Reconciling geodetic and geologic estimates of coastal vertical land motion around the British Isles

2021 ◽  
Author(s):  
Makan A. Karegar ◽  
Simon E. Engelhart ◽  
Jürgen Kusche ◽  
Glenn A. Milne ◽  
Sarah L. Bradley
Keyword(s):  
North America ◽  
Sea Level ◽  
Land Surface ◽  
Atlantic Coast ◽  
Glacial Isostatic Adjustment ◽  
British Isles ◽  
Isostatic Adjustment ◽  
Vertical Land Motion ◽  
Precise Analysis ◽  
Holocene Sea Level

<p><em>Karegar et al</em>. (<em>2016</em>, <em>GRL</em>) showed that independent estimates of vertical land motion from geodetic and geologic techniques are critical for understanding coastal surface motion caused by geological versus human-induced processes along the Atlantic coast of North America. Motivated by these results, <span>w</span>e extend our analysis to the British Isles where good quality and spatially dense constraints are available from a continuous G<span>NSS</span> network and a state-of-the-art Holocene sea-level database. Glacial Isostatic Adjustment (GIA) along the Atlantic coast of North America causes the land surface to sink (up to -1.5 <em>mm/yr</em>), exacerbating tidal-induced flooding effects of sea-level rise. The British Isles are also subjected to proglacial forebulge collapse associated with the GIA response to the ancient Fennoscandian and British-Irish Ice Sheets. Here, we present an up-to-date and precise analysis based on continuous GNSS (combined GPS and GlONASS observations) and geologic records of late Holocene sea-level change to examine residuals between rates on these different timescales to determine if there is a significant residual and, if so, the processes responsible for the rate change.</p>

A Standardized Database of Marine Isotope Stage 5a and 5c Paleo-Shoreline Indicators

2021 ◽  
Author(s):  
Schmitty B. Thompson ◽  
Jessica R. Creveling
Keyword(s):  
North America ◽  
Sea Level ◽  
Atlantic Coast ◽  
Ice Sheets ◽  
Climate Projections ◽  
Glacial Isostatic Adjustment ◽  
Last Interglacial ◽  
Comprehensive Overview ◽  
Isostatic Adjustment ◽  
The Caribbean

<p>Reconstructions of global mean sea level (GMSL) through interstadials such as Marine Isotope Stages (MIS) 5a and 5c provide important constraints on the rates of growth and collapse of major ice sheets during warm periods analogous to future climate projections. These reconstructions rely upon precisely dated geomorphic and sedimentological indicators for past sea level whose present elevations are complicated by tectonics and glacial isostatic adjustment (GIA). Compilations of MIS 5a and 5c paleo-sea level indicators that covering a wide geographic range can be used to minimize misfit with glacial isostatic adjustment models and thereby quantify and refine the convolved contribution of GMSL to the present elevation of paleo-shoreline indicators. Here we present a global compilation of previously published Marine Isotope Stages 5a and 5c local sea level indicators from 39 sites covering three main regions: the Pacific coast of North America, the Atlantic coast of North America and the Caribbean, and far field. We describe the standardized entry of these data into the World Atlas of Last Interglacial Shorelines (WALIS) database. Each entry within the MIS 5a and 5c WALIS database reproduces from the primary literature the indicator elevation, indicative meaning, and geochronology, along with a comprehensive overview of the literature for each site. While MIS 5a and 5c indicators sites are geographically widespread, these data are also patchy and preferentially represent the North American continent and the Caribbean and, hence, regions intermediate and far afield of the contemporaneous ice sheets. While this dataset will support future refinements to MIS 5a and 5c GMSL reconstructions arising from GIA modeling, it also motivates further data collection.</p>

Holocene sea-level changes along the North Carolina Coastline and their implications for glacial isostatic adjustment models

2009 ◽  
Vol 28 (17-18) ◽  
pp. 1725-1736 ◽  
Author(s):  
B.P. Horton ◽  
W.R. Peltier ◽  
S.J. Culver ◽  
R. Drummond ◽  
S.E. Engelhart ◽  
...  
Keyword(s):  
North Carolina ◽  
Sea Level ◽  
Glacial Isostatic Adjustment ◽  
Sea Level Changes ◽  
Isostatic Adjustment ◽  
The North ◽  
Holocene Sea Level

Spatio-temporal decomposition of geophysical signals in North America

2020 ◽  
Author(s):  
Aoibheann Brady ◽  
Jonathan Rougier ◽  
Bramha Dutt Vishwakarma ◽  
Yann Ziegler ◽  
Richard Westaway ◽  
...  
Keyword(s):  
North America ◽  
Sea Level Rise ◽  
Sea Level ◽  
Global Scale ◽  
Bayesian Hierarchical ◽  
Isostatic Adjustment ◽  
Modelling Framework ◽  
Vertical Land Motion ◽  
Early Results ◽  
Spatio Temporal

<p>Sea level rise is one of the most significant consequences of projected future changes in climate. One factor which influences sea level rise is vertical land motion (VLM) due to glacial isostatic adjustment (GIA), which changes the elevation of the ocean floor. Typically, GIA forward models are used for this purpose, but these are known to vary with the assumptions made about ice loading history and Earth structure. In this study, we implement a Bayesian hierarchical modelling framework to explore a data-driven VLM solution for North America, with the aim of separating out the overall signal into its GIA and hydrology (mass change) components. A Bayesian spatio-temporal model is implemented in INLA using satellite (GRACE) and in-situ (GPS) data as observations. Under the assumption that GIA varies in space but is constant in time, and that hydrology is both spatially- and temporally-variable, it is possible to separate the contributions of each component with an associated uncertainty level. Early results will be presented. Extensions to the BHM framework to investigate sea level rise at the global scale, such as the inclusion of additional processes and incorporation of increased volumes of data, will be discussed.</p>

Glacial Isostatic Adjustment with 3D Earth models: A comparison of case studies of deglacial relative sea level records of North America and Russian Arctic

2020 ◽  
Author(s):  
Tanghua Li ◽  
Nicole Khan ◽  
Simon Engelhart ◽  
Alisa Baranskaya ◽  
Peltier William ◽  
...  
Keyword(s):  
North America ◽  
Sea Level ◽  
3D Models ◽  
Viscosity Model ◽  
Glacial Isostatic Adjustment ◽  
Russian Arctic ◽  
Scaling Factors ◽  
Relative Sea Level ◽  
Isostatic Adjustment ◽  
Best Fit

<p>The Canadian landmass of North America and the Russian Arctic were covered by large ice sheets during the Last Glacial Maximum, and have been key areas for Glacial Isostatic Adjustment (GIA) studies. Previous GIA studies have applied 1D models of Earth’s interior viscoelastic structure; however, seismic tomography, field geology and recent studies reveal the potential importance of 3D models of this structure. Here, using the latest quality-controlled deglacial sea-level databases from North America and the Russian Arctic, we investigate the effects of 3D structure on GIA predictions. We explore scaling factors in the upper mantle (<em>β<sub>UM</sub></em>) and lower mantle (<em>β<sub>LM</sub></em>) and the 1D background viscosity model (<em>η<sub>o</sub></em>) with predictions of of the ICE-6G_C (VM5a) glaciation/deglaciation model of Peltier et al (2015, JGR) in these two regions, and compare with the best fit 3D viscosity structures.</p><p>We compute gravitationally self-consistent relative sea-level histories with time dependent coastlines and rotational feedback using both the Normal Mode Method and Coupled Laplace-Finite Element Method. A subset of 3D GIA models is found that can fit the deglacial sea-level databases for both regions. These databases cover both the near and intermediate field regions. However, North America and Russian Arctic prefer different 3D structures (i.e., combinations of (<em>η<sub>o</sub>, β<sub>UM</sub>, β<sub>LM</sub></em>)) to provide the best fits. The Russian Arctic database prefers a softer background viscosity model (<em>η<sub>o</sub></em>), but larger scaling factors (<em>β<sub>UM</sub>, β<sub>LM</sub></em>) than those preferred by the North America database.</p><p>Outstanding issues include the uncertainty of the history of local glaciation history. For example, preliminary modifications of the ice model in Russian Arctic reveal that the misfits of 1D models can be significantly reduced, but still fit less well than the best fit 3D GIA model.An additional issue concerns the extent to which the 3D models are able to improve both fits in North America and Russian Arctic when compared with 1D internal structure (ICE-6G_C VM5a & ICE-7G VM7), will be assessed in a preliminary fashion.</p>

scholarly journals The glacial isostatic adjustment signal at present day in northern Europe and the British Isles estimated from geodetic observations and geophysical models

Solid Earth ◽  
2018 ◽  
Vol 9 (3) ◽  
pp. 777-795 ◽  
Author(s):  
Karen M. Simon ◽  
Riccardo E. M. Riva ◽  
Marcel Kleinherenbrink ◽  
Thomas Frederikse
Keyword(s):  
Mass Loss ◽  
Barents Sea ◽  
Joint Inversion ◽  
Vertical Motion ◽  
Ice Age ◽  
Northern Europe ◽  
Glacial Isostatic Adjustment ◽  
British Isles ◽  
Isostatic Adjustment ◽  
Vertical Land Motion

Abstract. The glacial isostatic adjustment (GIA) signal at present day is constrained via the joint inversion of geodetic observations and GIA models for a region encompassing northern Europe, the British Isles, and the Barents Sea. The constraining data are Global Positioning System (GPS) vertical crustal velocities and GRACE (Gravity Recovery and Climate Experiment) gravity data. When the data are inverted with a set of GIA models, the best-fit model for the vertical motion signal has a χ2 value of approximately 1 and a maximum a posteriori uncertainty of 0.3–0.4 mm yr−1. An elastic correction is applied to the vertical land motion rates that accounts for present-day changes to terrestrial hydrology as well as recent mass changes of ice sheets and glaciered regions. Throughout the study area, mass losses from Greenland dominate the elastic vertical signal and combine to give an elastic correction of up to +0.5 mm yr−1 in central Scandinavia. Neglecting to use an elastic correction may thus introduce a small but persistent bias in model predictions of GIA vertical motion even in central Scandinavia where vertical motion is dominated by GIA due to past glaciations. The predicted gravity signal is generally less well-constrained than the vertical signal, in part due to uncertainties associated with the correction for contemporary ice mass loss in Svalbard and the Russian Arctic. The GRACE-derived gravity trend is corrected for present-day ice mass loss using estimates derived from the ICESat and CryoSat missions, although a difference in magnitude between GRACE-inferred and altimetry-inferred regional mass loss rates suggests the possibility of a non-negligible GIA response here either from millennial-scale or Little Ice Age GIA.

scholarly journals State-of-the-art in studies of glacial isostatic adjustment for the British Isles: a literature review

2015 ◽  
Vol 106 (3) ◽  
pp. 145-170 ◽  
Author(s):  
Julia Stockamp ◽  
Paul Bishop ◽  
Zhenhong Li ◽  
Elizabeth J Petrie ◽  
Jim Hansom ◽  
...  
Keyword(s):  
Literature Review ◽  
Sea Level ◽  
Glacial Isostatic Adjustment ◽  
British Isles ◽  
Data Types ◽  
Geological Evidence ◽  
Trend Surface ◽  
Isostatic Adjustment ◽  
Absolute Gravimetry ◽  
Mantle Rheology

ABSTRACTUnderstanding the effects of glacial isostatic adjustment (GIA) of the British Isles is essential for the assessment of past and future sea-level trends. GIA has been extensively examined in the literature, employing different research methods and observational data types. Geological evidence from palaeo-shorelines and undisturbed sedimentary deposits has been used to reconstruct long-term relative sea-level change since the Last Glacial Maximum. This information derived from sea-level index points has been employed to inform empirical isobase models of the uplift in Scotland using trend surface and Gaussian trend surface analysis, as well as to calibrate more theory-driven GIA models that rely on Earth mantle rheology and ice sheet history. Furthermore, current short-term rates of GIA-induced crustal motion during the past few decades have been measured using different geodetic techniques, mainly continuous GPS (CGPS) and absolute gravimetry (AG). AG-measurements are generally employed to increase the accuracy of the CGPS estimates. Synthetic aperture radar interferometry (InSAR) looks promising as a relatively new technique to measure crustal uplift in the northern parts of Great Britain, where the GIA-induced vertical land deformation has its highest rate. This literature review provides an in-depth comparison and discussion of the development of these different research approaches.

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