Stable Sea Research Articles

Crimes at sea: Exploring the nexus of maritime crimes across global EEZs

Maritime crime refers to conduct which is perpetrated wholly or partly at sea and is prohibited under applicable national and international law. It also represents an understudied sector of crime and security. Crimes including maritime piracy and armed robbery; illegal, unreported, and unregulated (IUU) fishing; terrorism; and illegal drug, arms, wildlife, and human trafficking occur across maritime zones and pose serious threats to international trade, national security, and maritime security. Notably, these crimes often do not occur in isolation. Previous research has documented the convergence of these crimes within the terrestrial space but is thus far lacking a similar analysis as it pertains to the maritime space, which accounts for one of the most commonly used trafficking modes. Therefore, using data from the Stable Seas database, we aim to understand how different types of maritime crimes geographically converge and what this intersection means for policy and practice. Specifically, data on maritime piracy and armed robbery; mixed migration; and maritime arms, cannabis, coca, opiate, synthetic drug, and wildlife trades are analyzed to (1) establish rankings of maritime crime importance; (2) develop typologies of maritime crime convergence; and (3) integrate predictor variables to understand why certain regions tend to experience more abundant crime than others. Given data availability and policy relevancy, analyses focused on coastal countries of Africa, Middle East, and the Indo-Pacific.

Records of deep-sea turbidity current activity in the Bengal Fan since the Last Glacial Maximum

The long-term evolution of deep-sea turbidity current activity is closely related to climate and sea level changes; however, the impact of abrupt climate change (e.g. millennial-scale events in high northern latitudes) is poorly known. In this paper, deep-sea turbidite records in the western part of the lower Bengal Fan were identified since the Last Glacial Maximum (LGM) to investigate the effects of abrupt climate change on the development of the Earth's largest deep-sea fan. Our records show a termination of turbidite activity in the western lower fan at 16.6 ka–15.4 ka almost contemporaneous with Heinrich 1 event (a cooling stadial in high northern latitudes). The trigger of this termination in turbidite activity may have been a sharp decrease in erosion rates during a time of relatively stable sea level and rapid source-sink processes. The subsequent episodes of the Bolling/Allerod warm interstadial and Younger Dryas cold stadial and the rapid sea level rise event that followed possibly induced adjustment of turbidity current activities in the Bengal Fan, as indicated by other published records. In summary, we show that close links exist between abrupt climate changes in the high-latitude Northern Hemisphere and deep-sea turbidity current activity in the low-latitude South Asia.

No Emergence of Deep Convection in the Arctic Ocean Across CMIP6 Models

AbstractAs sea ice disappears, the emergence of open ocean deep convection in the Arctic, which would enhance ice loss, has been suggested. Here, using 36 state‐of‐the‐art climate models and up to 50 ensemble members per model, we show that Arctic deep convection is rare under the strongest warming scenario. Only five models have convection by 2100, while 11 have had convection by the middle of the run. For all, the deepest mixed layers are in the eastern Eurasian basin. When that region undergoes a salinification and increasing wind speeds, the models convect; yet most models are freshening. The models that do not convect have the strongest halocline and most stable sea ice, but those that lose their ice earliest ‐because of their strongly warming Atlantic Water‐ do not have a persistent deep convection: it shuts down mid‐century. Halocline and Atlantic Water changes urgently need to be better constrained in models.

Uranium-series comminution ages constrain large catchment erosion and its response to climate change: A case study from the Changjiang

Catchment erosion not only plays an important role on landscape evolution, but also determines the exposure of rock debris in the regolith profile, and therefore impacts the chemical weathering and associated CO2 absorption and ultimately global climate. But climate also modulates erosion and complex interaction loops, especially at large scale can hamper a clear understanding of these processes. Here we mainly use Uranium-series Comminution Age (tcom) of core sediments from Changjiang estuary to reconstruct the catchment erosion, and the relationship with climate changes and human activities during the last 14 kyrs.Since 14 ka, the sea level has been rising continuously until current highstand system tract in the East China Sea where the Changjiang estuary is located. The sediments in the Changjiang estuary mainly come from the upper reaches erosion zone during this period, but the sediment supply from the middle and lower reaches has gradually increased since the Late Holocene. The period can be divided into two modes. The first mode happens from the Bølling-Allerød period to the Mid-Holocene when the sea level rose rapidly, and the tcom of sediment recorded the residence time in the upper reaches erosion zone, with a periodic pattern of tcom in a good agreement with climate changes. During the cold and dry periods, the longer tcom (average 460 kyrs) is consistent with less precipitation resulting in shallower erosion with transported material mainly coming from the soil with longer residence time. In contrast, during the warm and wet periods, the tcom is shorter (average 290 kyrs), with the more abundant precipitations that contribute to deeper erosion in the upper catchment, and more fresh material transported to the estuary through stronger hydrodynamic forces. The second mode is more chaotic and corresponds to 0 to 4 ka, when climate was warm and humid and stable sea level, but tcom fluctuated from 200 kyrs to 650 kyrs. The increasing river flooding caused by abundant precipitation leads to lateral migration of the river channel in the middle and lower reaches, and the sediments deposited in the floodplain were eroded and mobilized again. In addition, the rapid development of human activities since 2 ka has accelerated deforestation and agricultural cultivation, leading to localized erosion of the floodplain. These remobilized sediments were transported to the estuary and deposited, resulting in a larger tcom value. This study overall indicates that, in the millennial scale, the tcom of fine detrital fraction shows a sensitive and quick response to catchment erosion, and provides new insights into quantifying the time scale of sediment source to sink processes and inferring the paleoenvironment accurately climate changes.

Relationship between Large-Scale Variability of North Pacific Waves and El Niño-Southern Oscillation

Ocean waves are crucial for driving various oceanic processes. In this study, the spatial and temporal distribution of significant wave height (SWH) in the North Pacific (NP) is analyzed using the 42-year ERA5 reanalysis dataset from European Centre for Medium-Range Weather Forecasts (ECMWF). The presence of an ENSO signal is confirmed in wave fields of the North Pacific. Furthermore, the spatial distributions of swells and wind waves are analyzed using the Empirical Orthogonal Function (EOF) method, revealing that waves can transport large-scale signals from the NP to lower latitudes through swells. In addition, our research reveals a relationship between ENSO and Stokes drift in the NP. Stokes drift contributes positively to the maintenance of stable sea surface temperatures (SSTs) by transporting more (less) water towards the equatorial Pacific during El Niño (La Niña year) years. It is further noted that during strong ENSO events, the strength of the Stokes drift anomaly intensifies accordingly, which implies a strong link between wave-induced transport and ENSO.

Observed evidence for the impact of coastal currents on the recurrent Noctiluca scintillans blooms in the northwest Indian Ocean coast

Recently, South Eastern Arabian Sea (SEAS) experiences recurrent winter blooms of green Noctiluca scintillans with serious ecological consequences. Here, the analysis of green N. scintillans blooms in SEAS for the past three consecutive years (2018–2021) is presented. The daily monitoring showed intense winter blooms during November with stable sea surface temperatures, high nitrate-phosphate concentrations and relatively lower pH levels. Dissolved oxygen concentration decreased to near hypoxia in the later stages of the bloom. Our analysis finds that the increased occurrence of N. scintillans blooms along SEAS is driven by the coastal currents (EICC), which transport the bloom species from the east coast (south west Bay of Bengal) to west coast of India. Therefore, the N. scintillans seeding from the South west Bay of Bengal intensifies winter blooms in SEAS, thus unveils the influence of oceanic currents in deciding the phytoplankton blooms across the coastal regions of north Indian Ocean.

Late Holocene coastal dynamics south of the Chanthaburi estuary, eastern Gulf of Thailand

AbstractBeach ridges are depositional features that allow reconstruction of past sea-level variations, sediment dynamics, and storm activity. However, there are still very few systematic studies focusing on beach ridges available from the Gulf of Thailand. Along the east coast, satellite images provide evidence of beach ridges in the Chanthaburi Province, extending as far as 6 km inland, oriented parallel to the current coastline. These can be divided into a set of landward ridges (5.3–6.0 km inland) and seaward ridges (0.4–1.8 km inland) that are separated by an arm of the Chanthaburi estuary. Optically stimulated luminescence dating of 26 sand samples from 12 pits of ridge profiles suggests that the landward set of beach ridges formed ca. 3500 yr ago, while the seaward set of ridges formed between ca. 2100–1200 years ago, which also includes the modern active beach. It appears that the landward set of beach ridges developed during a period of relatively stable sea level followed by a rapid regression presently occupied by the arm of the Chanthaburi estuary. The seaward set of beach ridges apparently reflects a millennium of slowly retreating coastline until the modern beach ridge formed.

Feasibility and performance evaluation of low-cost GNSS devices for sea level measurement based on GNSS-IR

The low-cost GNSS devices are more convenient, flexible, and can be used as the low-cost Global Navigation Satellite System interferometric reflectometry (GNSS-IR) sensors. In this study, the feasibility and performance of low-cost GNSS devices for the temporary sea level measurement are assessed, by jointly utilizing signal-to-noise ratio (SNR) data from an Android smartphone Redmi Note 9 Pro and a low-cost antenna BT560 connected to a CHCNAV P5 GNSS receiver, while another identical receiver equipped with a standard geodetic-quality antenna and a pressure tide gauge (TG) were placed nearby for comparison. 80-hours of SNR data from multiple GNSS constellations were collected and processed. First, the SNR data from the three devices are compared and analyzed. In most cases, the SNR data of low-cost antennas have longer and clearer oscillations. But they are maybe more vulnerable due to the manufacturing of antennas or positioning modules. Second, quality control and height rate correction are crucial to stable sea level measurement of low-cost GNSS devices. Finally, the performance of sea level measurement of multiple GNSS constellations, dual-frequency, and dual-antenna was also assessed. It is found that the low-cost GNSS devices could yield stable sea level measurements, and have a root-mean-square error (RMSE) of about 16 cm, of which the performance is equivalent to or even slightly better than standard geodetic-quality devices, making it a promising solution for the temporary TGs.

Effects of Unsaturated Flow on Salt Distributions in Tidally Influenced Coastal Unconfined Aquifers

AbstractUnsaturated flow influences both the seawater extent under steady‐state conditions and the propagation of tides in coastal aquifers. However, its effects on salt distributions in tidally influenced coastal aquifers are little investigated. The present study used numerical simulations and data from laboratory experiments to analyze the effects of unsaturated flow on density‐dependent solute transport in coastal unconfined aquifers. The effects of the inland boundary condition (i.e., constant‐head or constant‐flux) were tested. Compared to a stable sea level, the results show that unsaturated flow has a more pronounced influence on salt distributions in coastal unconfined aquifers when tides are considered, regardless of the type of inland boundary condition. Neglect of unsaturated flow effects leads to expansion of the upper saline plume (USP), shrinkage of the saltwater wedge (seaward movement of saltwater wedge), and overestimation of water and salt exchange across the aquifer‐ocean interface. This is caused by a lower head in the nearshore area during high‐tide periods with the unsaturated zone effects removed. Thus, without the unsaturated zone, stronger head gradients within the nearshore aquifer occur at high tide, leading to stronger tidally driven seawater infiltration and hence a larger USP. Counterintuitively, ignoring unsaturated flow effects leads to greater average inland head over a tidal period, which shifts the saltwater wedge seaward. It is concluded that unsaturated zone effects should not be neglected for modeling tide‐affected seawater intrusion, especially if quantification of near‐shore conditions is important.

Susceptibility of the Climate Resilient Landforms of the Coastal Tract of Odisha and West Bengal, India

Abstract Wide sea beaches, beach ridges, barrier sand spits, sand dunes, and climate-sensitive tidal flats with mangrove forests on the coast of Odisha and West Bengal are the products of coastal process dynamics during the middle to late Holocene epoch under a stable sea level stage. These features are resilient to the global climate change phenomenon under natural conditions with the continuous supply of sediments and the spread of habitats that protect the coastal lowlands behind them against storms and inundations. Both the geomorphological and ecological systems of the depositional features were developed and optimized into matured stages before human intervention into the coastal system. These features were well developed along the storm-affected shoreline of the eastern coast of India with the supply of sediments into the coastal zones by river inputs, longshore current transport, cross-shore transport through storms, transgressive seas during the Holocene epoch, seasonal wind waves, and aeolian deposits. After assessing the climatic sensitivity stress, exposure index, adaptive capacities, and coastal vulnerabilities of the study area, the final result shows high susceptivity scores for the landforms that represent low resilient capacity; whereas, the coastal tracts of Purba Medinipur, and Sundarban represent low resilient capacity; and the coastal tract of Odisha reflects high to moderate resilient capacity. In the perspective of the global climate change phenomenon and human intervention into the coastal systems, the present study was conducted to find out the temporal changes of the coastal depositional features, to estimate the sensitivity of the features, and finally, to enquire about their susceptibility to the impact of cyclonic storms and the rapid rate of sea-level rise process currently occurring in the region of the tropical coast.

Comprehensive Satellite Observations and a Numerical Study of a Wintertime Shallow Sea Smoke Event in the Yellow Sea

Abstract A winter storm triggered a significant sea smoke with the northwesterly wind to the Yellow Sea, China, on 7 January 2021. The ocean responses to this event lasted about 3 days. Satellite observations show that the sea surface temperature dropped from 5.7° to 4.7°C on the following day and then recovered to the previous level; the chlorophyll-a, a bio-growth indicator, increased from 3.6 to 3.9 mg m−3 due to cooling-induced coastal upwelling between 7 and 9 January. Two buoys measurements showed that the air temperature dropped to −13.3°C and high relative humidity with a maximum value of 89.0% above the sea surface, creating favorable conditions for sea smoke generation. A Regional Ocean Modeling System (ROMS) and Weather Research and Forecasting (WRF) Model coupled model with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) chemical module was implemented to reproduce this sea smoke phenomenon and analyze the air–sea interaction. The 20°C temperature difference between extreme cold air (−13.3°C) and the relatively warm stable sea surface (4.7°–5.7°C) enhanced the seawater evaporation. In addition, we suppose the concentration of sea salt, a kind of condensation nucleus, with a particle diameter of 0.5–1.5 μm above the sea surface increased quickly on 7 January. The boiling-water-like sea surface was imaged on a synthetic aperture image. We developed an image analysis method to describe the cell-shaped texture characteristics imaged by Synthetic Aperture Radar (SAR). We also found that the sea surface imprints of sea smoke are governed by the thermal, not the dynamical instability. Significance Statement On 7 January 2021, a significant sea smoke event happened in the Yellow Sea. The ocean response to the event lasted 3 days. First, on a synoptic scale, this study presents the comprehensive satellite observations of the sea surface temperature drop and chlorophyll-a increase associated with the sea smoke. Second, a coupled air–sea interaction model with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) chemical module was implemented to reproduce this sea smoke phenomenon and identify which condensation nucleus induced such heavy sea smoke. Third, we developed an image analysis method to analyze high-resolution synthetic aperture radar images and found that the sea surface imprints of sea smoke are governed by the thermal, not the dynamical instability.

Lava deltas, a key landform in oceanic volcanic islands: El Hierro, Canary Islands

Marine and subaerial erosion of volcanic ocean islands form coastal cliffs and shore platforms, particularly during stable sea levels. Posterosional lava flows can spill over these coastal cliffs and fill the platforms, leading to the progradation of lava deltas. This work aims to analyze this volcanic rocky coast setting at the island scale and to assess the volcanic constructional and erosive degradational effects on the coast at the scale of one volcanic edifice. El Hierro Island, Canary Islands, exemplifies a rocky coast with an active sea-cliff profile, reflecting its early evolutionary stage as a young ocean volcanic island with no fringing reef. The occurrence of a contemporary insular shelf formed during the Holocene sea-level highstand (<7 ka) allows constraining the ages of those eruptions forming lava deltas affecting this geomorphological landform. A detailed bathymetry around the island allowed us to distinguish 17 eruptions fulfilling this criterion. The Montaña del Tesoro, which occurred about 1050 years BP, is one of these eruptions and was selected as a case study for morphometric modeling integrating subaerial and submarine data at the scale of a volcanic edifice. This eruption was a Strombolian basaltic volcanic event that produced a scoria cone, pyroclastic fall deposits, and lava flows that reached the ocean in the eastern rift zone of El Hierro island. We combine field-based observations with topographic and bathymetric data analysis to reconstruct the pre- and post-eruption Digital Elevation Models (DEMs) and, comparing with present-day DEM, to analyze morphometrically the influence of volcanism on the coastal landscape's development. The resulting landform complexity required the discretization of the lava field according to the coastline evolution and lava front sectors, and the subaerial or submarine lava placement. The pyroclastic materials' total erupted bulk volume (12,829,578 m3) corresponds to a volcanic eruption index (VEI) of 3. This event was primarily effusive. From a dense rock equivalent (DRE) volume of 25,615,424 m3, 87 % flowed as lava, 10 % formed the cinder cone, and 3 % the tephra fall deposits. We quantitatively demonstrate that dominant degradation occurs in the lava field, mainly disturbed by marine erosion. Marine erosion removed 9 % of the erupted volume of lava flows against 1 % by fluvial erosion. This work provides methods and results of great interest with different implications in oceanic volcanic islands, among which we can mention coastal planning (e.g., rock coast evolution) and volcanic risk assessment (e.g., the importance of Holocene sea-level rise on the development of shore platforms facilitating the progradation of lava deltas).

Constraining rapid sea level change through radiometric dating of corals growing over a range in paleowater depths

Corals do not all grow near the sea surface. Different species favour different ranges in depth and can survive at different depths from 0 to 5 m to over 0–100 m. Fossil corals, as markers of sea level, are the preferred choice in radiometric dating. Timing and magnitude of sea-level variations are determined from the location and age of a set of in-situ coral samples, and mark the lower bound in sea level. In addition, they have to be assigned an uncertainty to define the upper bound in sea level. This is referred to as the paleowater depth (PWD) and creates a major ambiguity in estimating the appropriate span of habitable depth in sea level. This uncertainty also has an impact on constraining the timing and magnitude of rapid changes in sea level. However, there are approaches that may minimize PWD uncertainties. These include assessing sea level data for groups of coral, during relatively stable sea levels, rather than individually. If samples were recovered in multiple drill-cores, along a sea-bed transect, tighter PWD constraints may apply for samples, in each core, depending on the magnitude of the slope of the sea bed. This method is particularly useful in cases of rapid sea level change over shallow continental shelves when the shift in the shoreline, with sea level change, is large. In these circumstances, the presence of a shallow-water reef established up or down-slope is indicative of a rapid change in sea level.

Early to mid-Holocene sedimentary evolution on the southeastern coast of Hangzhou Bay, East China, in response to sea-level change

Muddy coasts downdrift of large river mouths trap fine-grained sediments supplied from these rivers and have provided important settlement sites for prehistoric people, although the evolutionary history of such environments has not been well described. In this study, we integrate multi-proxy analyses (lithology, particle size, sedimentary structure, bioturbation, microfossil, and AMS 14C) on two new sediment cores (CC and ZF) from the Ningbo Plain, southeast of Hangzhou Bay, east China, with results from previous studies to explore the early to mid-Holocene sedimentary history of the palaeo-Ningbo Bay in response to post-glacial sea-level rise. The results show that the early to mid-Holocene stratigraphy in core CC was characterized by a muddy embayment succession before 7.3 cal kyr B.P. and an aggradational tidal flat to coastal marsh succession after that time. Rapid sediment accumulation occurred before ca. 7.7 cal kyr B.P. and at 7.3–7.2 cal kyr B.P., whereas periods of reduced sediment supply are recorded between 7.7 and 7.3 cal kyr B.P. and after 7.2 cal kyr B.P. At site ZF, in contrast, only sediments of coastal freshwater marsh overlay the last glacial stiff muds after ca. 7.5 cal kyr B.P. We suggest that the sheltered embayment favoured trapping of the fine-grained sediments during the early to mid-Holocene, while geometric changes of the bay in response to a phase of accelerated sea-level rise at ca. 7.7 cal kyr B.P. resulted in a reduced sedimentation rate and increased tidal energy. Abundant, large, and diverse (0.5–1.0 cm wide, 5–24 cm long) vertical burrows are present in core CC during 8.9–7.9 cal kyr B.P. and the trace fossils declined abruptly at 7.9 cal kyr B.P. We suggest this may have been induced by the exploitation of seafood by Neolithic people settled in the sheltered embayment, as supported by archaeological remains found at the Neolithic site. Rapid progradation of tidal flats and coastal marsh occurred since ca. 7.2 cal kyr B.P. in the palaeo-bay, which may reflect a response to a stable sea level after that time. The development of a thick early to mid-Holocene sediment sequence in the palaeo-Ningbo Bay and its relationship to sea-level changes indicate that such muddy embayments downdrift of large river mouths should be considered important in reconstructing the Holocene depositional system of the adjacent coast.

A revised mid-Pliocene composite section centered on the M2 glacial event for ODP Site 846

Abstract. The composite section from ODP Site 846 has provided key data sets for Pliocene stable isotope and paleoclimatic time series. We document here apparent outliers in previously published data sets for stable isotopes and alkenone-derived sea surface temperature (SST) estimates in the Pliocene interval containing the M2 glaciation (ca. 3.290–3.3 Ma) by tying high-resolution core measurements to a continuous downhole conductivity log. We generate a revised sequence of new stable isotopic and alkenone measurements across the M2 event that correlate well to the revised splices of color reflectance and gamma ray attenuation porosity evaluator data from Site 846, and to a new composite section produced at equatorial Pacific ODP Site 850. A new composite splice for Site 846 is proposed, along with composite isotope and alkenone time series that should be integrated into revised Pliocene paleoclimatic stacks.

Mid-Holocene coastline reconstruction from geomorphological sea level indicators in the Tràng An World Heritage Site, Northern Vietnam

In this paper we present a high resolution palaeo coastline model for the isolated limestone massif of Tràng An, Ninh Bình province, Vietnam. The archaeological and palaeoecological record here comprise rich archives of human activity set within a landscape that was cyclically transformed between inland and archipelagic states under the influence of past sea level changes. These records have become informative proxies in the study of current sea level rise. Well-preserved notches along the vertical limestone cliffs within the study property reveal several phases of prolonged stable sea levels that likely pertain to the Mid-Holocene marine transgression 8 ka BP to 4 ka BP and allow for detailed coastline reconstructions for parts of the Red River Delta (RRD). The resulting coastline model facilitates a closer look at past human responses to landscape and environmental changes at local and individual site-level, which improves our understanding of past human adaptations to climate-change induced sea level rise. These data also stand to inform current coastal vulnerability assessments and climate change response models.

Response of bay ostracod assemblages to Late Holocene sea-level, centennial-scale climate, and human-induced factors in northeast Beppu Bay, Japan

This study clarified the centennial-scale changes in meiobenthic bay ostracod assemblages in Japan over the past approximately 3000 years with relation to various human-induced and natural environmental factors. These factors were inferred via integrated multiproxy methods of high-resolution geological analyses of core sediments obtained from a shallow bay off a coastal plain, along with literature surveys of archeological and historical records. Five intervals were defined based on multivariate analyses of ostracod assemblages. The ostracod assemblage was stable before around the 6th century because of aggradational sedimentation related to gradual increases in sea level. Since then, the composite factors such as the development of a sandy spit near the study site, stable sea level, regional tectonics, regional centennial-scale climatic change possibly related to El Niño Southern Oscillation (ENSO), and flood mitigation by human settlement in the coastal plains triggered the formation of tidal flats and subtidal sandy areas with seagrass beds. This has markedly influenced offshore bay ostracod assemblages since around the 12th century. Anthropogenic impacts, such as reclamation and various artificial constructions since the late 20th century caused the disappearance of seagrass beds, input of coarser sediment into offshore bays, and increased nutrient loads. Therefore, ostracod assemblages have changed drastically. Ostracod assemblages near the boundary between land and sea have been affected by multiple complex factors, such as regional climate and depositional and human-induced processes during the Late Holocene.

Publisher’s note

Abstract This study clarified the centennial-scale changes in meiobenthic bay ostracod assemblages in Japan over the past approximately 3000 years with relation to various human-induced and natural environmental factors. These factors were inferred via integrated multiproxy methods of high-resolution geological analyses of core sediments obtained from a shallow bay off a coastal plain, along with literature surveys of archeological and historical records. Five intervals were defined based on multivariate analyses of ostracod assemblages. The ostracod assemblage was stable before around the 6th century because of aggradational sedimentation related to gradual increases in sea level. Since then, the composite factors such as the development of a sandy spit near the study site, stable sea level, regional tectonics, regional centennial-scale climatic change possibly related to El Nino Southern Oscillation (ENSO), and flood mitigation by human settlement in the coastal plains triggered the formation of tidal flats and subtidal sandy areas with seagrass beds. This has markedly influenced offshore bay ostracod assemblages since around the 12th century. Anthropogenic impacts, such as reclamation and various artificial constructions since the late 20th century caused the disappearance of seagrass beds, input of coarser sediment into offshore bays, and increased nutrient loads. Therefore, ostracod assemblages have changed drastically. Ostracod assemblages near the boundary between land and sea have been affected by multiple complex factors, such as regional climate and depositional and human-induced processes during the Late Holocene.

Making a Stable Sea: The Littorals of Eighteenth-Century Europe and the Origins of a Spatial Concept

AbstractSea level has become the almost unavoidable reference point of the impending environmental cataclysm. While inherently variable, sea level has been naturalized, in the form of mean sea leve...

Evolution of sedimentary environment in the Gulf of Thailand since the last deglaciation

Understanding marine sedimentary process and the land-sea interaction is vital to human production and life. Gulf of Thailand is a hotspot of such research due to the strong erosion, transportation, and deposition processes under the control of the monsoon climate in the region over the last deglaciation. Based on comprehensive analyses of lithology, grain size, and element index of core BT-7, we revealed that the sedimentary history of this region could be divided into three stages: (I) 13.5–7.5 cal ka BP, continental deposition period, when the central Gulf of Thailand was completely exposed to the surface; (II) 7.5–6.2 cal ka BP, land-sea interaction period, when the material source varied abruptly and the weathering intensity changed significantly, corresponding to frequent climate fluctuations between cold and warm, along with intermittent sea-level still stands; and (III) after 6.2 cal ka BP, period of stable marine sedimentary facies, when the seawater inundated the central Gulf of Thailand, the weathering intensity was slowly weakened with no significant change, and the climate fluctuated with a trend from warm to cold. Notably, since 3.5 cal ka BP, the weathering intensity has been rapidly weakened, entering a small ice age, and the relatively stable sea level has led to a consistent sedimentary environment in the Gulf of Thailand into modern times. Therefore, this study reveals the evolution of sedimentary environment at the interaction of the Indian Ocean and the Pacific Ocean over the last deglaciation. Based on the robust evidence, our findings could help improve the understanding of the sedimentary patterns and land-sea interactions in history.