On the geophysical processes impacting palaeo-sea-level observations

AbstractPast sea-level change represents the large-scale state of global climate, reflecting the waxing and waning of global ice sheets and the corresponding effect on ocean volume. Recent developments in sampling and analytical methods enable us to more precisely reconstruct past sea-level changes using geological indicators dated by radiometric methods. However, ice-volume changes alone cannot wholly account for these observations of local, relative sea-level change because of various geophysical factors including glacio-hydro-isostatic adjustments (GIA). The mechanisms behind GIA cannot be ignored when reconstructing global ice volume, yet they remain poorly understood within the general sea-level community. In this paper, various geophysical factors affecting sea-level observations are discussed and the details and impacts of these processes on estimates of past ice volumes are introduced.

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A standardized database of Last Interglacial sea-level indicators in southeast Asia: Records from coral reef terraces in a tectonically complex region

10.5194/egusphere-egu21-16151 ◽

2021 ◽

Author(s):

Kathrine Maxwell ◽

Hildegard Westphal ◽

Alessio Rovere

Keyword(s):

Coral Reef ◽

Southeast Asia ◽

Sea Level ◽

Tectonic Setting ◽

Sea Level Change ◽

The Philippines ◽

Sea Level Changes ◽

Last Interglacial ◽

Level Change ◽

Se Asia

The Last Interglacial (LIG), as well as other warmer periods in the Earth&#8217;s geologic history, provides an analogue for predicted warming conditions in the near future. Analysis of sea-level indicators during this period is important in constraining regional drivers of relative sea-level change (RSL) and in modeling future trajectories of sea-level rise. In southeast Asia, several studies have been done to examine LIG sea-level indicators such as coral reef terraces and tidal notches. A synthesis of the state-of-the-art of the LIG RSL indicators in the region, meanwhile, has yet to be done. We reviewed over 50 published works on the LIG RSL indicators in southeast Asia and used the framework of the World Atlas of Last Interglacial Shorelines (WALIS) in building a standardized database of previously published LIG RSL indicators in the region. In total, we identified 38 unique RSL indicators and inserted almost 140 ages in the database. Available data from Indonesia, the Philippines, and East Timor points to variable elevation of sea-level indicators during the LIG highlighting the complex tectonic setting of this region. Variable uplift rates (from as low as 0.02 to as high as 1.1 m/ka) were reported in the study areas echoing various collision and subduction processes influencing these sites. Although several age constraints and elevation measurements have been provided by these studies, more data is still needed to shed more light on the RSL changes in the region. With this effort under the WALIS framework, we hope to identify gaps in the LIG RSL indicators literature in SE Asia and recognize potential areas that can be visited for future work. We also hope that this initiative will help us further understand the different drivers of past sea-level changes in SE Asia and will provide inputs for projections of sea-level change in the future.

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Steric Sea-Level Change and its Impact on the Gravity Field caused by Global Climate Change

Earth Sciences and Mathematics ◽

10.1007/978-3-7643-8907-9_8 ◽

2008 ◽

pp. 1131-1151

Author(s):

Sabine Roedelsperger ◽

Michael Kuhn ◽

Oleg Makarynskyy ◽

Carl Gerstenecker

Keyword(s):

Climate Change ◽

Gravity Field ◽

Sea Level ◽

Global Climate Change ◽

Global Climate ◽

Sea Level Change ◽

Steric Sea Level ◽

Level Change

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Molecular fossils inferring Quaternary sea-level changes

10.5194/egusphere-egu2020-7153 ◽

2020 ◽

Author(s):

Martina Conti ◽

Martin Bates ◽

Natasha Barlow ◽

Richard Preece ◽

Kirsty Penkman ◽

...

Keyword(s):

Organic Matter ◽

Sea Level ◽

Sea Level Change ◽

Sea Level Changes ◽

Primary Producers ◽

Chlorophyll Pigments ◽

Molecular Fossils ◽

Level Change ◽

Targeted Analysis ◽

The Impact

Targeted analysis of organic matter in soils and sediments is useful for evaluating past environmental conditions, as specific compounds may be directly linked to organisms and hence to the conditions in which they inhabited the environment.&#160; Variations in molecular fossil distributions have become a powerful tool for understanding changes in palaeoclimate conditions.&#160; This work uses molecular fossils to give an insight into the impact of transgressive events on primary producers inhabiting the studied basin, and hence a more detailed record of sea-level change.The cores studied consisted of unconsolidated immature sediments from the mid-late Pleistocene (< 500,000 years) and the Holocene. &#160;Molecular fossils, such as chlorophyll pigments and lipids, exhibit fluctuations as a response to changes in palaeoenvironmental conditions, providing a useful marker for sea-level changes. &#160;Fluctuations in the pigment and n-alkane distribution reflect changes in primary producer activity, while the GDGT-based index of branched and isoprenoid tetraether lipids (BIT) differentiates between terrigenous and marine organic matter inputs. &#160;Lipids were analysed by GC-FID and HPLC-MS while analysis of chlorophyll pigments was carried out using a new UHPLC-DAD method.The results from biomarker analyses show excellent time-resolved agreement with previous lithological and ecological studies, but enabled a more sensitive response of different primary producers to changing conditions to be observed. &#160;The molecular fossils were able to detect the onset and cessation of the studied transgressions earlier than it was possible with microfossil evidence.&#160; Linking the pigment and lipid record with more secure dating will enable a more accurate record of Quaternary relative sea-level change.

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Controls on Albian-Cenomanian Carbonate Platform Sedimentation in Middle Eastern Region: Kesalon Event, a Middle Cretaceous Sea Level Change in Israel and Its Correlation with Global Sea Level Changes: ABSTRACT

AAPG Bulletin ◽

10.1306/94886fce-1704-11d7-8645000102c1865d ◽

1987 ◽

Vol 71 ◽

Author(s):

Moshe Braun, Francis Hirsch

Keyword(s):

Sea Level ◽

Carbonate Platform ◽

Middle Eastern ◽

Sea Level Change ◽

Eastern Region ◽

Sea Level Changes ◽

Level Change ◽

Global Sea Level

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Vegetation change in the Astrakhanskiy Biosphere Reserve (Lower Volga Delta, Russia) in relation to Caspian Sea level fluctuation

Environmental Conservation ◽

10.1017/s0376892999000259 ◽

1999 ◽

Vol 26 (3) ◽

pp. 169-178 ◽

Cited By ~ 14

Author(s):

E.A. BALDINA ◽

J. DE LEEUW ◽

A.K. GORBUNOV ◽

I.A. LABUTINA ◽

A.F. ZHIVOGLIAD ◽

...

Keyword(s):

Sea Level ◽

Time Scales ◽

Caspian Sea ◽

Biosphere Reserve ◽

Sea Level Change ◽

Rapid Progression ◽

Sea Level Changes ◽

Volga Delta ◽

Level Change ◽

Lower Volga

During the twentieth century the level of the Caspian Sea dropped from -26 m (1930) to -29 m (1977) below global sea level and subsequently rose again to -26.66 m in 1996. We aimed to describe responses of the vegetation in the lower Volga Delta to these substantial sea-level changes using an analysis of historic vegetation maps produced by aerial photography and satellite imagery.The sea level drop in the earlier part of the century was followed by rapid progression of the vegetation. The subsequent rapid sea-level rise in the 1980s did however not result in similarly rapid regression of the vegetation. This partial irreversibility of the vegetation response to sea-level change is explained by the wide flooding tolerance of the major emergent species, namely Phragmites australis. Floating vegetation increased in extent, most likely due to the increased availability of more favourable conditions, particularly for Nelumbo nucifera, a tropical plant reaching its northernmost distribution in the Volga Delta. This species increased in distribution from 3.5 ha in the 1930s throughout the entire Volga Delta to several thousands of hectares in the Astrakhanskiy Biosphere Reserve alone in the 1980s. The reported sea-level changes swept the ecosystems in the Astrakhanskiy Biosphere Reserve back and forth within the Reserve boundaries. At longer time scales, ten-fold greater sea-level change has been reported. The ecosystems for which the Reserve is renowned might be pushed completely out of the Reserve under these conditions. We therefore question whether the current Reserve will be sufficiently large to guarantee conservation of the biota in the lower Volga Delta at longer time scales.

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The land-ice contribution to 21st century dynamic sea-level rise

Ocean Science Discussions ◽

10.5194/osd-11-123-2014 ◽

2014 ◽

Vol 11 (1) ◽

pp. 123-169 ◽

Cited By ~ 1

Author(s):

T. Howard ◽

J. Ridley ◽

A. K. Pardaens ◽

R. T. W. L. Hurkmans ◽

A. J. Payne ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

21St Century ◽

Sea Level Change ◽

Sea Level Changes ◽

Mean Sea Level ◽

Ice Melt ◽

Level Change ◽

Global Mean ◽

Dynamic Sea Level

Abstract. Climate change has the potential to locally influence mean sea level through a number of processes including (but not limited to) thermal expansion of the oceans and enhanced land ice melt. These lead to departures from the global mean sea level change, due to spatial variations in the change of water density and transport, which are termed dynamic sea level changes. In this study we present regional patterns of sea-level change projected by a global coupled atmosphere–ocean climate model forced by projected ice-melt fluxes from three sources: the Antarctic ice sheet, the Greenland ice sheet and small glaciers and ice caps. The largest ice melt flux we consider is equivalent to almost 0.7 m of global sea level rise over the 21st century. Since the ice melt is not constant, the evolution of the dynamic sea level changes is analysed. We find that the dynamic sea level change associated with the ice melt is small, with the largest changes, occurring in the North Atlantic, contributing of order 3 cm above the global mean rise. Furthermore, the dynamic sea level change associated with the ice melt is similar regardless of whether the simulated ice fluxes are applied to a simulation with fixed or changing atmospheric CO2.

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Caspian Sea Level changes based on Satellite altimetry

10.21203/rs.3.rs-493306/v3 ◽

2021 ◽

Author(s):

Omid Memarian Sorkhabi

Keyword(s):

Sea Level ◽

Caspian Sea ◽

Satellite Altimetry ◽

Sea Water ◽

Sea Level Change ◽

High Accuracy ◽

Research Data ◽

Sea Level Changes ◽

The Caspian Sea ◽

Level Change

Abstract Today, despite the satellite altimetry, it is possible to determine the average sea level and determine the sea level change with high accuracy. In this research, data from 1992-2017 TOPEX / Poseidon, Jason1, OSTM and Jason3 altimeter satellites in the Caspian Sea have been used. The results show that every year the average of 75 mm of the Caspian Sea water level decreases and the downward trend.

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Caspian Sea Level changes based on Satellite altimetry

10.21203/rs.3.rs-493306/v2 ◽

2021 ◽

Author(s):

Omid Memarian Sorkhabi

Keyword(s):

Sea Level ◽

Caspian Sea ◽

Satellite Altimetry ◽

Sea Water ◽

Sea Level Change ◽

High Accuracy ◽

Research Data ◽

Sea Level Changes ◽

The Caspian Sea ◽

Level Change

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Relative land-sea-level changes in southeastern England during the Pleistocene

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1972.0034 ◽

1972 ◽

Vol 272 (1221) ◽

pp. 87-98 ◽

Cited By ~ 30

Keyword(s):

Sea Level ◽

Sea Level Change ◽

Estuarine Sediments ◽

Level Fluctuation ◽

Sea Level Changes ◽

Freshwater Sediments ◽

Marine Deposits ◽

Level Change ◽

Lower Pleistocene ◽

Sea Level Fluctuation

During the Pleistocene, a period covering the last two million years, sea level is known to have risen above and fallen below the present sea level. The evidence for such fluctuations comes from marine and estuarine sediments, including beaches, far above present sea level and from freshwater sediments, beaches and valley systems now submerged. In southeast England there are Lower Pleistocene marine deposits at 183 m O.D . at Netley Heath in Surrey and upper Pleistocene freshwater sediments at - 35 m O.D . in the Channel. Thus we have in this area evidence of an amplitude of sea-level fluctuation relative to the present sea level of some 218 m. While such limits of relative sea-level fluctuation are not so difficult to identify, very considerable difficulties arise in determining the relation of sea-level change to the passage of time, and in the analysis of sea-level change - whether it be a real lowering of sea level relative to land, or an uplift of land relative to sea level. Let us briefly consider each of these two fields of difficulty. To date a particular stand of sea level, we have to know the relation of a particular deposit, say beach or shallow marine sediment to sea level at the time, and we have to know the correlation of this deposit to a part of the sequence of geological events which make up the Pleistocene. Both of these aspects may be problematical. It may not be certain what depth of water a deposit was formed in, and the age and correlation of the deposit may be doubtful.

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Sea-Level Reconstructions and Archaeological Indicators: A Case Study from the Submerged Hellenistic Harbor at Akko, Israel

10.5194/egusphere-egu21-2376 ◽

2021 ◽

Author(s):

Alyssa Victoria Pietraszek ◽

Oded Katz ◽

Jacob Sharvit ◽

Beverly Goodman-Tchernov

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Sea Level Change ◽

Relative Sea Level ◽

Factors Affecting ◽

Sea Levels ◽

Level Change ◽

Structural Deterioration ◽

Short And Long Term

With the impending threat of continued sea-level rise and coastal inundation, it is important to understand the short- and long-term factors affecting sea-level in a particular region. Such a feat can be accomplished by turning to indicators of past sea-levels. This study aims to highlight the utility of archaeological indicators in sea-level reconstructions, using Akko on Israel&#8217;s northern Mediterranean micro-tidal coast as a case study. Here, installations belonging to the maritime metropolis&#8217; Hellenistic Period (3rd to 1st centuries BCE) harbor, which have well-constrained chronological and elevational limitations, were identified at depths averaging 1.1 to 1.2 meters below present sea-level (mbpsl). These features would have been located sub-aerially during the time of their construction and use, indicating a change in relative sea-level in the area since this time. Utilizing a multiple proxy approach incorporating marine sedimentological and geoarchaeological methodologies with previously recorded regional data, three possible explanations for this apparent sea-level change were assessed: structural deterioration, sea-level rise, and vertical tectonic movements. This study revealed that, although signs of structural deterioration are apparent in some parts of the quay, this particular harbor installation is well-established as in situ as it has a continuous upper surface and its southern edge is built directly on the underlying bedrock. Consequently, the harbor&#8217;s current submarine position can instead be attributed to sea-level change and/or vertical tectonic displacements. While this amount of sea-level rise (over 1 m) is in agreement with glacio-hydro-eustatic values suggested for other areas of the Mediterranean, it falls below those previously reported locally. In addition, most studies suggest that the tectonic movement along this stretch of coastline is negligible. These new data provide a reliable relative sea-level marker with very little error with regard to maximum sea-level, thereby renewing the overall consideration of the tectonic and sea-level processes that have been active along this stretch of coastline during the last 2,500 years.

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