Determining Coastal Mean Dynamic Topography by Geodetic Methods

Huang, Jianliang

doi:10.1002/2017gl076020

Cited by 23 publications

(26 citation statements)

References 22 publications

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“…By far the most important factor is the quality of the geoid, and in particular its fine scale structure corresponding to limiting the omission error in Eq 2. This is similar to what was seen by Huang (2017). This is illustrated by Figure 4, which repeats Figure 3 but with the EIGEN6-C4 geoid truncated at degree 300 roughly corresponding to the degree and order of a satellite only geoid from GOCE.…”

Section: Evaluation and Representativeness Of Tide Gauge Mdtsupporting

confidence: 82%

“…Currently SAR altimetry is becoming available with Cryosat-2 and Sentinel-3A/3B to improve the mapping of the short scales in the MSS (Huang, 2017). Hence we evaluate the potential of using SAR altimetry in future geodetic MDT models as SAR altimetry has not been used for MSS computation.…”

Section: Cryosat-2 Validation Of Goce++ Mdtmentioning

confidence: 99%

“…It is of interest to oceanographers to study the ocean's surface currents (Wunsch and Stammer 1997), and to geodesists for e.g. linking height datums globally, particularly in regions where geodetic land-ties (connection by levelling to the land vertical datum) through GNSS measured tide gauges are not possible (Woodworth et al 2013, Featherstone andFilmer 2012) The ocean MDT may be determined by the oceanographic approach or the geodetic approach (Huang, 2017;Woodworth et al 2013). The oceanographic approach involves the use of an ocean circulation models and the MDT is computed through temporal averaging over a given period.…”

Section: Introductionmentioning

confidence: 99%

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Improving the Coastal Mean Dynamic Topography by Geodetic Combination of Tide Gauge and Satellite Altimetry

et al. 2018

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The ocean mean dynamic topography (MDT) is the surface representation of the ocean circulation. The MDT may be determined by the ocean approach, which involves temporal averaging of numerical ocean circulation model information, or by the geodetic approach, wherein the MDT is derived using the ellipsoidal height of the mean sea surface (MSS), or mean sea level (MSL) minus the geoid as the geoid. The ellipsoidal height of the MSS might be estimated either by satellite or coastal tide gauges by connecting the tide gauge datum to the Earth-centered reference frame. In this paper we present a novel approach to improve the coastal MDT, where the solution is based on both satellite altimetry and tide gauge data using new set of 302 tide gauges with ellipsoidal heights through the SONEL network. The approach was evaluated for the Northeast Atlantic coast where a dense network of GNSS-surveyed tide gauges is available. The typical misfit between tide gauge and satellite or oceanographic MDT was found to be around 9 cm. This misfit was found to be mainly due to small scale geoid errors. Similarly we found, that a single tide gauge places only weak constraints on the coastal dynamic topography.

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Section: Evaluation and Representativeness Of Tide Gauge Mdtsupporting

confidence: 82%

Section: Cryosat-2 Validation Of Goce++ Mdtmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Improving the Coastal Mean Dynamic Topography by Geodetic Combination of Tide Gauge and Satellite Altimetry

et al. 2018

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“…Ice shelf surface height is now well mapped all around Antarctica at the O(10) km scales resolved by satellite altimeter missions (e.g., Bamber et al, 2009;Chuter & Bamber, 2015;Griggs & Bamber, 2011;Helm et al, 2014), including temporal changes during the last two decades (Paolo et al, 2015(Paolo et al, , 2016. However, conversion of surface height to ice thickness involves using models for ellipsoid to geoid conversion, mean dynamic topography of the ocean surface (e.g., Huang, 2017;Rio & Hernandez, 2004), and assumptions about firn air content (e.g., Fricker et al, 2001;Ligtenberg et al, 2014). Uncertainties in these corrections can introduce errors in ice thickness and ice draft of order 10-100 m (Chuter & Bamber, 2015;Griggs & Bamber, 2011).…”

Section: Tide Model Dependence On Geometrymentioning

confidence: 99%

Ocean Tide Influences on the Antarctic and Greenland Ice Sheets

Padman

Siegfried

Fricker

2018

Reviews of Geophysics

161

160

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Ocean tides are the main source of high‐frequency variability in the vertical and horizontal motion of ice sheets near their marine margins. Floating ice shelves, which occupy about three quarters of the perimeter of Antarctica and the termini of four outlet glaciers in northern Greenland, rise and fall in synchrony with the ocean tide. Lateral motion of floating and grounded portions of ice sheets near their marine margins can also include a tidal component. These tide‐induced signals provide insight into the processes by which the oceans can affect ice sheet mass balance and dynamics. In this review, we summarize in situ and satellite‐based measurements of the tidal response of ice shelves and grounded ice, and spatial variability of ocean tide heights and currents around the ice sheets. We review sensitivity of tide heights and currents as ocean geometry responds to variations in sea level, ice shelf thickness, and ice sheet mass and extent. We then describe coupled ice‐ocean models and analytical glacier models that quantify the effect of ocean tides on lower‐frequency ice sheet mass loss and motion. We suggest new observations and model developments to improve the representation of tides in coupled models that are used to predict future ice sheet mass loss and the associated contribution to sea level change. The most critical need is for new data to improve maps of bathymetry, ice shelf draft, spatial variability of the drag coefficient at the ice‐ocean interface, and higher‐resolution models with improved representation of tidal energy sinks.

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“…Determination of the MDT can be through the 'geodetic' or 'ocean' approaches (Woodworth et al 2012). The geodetic approach uses either: a) a MSS model obtained from satellite altimetry (e.g., Bingham et al 2008Bingham et al , 2014Andersen and Knudsen 2009;Knudsen et al 2011;Schaeffer et al 2012, Huang 2017, or b) mean sea level (MSL) observations at tide gauges expressed as ellipsoidal heights from colocated GNSS observations (e.g., Woodworth et al 2015;Hughes et al 2015;Lin et al 2015). In both of these geodetic approaches, a geoid model is subtracted from the MSS/MSL to derive the MDT.…”

Section: Mdt Estimation Approachesmentioning

confidence: 99%

Comparison between geodetic and oceanographic approaches to estimate mean dynamic topography for vertical datum unification: evaluation at Australian tide gauges

Filmer

Hughes

Woodworth

et al. 2018

J Geod

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The direct method of vertical datum unification requires estimates of the ocean's mean dynamic topography (MDT) at tide gauges, which can be sourced from either geodetic or oceanographic approaches. To assess the suitability of different types of MDT for this purpose, we evaluate 13 physics-based numerical ocean models and six MDTs computed from observed geodetic and/or ocean data at 32 tide gauges around the Australian coast. We focus on the viability of numerical ocean models for vertical datum unification, classifying the 13 ocean models used as either independent (do not contain assimilated geodetic data) or non-independent (do contain assimilated geodetic data). We find that the independent and non-independent ocean models deliver similar results. Maximum differences among ocean models and geodetic MDTs reach >150 mm at several Australian tide gauges, and are considered anomalous at the 99% confidence level. These differences appear to be of geodetic origin, but without additional independent information, or formal error estimates for each model, some of these errors remain inseparable. Our results imply that some ocean models have standard deviations of differences with other MDTs (using geodetic and/or ocean observations) at Australian tide gauges, and with levelling between some Australian tide gauges, of ~±50 mm. This indicates that they should be considered as an alternative to geodetic MDTs for the direct unification of vertical datums. They can also be used as diagnostics for errors in geodetic MDT in coastal zones, but the inseparability problem remains, where the error cannot be discriminated between the geoid model or altimeter-derived mean sea surface.

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Determining Coastal Mean Dynamic Topography by Geodetic Methods

Cited by 23 publications

References 22 publications

Improving the Coastal Mean Dynamic Topography by Geodetic Combination of Tide Gauge and Satellite Altimetry

Improving the Coastal Mean Dynamic Topography by Geodetic Combination of Tide Gauge and Satellite Altimetry

Ocean Tide Influences on the Antarctic and Greenland Ice Sheets

Comparison between geodetic and oceanographic approaches to estimate mean dynamic topography for vertical datum unification: evaluation at Australian tide gauges

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