scholarly journals A 500 kyr record of global sea-level oscillations in the Gulf of Lion, Mediterranean Sea: new insights into MIS 3 sea-level variability

2012 ◽  
Vol 8 (3) ◽  
pp. 1067-1077 ◽  
Author(s):  
J. Frigola ◽  
M. Canals ◽  
I. Cacho ◽  
A. Moreno ◽  
F. J. Sierro ◽  
...  
Keyword(s):  
Grain Size ◽  
Sea Level ◽  
Continental Margin ◽  
Time Scale ◽  
High Sensitivity ◽  
Gulf Of Lion ◽  
Sea Level Oscillations ◽  
Millennial Time Scale ◽  
The Impact ◽  
Upper Slope

Abstract. Borehole PRGL1-4 drilled in the upper slope of the Gulf of Lion provides an exceptional record to investigate the impact of late Pleistocene orbitally-driven glacio-eustatic sea-level oscillations on the sedimentary outbuilding of a river fed continental margin. High-resolution grain-size and geochemical records supported by oxygen isotope chronostratigraphy allow reinterpreting the last 500 ka upper slope seismostratigraphy of the Gulf of Lion. Five main sequences, stacked during the sea-level lowering phases of the last five glacial-interglacial 100-kyr cycles, form the upper stratigraphic outbuilding of the continental margin. The high sensitivity of the grain-size record down the borehole to sea-level oscillations can be explained by the great width of the Gulf of Lion continental shelf. Sea level driven changes in accommodation space over the shelf cyclically modified the depositional mode of the entire margin. PRGL1-4 data also illustrate the imprint of sea-level oscillations at millennial time-scale, as shown for Marine Isotopic Stage 3, and provide unambiguous evidence of relative high sea-levels at the onset of each Dansgaard-Oeschger Greenland warm interstadial. The PRGL1-4 grain-size record represents the first evidence for a one-to-one coupling of millennial time-scale sea-level oscillations associated with each Dansgaard-Oeschger cycle.

scholarly journals A 500 kyr record of global sea level oscillations in the Gulf of Lion, Mediterranean Sea: new insights into MIS 3 sea level variability

2011 ◽  
Vol 7 (6) ◽  
pp. 4401-4428
Author(s):  
J. Frigola ◽  
M. Canals ◽  
I. Cacho ◽  
A. Moreno ◽  
F. J. Sierro ◽  
...  
Keyword(s):  
Grain Size ◽  
Sea Level ◽  
High Sensitivity ◽  
Sea Levels ◽  
Gulf Of Lion ◽  
Sea Level Oscillations ◽  
Global Sea Level ◽  
The Impact ◽  
Upper Slope ◽  
Millennial Scale

Abstract. Borehole PRGL1-4 drilled in the upper slope of the Gulf of Lion provides an exceptional record to investigate the impact of Late Pleistocene orbitally-driven glacio-eustatic sea level oscillations on the sedimentary outbuilding of a river fed continental margin. High-resolution grain-size and geochemical records supported by oxygen isotope chronostratigraphy allow reinterpreting the last 500 ka upper slope seismostratigraphy of the Gulf of Lion which consists of five main sequences stacked during the sea level lowering phases of the last five glacial-interglacial 100-kyr cycles. The high sensitivity to sea level oscillations of the grain-size record along the borehole, favoured by the large width of the Gulf of Lion continental shelf, demonstrates that sea level driven changes in accommodation space over the shelf are able to cyclically modify the depositional mode of the entire margin. PRGL1-4 data also illustrate the imprint of sea level oscillations at millennial scale, as shown for Marine Isotopic Stage 3, and provide unambiguous evidence of relative high sea levels at the onset of each Dansgaard-Oeschger Greenland warm interstadial. The PRGL1-4 grain-size record represents the first evidence ever for a one-to-one coupling of millennial-scale sea level oscillations associated with each Dansgaard-Oeschger cycle.

scholarly journals A model of the methane cycle, permafrost, and hydrology of the Siberian continental margin

2014 ◽  
Vol 11 (6) ◽  
pp. 7853-7900
Author(s):  
D. Archer
Keyword(s):  
Continental Shelf ◽  
Sea Level ◽  
Continental Margin ◽  
Methane Flux ◽  
Soil Freezing ◽  
Sediment Surface ◽  
Atmospheric Methane ◽  
Pore Waters ◽  
Methane Cycle ◽  
The Impact

Abstract. A two-dimensional model of a passive continental margin was adapted to the simulation of the methane cycle on Siberian continental shelf and slope, attempting to account for the impacts of glacial/interglacial cycles in sea level, alternately exposing the continental shelf to freezing conditions with deep permafrost formation during glacial times, and immersion in the ocean in interglacial times. The model is used to gauge the impact of the glacial cycles, and potential anthropogenic warming in the deep future, on the atmospheric methane emission flux, and the sensitivities of that flux to processes such as permafrost formation and terrestrial organic carbon (Yedoma) deposition. Hydrological forcing drives a freshening and ventilation of pore waters in areas exposed to the atmosphere, which is not quickly reversed by invasion of seawater upon submergence, since there is no analogous saltwater pump. This hydrological pump changes the salinity enough to affect the stability of permafrost and methane hydrates on the shelf. Permafrost formation inhibits bubble transport through the sediment column, by construction in the model. The impact of permafrost on the methane budget is to replace the bubble flux by offshore groundwater flow containing dissolved methane, rather than accumulating methane for catastrophic release when the permafrost seal fails during warming. By far the largest impact of the glacial/interglacial cycles on the atmospheric methane flux is attenuation by dissolution of bubbles in the ocean when sea level is high. Methane emissions are highest during the regression (soil freezing) part of the cycle, rather than during transgression (thawing). The model-predicted methane flux to the atmosphere in response to a warming climate is small, relative to the global methane production rate, because of the ongoing flooding of the continental shelf. A slight increase due to warming could be completely counteracted by sea level rise on geologic time scales, decreasing the efficiency of bubble transit through the water column. The methane cycle on the shelf responds to climate change on a long time constant of thousands of years, because hydrate is excluded thermodynamically from the permafrost zone by water limitation, leaving the hydrate stability zone at least 300 m below the sediment surface.

scholarly journals Response of tidal flow regime and sediment transport in North Male' Atoll, Maldives to coastal modification and sea level rise

2020 ◽  
Author(s):  
Shuaib Rasheed ◽  
Simon C. Warder ◽  
Yves Plancherel ◽  
Matthew D. Piggott
Keyword(s):  
Grain Size ◽  
Sediment Transport ◽  
Sea Level Rise ◽  
Sea Level ◽  
Land Reclamation ◽  
Tidal Flow ◽  
Sediment Grain Size ◽  
Sediment Distribution ◽  
Time Periods ◽  
The Impact

Abstract. Changes to coastlines and bathymetry alter tidal dynamics and associated sediment transport process, impacting upon a number of threats facing coastal regions, including flood risk and erosion. Especially vulnerable are coral atolls such as those that make up the Maldives archipelago which has undergone significant land reclamation in recent years and decades, and is also particularly exposed to sea level rise. Here we develop a tidal model of Male' Atoll, Maldives, and use it to assess potential changes to sediment grain size distributions under sea level rise and coastline alteration scenarios. The results indicate that the impact of coastline modification over the last two decades at the island scale is not limited to the immediate vicinity of the modified island, but can also significantly impact the sediment grain size distribution across the wider atoll basin. Additionally, the degree of change in sediment distribution which can be associated with sea level rise that is projected to occur over relatively long time periods is predicted to occur over far shorter time periods with coastline changes, highlighting the need to better understand, predict and mitigate the impact of land reclamation and other coastal modifications before conducting such activities.

Sea-level and climate signatures recorded in the 1 Myr continental margin deposits from the Bohai Sea

2020 ◽  
Author(s):  
Zhengquan Yao ◽  
Xuefa Shi ◽  
Yanguang Liu ◽  
Shuqing Qiao
Keyword(s):  
Grain Size ◽  
Sea Level ◽  
Continental Margin ◽  
Principal Components ◽  
Bohai Sea ◽  
Sediment Accumulation ◽  
Fine Fraction ◽  
The Bohai Sea ◽  
Floodplain Deposits ◽  
And Sea Level

<p>Sediment accumulation in the continental margin is largely influenced by both sea-level fluctuations and climate changes during the Quaternary Period. However, the response of sediment accumulation to these changes at orbital timescale, remains poorly understood, mainly due to (i) the scarce of sedimentary records with high-resolution chronology and (ii) the difficulty of distinguishing the role of sea-level from climate signals. Here we present sediment color reflectance (c*), grain size and total organic carbon (TOC) data of core BH08 (212.4 m; ~1 Myr) recovered from the Bohai Sea, China. The chronology of core BH08 was constrained at orbital timescale by using magnetostratigraphy and astronomical tuning methods. Sedimentary facies analysis suggests that the core sequence is dominated by alternations of deltaic system and floodplain deposits. Principal components analysis on grain size data reveals two principal components (PCs), including PC1 (31–500 µm, coarse fraction) and PC2 (18–66 µm, fine fraction). Comparison of PC1, PC2, c* and TOC with sedimentary environments, we found that PC1 and c* corresponds well with cycles of deltaic and floodplain deposits at ~100/40-kyr cycles, while PC2 and TOC display ~20-kyr cycle, in addition to the ~100/40-kyr cycles. We interpret that PC1 and c* are mainly sea-level dependent, whereas PC2 and TOC are controlled by a combination of monsoonal climate and sea level. We suggest that Milankovitch-scale monsoon climate controlled the sediments supply to the Bohai Sea during the last 1 Myr, while the redistribution of sediments by marine process (e.g. tidal currents) seem to have obscured the monsoonal signal in the grain size proxy (e.g. PC1) which is sensitive to sea-level change. Our results provide an example of climate and sea-level influenced sediment accumulation in the shallow continental margin influenced by monsoonal climate in an icehouse world.</p>

Basin Resonances in the Equatorial Indian Ocean

2011 ◽  
Vol 41 (6) ◽  
pp. 1252-1270 ◽  
Author(s):  
Weiqing Han ◽  
Julian P. McCreary ◽  
Yukio Masumoto ◽  
Jérôme Vialard ◽  
Benét Duncan
Keyword(s):  
Indian Ocean ◽  
Sea Level ◽  
Rossby Wave ◽  
Time Scale ◽  
General Circulation ◽  
Equatorial Indian Ocean ◽  
Western Boundary ◽  
Kelvin Wave ◽  
Resonance Amplitude ◽  
The Impact

Abstract Previous studies have investigated how second-baroclinic-mode (n = 2) Kelvin and Rossby waves in the equatorial Indian Ocean (IO) interact to form basin resonances at the semiannual (180 day) and 90-day periods. This paper examines unresolved issues about these resonances, including the reason the 90-day resonance is concentrated in the eastern ocean, the time scale for their establishment, and the impact of complex basin geometry. A hierarchy of ocean models is used: an idealized one-dimensional (1D) model, a linear continuously stratified ocean model (LCSM), and an ocean general circulation model (OGCM) forced by Quick Scatterometer (QuikSCAT) wind during 2000–08. Results indicate that the eastern-basin concentration of the 90-day resonance happens because the westward-propagating Rossby wave is slower, and thus is damped more than the eastward-propagating Kelvin wave. Results also indicate that superposition with other baroclinic modes further enhances the eastern maximum and weakens sea level variability near the western boundary. Without resonance, although there is still significant power at 90 and 180 days, solutions have no spectral peaks at these periods. The key time scale for the establishment of all resonances is the time it takes a Kelvin wave to cross the basin and a first-meridional-mode (ℓ = 1) Rossby wave to return; thus, even though the amplitude of the 90-day winds vary significantly, the 90-day resonance can be frequently excited in the real IO, as evidenced by satellite-observed and OGCM-simulated sea level. The presence of the Indian subcontinent enhances the influence of equatorial variability in the north IO, especially along the west coast of India. The Maldives Islands weaken the 180-day resonance amplitude but have little effect on the 90-day resonance, because they fall in its “node” region. Additionally, resonance at the 120-day period for the n = 1 mode is noted.

scholarly journals Response of tidal flow regime and sediment transport in North Malé Atoll, Maldives, to coastal modification and sea level rise

Ocean Science ◽  
2021 ◽  
Vol 17 (1) ◽  
pp. 319-334
Author(s):  
Shuaib Rasheed ◽  
Simon C. Warder ◽  
Yves Plancherel ◽  
Matthew D. Piggott
Keyword(s):  
Grain Size ◽  
Sediment Transport ◽  
Sea Level Rise ◽  
Sea Level ◽  
Land Reclamation ◽  
Transport Processes ◽  
Sediment Grain Size ◽  
Sediment Distribution ◽  
Time Periods ◽  
The Impact

Abstract. Changes to coastlines and bathymetry alter tidal dynamics and associated sediment transport processes, impacting upon a number of threats facing coastal regions, including flood risk and erosion. Especially vulnerable are coral atolls such as those that make up the Maldives archipelago, which has undergone significant land reclamation in recent years and decades and is also particularly exposed to sea level rise. Here we develop a tidal model of Malé Atoll, Maldives, the first atoll-scale and multi-atoll-scale high-resolution numerical model of the atolls of the Maldives and use it to assess potential changes to sediment grain size distributions in the deeper atoll basin, under sea level rise and coastline alteration scenarios. The results indicate that the impact of coastline modification over the last two decades at the island scale is not limited to the immediate vicinity of the modified island but can also significantly impact the sediment grain size distribution across the wider atoll basin. Additionally, the degree of change in sediment distribution which can be associated with sea level rise that is projected to occur over relatively long time periods is predicted to occur over far shorter time periods with coastline changes, highlighting the need to better understand, predict and mitigate the impact of land reclamation and other coastal modifications before conducting such activities.

The pelagic archive of short-term sea-level change in the Cretaceous: a review of proxies linked to orbital forcing

2019 ◽  
Vol 498 (1) ◽  
pp. 39-56 ◽  
Author(s):  
Michael Wagreich ◽  
Veronika Koukal
Keyword(s):  
Grain Size ◽  
Sea Level ◽  
Gamma Ray ◽  
Clay Content ◽  
Sea Level Change ◽  
Point Of View ◽  
Heavy Minerals ◽  
Deep Time ◽  
Level Change ◽  
Sea Level Oscillations

AbstractDeep-time sea-level oscillations in the Milankovitch-band of orbital cyclicities govern deposition in the pelagic realm mainly by varying siliciclastic input. Pelagic sediments from the Cretaceous greenhouse climate phase provide a valuable archive for sea-level change. Although sea-level variations are of negligible amplitude compared with depositional water-depths, direct physical proxy data are based on higher and coarser siliciclastic input during sea-level lowstand and regressions, and include coarser grain size and grain-size parameters as well as the heavy mineral and clay content. Chemical proxies that relate to siliciclastics are manganese, titanium and zirconium, often normalized v. aluminium. Further proxies provide the ratios of strontium v. calcium, controlled by shelf carbonate erosion, and partly redox-sensitive elements like uranium and thorium. From a mineralogical point of view, the total amount of siliciclastics and their diversity relating to heavy minerals provides sea-level information in hemipelagites, as well as the phyllosilicate content v. biogenic pelagic background deposition of carbonate and siliceous microfossils in pelagites. In addition, measurements of gamma ray emission, linked to U, Th, K content and magnetic susceptibility may relate to sea-level cycles and various other more climate-dependent proxies like oxygen isotopes of fossil calcite and compositional maturity of hemipelagic sediments.

Phanerozoic Oxygen

2017 ◽  
Author(s):  
Donald Eugene Canfield
Keyword(s):  
Oxygen Consumption ◽  
Organic Carbon ◽  
Sea Level ◽  
Time Scale ◽  
Atmospheric Oxygen ◽  
Sea Level Change ◽  
Oxygen Production ◽  
Level Change ◽  
History Of ◽  
Geologic Processes

This chapter discusses the modeling of the history of atmospheric oxygen. The most recently deposited sediments will also be the most prone to weathering through processes like sea-level change or uplift of the land. Thus, through rapid recycling, high rates of oxygen production through the burial of organic-rich sediments will quickly lead to high rates of oxygen consumption through the exposure of these organic-rich sediments to weathering. From a modeling perspective, rapid recycling helps to dampen oxygen changes. This is important because the fluxes of oxygen through the atmosphere during organic carbon and pyrite burial, and by weathering, are huge compared to the relatively small amounts of oxygen in the atmosphere. Thus, all of the oxygen in the present atmosphere is cycled through geologic processes of oxygen liberation (organic carbon and pyrite burial) and consumption (weathering) on a time scale of about 2 to 3 million years.

NUMERICAL MODELING OF STORM SURGES, WIND WAVES AND FLOODING IN THE TAGANROG BAY

2017 ◽  
Author(s):  
Vladimir Fomin ◽  
Vladimir Fomin ◽  
Dmitrii Alekseev ◽  
Dmitrii Alekseev ◽  
Dmitrii Lazorenko ◽  
...  
Keyword(s):  
Sea Level ◽  
Wind Waves ◽  
Storm Surges ◽  
Atmospheric Model ◽  
Extreme Storm ◽  
Regional Atmospheric Model ◽  
Sea Level Oscillations ◽  
Flooding And Drying ◽  
Flooded Area ◽  
Taganrog Bay

Storm surges and wind waves are ones of the most important hydrological characteristics, which determine dynamics of the Sea of Azov. Extreme storm surges in Taganrog Bay and flooding in the Don Delta can be formed under the effect of strong western winds. In this work the sea level oscillations and wind waves in the Taganrog Bay were simulated by means of the coupled SWAN+ADCIRC numerical model, taking into account the flooding and drying mechanisms. The calculations were carried out on an unstructured mesh with high resolution. The wind and atmospheric pressure fields for the extreme storm from 20 to 28 of September, 2014 obtained from WRF regional atmospheric model were used as forcing. The analysis of simulation results showed the following. The western and northern parts of the Don Delta were the most flood-prone during the storm. The size of the flooded area of the Don Delta exceeded 50%. Interaction of storm surge and wind wave accelerated the flooding process, increased the size of the flooded area and led to the intensification of wind waves in the upper of Taganrog Bay due to the general rise of the sea level.

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