The effect of ocean tidal loading on satellite altimetry over Antarctica

Vertical displacements of emerged land caused by oceanic tidal loading are of the order of several tens of millimetres in polar regions. They constitute a long wavelength signal, the amplitude of which is comparable to elevation changes that might be associated with climate-driven changes in ice-sheet volume. Using bilinear interpolation on a 1° by 1° global grid, we examine the amplitudes and phases of vertical displacements caused at any given epoch by the eight most important ocean tide constituents of recent ocean tide models, extrapolated to high latitudes. This permits estimation of the oceanic tidal loading corrections to measurements made by a satellite altimeter along the satellite ground track. We have done so systematically over Antarctica, for a scenario flight of ICESAT, which carries the Geoscience Laser Altimeter System (GLAS), whose primary science goal is to monitor ice-sheet mass balance. Ocean loading tide corrections near the coast of Antarctica can reach several centimetres; overall they average about 10 min.

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A comparison of predicted and observed ocean tidal loading in Alaska

Geophysical Journal International ◽

10.1093/gji/ggaa323 ◽

2020 ◽

Vol 223 (1) ◽

pp. 454-470

Author(s):

H R Martens ◽

M Simons

Keyword(s):

Measurement Error ◽

Upper Mantle ◽

Ocean Tide ◽

Spherically Symmetric ◽

Surface Displacements ◽

Tidal Harmonics ◽

Earth Models ◽

Ocean Tidal Loading ◽

Tidal Loading ◽

Ocean Tide Models

SUMMARY We investigate the elastic and anelastic response of the crust and upper mantle across Alaska to mass loading by ocean tides. GPS-inferred surface displacements recorded by the Plate Boundary Observatory network are compared with predictions of deformation associated with the redistribution of ocean water due to the tides. We process more than 5 yr of GPS data from 131 stations using a kinematic precise point positioning algorithm and estimate tidal contributions using harmonic analysis. We also forward calculate load-induced surface displacements by convolving ocean-tide models with load Green’s functions derived from spherically symmetric Earth models. We make the comparisons for dominant tidal harmonics in three frequency bands: semidiurnal (M2), diurnal (O1) and fortnightly (Mf). Vector differences between predicted and observed ocean tidal loading (OTL) displacements are predominantly sub-mm in magnitude in all three frequency bands and spatial components across the network, with larger residuals of up to several mm in some coastal areas. Accounting for the effects of anelastic dispersion in the upper mantle using estimates of Q from standard Earth models reduces the residuals for the M2 harmonic by an average of 0.1–0.2 mm across the network and by more than 1 mm at some individual stations. For the relatively small Mf tide, the effects of anelastic dispersion (<0.03 mm) are undetectable within current measurement error. Incorporating a local ocean-tide model for the northeastern Pacific Ocean reduces the M2 vertical residuals by an average of 0.2 mm, with improvements of up to 5 mm at some coastal stations. Estimated RMS observational uncertainties in the vertical component for the M2 and O1 tides are approximately ±0.08 mm at the two-sigma level (±0.03 mm in the horizontal components), and ±0.21 mm for the Mf harmonic (±0.07 mm in the horizontal components). For the M2 harmonic, discrepancies between predicted and observed OTL displacements exceed observational uncertainties by about one order of magnitude. None of the ocean tide and Earth model combinations is found to reduce the M2 residuals below the observational uncertainty, and no single forward model provides a best fit to the observed displacements across all tidal harmonics and spatial components. For the O1 harmonic, discrepancies between predicted and observed displacements are generally several-fold larger than the observational uncertainties. For the Mf harmonic, the discrepancies are roughly within a factor of two of the observational uncertainties. We find that discrepancies between predicted and observed OTL displacements can be significantly reduced by removing a network-uniform tidal-harmonic displacement, and that the remaining discrepancies exhibit some regional-scale spatial coherency, particularly for the M2 harmonic. We suggest that the remaining discrepancies for the M2, O1 and Mf tides cannot be fully explained by measurement error and instead convey information about deficiencies in ocean-tide models and deviations from spherically symmetric Earth structure.

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Assessment of continental hydrosphere loading using GNSS measurements

Reports on Geodesy and Geoinformatics ◽

10.1515/rgg-2016-0020 ◽

2016 ◽

Vol 101 (1) ◽

pp. 36-53 ◽

Cited By ~ 1

Author(s):

Michał Zygmunt ◽

Marcin Rajner ◽

Tomasz Liwosz

Keyword(s):

Hydrological Model ◽

Water Volume ◽

International Gnss Service ◽

Surface Loading ◽

Vertical Displacements ◽

Ocean Tidal Loading ◽

Tidal Loading ◽

Gnss Measurements ◽

Gnss Observations ◽

Vertical Deformations

Abstract Presented paper is dedicated to problems of deformation of the Earth's crust as a response to the surface loading caused by continental waters. The aim of this study was to specify areas particularly vulnerable to studied deformation and to compare calculated and observed displacements. Information of the continental water volume was taken from the WaterGAP Global Hydrological Model. Calculated values of the deformations were verified with the results obtained with programs SPOTL and grat. Vertical deformations were almost 10 times higher than the deformation in the horizontal plane, for which reason later part of the paper focuses on the former. In order to check agreement of the calculated and observed deformation 23 stations of International GNSS Service (IGS) were selected and divided into three groups (inland, near the shoreline and islands). Before comparison outliers and discontinuities were removed from GNSS observations. Modelled and observed signals were centred. The analysed time series of the vertical displacements showed that only for the inland stations it is possible to effectively remove displacements caused by mass transfer in the hydrosphere. For stations located in the coastal regions or islands, it is necessary to consider additional movement effects resulting from indirect ocean tidal loading or atmosphere loading.

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Land-ice elevation changes from photon-counting swath altimetry: first applications over the Antarctic ice sheet

Journal of Glaciology ◽

10.3189/2015jog14j048 ◽

2015 ◽

Vol 61 (225) ◽

pp. 17-28 ◽

Cited By ~ 13

Author(s):

Duncan A. Young ◽

Laura E. Lindzey ◽

Donald D. Blankenship ◽

Jamin S. Greenbaum ◽

Alvaro Garcia De Gorordo ◽

...

Keyword(s):

Dynamic Change ◽

High Surface ◽

Photon Counting ◽

Ice Sheet ◽

Test Case ◽

Laser Altimeter ◽

Surface Slopes ◽

Elevation Changes ◽

The Alamo ◽

Cross Track

AbstractSatellite altimetric time series allow high-precision monitoring of ice-sheet mass balance. Understanding elevation changes in these regions is important because outlet glaciers along ice-sheet margins are critical in controlling flow of inland ice. Here we discuss a new airborne altimetry dataset collected as part of the ICECAP (International Collaborative Exploration of the Cryosphere by Airborne Profiling) project over East Antarctica. Using the ALAMO (Airborne Laser Altimeter with Mapping Optics) system of a scanning photon-counting lidar combined with a laser altimeter, we extend the 2003–09 surface elevation record of NASA’s ICESat satellite, by determining cross-track slope and thus independently correcting for ICESat’s cross-track pointing errors. In areas of high slope, cross-track errors result in measured elevation change that combines surface slope and the actual Δz/Δt signal. Slope corrections are particularly important in coastal ice streams, which often exhibit both rapidly changing elevations and high surface slopes. As a test case (assuming that surface slopes do not change significantly) we observe a lack of ice dynamic change at Cook Ice Shelf, while significant thinning occurred at Totten and Denman Glaciers during 2003–09.

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Ocean tidal loading models assessment using 28 months of gravimetric tidal records in Dublin, Ireland

10.5194/egusphere-egu21-2422 ◽

2021 ◽

Author(s):

Przemysław Dykowski ◽

Kamila Karkowska ◽

Marcin Sękowski ◽

Paul Kane

Keyword(s):

International Association ◽

Sampling Rate ◽

Remote Access ◽

Absolute Gravity ◽

Joint Analysis ◽

Raspberry Pi ◽

Ocean Tide ◽

Loading Effect ◽

Ocean Tidal Loading ◽

Tidal Loading

In June of 2018 a project for the establishment of a modern permanent Absolute Gravity Network&#160; on the island of Ireland was initiated by the National Mapping Agency of Ireland, Ordnance Survey Ireland (OSi) with the cooperation of &#160;Institute of Geodesy and Cartography (IGiK), and Land and Property Services (LPS) in Northern Ireland. The project assumes conducting absolute gravity surveys of the network using &#160;the A10 absolute gravimeter on approximately 60 stations homogenously distributed on the island of Ireland.Data processing includes time variable corrections for body tides, barometric pressure, polar motion as well as ocean tidal loading. For Ireland the ocean tidal loading effect can reach peaks of between 400 nm/s2 on the west coast and 200 nm/s2 on the east coast. This effect is significant and up to now the authors are unaware of previous historical data or&#160; tidal gravity records being performed in Ireland. Hence it was considered as a valid component of the overall Absolute Gravity Project to evaluate the current situation with ocean tidal loading effect in Ireland using gravimetric tidal records in order to validate available ocean tidal loading models.In order to assure the most optimal use of ocean tidal model as well as minimize the errors of including ocean tidal correction in absolute gravity processing the LaCoste&Romberg model G spring gravimeter was installed at OSi headquarters in Phoenix Park, Dublin, Ireland. Over a continuous period of 28 months gravity record with more than 99% data completeness at near 2Hz sampling rate was conducted.The project data was acquired through using a self-programmed Raspberry Pi computer allowing for automatic download and remote access to the data.A set of CSR, DTU, EOT, FES, GOT, TPXO (ocean tide loading provider &#8211; Chalmers, http://holt.oso.chalmers.se/loading/) ocean tidal loading models were used in a joint analysis with the collected tidal record. Analysis included performing tidal adjustment of the gravity data in the ETERNA 3.40 (ET34-X-V73) as well as comparison of IAG (International Association of Geodesy) recommended model combinations with the collected data.Recommendations by the project team as to which of the ocean tidal models is most suitable to be used in Ireland for the purpose of absolute gravity measurements were made.

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Tidal Gravimetry in Polar Regions: An Observation Tool Complementary to Continuous GPS for the Validation of Ocean Tide Models

Geodetic and Geophysical Observations in Antarctica ◽

10.1007/978-3-540-74882-3_15 ◽

2008 ◽

pp. 267-280 ◽

Cited By ~ 1

Author(s):

Mirko Scheinert ◽

Andrés F. Zakrajsek ◽

Sergio A. Marenssi ◽

Reinhard Dietrich ◽

Lutz Eberlein

Keyword(s):

Ocean Tide ◽

Polar Regions ◽

Continuous Gps ◽

Ocean Tide Models

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ACCURACY ASSESSMENT OF RECENT GLOBAL OCEAN TIDE MODELS AROUND ANTARCTICA

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xlii-2-w7-1521-2017 ◽

2017 ◽

Vol XLII-2/W7 ◽

pp. 1521-1528 ◽

Cited By ~ 4

Author(s):

J. Lei ◽

F. Li ◽

S. Zhang ◽

H. Ke ◽

Q. Zhang ◽

...

Keyword(s):

Accuracy Assessment ◽

Weddell Sea ◽

Global Ocean ◽

Ocean Tide ◽

Polar Regions ◽

Ice Shelf ◽

Ice Shelves ◽

Ross Ice Shelf ◽

Shelf Region ◽

Ocean Tide Models

Due to the coverage limitation of T/P-series altimeters, the lack of bathymetric data under large ice shelves, and the inaccurate definitions of coastlines and grounding lines, the accuracy of ocean tide models around Antarctica is poorer than those in deep oceans. Using tidal measurements from tide gauges, gravimetric data and GPS records, the accuracy of seven state-of-the-art global ocean tide models (DTU10, EOT11a, GOT4.8, FES2012, FES2014, HAMTIDE12, TPXO8) is assessed, as well as the most widely-used conventional model FES2004. Four regions (Antarctic Peninsula region, Amery ice shelf region, Filchner-Ronne ice shelf region and Ross ice shelf region) are separately reported. The standard deviations of eight main constituents between the selected models are large in polar regions, especially under the big ice shelves, suggesting that the uncertainty in these regions remain large. Comparisons with in situ tidal measurements show that the most accurate model is TPXO8, and all models show worst performance in Weddell sea and Filchner-Ronne ice shelf regions. The accuracy of tidal predictions around Antarctica is gradually improving.

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Tidal loading in Nova Scotia: results from improved ocean tide models

Canadian Journal of Earth Sciences ◽

10.1139/e78-106 ◽

1978 ◽

Vol 15 (6) ◽

pp. 981-993 ◽

Cited By ~ 4

Author(s):

Christopher Beaumont ◽

Ross Boutilier

Keyword(s):

Nova Scotia ◽

Atlantic Ocean ◽

North Atlantic ◽

North Atlantic Ocean ◽

Numerical Models ◽

Ocean Tide ◽

Ocean Tide Model ◽

Phase Calibration ◽

Tidal Loading ◽

Ocean Tide Models

A re-examination of tilt and gravity observations from Nova Scotia in light of recent ocean tide studies confirms previous assertions that the M2 tide in the western North Atlantic Ocean is intermediate between the numerical models of Tiron, Sergeev, and Michurin, and of Zahel.Tilt calculations, using a new M2 ocean tide model, reinforce the conclusion that the crust beneath Nova Scotia is of a transitional type between oceanic and thickened continental and is more easily deformed than most other crustal types.The tilt observations are in poor agreement with the Jachens–Kuo model, JK25, of the O1 tide in the western North Atlantic Ocean. It is suggested that the gravity observations, from which JK25 was inferred, were subject to amplitude and phase calibration errors. These errors are estimated from a comparison with the M2 results.

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Elevation changes on the Greenland ice sheet from comparison of aircraft and ICESat laser-altimeter data

Annals of Glaciology ◽

10.3189/172756405781813050 ◽

2005 ◽

Vol 42 ◽

pp. 77-82 ◽

Cited By ~ 11

Author(s):

R. Thomas ◽

E. Frederick ◽

W. Krabill ◽

S. Manizade ◽

C. Martin ◽

...

Keyword(s):

Ice Sheet ◽

Greenland Ice Sheet ◽

Altimeter Data ◽

Aircraft Measurements ◽

Drainage Basins ◽

Laser Altimeter ◽

Ice Cloud ◽

Spatial Coverage ◽

First Results ◽

Elevation Changes

AbstractPrecise measurements of surface elevation on the Greenland ice sheet have been made almost every year since 1991 by an airborne scanning laser altimeter operated by NASA/Wallops Flight Facility. Results show substantial thinning over large areas near the coast, with a general increase in thinning rates since 1997, in the drainage basins of thinning glaciers, and a recent thickening in the southeast associated with very high snowfall in this region during 2003. Here, we present first results from the comparison of the aircraft data with similar measurements from the laser altimeter aboard NASA’s Ice, Cloud and land Elevation Satellite (ICESat), which was launched in January 2003. These show very close agreement with results inferred solely from the aircraft measurements, indicating that accuracies are similar for both datasets. Broad spatial coverage by satellite, together with the baseline dataset of aircraft measurements, offers the prospects of routine surveys of ice-sheet elevation changes by ICESat and follow-on missions.

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