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 Reinterpreting the Bruun Rule in the Context of Equilibrium Shoreline Models

2021 ◽  
Vol 9 (9) ◽  
pp. 974
Author(s):  
Maurizio D’Anna ◽  
Deborah Idier ◽  
Bruno Castelle ◽  
Sean Vitousek ◽  
Goneri Le Cozannet
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Time Scales ◽  
Shoreline Change ◽  
Test Case ◽  
Unified Framework ◽  
Bruun Rule ◽  
Predictive Skill ◽  
Erosion Efficiency ◽  
Local Wave

Long-term (>decades) coastal recession due to sea-level rise (SLR) has been estimated using the Bruun Rule for nearly six decades. Equilibrium-based shoreline models have been shown to skillfully predict short-term wave-driven shoreline change on time scales of hours to decades. Both the Bruun Rule and equilibrium shoreline models rely on the equilibrium beach theory, which states that the beach profile shape equilibrates with its local wave and sea-level conditions. Integrating these two models into a unified framework can improve our understanding and predictive skill of future shoreline behavior. However, given that both models account for wave action, but over different time scales, a critical re-examination of the SLR-driven recession process is needed. We present a novel physical interpretation of the beach response to sea-level rise, identifying two main contributing processes: passive flooding and increased wave-driven erosion efficiency. Using this new concept, we analyze the integration of SLR-driven recession into equilibrium shoreline models and, with an idealized test case, show that the physical mechanisms underpinning the Bruun Rule are explicitly described within our integrated model. Finally, we discuss the possible advantages of integrating SLR-driven recession models within equilibrium-based models with dynamic feedbacks and the broader implications for coupling with hybrid shoreline models.

scholarly journals Multivariate spatio-temporal modelling for assessing Antarctica's present-day contribution to sea-level rise

2015 ◽  
Vol 26 (3) ◽  
pp. 159-177 ◽  
Author(s):  
Andrew Zammit-Mangion ◽  
Jonathan Rougier ◽  
Nana Schön ◽  
Finn Lindgren ◽  
Jonathan Bamber
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Temporal Modelling ◽  
Spatio Temporal

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>

scholarly journals A biological indicator for measuring and communicating local sea level rise captured in historic photographs.

2021 ◽  
Author(s):  
Philippe Max Rouja ◽  
Craig W Schneider ◽  
Vid Petrovic ◽  
Steve Blasco ◽  
Eric Lo ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Biological Indicator ◽  
Rocky Intertidal ◽  
Intergovernmental Panel ◽  
Blue Green Algae ◽  
Digital Twin ◽  
Upward Shift ◽  
Novel Approach ◽  
Spatio Temporal

Abstract This paper explores a novel approach to collecting and communicating local site-specific data on recent sea level rise (SLR) using black zone biotic levels left on historic coastal stone structures by a stable community of cyanobacteria (blue-green algae) at the Royal Naval Dockyard in Bermuda. Photographs taken at the Dockyard in 1870, 2007 and 2017 show an upward shift in this living cyanobacterial community. A spatio-temporal digital twin computed from historic and contemporary photo assets was created to test the viability of these black zone lines as a proxy for sea level rise (SLR) measurements in Bermuda. Shifts in these black zone lines when analyzed through the digital twin demonstrate an average upward shift of 2.2 mm per year between 1870 and 2007 and 2.7 mm per year between 1870 and 2017, somewhat lower than the Global estimates from the Intergovernmental Panel on Climate Change Assessment Report predictions. However, the digital twin showed a dramatic upward shift of 8.8 cm between 2007 and 2017, or 8.8 mm per year, which coincided with Bermuda's highest recorded tidal extent since 1932. Black zone cyanobacteria are highly SLR sensitive and over long time scales comparative imagery of black zones could present a proper indicator of average sea level rise. At timescales less than 10 years the black zone may be best indicative of episodic tidal extent. As SLR will continue to shift supralittoral cyanobacteria upwards in Bermuda and in warm rocky intertidal zones worldwide, tidal monitoring and black zone assessments may prove to be a useful combination in documenting and communicating the reality, extent and possible acceleration of local SLR.

scholarly journals Melting of Northern Greenland during the last interglacial

2011 ◽  
Vol 5 (6) ◽  
pp. 3517-3539 ◽  
Author(s):  
A. Born ◽  
K. H. Nisancioglu
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Last Interglacial ◽  
The South ◽  
High Accumulation ◽  
Positive Feedbacks ◽  
Geological Past

Abstract. The Greenland ice sheet (GrIS) is losing mass at an increasing rate, making it the primary contributor to global eustatic sea level rise. Large melting areas and rapid thinning at its margins has raised concerns about its stability. However, it is conceivable that these observations represent the transient adjustment of the fastest reacting parts of the ice sheet, masking slower processes that dominate the long term fate of the GrIS and its contribution to sea level rise. Studies of the geological past provide valuable information on the long term response of the GrIS to warm periods. We simulate the GrIS during the Eemian interglacial, a period 126 000 yr before present (126 ka) with Arctic temperatures comparable to projections for the end of this century. The northeastern part of the GrIS is unstable and retreats significantly, despite moderate melt rates. Unlike the south and west, strong melting in the northeast is not compensated by high accumulation, or fast ice flow. The analogy with the present warming suggests that in coming decades, positive feedbacks could increase the rate of mass loss of the northeastern GrIS, exceeding the currently observed melting in the south.

scholarly journals On the differences between two semi-empirical sea-level models for the last two millennia

2012 ◽  
Vol 8 (4) ◽  
pp. 3551-3581 ◽  
Author(s):  
M. Vermeer ◽  
S. Rahmstorf ◽  
A. Kemp ◽  
B. Horton
Keyword(s):  
North Carolina ◽  
Sea Level Rise ◽  
Sea Level ◽  
Time Scales ◽  
Long Time ◽  
Global Mean Sea Level ◽  
Semi Empirical ◽  
The Last Two Millennia ◽  
Global Mean

Abstract. We compare hindcasts of global mean sea level over the past millennium obtained using two semi-empirical models linking temperature and sea-level rise. The models differ in that one of them includes a term for a very long-term sea-level rise component unfolding over many millennia. On short (century) time scales, both models give very similar results. Proxy sea-level reconstructions from the northern (North Carolina) and southern (New Zealand and Tasmania) hemispheres are used to test the ability of both models to reproduce the longer-term sea-level evolution. In both comparisons the model including the second term produces a markedly better fit from 1000 AD to the present. When both models are used for generating sea-level projections, they behave similarly out to 2100 AD. Further out, to 2300–2500 AD, the projections differ significantly, in no small part due to different values for the sea-level response time scale τ obtained. We conclude that careful model validation on long time scales is important before attempting multi-century projections.

No evidence from the eastern Mediterranean for a MIS 5e double peak sea-level highstand

2018 ◽  
Vol 89 (2) ◽  
pp. 505-510 ◽  
Author(s):  
Barbara Mauz ◽  
Zhixiong Shen ◽  
Noureddine Elmejdoub ◽  
Giorgio Spada
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Eastern Mediterranean ◽  
Small Scale ◽  
Double Peak ◽  
Oxygen Isotope Stage ◽  
Average Value ◽  
Global Sea Level ◽  
Facies Succession ◽  
Mis 5E

AbstractTo understand past and future sea-level variability, it is important to know if during an interglacial the eustatic sea level is constant or oscillates by several meters around an average value. Several field sites within and outside the tropics have been interpreted to suggest such oscillations during Marine Oxygen Isotope Stage (MIS) 5e (129–116 ka). Here, we present our analysis of one such non-tropical site, Hergla, where a facies succession indicates two foreshore deposits above each other, previously interpreted as MIS 5e sea-level highstand amplified by a second rise. Our study, based on field, microfacies, and optical age Bayesian statistics shows a sea-level rise forming the upper foreshore strata that coincided with the global sea-level rise of the MIS 5a interstadial. The site does therefore not provide evidence for the MIS 5e double peak. We conclude from our analysis that the facies-based proxy is insensitive to small-scale sea-level oscillation. Likewise, uncertainties associated with age estimates are too large to robustly infer a short-term sea-level change.

scholarly journals Assessing population exposure to coastal flooding due to sea level rise

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Mathew E. Hauer ◽  
Dean Hardy ◽  
Scott A. Kulp ◽  
Valerie Mueller ◽  
David J. Wrathall ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Future Climate Change ◽  
Population Exposure ◽  
Temporal Heterogeneity ◽  
Annual Probability ◽  
Spatial And Temporal Heterogeneity ◽  
Differential Exposure ◽  
Spatio Temporal ◽  
The Impact

AbstractThe exposure of populations to sea-level rise (SLR) is a leading indicator assessing the impact of future climate change on coastal regions. SLR exposes coastal populations to a spectrum of impacts with broad spatial and temporal heterogeneity, but exposure assessments often narrowly define the spatial zone of flooding. Here we show how choice of zone results in differential exposure estimates across space and time. Further, we apply a spatio-temporal flood-modeling approach that integrates across these spatial zones to assess the annual probability of population exposure. We apply our model to the coastal United States to demonstrate a more robust assessment of population exposure to flooding from SLR in any given year. Our results suggest that more explicit decisions regarding spatial zone (and associated temporal implication) will improve adaptation planning and policies by indicating the relative chance and magnitude of coastal populations to be affected by future SLR.

scholarly journals Sea-level response to melting of Antarctic ice shelves on multi-centennial time scales with the fast Elementary Thermomechanical Ice Sheet model (f.ETISh v1.0)

2017 ◽  
Author(s):  
Frank Pattyn
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Time Scales ◽  
Power Law ◽  
Coulomb Friction ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Grounding Line ◽  
Basal Sliding

Abstract. The magnitude of the Antarctic ice sheet's contribution to global sea-level rise is dominated by the potential of its marine sectors to become unstable and collapse as a response to ocean (and atmospheric) forcing. This paper presents Antarctic sea-level response to sudden atmospheric and oceanic forcings on multi-centennial time scales with the newly developed fast Elementary Thermomechanical Ice Sheet (f.ETISh) model. The f.ETISh model is a vertically integrated hybrid ice sheet/ice shelf model with an approximate implementation of ice sheet thermomechanics, making the model two-dimensional. Its marine boundary is represented by two different flux conditions, coherent with power-law basal sliding and Coulomb basal friction. The model has been compared to a series of existing benchmarks. Modelled Antarctic ice sheet response to forcing is dominated by sub-ice shelf melt and the sensitivity is highly dependent on basal conditions at the grounding line. Coulomb friction in the grounding-line transition zone leads to significantly higher mass loss in both West and East Antarctica on centennial time scales, leading to 2 m sea level rise after 500 years for a moderate melt scenario of 20 m a−1 under freely-floating ice shelves, up to 6 m for a 50 m a−1 scenario. The higher sensitivity is attributed to higher driving stresses upstream from the grounding line. Removing the ice shelves altogether results in a disintegration of the West Antarctic ice sheet and (partially) marine basins in East Antarctica. After 500 years, this leads to a 4.5 m and a 12.2 m sea level rise for the power-law basal sliding and Coulomb friction conditions at the grounding line, respectively. The latter value agrees with simulations by DeConto and Pollard (2016) over a similar period (but with different forcing and including processes of hydro-fracturing and cliff failure). The chosen parametrizations make model results largely independent of spatial resolution, so that f.ETISh can potentially be integrated in large-scale Earth system models.

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