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>

Overcoming challenges in spatio-temporal modelling of large-scale (global) data

2021 ◽  
Author(s):  
Aoibheann Brady ◽  
Jonathan Rougier ◽  
Yann Ziegler ◽  
Bramha Dutt Vishwakarma ◽  
Sam Royston ◽  
...  
Keyword(s):  
Large Scale ◽  
Holistic Approach ◽  
Global Scale ◽  
Bayesian Hierarchical ◽  
Modelling Framework ◽  
Novel Approach ◽  
Level Data ◽  
Geophysical Processes ◽  
Spatio Temporal ◽  
Data Separation

<p>Modelling spatio-temporal data on a large scale presents a number of obstacles for statisticians and environmental scientists. Issues such as computational complexity, combining point and areal data, separation of sources into their component processes, and the handling of both large volumes of data in some areas and sparse data in others must be considered. We discuss methods to overcome such challenges within a Bayesian hierarchical modelling framework using INLA.</p><p>In particular, we illustrate the approach using the example of source-separation of geophysical signals both on a continental and global scale. In such a setting, data tends to be available both at a local and areal level. We propose a novel approach for integrating such sources together using the INLA-SPDE method, which is normally reserved for point-level data. Additionally, the geophysical processes involved are both spatial (time-invariant) and spatio-temporal in nature. Separation of such processes into physically sensible components requires careful modelling and consideration of priors (such as physical model outputs where data is sparse), which will be discussed. We also consider methods to overcome the computational costs of modelling on such a large scale, from efficient mesh design, to thinning/aggregating of data, to considering alternative approaches for inference. This holistic approach to modelling of large-scale data ensures that spatial and spatio-temporal processes can be sensibly separated into their component parts, without being prohibitively expensive to model.</p>

Sinking land intensifies sea-level rise: a global InSAR analysis of coastal cities

2021 ◽  
Author(s):  
Cheryl Tay ◽  
Eric Lindsey ◽  
Shi Tong Chin ◽  
Jamie McCaughey ◽  
David Bekaert ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Urban Areas ◽  
Global Scale ◽  
Interferometric Synthetic Aperture Radar ◽  
Coastal Cities ◽  
Vertical Land Motion ◽  
Global Mean Sea Level ◽  
Coastal Land ◽  
Global Mean

Abstract Coastal land is being lost worldwide at an alarming rate due to relative sea-level rise (RSLR) resulting from vertical land motion (VLM). This problem is understudied at a global scale, due to high spatial variability and difficulties reconciling VLM between regions. Here we provide self-consistent, high spatial resolution VLM observations derived from Interferometric Synthetic Aperture Radar for the 51 largest coastal cities, representing 22% of the global urban population. We show that peak subsidence rates are faster than current global mean sea-level rise rates and VLM contributions to RSLR are greater than IPCC projections in 90% and 53% of the cities respectively. Localized VLM worsens RSLR impacts on land and population in 73-75% of the cities, with Chittagong (Bangladesh), Yangon (Myanmar) and Jakarta (Indonesia) at greatest risk. With this dataset, accurate projections and comparisons of RSLR effects accounting for VLM are now possible for urban areas at a global scale.

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>

scholarly journals Depositional setting and limiting factors of early Late Cretaceous glaucony formation: implications from Cenomanian glauconitic strata (Elbtal Group, Germany)

Facies ◽  
2021 ◽  
Vol 67 (3) ◽  
Author(s):  
Markus Wilmsen ◽  
Udita Bansal
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Time Scales ◽  
Late Cretaceous ◽  
Limiting Factors ◽  
High Accumulation ◽  
Spatio Temporal ◽  
Facies Types ◽  
Facies Succession ◽  
Early Late

AbstractCenomanian strata of the Elbtal Group (Saxony, eastern Germany) reflect a major global sea-level rise and contain, in certain intervals, a green authigenic clay mineral in abundance. Based on the integrated study of five new core sections, the environmental background and spatio-temporal patterns of these glauconitic strata are reconstructed and some general preconditions allegedly needed for glaucony formation are critically questioned. XRD analyses of green grains extracted from selected samples confirm their glauconitic mineralogy. Based on field observations as well as on the careful evaluation of litho- and microfacies, 12 glauconitc facies types (GFTs), broadly reflecting a proximal–distal gradient, have been identified, containing granular and matrix glaucony of exclusively intrasequential origin. When observed in stratigraphic succession, GFT-1 to GFT-12 commonly occur superimposed in transgressive cycles starting with the glauconitic basal conglomerates, followed up-section by glauconitic sandstones, sandy glauconitites, fine-grained, bioturbated, argillaceous and/or marly glauconitic sandstones; glauconitic argillaceous marls, glauconitic marlstones, and glauconitic calcareous nodules continue the retrogradational fining-upward trend. The vertical facies succession with upwards decreasing glaucony content demonstrates that the center of production and deposition of glaucony in the Cenomanian of Saxony was the nearshore zone. This time-transgressive glaucony depocenter tracks the regional onlap patterns of the Elbtal Group, shifting southeastwards during the Cenomanian 2nd-order sea-level rise. The substantial development of glaucony in the thick (60 m) uppermost Cenomanian Pennrich Formation, reflecting a tidal, shallow-marine, nearshore siliciclastic depositional system and temporally corresponding to only ~ 400 kyr, shows that glaucony formation occurred under wet, warm-temperate conditions, high accumulation rates and on rather short-term time scales. Our new integrated data thus indicate that environmental factors such as great water depth, cool temperatures, long time scales, and sediment starvation had no impact on early Late Cretaceous glaucony formation in Saxony, suggesting that the determining factors of ancient glaucony may be fundamentally different from recent conditions and revealing certain limitations of the uniformitarian approach.

scholarly journals Refining Estimates of Polar Ice Volumes during the MIS11 Interglacial Using Sea Level Records from South Africa

2014 ◽  
Vol 27 (23) ◽  
pp. 8740-8746 ◽  
Author(s):  
Florence Chen ◽  
Sarah Friedman ◽  
Charles G. Gertler ◽  
James Looney ◽  
Nizhoni O’Connell ◽  
...  
Keyword(s):  
South Africa ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Sea Level Change ◽  
Polar Ice ◽  
Level Change ◽  
Isostatic Adjustment ◽  
West Antarctic ◽  
Numerical Predictions

Abstract Peak eustatic sea level (ESL), or minimum ice volume, during the protracted marine isotope stage 11 (MIS11) interglacial at ~420 ka remains a matter of contention. A recent study of high-stand markers of MIS11 age from the tectonically stable southern coast of South Africa estimated a peak ESL of 13 m. The present study refines this estimate by taking into account both the uncertainty in the correction for glacial isostatic adjustment (GIA) and the geographic variability of sea level change following polar ice sheet collapse. In regard to the latter, the authors demonstrate, using gravitationally self-consistent numerical predictions of postglacial sea level change, that rapid melting from any of the three major polar ice sheets (West Antarctic, Greenland, or East Antarctic) will lead to a local sea level rise in southern South Africa that is 15%–20% higher than the eustatic sea level rise associated with the ice sheet collapse. Taking this amplification and a range of possible GIA corrections into account and assuming that the tectonic correction applied in the earlier study is correct, the authors revise downward the estimate of peak ESL during MIS11 to 8–11.5 m.

A radiocarbon chronology of Holocene climate change and sea-level rise at the Delmarva Peninsula, US Mid-Atlantic Coast

The Holocene ◽  
2021 ◽  
pp. 095968362110482
Author(s):  
Kelvin W Ramsey ◽  
Jaime L. Tomlinson ◽  
C. Robin Mattheus
Keyword(s):  
Climate Change ◽  
North America ◽  
Sea Level Rise ◽  
Sea Level ◽  
Early Holocene ◽  
Eastern North America ◽  
Delmarva Peninsula ◽  
The Holocene ◽  
Cool Climate ◽  
And Sea Level

Radiocarbon dates from 176 sites along the Delmarva Peninsula record the timing of deposition and sea-level rise, and non-marine wetland deposition. The dates provide confirmation of the boundaries of the Holocene subepochs (e.g. “early-middle-late” of Walker et al.) in the mid-Atlantic of eastern North America. These data record initial sea-level rise in the early Holocene, followed by a high rate of rise at the transition to the middle Holocene at 8.2 ka, and a leveling off and decrease in the late-Holocene. The dates, coupled to local and regional climate (pollen) records and fluvial activity, allow regional subdivision of the Holocene into six depositional and climate phases. Phase A (>10 ka) is the end of periglacial activity and transition of cold/cool climate to a warmer early Holocene. Phase B (10.2–8.2 ka) records rise of sea level in the region, a transition to Pinus-dominated forest, and decreased non-marine deposition on the uplands. Phase C (8.2–5.6 ka) shows rapid rates of sea-level rise, expansion of estuaries, and a decrease in non-marine deposition with cool and dry climate. Phase D (5.6–4.2 ka) is a time of high rates of sea-level rise, expanding estuaries, and dry and cool climate; the Atlantic shoreline transgressed rapidly and there was little to no deposition on the uplands. Phase E (4.2–1.1 ka) is a time of lowering sea-level rise rates, Atlantic shorelines nearing their present position, and marine shoal deposition; widespread non-marine deposition resumed with a wetter and warmer climate. Phase F (1.1 ka-present) incorporates the Medieval Climate Anomaly and European settlement on the Delmarva Peninsula. Chronology of depositional phases and coastal changes related to sea-level rise is useful for archeological studies of human occupation in relation to climate change in eastern North America, and provides an important dataset for future regional and global sea-level reconstructions.

scholarly journals Measuring Sea Level Rise Along the Coast

Eos ◽  
2021 ◽  
Vol 102 ◽  
Author(s):  
David Shultz
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Solid Ground ◽  
Vertical Land Motion

Scientists created a global map of vertical land motion to show how the solid ground is moving relative to the planet’s rising seas.

Data-driven estimate of past and present surface loading over North America: Bayesian Hierarchical Modelling approach applied to GPS and GRACE observations

2021 ◽  
Author(s):  
Yann Ziegler ◽  
Bramha Dutt Vishwakarma ◽  
Aoibheann Brady ◽  
Stephen Chuter ◽  
Sam Royston ◽  
...  
Keyword(s):  
North America ◽  
Hydrological Cycle ◽  
Elastic Solid ◽  
Data Driven ◽  
Balance Model ◽  
Surface Loading ◽  
Bayesian Hierarchical ◽  
Hierarchical Modelling ◽  
Vertical Land Motion ◽  
Bayesian Hierarchical Modelling

<p>Glacial Isostatic Adjustment (GIA) and the hydrological cycle are both associated with mass changes, which are observed by GRACE, and vertical land motion (VLM), which is observed by GPS. Hydrology-related VLM results from the instantaneous response of the elastic solid Earth to surface loading by freshwater, whereas GIA-related VLM reveals the long-term response of the visco-elastic Earth mantle to past glacial cycles. Thus, observations of mass changes and VLM are interrelated and GIA and hydrology are difficult to investigate independently. Taking advantage of the differences in the spatio-temporal characteristics of the GIA and hydrology fields, we can separate the respective contributions of each process. In this work, we use a Bayesian Hierarchical Modelling (BHM) approach to provide a new data-driven estimate of GIA and time-evolving hydrology-related VLM for North America. We detail our processing strategy to prepare the input data for the BHM while preserving the content of the original observations. We discuss the separation of GIA and hydrology processes from a statistical and geophysical point of view. Finally, we assess the reliability of our estimates and compare our results to the latest GIA and hydrological models. Specifically, we compare our GIA solution to a forward-model global field, ICE-6G, and a recent GIA estimate developed for North America (Simon et al. 2017). Our time-evolving hydrology field is compared with WaterGAP, a global water balance model. Overall, for both GIA and hydrology, there is a good agreement between our results and the forward models, but we also find differences which possibly highlight deficiencies in these models.</p>

Preventing local extinctions of tidal marsh endemic Seaside Sparrows and Saltmarsh Sparrows in eastern North America

The Condor ◽  
2019 ◽  
Vol 121 (2) ◽  
Author(s):  
Samuel G Roberts ◽  
Rebecca A Longenecker ◽  
Matthew A Etterson ◽  
Chris S Elphick ◽  
Brian J Olsen ◽  
...  
Keyword(s):  
New Jersey ◽  
North America ◽  
Sea Level Rise ◽  
Sea Level ◽  
Salt Marshes ◽  
Local Population ◽  
Population Persistence ◽  
Vital Rates ◽  
Saltmarsh Sparrow ◽  
Management Actions

Abstract Globally limited to 45,000 km2, salt marshes and their endemic species are threatened by numerous anthropogenic influences, including sea-level rise and predator pressure on survival and nesting success. Along the Atlantic coast of North America, Seaside (Ammospiza maritima) and Saltmarsh (A. caudacuta) sparrows are endemic to salt marshes, with Saltmarsh Sparrows declining by 9% annually. Because vital rates and factors affecting population persistence vary for both species, local estimates are necessary to best predict population persistence in response to management actions. We used a metapopulation model to estimate the population viability of the breeding Seaside and Saltmarsh sparrow populations in coastal New Jersey over a 42-yr period. We incorporated empirical data on the vital rates and abundances of these populations and simulated the effect of low (0.35 m) and high (0.75 m) levels of sea-level rise. We found that the Seaside Sparrow population persisted under both sea-level rise scenarios; however, the Saltmarsh Sparrow population reached a quasi-extinction threshold within 20 yr. Using the same framework, we modeled potential management scenarios that could increase the persistence probability of Saltmarsh Sparrows and found that fecundity and juvenile survival rates will require at least a 15% concurrent increase for the local population to persist beyond 2050. Future field research should evaluate the feasibility and effectiveness of management actions, such as predator control, for increasing Saltmarsh Sparrow vital rates in order to maintain the species in coastal New Jersey.

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