Sea level changes forced ice breakouts in the Last Glacial cycle: new results from coral terraces

AbstractA widely used method for investigating palaeotemperatures is to analyze local proxy records (e.g. ice cores or deep-sea sediment cores). The interpretation of these records is often not straightforward, and global or hemispheric means cannot be deduced from local estimates because of large spatial variability. Using a different approach, temperature changes over the last glacial cycle can be estimated from sea-level observations by applying an inverse method to an ice-sheet model. In order to understand the underlying physical mechanisms, we used a 1-D ice-sheet model and a 3-D coupled thermodynamic ice-sheet–ice-shelf–bedrock model to investigate the importance of several physical processes for the inverse temperature reconstructions. Results show that (i) temperature reconstructions are sensitive to the employed formulation of mass balance, (ii) excluding thermodynamics in the ice sheet leads to a smaller temperature amplitude in the reconstruction and (iii) hysteresis in the non-linear relation between sea level and temperature occurs as a consequence of ice redistribution in the process of merging and separation of ice sheets. The ice redistribution does not occur if the geometry does not support the formation of a relatively flat dome, which tends to be preserved in warming conditions.

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Eustatic control of late Quaternary sea-level change in the Arabian/Persian Gulf

Quaternary Research ◽

10.1016/j.yqres.2014.03.002 ◽

2014 ◽

Vol 82 (1) ◽

pp. 175-184 ◽

Cited By ~ 14

Author(s):

Thomas Stevens ◽

Matthew J. Jestico ◽

Graham Evans ◽

Anthony Kirkham

Keyword(s):

Sea Level ◽

Persian Gulf ◽

Late Quaternary ◽

Osl Dating ◽

Sea Level Changes ◽

Last Interglacial ◽

Coastal Evolution ◽

Last Glacial ◽

Sea Level Variations ◽

The Last Glacial

AbstractAccurate sea-level reconstruction is critical in understanding the drivers of coastal evolution. Inliers of shallow marine limestone and aeolianite are exposed as zeugen (carbonate-capped erosional remnants) on the southern coast of the Arabian/Persian Gulf. These have generally been accepted as evidence of a eustatically driven, last-interglacial relative sea-level highstand preceded by a penultimate glacial-age lowstand. Instead, recent optically stimulated luminescence (OSL) dating suggests a last glacial age for these deposits, requiring >100 m of uplift since the last glacial maximum in order to keep pace with eustatic sea-level rise and implying the need for a wholesale revision of tectonic, stratigraphic and sea-level histories of the Gulf. These two hypotheses have radically different implications for regional neotectonics and land–sea distribution histories. Here we test these hypotheses using OSL dating of the zeugen formations. These new ages are remarkably consistent with earlier interpretations of the formations being last interglacial or older in age, showing that tectonic movements are negligible and eustatic sea-level variations are responsible for local sea-level changes in the Gulf. The cause of the large age differences between recent studies is unclear, although it appears related to large differences in the measured accumulated dose in different OSL samples.

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Relative sea-level changes and crustal movements in Britain and Ireland since the Last Glacial Maximum

Quaternary Science Reviews ◽

10.1016/j.quascirev.2018.03.031 ◽

2018 ◽

Vol 188 ◽

pp. 143-159 ◽

Cited By ~ 26

Author(s):

Ian Shennan ◽

Sarah L. Bradley ◽

Robin Edwards

Keyword(s):

Sea Level ◽

Last Glacial Maximum ◽

Glacial Maximum ◽

Sea Level Changes ◽

Relative Sea Level ◽

Crustal Movements ◽

Last Glacial ◽

The Last Glacial Maximum ◽

The Last Glacial

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Submarine Geomorphology of the Southwestern Sardinian Continental Shelf (Mediterranean Sea): Insights into the Last Glacial Maximum Sea-Level Changes and Related Environments

Water ◽

10.3390/w13020155 ◽

2021 ◽

Vol 13 (2) ◽

pp. 155

Author(s):

Giacomo Deiana ◽

Luciano Lecca ◽

Rita Teresa Melis ◽

Mauro Soldati ◽

Valentino Demurtas ◽

...

Keyword(s):

Continental Shelf ◽

Sea Level ◽

Last Glacial Maximum ◽

Glacial Maximum ◽

Sea Level Changes ◽

Side Scan Sonar ◽

Last Glacial ◽

Depositional Processes ◽

The Last Glacial Maximum ◽

The Last Glacial

During the lowstand sea-level phase of the Last Glacial Maximum (LGM), a large part of the current Mediterranean continental shelf emerged. Erosional and depositional processes shaped the coastal strips, while inland areas were affected by aeolian and fluvial processes. Evidence of both the lowstand phase and the subsequent phases of eustatic sea level rise can be observed on the continental shelf of Sardinia (Italy), including submerged palaeo-shorelines and landforms, and indicators of relict coastal palaeo-environments. This paper shows the results of a high-resolution survey on the continental shelf off San Pietro Island (southwestern Sardinia). Multisensor and multiscale data—obtained by means of seismic sparker, sub-bottom profiler chirp, multibeam, side scan sonar, diving, and uncrewed aerial vehicles—made it possible to reconstruct the morphological features shaped during the LGM at depths between 125 and 135 m. In particular, tectonic controlled palaeo-cliffs affected by landslides, the mouth of a deep palaeo-valley fossilized by marine sediments and a palaeo-lagoon containing a peri-littoral thanatocenosis (18,983 ± 268 cal BP) were detected. The Younger Dryas palaeo-shorelines were reconstructed, highlighted by a very well preserved beachrock. The coastal paleo-landscape with lagoon-barrier systems and retro-littoral dunes frequented by the Mesolithic populations was reconstructed.

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Dependence of late glacial sea-level predictions on 3D Earth structure

10.5194/egusphere-egu2020-7699 ◽

2020 ◽

Author(s):

Meike Bagge ◽

Volker Klemann ◽

Bernhard Steinberger ◽

Milena Latinovic ◽

Maik Thomas

Keyword(s):

Solid Earth ◽

Sea Level ◽

Seismic Tomography ◽

Earth Structure ◽

Glacial Cycle ◽

Relative Sea Level ◽

Last Glacial ◽

Earth Structures ◽

3D Earth Structure ◽

The Last Glacial

<p><span>Glacial isostatic adjustment is dominated by Earth rheology resulting in a variability of relative sea-level (RSL) predictions of more than 100 meters during the last glacial cycle. Seismic tomography models reveal significant lateral variations in seismic wavespeed, most likely corresponding to variations in temperature and hence viscosity. Therefore, the replacement of 1D Earth structures by a 3D Earth structure is an essential part of recent research to reveal the impact of lateral viscosity contrasts and to achieve a more consistent view on solid-Earth dynamics. Here, we apply the VIscoelastic Lithosphere and MAntle model VILMA to predict RSL during the last deglaciation. We create an ensemble of geodynamically constrained 3D Earth structures which is based on seismic tomography models while considering a range of conversion factors to transfer seismic velocity variations into viscosity variations. For a number of globally distributed sites, we discuss the resulting variability in RSL predictions, compare this with regionally optimized 1D Earth structures, and validate the model results with relative sea-level data (sea-level indicators). This study is part of the German Climate Modeling initiative PalMod aiming the modeling of the last glacial cycle under consideration of a coupled Earth system model, i.e. including feedbacks between ice-sheets and the solid Earth.</span></p>

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Contraction-expansion dynamics of reef species in response to sea-level changes

10.1101/2021.01.06.425656 ◽

2021 ◽

Author(s):

Thierry B Hoareau ◽

Petrus Pretorius

Keyword(s):

Sea Level ◽

Subsequent Development ◽

Population Level ◽

Marine Species ◽

Late Glacial ◽

Sea Level Changes ◽

Radiocarbon Dates ◽

Last Glacial ◽

Sea Level Fluctuations ◽

The Last Glacial

The contraction-expansion model (CEM) describes the dynamics of species that survived in refugia during the last glacial maximum (LGM) and expanded their range when environmental conditions slowly improved from the Late Glacial through to the Holocene. The CEM has been proposed to describe the dynamics of reef species in response to sea-level fluctuations from a range of disciplines, but genetic inferences rather suggest stable population sizes since the last glacial period. Here, we address this paradox by providing a new model of modern reef development, by assessing the effect of LGM bottlenecks using genetic simulations, and by using a survey of the literature on reef species to compile both estimates of times to expansion and applied rates of molecular evolution. Using previously published radiocarbon dates of core data, we propose a synthetic model for the dynamics of modern coral reefs in the Indo-Pacific region. This model describes both an initiation at 9.9 ka and subsequent development that confirms a strong influence of sea-level fluctuations on reef dynamics. Simulations based on mtDNA datasets showed that pre-LGM genetic signatures of expansion are lost. Recent literature shows that, although genetic expansions of tropical marine species are frequent (>95%), the onset of these expansions is old (median ~110 ka), which indicates that most populations have remained stable since before the LGM. These pre-LGM expansions are explained by the low mutation rates (1.66% changes/site/Myr) known to be inadequate to calibrate time at population level. Specific calibrations should help solve the paradox and generalise the CEM for reef species.

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