Gradual Sea-level Rise Research Articles

THE DEMISE OF THE MESSINIAN SALINITY CRISIS AND THE BEGINNING OF THE ZANCLEAN IN THE NORTHERN MEDITERRANEAN BASIN: INSIGHT FROM HIGH-RESOLUTION BIOMAGNETOSTRATIGRAPHY (POLLENZO SECTION, NW ITALY)

The Messinian-Zanclean boundary in the Mediterranean basin marks the end of the Messinian salinity crisis (MSC) at approximately 5.33 Ma. The mechanism behind the return to normal marine conditions after the MSC are debated, with two main hypotheses proposed: an instantaneous reflooding of the Mediterranean at the base of the Zanclean, following its near-complete desiccation, or a gradual sea level rise in a non-desiccated basin during the late MSC phase (Lago-Mare). Our objectives are to refine the age model of the Pollenzo section in the Piedmont basin, Italy, and to elucidate environmental variability during this phase. We employ high-resolution biomagnetostratigraphic and cyclostratigraphic analyses, integrated with statistical multivariate and cluster analyses, and tie the results with other Italian Mediterranean reference sections of the basal Zanclean. The proposed age model is based on biostratigraphic markers (planktic foraminifera and calcareous nannofossils), alongside the identification of the base of the Thvera subchron. Although no astrochronological tuning was proposed, the influence of orbital parameters variation on calcareous plankton was noted, especially at tie of eccentricity maxima. Our results indicate a gradual restoration of open marine conditions after the MSC, spanning from 5.33 to 5.23 Ma. We observe a transition from a more marginal environment to more open marine conditions at the termination of MSC. Our findings challenge the notion of an abrupt transition at the end of the MSC, emphasizing the gradual nature of environmental change in the northernmost Mediterranean basin, from the late Messinian to the early Zanclean.

Prediction of Sea Level Using Double Data Decomposition and Hybrid Deep Learning Model for Northern Territory, Australia

Sea level rise (SLR) attributed to the melting of ice caps and thermal expansion of seawater is of great global significance to vast populations of people residing along the world’s coastlines. The extent of SLR’s impact on physical coastal areas is determined by multiple factors such as geographical location, coastal structure, wetland vegetation and related oceanic changes. For coastal communities at risk of inundation and coastal erosion due to SLR, the modelling and projection of future sea levels can provide the information necessary to prepare and adapt to gradual sea level rise over several years. In the following study, a new model for predicting future sea levels is presented, which focusses on two tide gauge locations (Darwin and Milner Bay) in the Northern Territory (NT), Australia. Historical data from the Australian Bureau of Meteorology (BOM) from 1990 to 2022 are used for data training and prediction using artificial intelligence models and computation of mean sea level (MSL) linear projection. The study employs a new double data decomposition approach using Multivariate Variational Mode Decomposition (MVMD) and Successive Variational Mode Decomposition (SVMD) with dimensionality reduction techniques of Principal Component Analysis (PCA) for data modelling using four artificial intelligence models (Support Vector Regression (SVR), Adaptive Boosting Regressor (AdaBoost), Multilayer Perceptron (MLP), and Convolutional Neural Network–Bidirectional Gated Recurrent Unit (CNN-BiGRU). It proposes a deep learning hybrid CNN-BiGRU model for sea level prediction, which is benchmarked by SVR, AdaBoost, and MLP. MVMD-SVMD-CNN-BiGRU hybrid models achieved the highest performance values of 0.9979 (d), 0.996 (NS), 0.9409 (L); and 0.998 (d), 0.9959 (NS), 0.9413 (L) for Milner Bay and Darwin, respectively. It also attained the lowest error values of 0.1016 (RMSE), 0.0782 (MABE), 2.3699 (RRMSE), and 2.4123 (MAPE) for Darwin and 0.0248 (RMSE), 0.0189 (MABE), 1.9901 (RRMSE), and 1.7486 (MAPE) for Milner Bay. The mean sea level (MSL) trend analysis showed a rise of 6.1 ± 1.1 mm and 5.6 ± 1.5 mm for Darwin and Milner Bay, respectively, from 1990 to 2022.

A Critical Review of Climate Change Impacts on Groundwater Resources: A Focus on the Current Status, Future Possibilities, and Role of Simulation Models

The Earth’s water resources, totalling 1.386 billion cubic kilometres, predominantly consist of saltwater in oceans. Groundwater plays a pivotal role, with 99% of usable freshwater supporting 1.5–3 billion people as a drinking water source and 60–70% for irrigation. Climate change, with temperature increases and altered precipitation patterns, directly impacts groundwater systems, affecting recharge, discharge, and temperature. Hydrological models are crucial for assessing climate change effects on groundwater, aiding in management decisions. Advanced hydrological models, incorporating data assimilation and improved process representation, contribute to understanding complex systems. Recent studies employ numerical models to assess climate change impacts on groundwater recharge that could help in the management of groundwater. Groundwater vulnerability assessments vary with the spatial and temporal considerations, as well as assumptions in modelling groundwater susceptibility. This review assesses the vulnerability of groundwater to climate change and stresses the importance of accurate assessments for sustainable water resource management. It highlights challenges in assumptions related to soil and aquifer properties, multiple stressors, adaptive capacity, topography and groundwater contamination processes, gradual sea level rise scenarios, and realistic representations of the region of study. With the advancements in hydrological modelling, including the integration of uncertainty quantification and remote sensing data, artificial intelligence could assist in the efforts to improve models for assessing the impacts of climate change on hydrological modelling.

Forecasting and meta-features estimation of wastewater and climate change impacts in coastal region using manifold learning

South Asia's coastlines are the most densely inhabited and economically active ecosystems have already begun to shift due to climate change. Over the past century, climate change has contributed to a gradual and considerable rise in sea level, which has eroded shorelines and increased storm-related coastal flooding. The differences in estuary water quality over time, both seasonally and annually, have been efficiently controlled by changes in stream flow. Assessment requires digitized analytical platforms to lower the risk of catastrophes associated with climate change in coastal towns. To predict future changes in an area's vulnerability and waste planning decisions, a prospective investigation requires qualitative and quantitative scenarios. The paper concentrates on the development of a forecasting platform to evaluate the climate change and waste water impacts on the south coastal region of India. Due to the enhancement of Digitization, a multi-model ensemble combined with manifold learning is implemented on the multi-case models influencing the uncertainty probability rate of 23% and can be ignored with desired precaution on the coastal environmental. Because Manifold Learning Analysis results cannot be utilized directly in wastewater management studies because of their inherent biases, a statistical bias correction and meta-feature estimation have been implemented. Within the climate-hydrology modeling chain, the results demonstrate a wide range of expected changes in water resources in some places. Experimental statistics reveal that the forecasted rate of 91.45% will be the better choice to reduce the uncertainty of climatic change and wastewater management.

Изменение окружающей среды северо-западного сектора Японского моря в период последней дегляциации

Environment changes in the northwestern part of the Sea of Japan and adjacent land during last 21.0 kyr was reconstructed based on the analysis of pollen and diatom data with a high temporal resolution. Relatively dry climate caused a wide distribution of forest-steppe landscapes in the region between 21.0 to 16.6 ka. Boreal forests covered mountain slopes. Broad-leaved trees survived in refugia located in lower mountain belts. The low sea level during the Last Glacial Maximum (LGM) changed the general patterns in the sea circulation and longshore current directions, which transported the waters formed in the shallow areas of the northwestern and northern parts of the Sea of Japan. A slight increase in sublittoral benthic diatoms indicates the lowered sea level during the LGM. Occurrence of Betula indicates the start of warming after 18.5 ka; it was interrupted by the cold event Heinrich 1 and marked by the spread of coniferous Larix, Picea, and sphagnum bogs. The beginning of late glacial climatic amelioration Bølling-Allerød (BA) is contributed to dispersal of Quercus and Polypodiaceae ferns. The distribution of conifers Larix and Picea as well as of sphagnum bogs is correlated with the Younger Dryas (YD) cooling. Significant changes in vegetation occurred in the Holocene. The high percentage of sublittoral planktonic diatoms reflects a gradual rise in sea level during the BA and YD. A greater component of oceanic diatom species in the Holocene indicates the inflow of the Pacific waters through both the Tsushima and Tsugaru straits. Some increase in the participance and species diversity of relatively warm-water diatoms was noticed in the warming periods. The study of pollen and diatom records demonstrates a clear response to climatic fluctuations and changes in the Sea of Japan level in the Late Pleistocene and Holocene.

Urban Planning of Coastal Adaptation under Sea-Level Rise: An Agent-Based Model in the VIABLE Framework

Coastal flood risk and sea-level rise require decisions on investment in coastal protection and, in some cases, the relocation of urban areas. Models that formalize the relations between flooding costs, protective investments, and relocation can improve the analysis of the processes and issues involved and help to support decision-making better. In this paper, an agent-based model of a coastal city is represented in NetLogo. This model is based on the VIABLE modeling framework and describes adaptive dynamic agent behavior in a changing system. The hypothetical city faces damage caused by gradually rising sea levels and subsequent extreme sea-level events. To mitigate these risks, an “urban planner” agent has two adaptation measures at their disposal: developing coastal defenses or, as a more extreme measure, relocating vulnerable areas inland. As the simulation progresses and the decisions change with rising sea levels, the agent alters investments in these two measures to increase its value function, resulting in dynamic reactive behavior. Additionally, gradual sea-level rise is implemented in various modes, along with extreme sea-level events that cause severe short-term damage. The results of simulations under these modes and with multiple scenarios of agent action are presented. On average, agent behavior is quite reactive under limited foresight. Individual simulations yield a ‘priming’ effect when comparing different timings of extreme sea-level events, wherein an earlier extreme event primes the agent to adapt and thus be better prepared for subsequent events. Agent success with adaptation is also found to be sensitive to the costs involved, and these varying degrees of adaptation success are quantified using three parameters of adaptation success.

The Role of National Green Tribunal on mitigating the effects of Climate Change

Climate change is the worldwide problem facing by all the countries. The main cause behind the climate change is the disturbance of ecology and natural environment. We need an attention for saving our environment by balancing our needs. Climate is the long-term average of a region’s weather events. The earth’s climate is not static. Over the billions of years of earth’s existence, it has changed many times in response to natural causes like sun spot, ice age glaciations etc. Climate change is defined as a change in the climate that may be directly or indirectly linked to human activity that modifies the global atmosphere. This shift is distinct from the natural climate variability that has been documented throughout comparable time periods. The phrase climate change represents a change in the long-term weather patterns. Climate change is not a change of weather in particular day; it is the cumulative change of long-term weather pattern i.e. changes in climate. Climate change is the measurable effect of the continual warming trend. Climate change is usually measured in major shifts in temperature, rainfall, snow and wind patterns lasting decades or more. Humans are creating climate change by burning large amounts of fossil fuels (Coal, oil, natural gas), deforestation. (When forests are cut down or burned, they can no longer store carbon is released to the atmosphere). Gradual rise in sea level, Rise in global temperature, Ocean water getting warmer, Greenland and Atlantic ice sheath are shrinking, Arctic sea ice have also thinned out, Melting of glaciers, Severity in seasons along with the intensity and frequency of climate hazards has greatly increased (floods, heavy rainfall, dry spell, cyclones etc.), Acidification of oceans, Death of corals etc. are nothing but the pure evidences of climate change. These evidence shows two kinds of impacts, that is bifurcated broadly into environmental and agricultural aspect.

Fresh Water availability and Its Global challenge

Water is prime natural resources fulfilling our needs in a precisious assets.we must acts to preserve and utilize every drop of water.water resources can be assessed on the basis of surface and subsurface water bodies.Climate change impact on ground Water the impact of climate change on ground water has been studied much less than the impact on surface waters. Ground water reacts to climate change mainly due to change in ground water recharge,but also change in river level in response to increase in mean Temperature,precipitation ,variability and sea level as mean precipitations.Changing land use pattern due to increasing ,urbanization, industrialization and agriculture activities are serious issues that causing increase ground water with drawal resulting in depletion of ground water resources and mining of ground water resources,along with deterioration of water quality.Rainfall is highly irregular and erratic and declining year to year due to change climatic conditions as result of serious deforestation global warming etc.Human health is affected by change in biodiversity and ecosystem.Climate change will affect the quality of drinking water and impact of fresh water availability and impact on public health. About 70% of Earth’s surface is water of which 97.5% is salty water and 2.5% is fresh water. Less than 1% of this 2.5% amount of freshwater is accessible. As sea water rise’s , salt water of ocean in filtrate as coastal fresh water due heavy rainfall and flooding waste more fertilizer and municipal sewage mixed with costal fresh water and change alter into more oxygen dead zone. Weather extreme and climate variability is main driver of food production in recent global challenge. Recent global challenge food security, fresh water availability, increase incidence of extreme high sea level. Loss of agriculture reproduction and increase in food prices and changes in weather patterns and alter availability and quality of water in many part of world. Climate change is an on-going phenomenon. This will inevitably bring about numerous environmental problems, including alterations to the hydrological cycle, which is already heavily influenced by anthropogenic activity.Chemical fertlizer’s has been adversely affecting the flora, fauna as well as soil quality . more ever every year plant pathogen are causing loss of 10 to 20% of agricultural production worldwide. Ground water will be vital to alleviate some of the worst drought situations. flooding and contaiminated water supplies, more intense weather events are likely to increase to risk of infectious disease epidemics and erosion of low-lying and costal land. Climate Chang will affect the quality of drinking Water and impact of fresh water availlablity and impact on public health it’s better to use UV Water purifiers.This paper will explore what climate change. Water is prime natural resources fulfilling our needs in a precisious assets.we must acts to preserve and utilize every drop of water.water resources can be assessed on the basis of surface and subsurface water bodies.Climate change imapact on ground Water the impact of climate change on ground water has been studied much less than the impact on surface waters. Ground water reacts to climate change mainly due to change in ground water recharge,but also change in river level in response to increase in mean Temperature,precipitation ,variability and sea level as mean precipitations.Changing land use pattern due to increasing ,urbanization, industrialization and agriculture activities are serious issues that causing increase ground water with drawal resulting in depletion of ground water resources and mining of ground water resources,along with deterioration of water quality.Rainfall is highly irregular and erratic and declining year to year due to change climatic conditions as result of serious global warming .Impacts of sea level rise on salinity intrusion global climate change has resulted in gradual sea level rise. sea level rise can cause saline water to migrate up stream in estuaries and rivers,thereby threating fresh water habitat and drinking- water supplies.Hydrology all the costal margin; fresh ground water flowing in land areas meets with saline ground water from the ocean. the fresh ground water flows from in land areas towards the coast where elevation and groundwater level are lower because salt water has higher content of dissolved salt and minerals. it denser the fresh water,causing it to have hydraulic head than freshwater. hydraulic head refers to the liquid pressure exerted by water column. the higher pressure density of salt water causes it to move into costal aquifiers in a a wedge shape under the freshwater. the salt water and fresh water meets in a transition zone where mixing occurs through dispersion and diffusion.

Biostratigraphy of Bajocian–Oxfordian strata based on dinoflagellate cysts and ammonites from the Dalichai Formation, northeastern Iran

The Bajocian–Oxfordian Dalichai Formation of the Binalud Mountains (northeastern Iran) consists of marls, marly limestones and limestones that were sampled and studied in detail for their palynomorph and ammonite contents. Palynological studies enabled differentiation of three marine biozones (Cribroperidinium crispum, Dichadogonyaulax sellwoodii, and Ctenidodinium continuum) within the lower interval of the formation. The palynofacies analysis shows a gradual sea-level rise during the depositional period of the rock unit, while terrestrial palynomorphs (spores and pollen grains) revealed a predominantly tropical climate for the time interval. Furthermore, a large number of ammonites were recovered from the formation, based on which 12 families, 22 genera, 30 species and 12 biozones (Zigzag, Aurigerus, Retrocostatum, Discus, Bullatus, Gracilis, Anceps, Coronatum, Athleta, Transversarium, Bifurcatus, and Bimammatum) were differentiated. When comparing the dinoflagellate cyst zones with the ammonite zones, the Dichadogonyaulax sellwoodii dinoflagellate cyst zone was correlated with the ammonite zones of Zigzag, Aurigerus, Retrocostatum, Discus, Bullatus, and Gracilis and the Ctenidodinium continuum dinocyst zone was correlated with the Gracilis and Anceps ammonite zones. The dinocyst and ammonite assemblages of the Binalud Mountains are similar to assemblages described from northern and northeastern Iran (Alborz and Koppeh-Dagh basins) as well as Northwest Europe. This suggests marine connections between these sedimentary basins during the Bajocian–Oxfordian. Consequently, the integrated dinocyst and ammonite zonation established here can be utilized also in other parts of the northern Tethyan Realm. The diachroneity of the upper boundary of the Dichadogonyaulax sellwoodii Zone between the Binalud Mountains and Northwest Europe is however revealed by comparison with the ammonite zones.

Fresh Water availability and It’s Global challenge

Water is prime natural resources fulfilling our needs in a precisious assets. We must acts to preserve and utilize every drop of water. Water resources can be assessed on the basis of surface and subsurface water bodies. Climate change impact on ground Water the impact of climate change on ground water has been studied much less than the impact on surface waters. Ground water reacts to climate change mainly due to change in ground water recharge, but also change in river level in response to increase in mean Temperature, precipitation ,variability and sea level as mean precipitations. Changing land use pattern due to increasing, urbanization, industrialization and agriculture activities are serious issues that causing increase ground water with drawal resulting in depletion of ground water resources and mining of ground water resources, along with deterioration of water quality. Rainfall is highly irregular and erratic and declining year to year due to change climatic conditions as result of serious deforestation global warming etc. Human health is affected by change in biodiversity and ecosystem. Climate change will affect the quality of drinking water and impact of fresh water availability and impact on public health. About 70% of Earth’s surface is water of which 97.5% is salty water and 2.5% is fresh water. Less than 1% of this 2.5% amount of freshwater is accessible. As sea water rise’s, salt water of ocean in filtrate as coastal fresh water due heavy rainfall and flooding waste more fertilizer and municipal sewage mixed with coastal fresh water and change alter into more oxygen dead zone. Weather extreme and climate variability is main driver of food production in recent global challenge. Recent global challenge food security, fresh water availability, increase incidence of extreme high sea level. Loss of agriculture reproduction and increase in food prices and changes in weather patterns and alter availability and quality of water in many part of world. Climate change is an on-going phenomenon. This will inevitably bring about numerous environmental problems, including alterations to the hydrological cycle, which is already heavily influenced by anthropogenic activity. Chemical fertlizer’s has been adversely affecting the flora, fauna as well as soil quality . more ever every year plant pathogen are causing loss of 10 to 20% of agricultural production world wide. Ground water will be vital to alleviate some of the worst drought situations. flooding and contaiminated water supplies, more intense weather events are likely to increase to risk of infectious disease epidemics and erosion of low-lying and costal land. Climate Chang will affect the quality of drinking Water and impact of fresh water availlablity and impact on public health it’s better to use UV Water purifiers. This paper will explore what climate change. Water is prime natural resources fulfilling our needs in a precisious assets.we must acts to preserve and utilize every drop of water. water resources can be assessed on the basis of surface and subsurface water bodies. Climate change imapact on ground Water the impact of climate change on ground water has been studied much less than the impact on surface waters. Ground water reacts to climate change mainly due to change in ground water recharge, but also change in river level in response to increase in mean Temperature, precipitation, variability and sea level as mean precipitations. Changing land use pattern due to increasing, urbanization, industrialization and agriculture activities are serious issues that causing increase ground water with drawal resulting in depletion of ground water resources and mining of ground water resources, along with deterioration of water quality. Rainfall is highly irregular and erratic and declining year to year due to change climatic conditions as result of serious global warming .Impacts of sea level rise on salinity intrusion global climate change has resulted in gradual sea level rise. sea level rise can cause saline water to migrate up stream in estuaries and rivers, thereby threating fresh water habitat and drinking- water supplies. Hydrology all the costal margin; fresh ground water flowing in land areas meets with saline ground water from the ocean. the fresh ground water flows from in land areas towards the coast where elevation and groundwater level are lower because salt water has higher content of dissolved salt and minerals. it denser the fresh water, causing it to have hydraulic head than freshwater. hydraulic head refers to the liquid pressure exerted by water column. the higher pressure density of salt water cause it to move into costal aquifiers in a wedge shape under the freshwater. the salt water and fresh water meets in a transition zone where mixing occurs through dispersion and diffusion.

Effects of Future Increases in Tidal Flooding on Salinity and Groundwater Dynamics in Coastal Aquifers

AbstractFuture increases in the frequency of tidal flooding due to sea level rise (SLR) are likely to affect pore water salinities in coastal aquifers. In this study, we investigate the impact of increased tidal flooding frequency on salinity and flow dynamics in coastal aquifers using numerical variable‐density variably‐saturated groundwater flow and salt transport models. Short (sub‐daily) and long (decadal) period tides are combined with SLR projections to drive continuous 80‐year models of flow and salt transport. Results show that encroaching intertidal zones lead to both periodic and long‐term vertical salinization of the upper aquifer. Salinization of the upper aquifer due to tidal flooding forces the lower interface seaward, even under SLR. System dynamics are controlled by the interplay between SLR and long period tidal forcing associated with perigean spring tides and the 18.6‐year lunar nodal cycle. Periodic tidal flooding substantially enhances intertidal saltwater‐freshwater mixing, resulting in a 6‐ to 10‐fold expansion of the intertidal saltwater‐freshwater mixing area across SLR scenarios. The onset of the expansion coincides with extreme high water levels resulting from lunar nodal cycling of tidal constituent amplitudes. The findings are the first to demonstrate the combined effects of gradual SLR and short and long period tides on aquifer salinity distributions, and reveal competing influences of SLR on saltwater intrusion. The results are likely to have important implications for coastal ocean chemical fluxes and groundwater resources as tidal flooding intensifies worldwide.

Facies Changes, Evolution of Biogenic Structures, and Carbon Isotope Stratigraphy of the Cambrian Series 2 to Miaolingian Transition on the Southern North China Craton

The Cambrian Series 2–Miaolingian transition is a pivotal period during Earth history, which witnessed the decline of biodiversity and the reduction in biomass, i.e., the redlichiid–olenellid trilobite extinction. The notable δ13C excursion (RECE) near the Cambrian Series 2–Miaolingian boundary in east Gondwana and China apparently corresponds with the redlichiid trilobite extinction. To better understand the causal mechanism of this biotic crisis, we report the carbon isotope stratigraphy and facies changes from Cambrian Series 2–Miaolingian transition of the Mantou Formation on the southern North China Craton. The carbon isotope excursions at the Cambrian Series 2–Miaolingian transition in the study area are 0.7‰ in the Chishanhe section and −0.2‰ in the Luoquan section, respectively, showing a weak negative excursion or even no negative excursion. The sedimentary environments in the study area gradually changed through time from a clastic tidal flat to a carbonate platform across the transition, which indicated a gradual rise in sea level, with anoxic conditions occurring predominantly before the RECE δ13C excursion. Microbially induced sedimentary structures and oncoids occurred widely at the top of Cambrian Series 2. Abundant metazoan trace fossils were preserved in the Miaolingian Series of the study area. The evolution of biogenic structures across the Cambrian Series 2–Miaolingian transition indicates the emergence of harsh environments associated with the proliferation of MISS and oncoids at the RECE horizon and the recovery of benthic metazoan fauna after the RECE biotic crisis.

Climate-Proof Planning for an Urban Regeneration Strategy

This paper deals with the issue of the relationship between climate change and the government’s land management policies, investigating how urban planning regulation may provide responses to the need for planning and designing the coastal urban settings affected by flooding phenomena as a consequence of gradual sea-level rise (SLR).In this frame of reference, comparison among the strategic planning experiences put into play in a variety of national and international settings suggests the urgency for policymakers to implement knowledge frameworks on planning instruments, in order to identify– as a prerequisite for defining site-specific design actions – the territorial settings affected by the phenomenon of flood risk.

Environmental changes clarified by pollen and diatom proxy records in the sedimentary archive of the northwestern Japan Sea during last 21.0 kyr

High-temporal resolution pollen and diatom records from the northwestern Japan Sea document environmental changes over the last 21.0 kyr. Vegetation and climate changes were evaluated using the forest-steppe (SFI) and the pollen temperature (Tp) indices. The highest SFI occurred between ca. 21.0 ka and 16.6 ka and indicates the presence of a relatively dry climate and large areas of forest-steppe in the region. Boreal forests covered the mountain slopes. The broad-leaved trees survived in refugia located in lower mountain belts. Beginning ca. 16.6 ka, SFI decreases, while Tp increases, especially between ca. 11.0 ka and 5.7 ka. However, variations in these indices indicate fluctuating climates during the deglaciation. Significant vegetation changes occurred in the Holocene. Mixed deciduous forests with a predominance of Quercus became widely present beginning ca. 9.8 ka. The area of forest-steppe was reduced occurring only in local habitats. Pinus became one of the most common taxa in the forest ca. 5.3 ka. The geographic features of the coring area have determined in the past the persistence throughout the record of cold-water diatom flora. Cold-water diatoms have dominated in both cool and warm intervals; however, a small increase in the percentage and species diversity of warm-water diatoms was noted for warming. Low sea level during the Last Glacial Maximum (LGM) and early Holocene changed the general patterns in the sea circulation and in the vectors of the longshore currents, which transported the waters formed in the shallow areas of the northeastern and northern parts of the Japan Sea. A slight increase in sublittoral benthic diatoms indicates a lowered sea level during the LGM. The increase in sublittoral planktonic diatoms reflects a gradual rise in sea level during the Bølling–Allerød (BA) and Younger Dryas (YD). A greater component of oceanic diatom species at Holocene indicates the inflow of Pacific waters across both the Tsushima and Tsugaru straits. This study of pollen and diatom records demonstrates a clear response to climatic fluctuations and sea level changes in the Japan Sea during the Late Pleistocene and Holocene.

Cyclic variations in paleoenvironment and organic matter accumulation of the Upper Ordovician–Lower Silurian black shale in the Middle Yangtze Region, South China: Implications for tectonic setting, paleoclimate, and sea-level change

During the Ordovician–Silurian transition, the Yangtze Block in South China experienced intense tectonic movements and climate change and was covered by the widely distributed black shales of the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation, which recorded key information about these major geological events. By geochemical and petrological analyses of three profiles located in the Middle Yangtze Region, at least four long-term sedimentary cycles can be identified in the Upper Ordovician–Lower Silurian black shale. These cycles are mainly controlled by paleoclimate changes and tectonic activity. The Late Ordovician tectonic subsidence related to the Kwangsian Orogeny promoted a gradual sea-level rise and the deposition of the Wufeng black shale in the Middle Yangtze Region, while a significant sea-level fall related to the Hirnantian intensifying glaciation terminated this process. Subsequently, post-Hirnantian warming climate and glacier ablation triggered a significant sea-level rise, reduced the water restriction, increased the productivity, and intensified the anoxic environment, promoting the deposition of black shale in the second sedimentary cycle. However, after the short period of climate warming, global climate cooling occurred again with a regional tectonic uplift in the study area. This led to a gradual sea-level fall, reduced anoxic environment, and increased water restriction during the Rhuddanian, as well as the deposition of black shale with a decreased amount of organic matter. Moreover, intensified glaciation occurred during the Rhuddanian–Aeronian transition significantly accelerated the falling speed of the relative sea level, resulting in a stratigraphic gap and a small thickness of the Silurian black shale in the Middle Yangtze Region. Afterward, the study area experienced a significant climate warming event during the Early Aeronian, which led to a large-scale glacier ablation and a short period of sea-level rise. This promoted the deposition of the Aeronian black shale in the third sedimentary cycle. Nevertheless, the intensified weathering condition related to a continuously warming climate and tectonic uplift led to sufficient supply of terrigenous deposits, sustained sea-level fall, and finally terminated the development of Ordovician–Silurian black shale in the Yangtze region. Thus, these cyclic variations of the black shale not only recorded the shift of the Ordovician–Silurian tectonic movement (from Ordovician subsidence to Silurian uplift) in the Middle Yangtze area and the Hirnantian glaciation, but also provide strong evidence for the global intensified glaciation during the Rhuddanian–Aeronian transition and the subsequent climate-warming event. In addition, this study also provides new perspectives for the understanding of global sea-level change during the Ordovician–Silurian transition.

The morphometric acclimation to depth explains the long-term resilience of the seagrass Cymodocea nodosa in a shallow tidal lagoon

Cadiz Bay is a shallow mesotidal lagoon with extensive populations of the seagrass Cymodocea nodosa at intertidal and shallow subtidal elevations. This work aims to understand the mechanisms behind the resilience of this species to gradual sea level rise by studying its acclimation capacity to depth along the shallow littoral, and therefore, to gradual variations in the light environment. To address this objective, these populations have been monitored seasonally over a 10 year period, representing the longest seasonal database available in the literature for this species. The monitoring included populations at 0.4, −0.08 and −0.5 m LAT. The results show that C. nodosa has a strong seasonality for demographic and shoot dynamic properties – with longer shoots and larger growth in summer (high temperature) than in winter (low temperature), but also some losses. Moreover, shoots have different leaf morphometry depending on depth, with small and dense shoots in the intertidal areas (0.4 m) and sparse large shoots in the subtidal ones (−0.08 and 0.5 m). These differences in morphometry and shoot dynamic properties, combined with the differences in shoot density, explain the lack of differences in meadow production balance (i.e. meadow growth – meadow losses) between the intertidal (0.4 m) and the deepest population (−0.5 m), supporting the long term resilience of Cymodocea nodosa in Cadiz Bay. This study contributes to the understanding of the mechanisms behind seagrass stability and resilience, which is particularly important towards predicting the effects of climate change on these key coastal ecosystems, and also highlights the value of continuous long-term monitoring efforts to evaluate seagrass trajectories.

Middle Jurassic evolution of a northern Tethyan carbonate ramp (Alborz Mountains, Iran)

Here, we provide a detailed facies and depositional record from a NE-SW-directed, 250-km-long transect across a distally steepened, Middle Jurassic carbonate ramp in the northern Tethyan realm (Iran). Among the six main facies types described, two stand out because of their beyond-regional significance: (i) Middle Callovian microbial and microbial-skeletal mounds embedded in muddy intermound sediment and (ii) Upper Callovian conglomeratic debris-flow deposits truncating the mound unit. The mound features described here did not evolve into reefal structures and evidence for a framestone structure is lacking. They occur as low-relief, mud-dominated domical structures (a few metres wide). The development of the Middle Callovian mounds is perhaps best linked to a period of minimum sedimentation rates and sufficient accommodation space resulting from a long-term gradual sea-level rise commencing in the Late Bajocian. With respect to the Upper Callovian conglomeratic deposits overlying the mound interval, the absence of sedimentary structures such as grading, the nature of the sub-angular or rounded clasts and the very poor sorting are indicative of a catastrophic debris flow origin. Based on data compiled here, the conglomeratic deposits likely formed due to relative sea-level fall inducing the reworking of mound facies by the lowered wave base and currents, and basinward transport of reworked material to the distal outer ramp. Our findings are compared with coeval deposits from the western Tethyan domain and placed into a process-oriented context. The described northern Tethyan Late Bajocian to Middle Callovian deepening-upward trend, followed by relative sea-level fall in the Late Callovian near the Middle-Late Jurassic transition, is in agreement with observations from other coeval Tethyan basins/platforms. Data shown here have wider relevance for workers concerned with the Jurassic evolution of the Tethyan Ocean in general and shed light on the intricate relation of changes in accommodation space and ramp architecture.

Environmental constraints on the distribution of matground and mixground ecosystems across the Cambrian Series 2–Miaolingian boundary interval in Iran: A case study for the central sector of northern Gondwana

The stratigraphic architecture, changes of depositional systems in lateral and vertical extent, and 3D-stacking pattern of second- and third-order sequences of the Cambrian successions on the northern Gondwanan margin indicates a distinct sea-level fall in the Alborz Zone and Central Iran corresponding with global sea-level fluctuations. The peak of the sea-level fluctuations is located at the boundary between the Lalun Formation and the base of the overlying Mila Group. A vertical trend from gradual sea-level rise during the Cambrian Series 2 (recorded as thick transgressive deposits of the Lalun Formation) to transgressive valley-fill system at the base of the Fasham Formation and overlying highstand subtidal carbonates (carbonate platform of the Deh-Sufiyan Formation) can be observed. This trend is paralleled by a change from mixgrounds with metazoan body fossils to microbial matgrounds and microbial boundstones (thrombolites and stromatolites). The general increase in vagile bilaterian metazoans led to a distinct proliferation in ichnofossils in the Lalun Formation indicating a considerable increase in progressive ecospace utilization and tiering complexity. These are associated with biodiffusion, sediment reworking and bioirrigation so that matgrounds were disrupted and mixed layer substrates developed. A proliferation of microbes took place at the base of the Mila Group, which is regarded as a reaction to unfavourable environmental conditions and considerable challenges for metazoans. Consequently, a dramatic degradation of marine bottom communities followed the major eustatic sea-level fall at the Cambrian Series 2–Miaolingian boundary interval and led to the decrease in ichnodiversity, bioturbation intensity, depth of bioturbation and burrow size at the base of the Mila Group. The amount of biogenic mixing significantly decreased, and eventually sedimentary mixed layers disappeared.

Minimal stratigraphic evidence for coseismic coastal subsidence during 2000 yr of megathrust earthquakes at the central Cascadia subduction zone

AbstractLithology and microfossil biostratigraphy beneath the marshes of a central Oregon estuary limit geophysical models of Cascadia megathrust rupture during successive earthquakes by ruling out >0.5 m of coseismic coastal subsidence for the past 2000 yr. Although the stratigraphy in cores and outcrops includes as many as 12 peat-mud contacts, like those commonly inferred to record subsidence during megathrust earthquakes, mapping, qualitative diatom analysis, foraminiferal transfer function analysis, and 14C dating of the contacts failed to confirm that any contacts formed through subsidence during great earthquakes. Based on the youngest peat-mud contact’s distinctness, >400 m distribution, ∼0.6 m depth, and overlying probable tsunami deposit, we attribute it to the great 1700 CE Cascadia earthquake and(or) its accompanying tsunami. Minimal changes in diatom assemblages from below the contact to above its probable tsunami deposit suggest that the lower of several foraminiferal transfer function reconstructions of coseismic subsidence across the contact (0.1–0.5 m) is most accurate. The more limited stratigraphic extent and minimal changes in lithology, foraminifera, and(or) diatom assemblages across the other 11 peat-mud contacts are insufficient to distinguish them from contacts formed through small, gradual, or localized changes in tide levels during river floods, storm surges, and gradual sea-level rise. Although no data preclude any contacts from being synchronous with a megathrust earthquake, the evidence is equally consistent with all contacts recording relative sea-level changes below the ∼0.5 m detection threshold for distinguishing coseismic from nonseismic changes.

Influence of aquifer heterogeneity on sea level rise-induced seawater intrusion: A probabilistic approach

Seawater intrusion (SWI) is influenced by a variety of coastal phenomena, such as sea level rise (SLR), inundation of low-lying coastal regions, coastal storms, recharge rate variations, and pumping-induced saltwater upconing. Quantification of the influence of heterogeneity in the hydraulic conductivity field on SWI combined with SLR, land-surface inundation, and recharge rate variations in an unconfined aquifer is the main objective of the present study. The principal SWI indicators used in this study are length of the SWI wedge, seawater volume, and weighted average transition zone width. Characterized by the hydraulic conductivity field variance (σlnk2), the longitudinal correlation length (λx), the type of SLR (gradual or instantaneous SLR), the land-surface inundation consideration, and the recharge rate variations, 72 scenarios have been introduced, and for each of them, 50 sets of heterogeneous hydraulic conductivity fields have been generated. Based on two approaches, namely ensemble Monte-Carlo and a Bayesian framework, it is demonstrated that: (1) the land-surface inundation consideration increases the SWI wedge length and the seawater volume regardless of the type of SLR, while it decreases the weighted average transition zone width in gradual SLR scenarios; (2) λx has a more significant impact on SWI characteristics compared to σlnk2; (3) increasing the degree of aquifer heterogeneity results in larger effective dispersion values; (4) Numerical bootstrapping suggests that the introduced Bayesian framework could be adopted as an alternative to computationally demanding methods such as bootstrapping for stochastic analysis of SWI; (5) Reliability analysis indicates the general belief that considering the heterogeneity decreases the SWI wedge length and the seawater volume, while increases the transition zone width compared to the homogeneous modeling is associated with huge amounts of uncertainty proportional to the aquifer heterogeneity itself; and (6) the results show that the impact of heterogeneity on the SWI indicators is similar under different recharge rates.