scholarly journals Sea-level fingerprints emergent from GRACE mission data

2019 ◽  
Vol 11 (2) ◽  
pp. 629-646 ◽  
Author(s):  
Surendra Adhikari ◽  
Erik R. Ivins ◽  
Thomas Frederikse ◽  
Felix W. Landerer ◽  
Lambert Caron
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Ocean Circulation ◽  
Reference Frames ◽  
Sea Surface ◽  
Ocean Tide ◽  
Mantle Flow ◽  
Systematic Calculation ◽  
Ocean Tide Models ◽  
Grace Mission

Abstract. The Gravity Recovery and Climate Experiment (GRACE) mission data have an important, if not revolutionary, impact on how scientists quantify the water transport on the Earth's surface. The transport phenomena include land hydrology, physical oceanography, atmospheric moisture flux, and global cryospheric mass balance. The mass transport observed by the satellite system also includes solid Earth motions caused by, for example, great subduction zone earthquakes and glacial isostatic adjustment (GIA) processes. When coupled with altimetry, these space gravimetry data provide a powerful framework for studying climate-related changes on decadal timescales, such as ice mass loss and sea-level rise. As the changes in the latter are significant over the past two decades, there is a concomitant self-attraction and loading phenomenon generating ancillary changes in gravity, sea surface, and solid Earth deformation. These generate a finite signal in GRACE and ocean altimetry, and it may often be desirable to isolate and remove them for the purpose of understanding, for example, ocean circulation changes and post-seismic viscoelastic mantle flow, or GIA, occurring beneath the seafloor. Here we perform a systematic calculation of sea-level fingerprints of on-land water mass changes using monthly Release-06 GRACE Level-2 Stokes coefficients for the span April 2002 to August 2016, which result in a set of solutions for the time-varying geoid, sea-surface height, and vertical bedrock motion. We provide both spherical harmonic coefficients and spatial maps of these global field variables and uncertainties therein (https://doi.org/10.7910/DVN/8UC8IR; Adhikari et al., 2019). Solutions are provided for three official GRACE data processing centers, namely the University of Texas Austin's Center for Space Research (CSR), GeoForschungsZentrum Potsdam (GFZ), and Jet Propulsion Laboratory (JPL), with and without rotational feedback included and in both the center-of-mass and center-of-figure reference frames. These data may be applied for either study of the fields themselves or as fundamental filter components for the analysis of ocean-circulation- and earthquake-related fields or for improving ocean tide models.

scholarly journals Sea-level fingerprints emergent from GRACE mission data

2019 ◽  
Author(s):  
Surendra Adhikari ◽  
Erik R. Ivins ◽  
Thomas Frederikse ◽  
Felix W. Landerer ◽  
Lambert Caron
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Ocean Circulation ◽  
Sea Surface ◽  
Ocean Tide ◽  
Mantle Flow ◽  
Data Set ◽  
Systematic Calculation ◽  
Ocean Tide Models ◽  
Grace Mission

Abstract. The Gravity Recovery and Climate Experiment (GRACE) mission data set has an important, if not revolutionary, impact on how scientists quantify the water transport on the Earth's surface. The transport phenomena include land hydrology, physical oceanography, atmospheric moisture flux, and climate related changes to the cryosphere. The mass transport observed by the satellite system also includes solid Earth motions caused by, for example, great subduction zone earthquakes and glacial isostatic adjustment (GIA) processes. When coupled with altimetry, this space gravimetry data provides a powerful framework for studying climate related changes on interdecadal time scales, such as ice mass loss and sea-level rise. As the changes in the latter are significant over the past two decades, there is a concomitant self-attraction and loading phenomenon generating ancillary changes in gravity, sea surface, and solid Earth deformation. These generate a finite signal in GRACE and ocean altimetry and it may often be desirable to isolate and remove them for the purpose of understanding, for example, ocean circulation changes and post-seismic viscoelastic mantle flow, or GIA, occurring beneath the sea floor. Here we provide a systematic calculation of sea-level fingerprints of continental (water) mass changes using monthly Release-06 GRACE Level-2 Stokes coefficients for the span April 2002 to August 2016 (Adhikari et al., 2019, https://doi.org/10.7910/DVN/8UC8IR), which result in a set of spherical harmonic coefficients for the time-varying geoid, sea surface, and vertical bedrock motion. A simple sum of the spectra yield monthly maps of the desired field and uncertainties therein. These may be applied for either study of the fields themselves or as fundamental filter components for the analysis of ocean circulation and earthquake related fields, or for improving ocean tide models.

scholarly journals Reduction of the 59-day error signal in the Mean Sea Level derived from TOPEX/Poseidon, Jason-1 and Jason-2 data with the latest FES and GOT ocean tide models

2016 ◽  
Author(s):  
Lionel Zawadzki ◽  
Michaël Ablain ◽  
Loren Carrere ◽  
Richard D. Ray ◽  
Nikita P. Zelensky ◽  
...  
Keyword(s):  
Sea Level ◽  
Ocean Circulation ◽  
Global Ocean ◽  
Ocean Tide ◽  
Frequency Error ◽  
Mean Sea Level ◽  
Global Ocean Circulation ◽  
Ocean Tide Models ◽  
Annual Signal ◽  
Societal Interest

Abstract. Mean sea level (MSL) is a prominent indicator of climatic change (Ablain et al., 2015; Cazenave et al., 2014; Leuliette and Willis, 2011), and is therefore of great scientific and societal interest. Since the beginning of the altimeter mission TOPEX/Poseidon, followed by Jason-1 and Jason-2 on similar orbits, and many other missions on different orbits (ERS, EnviSat, etc.), MSL products became essential to the comprehension of Global ocean circulation. Since early in the TOPEX/Poseidon mission (Nerem, 1995) a suspicious signal, having period near 59 days and amplitude of roughly 5 mm, was apparent in the GMSL record. Compared with the 4–5 mm amplitude of the annual signal (Minster et al., 1999), the suspicious 59-day signal has understandably attracted attention. Moreover, the same signal has been subsequently detected in Jason-1 and later Jason-2 MSLs. In 2010, it was the subject of a dedicated session at the Ocean Surface Topography Science Team (OSTST) meeting in Lisbon. The conclusions were this signal is the aliasing of a higher frequency error inherited from the tide model correction: the semi-diurnal wave S2. The source of this error was mainly attributed to TOPEX measurements which are assimilated in ocean tide models. When these models are used in the computation of TOPEX/Poseidon MSL, most of the error cancels. However, this error is communicated to Jason-1 and Jason-2 MSLs. Since 2010, considerable efforts have been undertaken within the ocean tide community in order to correct ocean tide S2-waves from this error, particularly in the Goddard Ocean Tide (GOT) and Finite Element Solution (FES) latest versions. The present paper aims at assessing, quantifying and characterizing the reduction of the 58.77-day error thanks to the latest releases.

scholarly journals Regional Evaluation of Minor Tidal Constituents for Improved Estimation of Ocean Tides

2021 ◽  
Vol 13 (16) ◽  
pp. 3310
Author(s):  
Michael G. Hart-Davis ◽  
Denise Dettmering ◽  
Roman Sulzbach ◽  
Maik Thomas ◽  
Christian Schwatke ◽  
...  
Keyword(s):  
Sea Level ◽  
Satellite Altimetry ◽  
Tide Gauge ◽  
Sea Surface ◽  
Global Ocean ◽  
Ocean Tide ◽  
Ocean Tides ◽  
Tidal Constituents ◽  
Ocean Tide Models ◽  
Tidal Correction

Satellite altimetry observations have provided a significant contribution to the understanding of global sea surface processes, particularly allowing for advances in the accuracy of ocean tide estimations. Currently, almost three decades of satellite altimetry are available which can be used to improve the understanding of ocean tides by allowing for the estimation of an increased number of minor tidal constituents. As ocean tide models continue to improve, especially in the coastal region, these minor tides become increasingly important. Generally, admittance theory is used by most global ocean tide models to infer several minor tides from the major tides when creating the tidal correction for satellite altimetry. In this paper, regional studies are conducted to compare the use of admittance theory to direct estimations of minor tides from the EOT20 model to identify which minor tides should be directly estimated and which should be inferred. The results of these two approaches are compared to two global tide models (TiME and FES2014) and in situ tide gauge observations. The analysis showed that of the eight tidal constituents studied, half should be inferred (2N2, ϵ2, MSF and T2), while the remaining four tides (J1, L2, μ2 and ν2) should be directly estimated to optimise the ocean tidal correction. Furthermore, for certain minor tides, the other two tide models produced better results than the EOT model, suggesting that improvements can be made to the tidal correction made by EOT when incorporating tides from the two other tide models. Following on from this, a new approach of merging tidal constituents from different tide models to produce the ocean tidal correction for satellite altimetry that benefits from the strengths of the respective models is presented. This analysis showed that the tidal correction created based on the recommendations of the tide gauge analysis provided the highest reduction of sea-level variance. Additionally, the combination of the EOT20 model with the minor tides of the TiME and FES2014 model did not significantly increase the sea-level variance. As several additional minor tidal constituents are available from the TiME model, this opens the door for further investigations into including these minor tides and optimising the tidal correction for improved studies of the sea surface from satellite altimetry and in other applications, such as gravity field modelling.

Impact of sea level variations on hydrographic survey around Taiwan

2020 ◽  
Author(s):  
Wen-Hau Lan ◽  
Chung-Yen Kuo ◽  
Sheng-Fong Lin ◽  
Chien-Hsing Lu
Keyword(s):  
Sea Level ◽  
Tide Gauge ◽  
Temporal Changes ◽  
Altimeter Data ◽  
Ocean Tide ◽  
Ocean Tides ◽  
Sea Level Anomalies ◽  
Sea Level Variations ◽  
Ocean Tide Models ◽  
And Sea Level

<p>Taiwan is an island entirely surrounded by oceans, so living and economics are significantly influenced by the oceans. The electronic navigational chart system is extremely important for improving the safety of marine navigation and ocean depth is the essential data for electronic charts. Sea surface variations affected by ocean tide and sea level change are the main error sources in hydrographic surveys since the traditional tidal correction only using tide gauge stations, ignoring geographically non-uniform ocean tides and sea level anomalies around Taiwan. In this research, we evaluate two factors impacting the accuracy of hydrographic surveys, including ocean tides and seasonal sea level variations, using tide gauge records, satellite altimeter data and ocean tide models around Taiwan, and also analyze the accuracy of the ocean tide models around Taiwan. In addition, sea level anomalies are strongly influenced by climate changes in recent years. An understanding of seasonal sea level cycle and its spatial and temporal changes are importance because its temporal changes can result in the variation of the frequency and magnitude of coastal hazards. Therefore, we will apply the Ensemble Empirical Mode Decomposition to sea level data to assess the stability of the long-term seasonal sea level fluctuations with time.</p>

scholarly journals The sensitivity of ocean tide loading displacements to the structure of the upper mantle and crust of Taiwan Island

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Xiaowen You ◽  
Linguo Yuan
Keyword(s):  
Shear Modulus ◽  
Solid Earth ◽  
Upper Mantle ◽  
Vertical Component ◽  
Ocean Tide ◽  
Model Errors ◽  
Ocean Tide Loading ◽  
Taiwan Island ◽  
Ocean Tide Models ◽  
Physical Quantities

AbstractOcean tide loading (OTL) displacements are sensitive to the shallow structure of the solid Earth; hence, the high-resolution spatial pattern of OTL displacement can provide knowledge to constrain the shallow Earth structure, especially in coastal areas. In this study, we investigate the sensitivity of the modeled M2 OTL displacement over Taiwan Island to perturbations of three physical quantities, namely, the density, bulk modulus, and shear modulus in the upper mantle and crust. Then, we compare the sensitivity of the modeled M2 OTL displacement to Earth models with the sensitivity to ocean tide models using root mean square (RMS) differences. We compute the displacement Green’s function and OTL displacement relative to the center of mass of the solid Earth (CE) reference frame, analyze the sensitivity to the three physical quantities in the CRUST1.0 model and the Preliminary Reference Earth Model (PREM), and present their spatial patterns. We find that displacement Green’s functions and OTL displacements are more sensitive to the two elastic moduli than the density in the upper mantle and crust. Moreover, their distinctive sensitivity patterns suggest that the three physical quantities might be constrained independently. The specific relationships between the perturbed structural depths and the distance ranges of peak sensitivities from the observation points to the coastline revealed by the shear modulus can mitigate the nonuniqueness problem in inversion. In particular, the horizontal tidal components observed by the Global Positioning System (GPS) can yield better results in inversions than the vertical component owing to the smaller OTL model errors and the higher structural sensitivity (except for the shear modulus in the asthenosphere).

scholarly journals Comparison of Two Methods to Assess Ocean Tide Models

2012 ◽  
Vol 29 (8) ◽  
pp. 1159-1167 ◽  
Author(s):  
Xiaochun Wang ◽  
Yi Chao ◽  
C. K. Shum ◽  
Yuchan Yi ◽  
Hok Sum Fok
Keyword(s):  
Root Mean Square ◽  
Current Method ◽  
Spatial Location ◽  
Sea Surface ◽  
Root Mean Square Difference ◽  
Ocean Tide ◽  
Mean Square ◽  
Discrepancy Method ◽  
Mean Square Difference ◽  
Ocean Tide Models

Abstract Two methods to assess ocean tide models, the current method and the total discrepancy method, are compared from the perspective of their relationship to the root-mean-square difference of tidal sea surface height (total discrepancy). These two methods are identically the same when there is only one spatial location involved. When there is more than one spatial location involved, the current method is the root-mean-square difference of total discrepancy at each location, and the total discrepancy method is the averaged total discrepancy. The result from the current method is always larger than or equal to that from the total discrepancy method. Monte Carlo simulation indicates that the difference between their results increases with increasing spatial variability of total discrepancy. Both of these two methods are then used to compare the two tide models of the Ocean Surface Topography Mission (OSTM)/Jason-2. The discrepancy of these two models as measured by the total discrepancy method decreases monotonically from around 11.4 to 2.2 cm with depth increasing from 50 to 1000 m. In contrast, the discrepancy measured by the current method varies from 21.6 to 2.9 cm. Though the discrepancy measured by the current method decreases with increasing depth in general, there are abrupt increases at several depth ranges. These increases are associated with large spatial variability of total discrepancy and their physical explanation is elusive. Because the total discrepancy method is consistent with the root-mean-square difference of tidal sea surface height and its interpretation is straightforward, its usage is suggested.

A new high resolution Mean Sea Surface (DTU21MSS) for improved sea level monitoring

2021 ◽  
Author(s):  
Ole Baltazar Andersen ◽  
Adil Abulaitijiang ◽  
Shengjun Zhang ◽  
Stine Kildegaard Rose
Keyword(s):  
Sea Level ◽  
Sea Surface ◽  
Ocean Tide ◽  
Simultaneous Estimation ◽  
Polar Regions ◽  
Annual Variations ◽  
Sea Level Anomalies ◽  
Ocean Tide Model ◽  
Mean Sea Surface ◽  
The Mean

<p>A new Mean Sea Surface (DTU21MSS) for referencing sea level anomalies from satellite altimetry is presented. The major new advance leading up to the release of this MSS the use of 5 years of Sentinel-3A and an improved 10 years Cryosat-2 LRM+SAR+SARin record including retracked altimetry in Polar regions using the SAMOSA+ physical retracker via the ESA GPOD facility.</p><p>A new processing chain with updated editing and data filtering has been implemented. The filtering implies, that the 20Hz sea surface height data are filtered using the Parks-McClellan filter to derive 1Hz. This has a clear advantage over the 1 Hz boxcar filter in not introducing sidelobes degrading the MSS in the 10-40 km wavelength band. Similarly, the use of consistent ocean tide model for the Mean sea surface improves the usage of sun-syncronous satellites in high latitudes.</p><p>The presentation will also focus on the difficult issues to consolidating Cryosat-2 and Sentinel-3 onto a past 20 year mean sea surface. This is implemented using simultaneous estimation of the mean, sea level trend and annual and semi-annual variations in sea level.  </p>

scholarly journals Nemo-Nordic 2.0: operational marine forecast model for the Baltic Sea

2021 ◽  
Vol 14 (9) ◽  
pp. 5731-5749
Author(s):  
Tuomas Kärnä ◽  
Patrik Ljungemyr ◽  
Saeed Falahat ◽  
Ida Ringgaard ◽  
Lars Axell ◽  
...  
Keyword(s):  
Sea Ice ◽  
Baltic Sea ◽  
Water Temperature ◽  
Sea Level ◽  
Ocean Circulation ◽  
Circulation Model ◽  
Sea Surface ◽  
Model Assessment ◽  
The Baltic Sea ◽  
The Baltic

Abstract. This paper describes Nemo-Nordic 2.0, an operational marine model for the Baltic Sea. The model is used for both near-real-time forecasts and hindcast purposes. It provides estimates of sea surface height, water temperature, salinity, and velocity, as well as sea ice concentration and thickness. The model is based on the NEMO (Nucleus for European Modelling of the Ocean) circulation model and the previous Nemo-Nordic 1.0 configuration by Hordoir et al. (2019). The most notable updates include the switch from NEMO version 3.6 to 4.0, updated model bathymetry, and revised bottom friction formulation. The model domain covers the Baltic Sea and the North Sea with approximately 1 nmi resolution. Vertical grid resolution has been increased from 3 to 1 m in the surface layer. In addition, the numerical solver configuration has been revised to reduce artificial mixing to improve the representation of inflow events. Sea ice is modeled with the SI3 model instead of LIM3. The model is validated against sea level, water temperature, and salinity observations, as well as Baltic Sea ice chart data for a 2-year hindcast simulation (October 2014 to September 2016). Sea level root mean square deviation (RMSD) is typically within 10 cm throughout the Baltic basin. Seasonal sea surface temperature variation is well captured, although the model exhibits a negative bias of approximately −0.5 ∘C. Salinity RMSD is typically below 1.5 g kg−1. The model captures the 2014 major Baltic inflow event and its propagation to the Gotland Deep. The model assessment demonstrates that Nemo-Nordic 2.0 can reproduce the hydrographic features of the Baltic Sea.

scholarly journals INFLUENCE OF HISTORICAL BATHYMETRIC CHANGES DUE TO URBANIZATION ON THE VULNERABILITY OF STORM SURGE IN TOKYO BAY

2017 ◽  
pp. 22 ◽  
Author(s):  
Akifumi Tatekoji ◽  
Ryota Nakamura ◽  
Tomoya Shibayama
Keyword(s):  
Sea Level ◽  
Storm Surge ◽  
Great Influence ◽  
Water Area ◽  
Tokyo Bay ◽  
Ocean Tide ◽  
Shallow Water Area ◽  
Shallow Area ◽  
Ocean Tide Models ◽  
Bathymetric Changes

In this study, the influence of historical changes on bathymetry to the intensity and features of the storm surge in the Tokyo Bay is evaluated using the meteorology-ocean-tide models. In detail, storm surge of 1917 is reproduced using an historical Taisho Typhoon of 1917 in order to quantify the influence of bathymetric changes. This paper possesses two important findings. The first is that past storm surge occurred mainly because of shallow water area spanning over the inner bay which can be characteristics of past bathymetry. The second is that the high vulnerable area affected by storm surge has been shifted from mudflat shallow area in the inner bay to the below-sea-level inland area, due to landfill and urbanization which have continued approximately 100 years after the storm. As a conclusion, the bathymetry shifting due to human activity has a great influence to changing the effects of coastal disasters even in the same location.

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