminated.

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Assessment of the Jason-2 Extension to the TOPEX/Poseidon, Jason-1 Sea-Surface Height Time Series for Global Mean Sea Level Monitoring

Marine Geodesy ◽

10.1080/01490419.2010.491029 ◽

2010 ◽

Vol 33 (sup1) ◽

pp. 447-471 ◽

Cited By ~ 53

Author(s):

B. D. Beckley ◽

N. P. Zelensky ◽

S. A. Holmes ◽

F. G. Lemoine ◽

R. D. Ray ◽

...

Keyword(s):

Time Series ◽

Sea Level ◽

Sea Surface Height ◽

Sea Surface ◽

Mean Sea Level ◽

Global Mean Sea Level ◽

Global Mean ◽

Level Monitoring

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An Assessment of Vertical Land Movement to Support Coastal Hazards Planning in Washington State

Water ◽

10.3390/w13030281 ◽

2021 ◽

Vol 13 (3) ◽

pp. 281

Author(s):

Tyler J. Newton ◽

Ray Weldon ◽

Ian M. Miller ◽

David Schmidt ◽

Guillaume Mauger ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Tide Gauge ◽

Puget Sound ◽

Global Navigation Satellite Systems ◽

Coastal Hazards ◽

Cascadia Subduction Zone ◽

Tide Gauge Records ◽

Relative Sea Level ◽

Satellite Systems

The sea and land change elevation spatially and temporally from a multitude of processes, so it is necessary to constrain the movement of both to evaluate how coastlines will evolve and how those evolving coastlines will impact the natural and built environment over time. We combine land movement observations from global navigation satellite systems (GNSSs), leveling of geodetic monuments, and tide gauge records with a tectonic model of the Cascadia subduction zone to constrain absolute rates of vertical land movement in coastal Washington. We infer rates of vertical land movement in areas lacking direct observations by interpolating high-quality land movement observations and a discretely sampled interseismic locking model. Here we present a model of absolute vertical land movement that is combined with sea level rise estimates to inform local relative sea level projections on a community-scale. The most rapid vertical uplift (~3.5 mm/year) of the land is found across the northwest Olympic Peninsula, which currently outpaces sea level rise. Conversely, some areas, including a stretch of the northern Pacific Ocean coast from La Push to Kalaloch and the southern Puget Sound, are found to be subsiding at 0.5–1.0 mm/year, exacerbating the rate of relative sea level rise and thereby increasing the vulnerability of coastal communities.

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Constraining Wind Stress Products with Sea Surface Height Observations and Implications for Pacific Ocean Sea Level Trend Attribution*

Journal of Climate ◽

10.1175/jcli-d-12-00105.1 ◽

2012 ◽

Vol 25 (23) ◽

pp. 8164-8176 ◽

Cited By ~ 65

Author(s):

Shayne McGregor ◽

Alexander Sen Gupta ◽

Matthew H. England

Keyword(s):

Sea Level ◽

Wind Stress ◽

Surface Wind ◽

Sea Surface Height ◽

Sea Surface ◽

Water Model ◽

Mean Sea Level ◽

Sea Level Trend ◽

Global Mean Sea Level ◽

Global Mean

Abstract A number of global surface wind datasets are available that are commonly used to examine climate variability or trends and as boundary conditions for ocean circulation models. However, discrepancies exist among these products. This study uses observed Archiving, Validation, and Interpretation of Satellite Oceanographic (AVISO) sea surface height anomalies (SSHAs) as a means to help constrain the fidelity of these products in the tropical region. Each wind stress product is used to force a linear shallow water model (SWM) and the resulting hindcast thermocline depth anomalies are converted to SSHAs. The resulting SSHAs are then assessed to see how well they reproduce the dominant EOF modes of observed variability and the regional (global mean removed) sea level trend (1993–2007) in each of the three ocean basins. While the results suggest that all wind datasets reproduce the observed interannual variability with reasonable fidelity, the two SWM hindcasts that produce the observed linear trend with the highest fidelity are those incorporating interim ECMWF Re-Analysis (ERA-Interim) and Wave- and Anemometer-Based Sea Surface Wind (WASWind) forcing. The role of surface wind forcing (i.e., upper ocean heat content redistribution) versus global mean sea level change (i.e., including the additional contributions of glacier and ice sheet melt along with ocean thermal expansion) on the recent dramatic increase in western equatorial Pacific island sea level is then reassessed. The results suggest that the recent sea level increase cannot be explained solely by wind stress forcing, regardless of the dataset used; rather, the global mean sea level signal is required to fully explain this observed recent abrupt sea level rise and to better explain the sea level variability of the last 50–60 years.

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Measuring Coastal Absolute Sea-Level Changes Using GNSS Interferometric Reflectometry

Remote Sensing ◽

10.3390/rs13214319 ◽

2021 ◽

Vol 13 (21) ◽

pp. 4319

Author(s):

Dongju Peng ◽

Lujia Feng ◽

Kristine M. Larson ◽

Emma M. Hill

Keyword(s):

Sea Level ◽

Satellite Altimetry ◽

Tide Gauge ◽

Global Navigation Satellite Systems ◽

Coastal Zones ◽

Sea Level Changes ◽

Tide Gauge Records ◽

Sea Levels ◽

Satellite Systems ◽

Linear Trends

Rising sea levels pose one of the greatest threats to coastal zones. However, sea-level changes near the coast, particularly absolute sea-level changes, have been less well monitored than those in the open ocean. In this study, we aim to investigate the potential of Global Navigation Satellite Systems Interferometric Reflectometry (GNSS-IR) to measure coastal absolute sea-level changes and tie on-land (coastal GNSS) and offshore (satellite altimetry) observations into the same framework. We choose three coastal GNSS stations, one each in regions of subsidence, uplift and stable vertical land motions, to derive both relative sea levels and sea surface heights (SSH) above the satellite altimetry reference ellipsoid from 2008 to 2020. Our results show that the accuracy of daily mean sea levels from GNSS-IR is <1.5 cm compared with co-located tide-gauge records, and amplitudes of annual cycle and linear trends estimated from GNSS-IR measurements and tide-gauge data agree within uncertainty. We also find that the de-seasoned and de-trended SSH time series from GNSS-IR and collocated satellite altimetry are highly correlated and the estimated annual amplitudes and linear trends statistically agree well, indicating that GNSS-IR has the potential to monitor coastal absolute sea-level changes and provide valuable information for coastal sea-level and climate studies.

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Identifying 2010 Xynthia Storm Signature in GNSS-R-Based Tide Records

Remote Sensing ◽

10.3390/rs11070782 ◽

2019 ◽

Vol 11 (7) ◽

pp. 782 ◽

Cited By ~ 5

Author(s):

Phuong Lan Vu ◽

Minh Cuong Ha ◽

Frédéric Frappart ◽

José Darrozes ◽

Guillaume Ramillien ◽

...

Keyword(s):

Atmospheric Pressure ◽

Tide Gauge ◽

Signal To Noise Ratio ◽

Atlantic Coast ◽

Singular Spectrum Analysis ◽

Global Navigation Satellite Systems ◽

Blind Separation ◽

Tide Gauge Records ◽

Satellite Systems ◽

Global Navigation Satellite

In this study, three months of records (January–March 2010) that were acquired by a geodetic Global Navigation Satellite Systems (GNSS) station from the permanent network of RGP (Réseau GNSS Permanent), which was deployed by the French Geographic Institute (IGNF), located in Socoa, in the south of the Bay of Biscay, were used to determine the tide components and identify the signature of storms on the signal to noise ratio (SNR) during winter 2010. The Xynthia storm hit the French Atlantic coast on the 28th of February 2010, causing large floods and damages from the Gironde to the Loire estuaries. Blind separation of the tide components and of the storm signature was achieved while using both a singular spectrum analysis (SSA) and a continuous wavelet transform (CWT). A correlation of 0.98/0.97 and root mean square error (RMSE) of 0.21/0.28 m between the tide gauge records of Socoa and our estimates of the sea surface height (SSH) using the SSA and the CWT, respectively, were found. Correlations of 0.76 and 0.7 were also obtained between one of the modes from the SSA and atmospheric pressure from a meteorological station and a mode of the SSA. Particularly, a correlation reaches to 0.76 when using both the tide residual that is associated to surges and atmospheric pressure variation.

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