Resolving discrepancies between field and modelled relative sea-level data: lessons from western Ireland

AbstractHolocene shore-face and beach-face deposits form plains <5 m above present sea level along Taiwan Strait. We measured the 14C ages of detrital mollusk shells and coral in such deposits at the Penghu Islands. Twelve carbonate samples—mainly from the largest island, Makung—were dated. Age measurements for two coral samples and one mollusk sample from the same outcrop imply that the 14C ages of mollusk shells give the best approximation of depositional age. The highest Holocene relative sea level in the Penghu Islands occurred about 4700 years ago with a height about 2.4 m above the present sea level. Thereafter, relative sea level appreciably fell without detectable fluctuations to its recent position. Our sea level data are consistent with other studies from the central and western Pacific, except for the timing of peak sea level position. This variation may reflect local crustal response to hydroisostatic effects on the continental shelf.

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Holocene relative sea-level data for the East Frisian barrier coast, NW Germany, southern North Sea

Netherlands Journal of Geosciences – Geologie en Mijnbouw ◽

10.1017/njg.2021.11 ◽

2021 ◽

Vol 100 ◽

Cited By ~ 1

Author(s):

Friederike Bungenstock ◽

Holger Freund ◽

Alexander Bartholomä

Keyword(s):

Sea Level ◽

North Sea ◽

Level Curve ◽

Relative Sea Level ◽

Southern North Sea ◽

Isostatic Adjustment ◽

Landscape Reconstruction ◽

Time Period ◽

Level Data ◽

Age Constraints

Abstract Collecting sea-level data from restricted coastal areas is essential for understanding local effects on relative sea level. Here, a revised relative mean sea-level curve for the area of the East Frisian island Langeoog, northwestern Germany, for the time period from 7200 cal BP until Recent is presented. The revision is based on the reinterpretation of previously published and unpublished data following the HOLSEA standardisation of data handling. Altogether 68 sea-level data taken from 32 cores and outcrops from Langeoog, its back-barrier and the adjacent mainland, which have been collected since the 1950s for mapping and landscape reconstruction purposes, are presented. The age constraints, derived from radiocarbon ages of basal peat, intercalated peat and molluscs and optical dating of tidal deposits, were evaluated in terms of the HOLSEA sea-level protocol and their stratigraphic context. For 7200 cal BP until modern times, 30 sea-level index points with different uncertainty ranges were defined. Additionally, a factor of decompaction was estimated for the remaining basal peat samples as well as for the underlying sediments of intercalated peat samples. The comparison of the Langeoog relative sea-level curve with the relative sea-level curve from the western Netherlands shows that the Langeoog curve lies up to 0.80 m lower than the Dutch curve and diverges for the time before 6000 cal BP. Though the offset coincides with the overall predicted trend of glacial-isostatic adjustment, it is less than predicted. Our study provides a useful assessment of legacy data and contributes to an improved sea-level index dataset for the southern North Sea coast.

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Using Holocene relative sea-level data to inform future sea-level predictions: An example from southwest England

Global and Planetary Change ◽

10.1016/j.gloplacha.2011.05.013 ◽

2011 ◽

Vol 78 (3-4) ◽

pp. 116-126 ◽

Cited By ~ 16

Author(s):

W. Roland Gehrels ◽

David A. Dawson ◽

Jon Shaw ◽

William A. Marshall

Keyword(s):

Sea Level ◽

Relative Sea Level ◽

Level Data

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Relative sea-level data from southwest Scotland constrain meltwater-driven sea-level jumps prior to the 8.2 kyr BP event

Quaternary Science Reviews ◽

10.1016/j.quascirev.2016.06.013 ◽

2016 ◽

Vol 151 ◽

pp. 292-308 ◽

Cited By ~ 22

Author(s):

Thomas Lawrence ◽

Antony J. Long ◽

W. Roland Gehrels ◽

Luke P. Jackson ◽

David E. Smith

Keyword(s):

Sea Level ◽

Relative Sea Level ◽

Level Data

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Holocene relative sea-level data for the East Frisian barrier coast, NW Germany, southern North Sea – CORRIGENDUM

Netherlands Journal of Geosciences – Geologie en Mijnbouw ◽

10.1017/njg.2021.16 ◽

2022 ◽

Vol 101 ◽

Author(s):

Friederike Bungenstock ◽

Holger Freund ◽

Alexander Bartholomä

Keyword(s):

Sea Level ◽

North Sea ◽

Nw Germany ◽

Relative Sea Level ◽

Southern North Sea ◽

Level Data

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Inferring mantle viscosity through data assimilation of relative sea level observations in a glacial isostatic adjustment model

10.5194/egusphere-egu21-1261 ◽

2021 ◽

Author(s):

Reyko Schachtschneider ◽

Jan Saynisch-Wagner ◽

Volker Klemann ◽

Meike Bagge ◽

Maik Thomas

Keyword(s):

Data Assimilation ◽

Sea Level ◽

Glacial Isostatic Adjustment ◽

Layer Model ◽

Relative Sea Level ◽

Isostatic Adjustment ◽

Mantle Viscosity ◽

Level Data ◽

The Time Domain ◽

Spectral Finite Element

<p>We suggest to apply data assimilation in glacial isostatic adjustment (GIA) to constrain the mantle viscosity structure based on sea level observations. We apply the Parallel Data Assimilation Framework (PDAF) to assimilate sea level data into the time-domain spectral-finite element code VILMA in order to obtain better estimates of the mantle viscosity structure. In a first step, we reduce to a spherically symmetric earth structure and prescribe the glaciation history. A particle filter is used to propagate an ensemble of models in time. At epochs when observations are available, each particle's performance is estimated and the particles are resampled based on their performance to form a new ensemble that better resembles the true viscosity distribution.</p><p>Using this algorithm, we show the ability to recover mantle viscosities from a set of synthetic relative sea level observations. Those synthetic observations are obtained from a reference run with a given viscosity structure that defines the target viscosity values in our experiments. The viscosity estimation is applied to a three-layer model with an elastic lithosphere and two mantle layers, and to a multi-layer model with a smoother viscosity profile. We use various subsets of realistic observation locations (e.g. only observations from Fennoscandia) and show that it is possible to obtain the target viscosity values in those cases. We also vary the time from which observations are available to evolve the test cases towards a realistic scenario for the availability of relative sea level observations. The most relevant cases start at 26.5ka BP and at 10ka BP as they mark the beginning of the maximum glaciation and the end of deglaciation with a larger amount of observations following, respectively, and end at present day.</p>

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An inverse problem in glacial geology: The reconstruction of glacier thinning in glacier bay, alaska between A.D. 1910 and 1960 from relative sea-level data

Journal of Glaciology ◽

10.1017/s0022143000021158 ◽

1977 ◽

Vol 18 (80) ◽

pp. 481-503 ◽

Cited By ~ 20

Author(s):

James A. Clark

Keyword(s):

Sea Level ◽

Inverse Theory ◽

Glacial History ◽

Relative Sea Level ◽

Glacier Bay ◽

Past Half Century ◽

Level Data ◽

Least Squares Fit ◽

Additional Data Collection ◽

Model Independent

Abstract Inverse theory is applied to relative sea-level data to reconstruct a glacial history that is consistent with the emergence data near Glacier Bay, Alaska over the past half century. A comparison between the predicted glacial thinning and observed thinning indicates that a combination of elastic uplift of the ground and a fall in the geoid defining the ocean surface, causes 25% to 35% of the observed emergence of the coast line. Because of errors in the sea-level data, inverse theory cannot provide a unique solution in terms of glacier response, and, in fact, the least-squares fit is very inaccurate. However, by considering (1) the error of fit to the data, (2) the accuracy of the model, (3) the variation in the model, and (4) the model resolution, a physically realistic glacial history can be deduced. The advantage of inverse calculations is not only in its efficient means of finding a model that fits the data, but more importantly, it provides a means of assessing the reliability of the model by indicating the accuracy of the model and the range of other glacial histories that also fit the data. This approach also allows an estimate of the extent to which each data point constrains the model, independent of the actual data values. From this information, the most useful areas for additional data collection may be delimited.

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Predicting marsh vulnerability to sea-level rise using Holocene relative sea-level data

Nature Communications ◽

10.1038/s41467-018-05080-0 ◽

2018 ◽

Vol 9 (1) ◽

Cited By ~ 19

Author(s):

Benjamin P. Horton ◽

Ian Shennan ◽

Sarah L. Bradley ◽

Niamh Cahill ◽

Matthew Kirwan ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Relative Sea Level ◽

Level Data

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An inverse problem in glacial geology: The reconstruction of glacier thinning in glacier bay, alaska between A.D. 1910 and 1960 from relative sea-level data

Journal of Glaciology ◽

10.3189/s0022143000021158 ◽

1977 ◽

Vol 18 (80) ◽

pp. 481-503 ◽

Cited By ~ 1

Author(s):

James A. Clark

Keyword(s):

Sea Level ◽

Inverse Theory ◽

Glacial History ◽

Relative Sea Level ◽

Glacier Bay ◽

Past Half Century ◽

Level Data ◽

Least Squares Fit ◽

Additional Data Collection ◽

Model Independent

AbstractInverse theory is applied to relative sea-level data to reconstruct a glacial history that is consistent with the emergence data near Glacier Bay, Alaska over the past half century. A comparison between the predicted glacial thinning and observed thinning indicates that a combination of elastic uplift of the ground and a fall in the geoid defining the ocean surface, causes 25% to 35% of the observed emergence of the coast line. Because of errors in the sea-level data, inverse theory cannot provide a unique solution in terms of glacier response, and, in fact, the least-squares fit is very inaccurate. However, by considering (1) the error of fit to the data, (2) the accuracy of the model, (3) the variation in the model, and (4) the model resolution, a physically realistic glacial history can be deduced. The advantage of inverse calculations is not only in its efficient means of finding a model that fits the data, but more importantly, it provides a means of assessing the reliability of the model by indicating the accuracy of the model and the range of other glacial histories that also fit the data. This approach also allows an estimate of the extent to which each data point constrains the model, independent of the actual data values. From this information, the most useful areas for additional data collection may be delimited.

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