Reconstruction Of Sea-level Changes Research Articles

Probabilistic reconstruction of sea-level changes and their causes since 1900

Abstract. Coastal communities around the world are increasingly exposed to extreme events that have been exacerbated by rising sea levels. Sustainable adaptation strategies to cope with the associated threats require a comprehensive understanding of past and possible future changes. Yet, many coastlines lack accurate long-term sea-level observations. Here, we introduce a novel probabilistic near-global reconstruction of relative sea-level changes and their causes over the period from 1900 to 2021. The reconstruction is based on tide gauge records and incorporates prior knowledge about physical processes from ancillary observations and geophysical model outputs, allowing us, for the first time, to resolve individual processes and their uncertainties. We demonstrate good agreement between the reconstruction and satellite altimetry and tide gauges (if local vertical land motion is considered). Validation against steric height estimates based on independent temperature and salinity observations over their overlapping periods shows moderate to good agreement in terms of variability, though with larger reconstructed trends in three out of six regions. The linear long-term trend in the resulting global-mean sea-level (GMSL) record is 1.5 ± 0.19 mm yr−1 since 1900, a value consistent with central estimates from the 6th Assessment Report of the Intergovernmental Panel on Climate Change. Multidecadal trends in GMSL have varied; for instance, there were enhanced rates in the 1930s and near-zero rates in the 1960s, although a persistent acceleration (0.08 ± 0.04 mm yr−2) has occurred since then. As a result, most recent rates have exceeded 4 mm yr−1 since 2019. The largest regional rates (>10 mm yr−1) over the same period have been detected in coastal areas near western boundary currents and the larger tropical Indo-Pacific region. Barystatic mass changes due to ice-melt and terrestrial-water-storage variations have dominated the sea-level acceleration at global scales, but sterodynamic processes are the most crucial factor locally, particularly at low latitudes and away from major melt sources. These results demonstrate that the new reconstruction provides valuable insights into historical sea-level change and its contributing causes, complementing observational records in areas where they are sparse or absent. The Kalman smoother sea-level reconstruction dataset can be accessed at https://doi.org/10.5281/zenodo.10621070 (Dangendorf, 2024).

A fossil diatom-based reconstruction of sea-level changes for the Late Pleistocene and Holocene period in the NW South China Sea

Marine transgressions-regressions have profoundly shaped marginal seas following global sea-level fluctuations driven by climate change. This study on a sedimentary core profile SO219/31-4 from the Beibu Gulf, northwestern South China Sea (SCS), reveals information about paleoenvironment, paleoceanography and paleoclimate changes through fossil diatom assemblages and grain size distributions during the last ca. 12900 cal. yr. BP. Eight local diatom assemblage zones were distinguished and assigned to paleoenvironmental fluctuations recording sea-level and depositional environment changes in eight stages, ca. 12900–11700 (stage 1), ca. 11700–9500 (stage 2), ca. 9500–7200 (stage 3), ca. 7200–5800 (stage 4), ca. 5800–3800 (stage 5), ca. 3800–2400 (stage 6), ca. 2400–800 (stage 7) and ca. 800–0 (stage 8), cal. yr. BP. After the low sea level of stage 1 within the last deglaciation, rapid increases in sea level in stages 2 and 3 were recorded as meltwater events pulse-1B and pulse-1C resulting in marine transgression rates of ca. 16 m/kyr and 8 m/kyr, respectively. The high sea level, above the present level, in stages 4 and 5, in the Middle Holocene Climatic Optimum period, was clearly documented by more significant open sea/tropical diatom species and coastal planktonic species percentages, respectively. The late Holocene regression of sea levels was marked by a pronounced reversion of diatom taphocoenosis, responding to neoglacial climate. Fossil diatom assemblages outlined responded to paleoclimate of global warming in the deglacial and early Holocene. This study provides additional insights into the late Pleistocene and Post-glacial history of a tropical-subtropical shallow water gulf, in the NW-SCS.

Reconstruction of Sea Level Changes using Magnetic Susceptibility Variations in Southeastern Caspian Sea

Reconstruction of Sea Level Changes using Magnetic Susceptibility Variations in Southeastern Caspian Sea

Testing the relationship between testate amoeba community composition and environmental variables in a coastal tropical peatland

We investigated the ecology of testate amoebae (TA) in a coastal tropical peatland to evaluate their potential as environmental indicators in these ecosystems. At 10 positions in five locations in a transect running into the peatland away from the coast, we measured pore-water pH, pore-water electrical conductivity, soil moisture content (MC), and water-table depth (WTD). The WTD data were collected using dipwells fitted with self-recording pressure transducers that logged at 10-min intervals over a 25-day period. Multivariate statistical analysis showed that hydrological metrics (WTD and MC) were the strongest environmental controls on TA (p < 0.001) in this site, corroborating the single previous study from western Amazonia. Changes in pH and electrical conductivity, reflecting marine influence, were also significant, but less so (p < 0.05; p < 0.01 respectively). Transfer functions for WTD and MC were developed using weighted averaging partial least-squares regression, and were found to perform well under ‘leave-one-out’ cross validation (R2 = 0.80, RMSEP = 4.64 cm; R2 = 0.89; RMSEP = 1.57 cm). Our results clarify the autecology of several taxa found in tropical peatlands. Centropyxis aculeata is an unambiguous indicator of surface water, Hyalosphenia subflava “minor” (<60 μm length) is a dry indicator, whereas Hyalosphenia subflava “major” (>60 μm length) lives in wetter conditions. The difference in habitat preference of the two forms of Hyalosphenia subflava suggests that this taxon is most probably a species complex. We use the new high-quality dataset to test an existing transfer function from western Amazonia: the results show that the previous model has good predictive power for reconstructing past WTDs in tropical peatlands (r = 0.87; p < 0.005). The reconstruction of sea-level change from tropical coastal wetlands may prove problematic because the key indicators of marine influence, reflected in pH and electrical conductivity, are taxa with weak idiosomic tests that do not preserve readily in the peat archive (e.g. Tracheleuglypha dentata, Trinema lineare). Our work shows the potential of using high-quality hydrological measurements for increasing the precision of transfer function models.

Response of A Coarse-Grained, Fluvial To Coastal Depositional System To Glacio-Eustatic Sea-Level Fluctuation Since the Last Glacial Maximum: An Example From the Tenryu River, Japan

Modern coarse-grained deltas are common in tectonically active coastal zones. However, the stratigraphic architecture and evolution of these deltas in relation to allogenic forcing are poorly understood compared with fine-grained deltas, mainly because of short vertical exposure in outcrop and lack of detailed ages. This paper investigates the coarse-grained delta in the lower reaches of the Tenryu River developed at an island-arc collision coast through analyses of radiocarbon-dated core sediments and borehole data. The vertical successions of the proximal and distal part of the delta constitute basal, coarse-grained braided-river deposits overlain by fine-grained sand and mud accumulated under temporary marine influence. The fine-grained deposits in turn are covered mainly with coarse-grained braided-river deposits in the proximal part and upper shoreface to beach sand and gravel in the distal part. At the apex of the delta, in contrast, the fine-grained deposits are almost absent and thick gravels dominate. Allogenic forcing, especially the rate of glacioeustatic sea-level change, has influenced the accumulation rates and stacking pattern of the delta. Most of the sediment may have been transported to the deep sea via a canyon, and deposition has been minimal under the present subaerial delta before 14 ka. Although aggradation almost equivalent to rapid sea-level rise (∼ 15 mm/yr) is found at the proximal part between ca. 11.5 and 8 ka, even with significant basin sediment yield and supply, transgression occurred and gravel supply to the coast waned. Notably, only 30% of the sediment yield from the upstream catchment might have been trapped under the present delta plain during that period. This means that large amounts of sediment were transported farther offshore or alongshore. In contrast, slow aggradation in the proximal part and apex of the delta accompanied by progradation in the distal part might become dominant during the past 8 ka, when the rate of sea-level rise decreased to ∼ 10 mm/yr. A similar response was also observed at other Holocene fluvio-deltaic systems, although they are very different in their geological setting such as sediment supply, water discharge, tectonic movement, and gradient of river and shelf. The results imply that the rate of sea-level rise and its change have a greater significance on coastal depositional systems than other factors such as fluvial sediment supply. This study contributes to an improved understanding of evolution of modern and ancient coarse-grained deltas and reconstruction of sea-level change from geological data.

Lower- to Middle Pleistocene flank margin caves at Custonaci (Trapani, NW Sicily) and their relation with past sea levels

The peninsula of San Vito Lo Capo, 50 km West of Palermo (Sicily), is characterised by the presence of a wide set of evidences of past sea level changes, such as marine terraces, notches, marine and coastal caves with phreatic overgrowths on speleothems, and continental and marine deposits. The exceptional good preservation of these landforms and deposits has been used by different authors for the reconstruction of sea level changes and neotectonic movements. Among the many caves discussed by previous authors, most are of marine origin and can preserve signs of old sea level highstands such as notches and marine or continental sediments. However, two caves in particular, Fantasma Cave and Falesia Rocca Rumena I cave, show evidences to be flank margin caves. Both caves are records of rising and falling sea level, and their position and the correlation with marine terraces suggest them to be around 0.8 and 1.1–1.2 Ma old respectively. This study shows that not all sea level high stands are preserved in the stratigraphical and geomorphological record.Keywords: telogenetic limestones, coastal karst, mixing zone speleogenesis, sea level changes, Quaternary.

Reconstruction of sea level change in Southeast Asia waters using combined coastal sea level data and satellite altimetry data

Reconstruction of sea level change in Southeast Asia waters using combined coastal sea level data and satellite altimetry data

A two-step expansion of the dinocyst Lingulodinium machaerophorum in the Caspian Sea: the role of changing environment

Dinoflagellate cyst assemblages were analysed in four short sediment cores collected in the south Basin of the Caspian Sea for assessing environmental changes over the last few millennia. Two of these cores were dated by radionuclides. The sedimentation rate of one of them was very high, in the order of 20 mm per year. The interpretation of the four sequences is supported by a collection of 27 lagoonal or marine surface sediment samples. A sharp increase in the concentration of the dinocyst occurs after 1967, especially owing to Lingulodinium machaerophorum. Considering nine other cores covering parts or the whole of Holocene, it became clear that this species started to develop in the Caspian Sea only during the last three millennia. By analysing instrumental data and collating existing reconstructions of sea level changes over the last decades, we show that the main forcing for the recent increase of L. machaerophorum percentages and concentration is global climate change, especially sea surface temperature increase. Sea level fluctuations likely only have a minor impact. We argue that the recent increase in L. machaerophorum indicates that the Caspian Sea clearly is in the Anthropocene.

Palaeoecology of transported brachiopod assemblages embedded in black shale, Cape Phillips Formation (Silurian), Arctic Canada

Brachiopod communities have been widely used for palaeoecological studies and reconstruction of sea-level changes in Earth history. Previous studies of brachiopod communities emphasised sampling benthic shelly fossils preserved in situ to avoid preservation bias. Silurian (Wenlock) brachiopod assemblages are well preserved as debris-turbidity flows, including calcareous concretions, embedded in thick sequences of black shale of the Cape Phillips Formation, with a mixture of deep-water brachiopods and transported shallow-water forms. In this study, the first attempt is made to use the transported assemblages to reconstruct Silurian brachiopod communities that once lived along a palaeogradient from the shallow-water Arctic Platform to the deep-water Franklinian Basin. Seven transported brachiopod assemblages were recognised using multivariate analyses (cluster analysis and principal components analysis), with varying ratios of shallow- versus deep-water shells, segregated according to their known palaeobathymetric ranges in other regions. The Wenlock–early Ludlow sea-level fluctuations in the study area, reconstructed using the percentage values of shallow- and deep-water brachiopod specimens as a proxy, have a high degree of agreement with the Arctic Silurian sea-level curve and moderate agreements with global sea-level histories of other regions such as the British Isles and Gotland interpreted from graptolite abundance and diversity changes, and sequence and event stratigraphical methods, respectively.

Climate-controlled mass extinctions, facies, and sea-level changes around the Devonian–Carboniferous boundary in the eastern Anti-Atlas (SE Morocco)

Detailed sedimentological and biostratigraphical studies of successions in the eastern Anti-Atlas (SE Morocco) focused on changing depositional environments and reconstructions of sea-level changes during the late Famennian to middle Tournaisian. The investigations cover a transect from the central Maider to the easternmost and southern Tafilalt regions near the Moroccan/Algerian border. The Moroccan data are compared with the standard succession of the German Rhenish Massif and with the regional and global stratigraphic record. The results testify to high-frequency sea-level changes, including two global transgressive and anoxic events: the main Hangenberg Event (Hangenberg Black Shale level) at the top of the Wocklumeria Zone (Upper Devonian VI-E), and the Lower Alum Shale Event at the lower/middle Tournaisian (Lower Carboniferous I/II) boundary. Regionally, both anoxic intervals coincided with mass extinctions, followed by rapid radiation, especially of pelagic biota. A significant shallowing and regression occurred just below the Devonian–Carboniferous boundary at the northern margin of Gondwana and caused the sudden N/NW progradation of a large deltaic complex over 300–500 km. Thick siliciclastic successions filled fast subsiding synsedimentary troughs of the Maider and Amessoui Syncline (southern Tafilalt). Correlation with the glacial phases of southern Gondwana (South America, South Africa) indicates a glacial-eustatic origin of sea-level changes and a major sea-level fall in the scale of 100 m or more, coinciding with the main regressive phase of the extended Hangenberg Crisis interval. The new results are in accord with the hypothesis of an episode of cool-humid climate at the end of the Devonian that allowed contemporaneous glacial buildup in high latitudes and extensive clastic discharge in the middle latitudes of NW Africa.

Arenig (Middle Ordovician) ostracods from Baltoscandia: Fauna, assemblages and biofacies

The Arenig ostracod fauna of Baltoscandia is the oldest known and amongst the most thoroughly studied ostracod faunas in the world. The fauna is dominated by eridostracans and palaeocopes, and comprises altogether about fifty species from seven suborders. The ten most abundant ostracod species make up 90% of the total Arenig fauna. Overall ostracod diversity estimates in the Arenig of the Baltoscandian Palaeobasin are low, but show gradual increase in diversity at younger horizons. Low diversity may be due to unfavourable climate conditions in the Baltoscandian Palaeocontinent during the earlier Arenig and may also be due to the early stage of evolution of ostracod faunas (i.e. pre their main diversification during the Llanvirn). Thirteen facies related Arenig ostracod assemblages are distinguished in the Baltoscandian Palaeobasin. In early- and mid-Volkhov time, the assemblages show almost basinwide distribution suggesting many ostracod species were environmental generalists. Major distinctions between different ostracod biofacies zones can be seen from the late Volkhov onwards, when the differentiation of ostracod biofacies in the Palaeobasin marks the onset of major depth differences. Ostracod assemblage-based reconstruction of sea-level changes in the studied area agrees well with the sequence stratigraphic interpretation of the succession and with a sea level curve determined on the basis of sedimentological data.

A Search for Scale in Sea-Level Studies

Many researchers assume a proportional relationship among the atmospheric CO2 concentration, temperature, and sea level. Thus, the rate of sea-level rise should increase in concert with the documented exponential increase in CO2. Although sea surface temperature has increased in places over the past century and short-term sea level rose abruptly during the 1990s, it is difficult to demonstrate a proportional relationship using existing geologic or historic records. Tide gauge records in the United States cover too short a time interval to verify acceleration in the rate of sea-level rise, although multicentury tide gauge and staff records from the Netherlands and Sweden suggest a mid-19th-century acceleration in sea-level rise. Reconstructions of sea-level changes for the past 1000 years derived using benthic foraminifer data from salt marshes along the East Coast of the United States suggest an increased rate of relative sea-level rise beginning in the 1600s. Geologic records of relative sea-level rise for the past 6000 years are available for several sites along the US East Coast from 14C-dated basal peat below salt marshes and estuarine sediments. When these three scales of sea-level variation are integrated, adjusted for postglacial isostatic movement, and replotted, the range of variation in sea level suggested by basal peat ages is within ±1 meter of the long-term trend. The reconstruction from Long Island Sound data shows a linear rise in sea level beginning in the mid-1600s at a rate consistent with the historic record of mean high water. Long-term tide gauge records from Europe and North America show similar trends since the mid–19th century. There is no clear proportional exponential increase in the rate of sea-level rise. If proportionality exists among sea level, atmospheric CO2, and temperature, there may be a significant time lag before an anthropogenic increase in the rate of sea-level rise occurs.

Middle to Late Holocene relative sea-level changes recorded on the coast of Apulia (Italy) / Variations relatives du niveau marin pendant l'Holocène moyen et supérieur le long des côtes méridionales des Pouilles (Italie)

Abstract This paper uses a combination of archaeological, géomorphologie and radiometric data from the coast of Southern Apulia between Bari and Taranto for the reconstruction of sea-level changes during the middle and late Holocene. In particular, beach sequences and wave- cut platforms suggest a relative sea-level highstand at about 1 ± 0.5 m a.s.l. at about 7.0-7.5 ka BP. Archaeological remains have been used as land or sea level indicators, the former represented by tombs, quarries, cisterns, the latter by harbour structures. The collated data show that sea level was lower than -3 m during the Bronze Age; the catenae casts recognised on the submerged structures of the Roman imperial harbour of Egnatia (1st century ВС) indicate a position of high tide sea level at about 3 m below present mean position. In summary, the comparison between géomorphologie, archaeological and radiometric data suggests a high sea-level stand corresponding to a maximum Holocene transgression at about 7.0-7.5 ka BP followed firstly by a fall of sea level until the Bronze Age and then by a rise to the present position. This evidence is in contrast with the results of glacio-eustatic models and could be due to the fact that southern Italy is not involved in the flexural response to Northern Hemisphere déglaciation.

Using foraminiferal transfer functions to produce high-resolution sea-level records from salt-marsh deposits, Maine, USA

Quantitative analyses of foraminiferal distributions along the coast of Maine are used to provide transfer functions for reconstruction of sea-level changes from fossil foraminiferal assemblages. The indicative meaning of fossil assemblages is most accurately predicted by a training set that incorporates live and dead foraminifera and that uses flooding duration, not height, as the predictor variable. Sea-level records are produced for two sites in Maine (USA): a middle marsh site in Scarboro and a high marsh site in Machiasport. These records offer temporal resolution of five to seven years and span the past century. They are compared with instrumental data from a nearby tidal station to assess their accuracy. Strong correlations are found between the geologic records and the observational data, in particular between the foraminiferal record from Machiasport and the tide-gauge record from Eastport (r2 = 0.83, p = 0.005). Thus a foraminifera-based transfer-function approach offers great potential for resolving decadal-scale sea-level changes from the geologic record.

Radiocarbon dating and the reconstruction of late Quaternary sea-level changes in Hong Kong

Abstract Radiocarbon dating is used widely for the reconstruction of late Quaternary sea-level changes. In the present study, eight case studies in Hong Kong have been chosen to highlight the difficulty in obtaining reliable radiocarbon dates. Pre-Holocene radiocarbon dates exceeding about 8100 yr BP have been found to show a young age bias. A shell sample dated by two separate radiocarbon laboratories gave last interstadial ages differing by almost 9500 years while an oxygen-isotope stage 5e age was obtained using uranium-series dating. Other evidence including stratigraphy have shown that only the last interglacial age is acceptable. The young age bias is attributed mainly to the post-depositional introduction of ‘young’ carbon into the sample. For the reconstruction of sea-level changes, it is essential to select samples immediately above of the base of the Holocene transgressive unit in offshore boreholes and excavations to satisfy the criteria of rapid burial. These samples should preferably include mud, plant matter and shells to facilitate interpretation. Furthermore, as many samples as possible from a range of water depth down to about 130 m below the present sea level should be dated to reduce error introduced by counting statistics so the true signal of sea-level changes can be reflected.

Holocene sea level changes and reef development in the southwestern Indian Ocean

The sedimentological and chronological study of Holocene reef sequences recovered in drill cores through modern reefs of Mauritius, Reunion Island and Mayotte allows the reconstruction of sea level changes and reef growth patterns during the Holocene. The branching-coral facies systematically predominates over coral head facies throughout the Holocene reef sequences, and Acropora is the main frame builder among the branching forms. The reconstructed sea level curves, based both on identification of coral assemblages and on radiometric U/Th ages, are characterized by a rapid rise between 10 and 7.5 ky BP, followed by a clear inflection between 7.5 and 7 ky BP. The stabilization of sea level at its present level occurred between 2000 and 3000 years ago, probably without a higher sea level stand. Rates of vertical reef accretion range between 0.9 and 7 mm. y-1. In Mauritius, and also probably in Reunion Island, the reef first tracked, then caught-up to sea level to reach an equilibrium position (“catch-up” growth), while the barrier reef margin off Mayotte has been able to keep pace with rising sea level (“keep-up” growth).

日本における完新世相対的海面変化とそれに関する問題 １９８０〜１９８８における研究の展望

This paper reviews studies conducted between 1980 and 1988 on relative sea level changes and coastal evolution during the Holocene in Japan. The Japanese Working Group of IGCP Project 200, on “late Quaternary sea level changes, ” compiled the two-volume “Atlas of Sea Level Records in the late Quarternary in Japan” in 1987, which included materials related to this topic, based on papers published since 1980. The group also compiled the “Middle Holocene Shoreline Map of Japan (1:200, 000), which demonstrated the location of the middle Holocene shoreline with numerous data on height and radiocarbon age representing the sea level of that stage, and with 15 insets, considered to be typical examples of various types of study. Numbers of papers by year in terms of research field and study area are summarized in Figs. 1 and 2. Several review papers on sea level study have been also published in the last several years, in addition to local studies.Relative sea level curves published in the past 10 years are shown in Fig. 3. The curve patterns show noticeable local or regional differences, reflecting tectonic factors with a different amount and character in each area. Some areas characterized by a rather late culmination age of the postglacial transgression contrast with most of the Japanese coast, which has a culmination age of ca. 6, 000 to 6, 500y.B.P. Two minor fluctuations of Holocene sea level which were pointed out by OTA et al. (1982), have been recognized in several areas; a eustatic origin for such fluctuation is most likely, judging by the nearly coincident occurrence of climatic fluctuation revealed by pollen analyses, molluscan assemblage analyses and submarine core data.The following topics are discussed in particular detail in this paper: 1) Progress of excavation on the Holocene lowland and coral reefs, in order to obtain systematic samples for identification of marine limits and samples for analyses of various fossils and for dating. 2) Holocene marine terrace study with special reference to coseismic uplift and volcanic activity. 3) Identification of the former sea level on the rocky coast. Barnacles and tube worms (Pomatoleios kraussii) as sea level indicators are discussed, including problems with accuracy of radiocarbon dating. 4) Problems concerning the recognition and accuracy of former shorelines in the large alluvial plain. 5) The significance of small drowned valleys as a suitable field for the reconstruction of sea level change. 6) Climatic fluctuation during the Holocene, with relation to sea level fluctuation. 7) Increased overseas studies on Holocene sea level change by Japanese scientists.