Rapid Sea-level Rise Research Articles

Effects of sea-level rise on blue carbon stocks of mangrove ecosystems: insights from Pohnpei Island, Federated States of Micronesia

Carbon storage processes in mangrove ecosystems are summarized and future research directions are discussed based on findings from our long-term monitoring studies on Pohnpei Island in the Federated States of Micronesia. On Pohnpei, where coral reef-type mangrove forests dominate, Rhizophora communities maintain their habitat by accumulating mangrove peat at over 5 mm year-1 in response to rapid sea-level rise, but surface erosion is progressing in communities where the tree density of Rhizophora spp. has declined through succession. However, high-resolution aerial photographs taken by drones have identified trees with reduced vigor even in Rhizophora forests, and if sea-level rise occurs at a rate close to the IPCC's maximum prediction, then Rhizophora forests, which are valuable carbon storage sites due to mangrove peat accumulation, are likely to disappear. The impact of relative sea-level rise is determined by the sum of the rate of ground-level change by the external sediment budget and the rate of ground-level rise with mangrove peat accumulation. In the future, each region will need to conduct its own quantitative evaluation.

A new deglacial climate and sea-level record from 20 to 8 ka from IODP381 site M0080, Alkyonides Gulf, eastern Mediterranean

Records of relative sea-level rise for the last deglaciation are mostly limited to coral reef records and geophysical model estimates, but observational data from regions with temperate climates is sparse. We present a new relative climatic and regional sea-level rise record for glacial Termination 1 (Marine Isotope Stages [MIS] 2–1) based on ostracode paleoecology from the upper 8 m of the International Ocean Discovery Program (IODP) Site M0080 collected on Expedition 381, in the Gulf of Alkyonides, eastern Corinth basin of the Mediterranean Sea. Results show a series of major faunal transitions from lacustrine (Ponto-Caspian, Lake Corinth) glacial-age assemblages to fully marine (Mediterranean) interglacial assemblages between 20 and 8 ka. During glacial and early deglacial intervals, the Gulf of Alkyonides was characterized by non-marine lacustrine conditions with episodic sediment input from coastal, saline lake environments. Relatively stable lake shoreline conditions marked by the distinctive Tuberoloxoconcha sp. Existed from ∼17.5 to 15 ka. During the peak deglacial interval, the BØlling-AllerØd (B-A, ∼15–13.5 ka), rapid sea-level rise is indicated by a fully marine ostracode fauna colonization, which persisted from 13.5 to 7.5 ka (Late Pleistocene-Early to Middle Holocene).The transition from lacustrine to marine environments confirms that during the last glacial maximum (LGM) low sea level (130 - 125 m below present day), the Corinth-Alkyonides depocentres were lacustrine. Marine water breached the shallow Rion and Acheloos-Cape Pappas sills, which today are ∼50–60 m deep, separating the Mediterranean and Corinth-Alkyonides system beginning about 15 ka. Based on Alkyonides sedimentation rates, mean rates of sea-level rise during the B-A flooding of the Corinth-Alkyonides system are comparable to those obtained from coral reef sea level (SL) records, at least 10–20 mm yr−1. Changes in sedimentation and sill depths in this tectonically active region may have played a role in reconnection of the Mediterranean and Corinth/Alkyonides system over a prolonged period. However, the ages and scale of the faunal changes and their clear correspondence with previously published global sea-level curves and the regional sea-level curve based on deglacial land elevation changes predicted by the ICE-7G model suggests the M0080A deglacial is dominated by the glacio-eustatic sea-level rise and records details of global climate changes during Termination 1.

Deconstructing the causes of July sea level variability in the East Sea from 1994 to 2021

In 2021 the East Sea experienced its highest July sea level (65.09 cm), as well as the highest July sea surface and atmospheric temperatures, in the 29 years between 1993 and 2021. We present several methodologies to identify the more important causes of sea level change (SLC) in a semi-enclosed sea and explore the critical fluctuation of ocean mass transport divergence during a period of rapid sea level rise. Based on satellite altimeter data in the East Sea, the SLC, as reflected in the absolute dynamic topography (ADT), which is the ADT difference between the last and first days of a month, was 7.18 cm in July 2021. This may reflect a combination of oceanic and atmospheric factors: ocean heat transport divergence among the Korea, Tsugaru, and Soya Straits was found to contribute 2.32 cm of SLC, atmospheric heat flux at the sea surface contributed 2.87 cm of SLC, and mass divergence (including errors) accounted for 1.98 cm of SLC. The monthly mean sea level (ADT) variation in the East Sea should be examined in terms of the oceanic and atmospheric fluxes, and the SLC sources can additionally be divided into heat and others (mass + errors). The proportional contribution of heat to SLC from 1994 to 2021 was 97.4%. Although the contributions of mass and errors were small, there were substantial temporal fluctuations, as their standard deviation reached up to 96.7% of that of SLC in ADT. In the near future, a more precise analysis of the contributions of mass and errors to SLC is required.

Holocene coastal sedimentary evolution and neolithic human adaption in response to sea level changes in the Palaeo-Taihu valley, East China

The neolithic human-land relationship in the eastern coastal plain of China, interlinked sedimentary evolution and sea level changes, has been central to numerous studies. Here, we focus on the evolution of the sedimentary environment and its impacts on human activity in the Palaeo-Taihu valley (PTV) within the northern wing of Hangzhou Bay in response to post-glacial sea level rise. We employ multi-proxy analyses (lithology, AMS 14C, grain size, elements, TOC, and microfossil) on a new sediment core (WZ05) of comparatively analyze a series of previous radiocarbon-dated cores. Our results indicate that since the last deglaciation, the sedimentary environment of Core WZ05 has undergone the floodplain, upper tidal flat, estuary, upper tidal flat, coastal marsh, and fluvial plain, respectively. Regional cores comparisons display three stages: (1) A late Pleistocene incised valley (older than 9600 cal yr BP) dominated by terrestrial deposits accompanied by pottery sherds and rice phytoliths revealing that human activity on the floodplain can be dated to ca. 10600-10300 cal yr BP; (2) An early-mid Holocene transgression stage (9600-7800 cal yr BP) resulted from rapid sea level rise, causing widespread seawater inundation of the floodplain which interrupted early human activity. The transgression maximum during 8000-7800 cal yr BP was marked by the highest sedimentation rates and the coexistence of deep and shallow water species of foraminifera, corresponding to the appearance of a semi-enclosed estuary; (3) Finally, mid-late Holocene terrestrial deposits are the response to a slower sea-level rise and the seaward migration of the coast as the sediment supply exceeded sea level rise at 7800 cal yr BP. Tidal flats and coastal marshes dominated the PTV until 6500 cal yr BP, thereafter sediments continue to fill the PTV such that it develops into a subaerial plain. The reappearance of a freshwater environment since ∼ 7600 cal yr BP allowed the recovery of rice cultivation in the region. Saltwater deposits interspersed with terrestrial deposits between 7000-6500 cal yr BP probably reflect marine inundation during storm events and would have depressed rice domestication.

Sea level variation in the Arctic Ocean since 1979 based on ORAS5 data

The Arctic is currently experiencing unprecedented changes across all components of the climate system, primarily driven by global warming. As an important indicator of climate change in the Arctic, sea level reflects variations in both the atmosphere and ocean. This paper analyzes the sea level variation of the Arctic Ocean over the past four decades using ORAS5 data, which is the product of the latest reanalysis-analysis system produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). ORAS5 accurately reproduces the main spatial features of the climatology and temporal evolution of sea surface height (SSH) in the Arctic Ocean, as observed by satellite altimeters, and reveals that seasonal variability is the most significant property of the sea level variation in this region. The seasonal cycle of SSH is closely linked to atmospheric circulation and sea ice formation. The first two dominant modes of the annual-mean SSH in the Arctic Ocean exhibit significant decadal variability. The first mode can be explained by the Ekman transport of wind related to the Arctic Oscillation (AO), which leads to antiphase changes in SSH on the continental shelves and in the deep basins. The second mode shows an antiphase oscillation of SSH between the Eurasian and Canadian Arctic Archipelago (CAA) sides and is driven by the wind anomaly associated with the Arctic dipole anomaly (DA). Due to the decadal variations associated with climate modes, particularly the AO, sea level in the Arctic Ocean has been continuously rising since the mid-1990s or early 2000s, with the most rapid sea level rise occurring in the Beaufort Sea.

Fossil Benthic Foraminifera in the Nakdong River Delta (Southeast Korea) and off Fukuoka (Southwestern Japan) during the Early Holocene –Responses of the Neritic Faunas Under the Holocene Rapid Sea-Level Rise–

We studied fossil benthic foraminifera in three and seven sediment cores from the Nakdong River delta and of off Fukuoka, respectively, to assess sedimentation along the coasts of the strait between Korea and Japan during the early Holocene. Fossil benthic foraminifera in coarse-grained deposits/sandy sediments from ∼9.4–9.3 ka in cores ND-01 and KND-3 of the Nakdong River delta are characterized by a mixture of shallow-water and offshore species. These data suggest the development of transgressive deposits at ∼9.4–9.3 ka, likely associated with sea-level rise driven by the rapid retreat of glaciers at high latitudes (e.g. Laurentide Ice Sheet). Off Fukuoka, two clusters represent high-energy conditions characterized by common occurrences of attached benthic foraminifera; these clusters became dominant in the upper parts of our study intervals. Such attached species occurred commonly earlier, at around 10 ka, at deep offshore sites (> 60 m water depth) relative to shallow sites (< 60 m water depth). These findings are consistent with the development of current-dominated deposits at deep offshore sites at around 10 ka. Transgressive deposits in the Nakdong River delta and abundant attached species off Fukuoka at around 9 ka likely resulted from sea-level rise along the coasts of the strait between Korea and Japan driven by intermittent enhancement of the Tsushima Warm Current.

Vulnerability of Farmers to Climate Change in Central Dry Zone of Karnataka

Changing climatic parameters will have a huge effect on life and nature. Climate change will be best viewed through the increase in temperature, melting of ice and rapid rise in sea level. Such changes causes severe problems to human beings and other forms of life. Vulnerability to climate change is intimately related to poverty, as the poor are least able to respond to climatic stimuli. Further, certain regions of the world are more harshly affected by the effects of climate change than others. With this background the present study was carried out know the vulnerability of farmers to climate change in the Central Dry Zone of Karnataka with exposure, sensitivity and adaptive capacity as the dimensions. The study was conducted in the Central Dry Zone (Zone - IV) of Karnataka, India. Tiptur and Chiknayakanahalli taluks from Tumakuru district, Kadur from Chikmagalore district, Arsikere from Hassan district and Challakere from Chitradurga district were selected purposively for the study. The data was collected from 150 respondents. To exposure of farmers to climate change, rainfall and temperature were selected and the majority of farmers were severely exposed (0.822) and sensitive (0.894) to climate change with lower adaptive capacity (0.576) between the year 2013-2017. It shows that, 0.186, 0.226, 0.224, 0.220 and 0.241 was the Climate Vulnerability Index (CVI) of Arsikere, Kadur, Tiptur, Chiknayakanahalli and Challakere taluk, respectively. The overall CVI value of all taluks was 0.218. As per the result, all taluks were severely vulnerable to climate change.

Multiple geological events controlling rock types development: A case study of Wufeng-Longmaxi formation in southern Sichuan Basin, China

During Late Ordovician to Early Silurian, global geological events such as volcanic activity, glaciation, and mass extinction affected sedimentary environments and organic matter (OM) accumulation, and controlled the development of organic-rich shales. Taking the Wufeng-Longmaxi Formation (WF-L Fm) shales in southern Sichuan Basin as the research object, based on the core, thin section and scanning electron microscopy (SEM) observations, combined with X-ray fluorescence (XRF) two-dimensional element distribution maps, X-ray diffraction (XRD), trace elements, carbon isotope composition and total organic carbon (TOC) data, the relationship between geological events and sedimentary environments, OM accumulation as well as rock types development are analyzed, and the sedimentary environments response to geological events is elaborated. Eight rock types have been identified, and the minerals occurrence model has been characterized. By using Cu content, Mo content, δ13C and TOC to measure paleoproductivity, Sr content and Sr/Cu to judge paleoclimate, Sr/Ba to measure paleosalinity, and U/Th, V/Cr, V/Ni, and Ni/Co to analyze redox conditions, the sedimentary environments of the WF-L Fm shales can be furtherly divided into 7 intervals. In general, the deep water hypoxic-anoxic environments from Interval Ⅰ to Interval Ⅴ is conducive to the formation of organic-rich shales. The organic-rich shales formed in the anoxic environments from Interval Ⅰ to Interval Ⅴ are related to the fact that volcanic activities not only release a large amount of nutrients, promote biological prosperity and improve productivity, but also make the water in a sulfide anoxic environment, which is conducive to the preservation of OM. The rapid rise and fall of sea level caused by the Hirnantian glaciation harmed the living environments of organisms, led to the mass extinctions and provided material sources for OM accumulation, resulting in high TOC in the rock types of Interval IV. Irregular gravity flow can enhance terrigenous input in deep water for a short time and dilute OM, which is one of the reasons for the low TOC in the rock types of Interval Ⅵ to Interval VII. Upwelling current enhances nutrient flux in surface water and improves primary productivity of water, thus affecting the development of WF-L Fm organic-rich shales. Based on the aforementioned interpretations, the sedimentary model of the southern Sichuan Basin was established.

Eolian versus fluvial supply to the northern Arabian Sea during the Holocene based on Nd isotope and geochemical records

The north-eastern Arabian Sea (NE-AS) comes under a strong influence of land–ocean–climate interactions and regulates biogeochemical processes through the supply of huge amounts of dissolved and particulate materials and nutrients via eolian and fluvial supply. These processes underwent dramatic changes in the coastal regions due to sea-level rise and climate change during the Holocene; however, their relative roles remain elusive. The NE-AS receives large amounts of dissolved and particulate fluxes, and therefore, reconstruction of the past surface water Nd isotope composition (εNd) and tracing the provenance of sediment using detrital εNd and geochemical records would enable us to assess the role of various processes controlling these fluxes to the northern Arabian Sea. In this study, we have generated authigenic and detrital εNd records and geochemical records in a sediment core from the coastal region of the NE-AS, offshore Saurashtra. We found that the authigenic εNd profile closely followed the Holocene sea-level records; early Holocene less radiogenic values (∼ −8) were sharply shifted to more radiogenic values (∼ −5.5) during the mid-Holocene (6–7 ka) and thereafter remained stable, close to the modern surface water εNd value. The detrital εNd record broadly followed the authigenic εNd record, however, they differ in magnitude. The geochemical records based on major and trace elemental abundances show a similar trend to the authigenic εNd record and concomitant changes with the Holocene sea-level. Our investigation reveals that lower sea-level stand combined with a stronger monsoon during the early Holocene resulted in enhanced fluvial weathering fluxes from the west-flowing rivers and contributed to less radiogenic Nd. This situation changed dramatically during the mid-Holocene due to the weakening of the south-west monsoon and rapid sea level rise, which caused enhanced influence of open ocean water characterised by more radiogenic εNd (∼6) derived from the dissolution of dust from Arabia and African desserts. This dramatic shift in εNd profile indicates the enhanced influence of eolian over the fluvial supply of chemical weathering and erosion fluxes during the mid-Holocene. This observation is also consistent with the higher sedimentation rates with more radiogenic detrital supply. The finding of enhanced influence of eolian over fluvial mode of weathering and erosional inputs to the northern Arabian Sea has important implications for past nutrient supply (fluxes and compositions) and its impact on biogeochemical processes in the Arabian Sea.

The glacial geomorphology of the Mackenzie Mountains region, Canada

ABSTRACT During the Last Glacial Maximum, the Mackenzie Mountains region was glaciated by three distinct ice sources; the Laurentide Ice Sheet, the Cordilleran Ice Sheet, and independent montane glaciers. Rapid ice sheet thinning of the Laurentide-Cordilleran ice saddle in the south of this region contributed to rapid sea level rise events and influenced the style of deglaciation to the north. The current understanding of the glacial history of the broader region has been established through mapping from aerial imagery and early surveys between the early 1970s to the 2010s. The central portions of the Mackenzie Mountains have not yet been mapped. We present a new glacial geomorphological map for the Mackenzie Mountains region covering over 220,000 km2. This updated geomorphological map will form the basis of future work to reconstruct the former maximum ice extents, flow dynamics, and retreat pattern.

The potential for stabilizing Amundsen Sea glaciers via underwater curtains.

Rapid sea level rise due to an ice sheet collapse has the potential to be extremely damaging the coastal communities and infrastructure. Blocking deep warm water with thin flexible buoyant underwater curtains may reduce melting of buttressing ice shelves and thereby slow the rate of sea level rise. Here, we use new multibeam bathymetric datasets, combined with a cost-benefit model, to evaluate potential curtain routes in the Amundsen Sea. We organize potential curtain routes along a "difficulty ladder" representing an implementation pathway that might be followed as technological capabilities improve. The first curtain blocks a single narrow (5 km) submarine choke point that represents the primary warm water inflow route towards western Thwaites Glacier, the most vulnerable part of the most vulnerable glacier in Antarctica. Later curtains cross larger and deeper swaths of seabed, thus increasing their cost, while also protecting more of the ice sheet, increasing their benefit. In our simple cost-benefit analysis, all of the curtain routes achieve their peak value at target blocking depths between 500 and 550 m. The favorable cost-benefit ratios of these curtain routes, along with the trans-generational and societal equity of preserving the ice sheets near their present state, argue for increased research into buoyant curtains as a means of ice sheet preservation, including high-resolution fluid-structural and oceanographic modeling of deep water flow over and through the curtains, and coupled ice-ocean modeling of the dynamic response of the ice sheet.

Prehistoric human migration between Sundaland and South Asia was driven by sea-level rise

Rapid sea-level rise between the Last Glacial Maximum (LGM) and the mid-Holocene transformed the Southeast Asian coastal landscape, but the impact on human demography remains unclear. Here, we create a paleogeographic map, focusing on sea-level changes during the period spanning the LGM to the present-day and infer the human population history in Southeast and South Asia using 763 high-coverage whole-genome sequencing datasets from 59 ethnic groups. We show that sea-level rise, in particular meltwater pulses 1 A (MWP1A, ~14,500–14,000 years ago) and 1B (MWP1B, ~11,500–11,000 years ago), reduced land area by over 50% since the LGM, resulting in segregation of local human populations. Following periods of rapid sea-level rises, population pressure drove the migration of Malaysian Negritos into South Asia. Integrated paleogeographic and population genomic analysis demonstrates the earliest documented instance of forced human migration driven by sea-level rise.

Microfacies types and distribution of epicontinental shale: A case study of the Wufeng–Longmaxi shale in southern Sichuan Basin, China

For black shales, laminae and bedding are hard to identify, grain size is difficult to measure, and trace fossils do not exist. Taking the Ordovician Wufeng – Silurian Longmaxi shale in southern Sichuan Basin, China, as an example, the types, characteristics and models of microfacies in epicontinental shale are analyzed by means of full-scale observation of large thin sections, argon-ion polishing field emission-scanning electron microscopy (FE-SEM), and kerogen microscopy. The epicontinental sea develops delta, tidal flat and shelf facies, with black shale found in microfacies such as the underwater distributary channel and interdistributary bay under delta front facies, the calcareous and clayey flats under intertidal flat facies, the calcareous and clayey shelfs under shallow shelf facies, the deep slope, deep plain and deep depression under deep shelf facies, and the overflow under gravity flow facies. Basinward, silty lamina decreases and clayey lamina increases, the grain size changes from coarse silt to fine mud, the silica content increases from about 20% to above 55%, the carbonate and clay minerals content decreases from above 40% to around 10%, and the kerogen type changes from type II2 to type II1 and type I. Provenance and topography dominate the types and distribution of shale microfacies. The underwater distributary channel, interdistributary bay, clayey flat, clayey shelf, and overflow microfacies are developed in areas with sufficient sediment supply. The calcareous flat and calcareous shelf are developed in areas with insufficient sediment supply. The deep shelf shale area is divided into deep slope, deep plain, and deep depression microfacies as a result of three breaks. The formation of epicontinental shale with different microfacies is closely related to the tectonic setting, paleoclimate, and sea level rise. The relatively active tectonic setting increases the supply of terrigenous clasts, forming muddy water fine-grained sediment. The warm and humid paleoclimate is conducive to the enrichment of organic matter. The rapid sea level rise is helpful to the widespread black shale.

Late Pleistocene to Holocene sedimentary history in the Pearl River Delta revealed by OSL and radiocarbon dating

A reliable chronology is essential to understand deltaic sedimentation processes in response to sea-level fluctuations and climatic changes. In the Pearl River Delta (PRD), high-resolution chronostratigraphy is still limited which hinders the detailed interpretation of sedimentary history. In this study, optically stimulated luminescence (OSL) dating and radiocarbon (14C) dating were applied to establish a chronological framework of core P5-4 (30 m depth) in the southern PRD. Fifteen OSL and four 14C samples produced ages ranging from c. 8 ka to 0.5 ka, and two older OSL samples produced minimum ages of 75 and 62 ka. 14C ages are generally older (up to c. 1 ka) than the corresponding OSL ages and the discrepancy increases with depth. The ages and sedimentary data of sixteen published cores have been compiled to correlate the regional stratigraphy and reconstruct the late Pleistocene to Holocene deltaic process. It is concluded that: (1) The bottom subaerially-exposed deposits of core P5-4 were dated to marine isotope stage (MIS) 5, which is consistent with similar OSL-based records in the PRD. The laterally correlation shows that a depositional hiatus during c. 70–8 ka prevailed in the PRD and may attribute to strong erosion due to weathering and fluvial scouring. (2) Due to the relatively high altitude of bedrock, the post-glacial marine deposition of the PRD started at c. 8 ka, postdating other megadeltas by at least 2–4 ka. During 8–0.5 ka, a three-stage sedimentary process that is common in the PRD occurred in P5-4, i.e., early-Holocene (8–6 ka) rapid accumulation rate (5.44 m/ka) associated with rapid sea level rise, followed by mid-Holocene (6–3 ka) decelerated sedimentation rate (1.17 m/ka) in response to reduced sediment supply and strong tidal forces and late-Holocene (3–0.5 ka) accelerated sedimentation rate (2.28 m/ka) due to enhanced human activity.

Deglacial records of terrigenous organic matter accumulation off the Yukon and Amur rivers based on lignin phenols and long-chain n-alkanes

Abstract. Arctic warming and sea level change will lead to widespread permafrost thaw and subsequent mobilization. Sedimentary records of past warming events during the Last Glacial–interglacial transition can be used to study the conditions under which permafrost mobilization occurs and which changes in vegetation on land are associated with such warming. The Amur and Yukon rivers discharging into the Okhotsk and Bering seas, respectively, drain catchments that have been, or remain until today, covered by permafrost. Here we study two marine sediment cores recovered off the mouths of these rivers. We use lignin phenols as biomarkers, which are excellently suited for the reconstruction of terrestrial higher plant vegetation, and compare them with previously published lipid biomarker data. We find that in the Yukon basin, vegetation change and wetland expansion began already in the early deglaciation (ED; 14.6–19 ka). This timing is different from observed changes in the Okhotsk Sea reflecting input from the Amur basin, where wetland expansion and vegetation change occurred later in the Pre-Boreal (PB). In the two basins, angiosperm contribution and wetland extent all reached maxima during the PB, both decreasing and stabilizing after the PB. The permafrost of the Amur basin began to become remobilized in the PB. Retreat of sea ice coupled with increased sea surface temperatures in the Bering Sea during the ED might have promoted early permafrost mobilization. In modern Arctic river systems, lignin and n-alkanes are transported from land to the ocean via different pathways, i.e., surface runoff vs. erosion of deeper deposits, respectively. However, accumulation rates of lignin phenols and lipids are similar in our records, suggesting that under conditions of rapid sea level rise and shelf flooding, both types of terrestrial biomarkers are delivered by the same transport pathway. This finding suggests that the fate of terrigenous organic matter in the Arctic differs on both temporal and spatial scales.

Prediction of the joint impacts of sea level rise and land development on distribution patterns of mangrove communities

Mangrove distribution along shorelines shows distinct zonation patterns; thus, different communities may face various influences from sea level rise (SLR) and land use. However, long-term change predictions are usually based only on the total extent of mangroves. Few studies have revealed how SLR and land development such as agriculture, aquaculture, and urbanization jointly affect different intertidal mangrove communities. This study proposed a novel framework combining SLAMM (Sea Level Affecting Marshes Model) and the CLUE-S (Conversion of Land Use and its Effect at Small regional extent) model to assess the potential impacts on upper and lower intertidal mangrove communities. Maoweihai in Guangxi, China, was selected as the study area and the potential impacts from the squeeze effect and mangrove expansion potential were evaluated. We established three scenarios combining SLR and land use patterns to predict mangrove coverage projections by 2070. The results showed that, under a single SLR driver, the upper intertidal mangroves would be more adaptive to rapid SLR than the lower intertidal mangroves. However, under the combined influence of the two drivers, the upper intertidal mangroves would experience larger squeeze effects than the lower intertidal mangroves, with up to 80.5% of suitable habitat lost. Moreover, the expansion potential of upper intertidal mangroves would be considerably more limited than that of lower intertidal mangroves. The length of the expandable habitat patch boundary of upper intertidal mangroves only reached 1.4–1.8 ​km, while that of the lower intertidal mangroves reached up to 99.2–111.2 ​km. Further, we found that aquaculture ponds and cropland are the top two land development types that could occupy suitable habitat and restrict the mangrove expansion potential. Our results highlight that timely improvement of land use policies to create available landward accommodation space for mangrove migration is essential to maintain the coverage and diversity of mangrove communities under SLR. The proposed method can be a helpful tool for adaptive mangrove conservation and management under climate change.

Mangrove sediment erosion in the Sunda Shelf during meltwater pulses: Insights from biomarker records

Mangroves have received increasing attention in recent years for their high carbon storage capacity. The effects of sea-level change during the last glacial period on terrestrial deposition and coastal mangrove ecosystems were investigated using various organic lipid proxies in marine sediment cores from the Sunda Shelf in the southern South China Sea (SCS). The gradual reduction in the content of long-chain n-alkanes and n-alkanols, BIT index, and increasing δ13Corg trend from the last glacial to the Holocene indicated that the depocenter moved landward from the studied location during the deglacial sea-level rise. Remarkable peaks in the mangrove proxy (Taraxerol/n-C28 alcohol ratio) occurred during meltwater pulse (MWP) events in the Sunda Shelf area, associated with the drowning and destruction of mangroves that could not withstand the rapid sea-level rise. The decomposition of carbon-rich mangrove deposits may have contributed to atmospheric CO2 concentration during two strong MWP events in Sunda Shelf. Our results suggest the vulnerability of mangrove systems upon rapid sea level change with positive feedback for global warming.

Tidal influence on dissolved CO2 at Sapelo Island, Georgia, USA

Measuring carbon (C) loss through different pathways is essential for understanding the net ecosystem exchange of carbon dioxide (CO2) in tidal wetlands, especially in a reality where wetland mitigation and protecting coastlines from rapid sea-level rise is a growing priority. Tracking C loss can help reveal where an ecosystem is storing the most C, but it can also help scientists understand near- and long-term impacts of wetland restoration on climate. A recently developed partial pressure of dissolved CO2 platform was tested in a subtropical salt marsh with an apparatus that raised and lowered sensor housing with the tide. Additional low-cost water quality sensors were installed nearby for measuring turbidity and salinity. Here, we evaluated how well this floating sensor platform along with 28 d of biogeochemical data from a tidal salt marsh could detect C import and export from tidal effects. This work provides a pathway to low-cost, routine in-situ C exchange measurements which serve the needs of environmental managers, researchers, and others interested in better estimating wetland C storage and transport.

The Paris Agreement and Climate Justice: Inequitable Impacts of Sea Level Rise Associated With Temperature Targets

AbstractAnthropogenic greenhouse gas emissions are causing unprecedented changes to the climate. In 2015, at the United Nations (UN) Conference of the Parties in Paris, France, countries agreed to limit the global mean temperature (GMT) increase to 2°C above preindustrial levels, and to pursue efforts to limit warming to 1.5°C. Due to the long‐term irreversibility of sea level rise (SLR), risks to island and coastal populations are not well encapsulated by the goal of limiting GMT warming by 2100. This review article investigates the climate justice implications of temperature targets in light of our increasing understanding of the spatially variable impact and long temporal commitment to rising seas. In particular we highlight the impact that SLR will have on island states and the role of the Alliance of Small Island States (AOSIS) in UN climate negotiations. As a case study we review dual impacts from the Antarctic Ice Sheet under a changing climate: (a) recent climate and ice sheet modeling shows that Antarctic melt has the potential to cause rapid SLR with a distinct spatial pattern leading to AOSIS nations experiencing SLR at least 11% higher than the global average and up to 33% higher; and (b) future ice sheet melt will result in a negative feedback on GMT, thus delaying temperature rise. When considering these impacts in conjunction, justice concerns associated with the Paris Agreement are exacerbated.

Detrital zircons of the Devonian-Permian sandstones in the Qiangtang terrane, Tibet: Implication for Qiangtang rifting from Gondwana and uplift history of the Central Uplift

• New zircon ages of Devonian-Triassic deposits reveal sedimentary provenance change. • The breakup of the Qiangtang terrane from Gondwana occurred at about 288 Ma. • Primitive uplift of the Central Uplift occurred during the late Permian. • Closure of the Paleo-Tethys Ocean resulted in the uplift of the Central Uplift. This article reports new zircon U-Pb ages of the Devonian-Permian sedimentary rocks exposed in the central Qiangtang to reveal the change of sedimentary provenances through time. The age spectra of the Devonian and Carboniferous strata in the Qiangtang terrane are generally similar. They are typically characterized by two primary age populations at 520–700 Ma and 900–1000 Ma, indicating a Gondwana affinity. The Qiangtang terrane was part of the Gondwana supercontinent during a long period from the Ordovician to early Permian. The breakup time of the Qiangtang terrane from Gondwana is at ∼288 Ma, which is characterized by a drastic provenance change. The sedimentary evolution, together with detrital zircon ages also provides important perspectives on the uplift process of the Central Uplift in the Qiangtang terrane. Our data reveal that a primitive uplift of the Central Uplift occurred at the Late Permian. Although a continuous uplift has developed during the Early-earlier Middle Triassic, the Central Uplift was still an underwater environment due to rapid sea level rise. The final closure of the Paleo-Tethys Ocean and its branch gave rise to the uplift of the Central Uplift at the late Middle-earlier Late Triassic.