Rapid Sea-level Rise Research Articles

Holocene sea-level rise and coastal aquifer interactions: Triggering mechanisms for environmental change and impacts on human settlement patterns at Dor, Israel

Future sea-level rise is expected to affect coastal aquifers and environments and have significant impacts on coastal communities. Here, we describe the impact of early to late Holocene sea-level variations on the coastal environment and human settlements of the Carmel Coast, Israel. One of these ancient communities, Tel Dor, was settled initially during the Late Pottery Neolithic (ca. 7 ka) on a wetland surface and then abandoned for ca. 1.5 ka before resettlement occurred on the adjacent aeolianite ridge from the Middle Bronze Age to the Crusader period (4.3–0.9 cal Ka BP). For the first time, high resolution chrono-bio-chemo-stratigraphy of sediment cores collected landward of the current shoreline at Dor are presented capturing a record of poorly sorted sand mixed with marine shells, well sorted aeolian sand and silty clay deposits. The record represents a series of brackish-freshwater wetlands formed in the coastal area of Dor between ca. 15 to 7 ka in response to relative sea-level rise and resulting rise of the coastal aquifers. After 7 ka, due to rising sea level and a transgressing shoreline, sand largely derived from the Nile Delta, reached the coast including the coastal wetland. Landward from the current shoreline, the period between ca. 7 to 4 ka is represented by alternating sand-silt facies consisting of reworked marine shells and brackish-fresh water biota. These lithological cycles reflect fluctuations between coastal and wetland environments governed by the response of the coastal aquifer to sea-level rise. Rapid sea-level rise led to a rise in the groundwater table and inundation of the area around Tel Dor, while periods with slower rates of sea-level rise resulted in coastal sand deposition. The settlement gap at Dor between 7 and 5.6 ka possibly reflects the behavioral response of the coastal settlers to sea-level fluctuation, and sediment depositional variation instigating aquifer inundation coastal marsh development and mobilization of sand bodies. This study provides a record of beach profile build-up along the Mediterranean coast of Israel and serves as an example of how sea-level rise affect unconfined coastal aquifers and the formation of wetlands due to rising water tables in low elevation coasts. Coastal inundation is a long-term risk factor for densely populated low-lying coastal regions that require a proactive approach for solving cascading impacts of sea-level rise.

Rapid sea-level rise during the first phase of the Littorina transgression in the western Baltic Sea

Glacio-isostatic adjustment (GIA) corrected limiting non-marine and marine sea-level data from the western Baltic Sea indicate a rapid relative sea-level (RSL) rise of 18 m for the first phase of the Littorina transgression using a linear age-elevation model. This accelerated RSL rise occurred in the time period 8.57 to 8.0 ka before present (BP) with an RSL rise rate of 31.5 mm/year. RSL rose from 28 m to 10 m below the mean relative sea level (bmrsl) during the time period of less than 600 years. The first phase of Littorina transgression documents the last big meltwater pulse (MWP), which has been reported also from various other regions in the world as a consequence of the final decay of the Laurentide ice sheet and additional meltwater sources from Antarctica.

The structure of the nonmarine fossil record: predictions from a coupled stratigraphic–paleoecological model of a coastal basin

AbstractPresented here is a coupled model of the nonmarine fossil record, based on a geometric model of deposition, a random-branching model of evolution, and an ecological model based on an elevation gradient. This model provides testable predictions about the stratigraphy and fossil occurrences in coastal nonmarine settings under three scenarios of sea-level change. A slow relative rise in sea level causes a declining ratio of channel to floodplain deposits, plus changes in community composition that reflect an upward increase in elevation relative to sea level. A rapid relative rise in sea level drives increasing aggradation rates, decreases the ratio of channel to floodplain deposits, and triggers a shift from higher-elevation (more inland) to lower-elevation (more coastal) communities. A fall in sea level produces an unconformity, manifested by valleys separated by interfluves. The resumption of deposition following the sea-level fall causes an abrupt shift in community composition across the unconformity, reflecting the duration of the hiatus and the increased elevation relative to sea level. This produces a cluster of first and last occurrences at the unconformity, and it is the only sequence-stratigraphic source of such clusters in a nonmarine system, in contrast to the multiple mechanisms for generating these clusters in marine systems. A central prediction of these models is that the nonmarine fossil record preserves systematic changes in community composition that reflect elevation (or equivalently, distance from shore). Diagnosing these gradients in ancient systems is a promising avenue of future research.

A 1.5 Ma Marine Record of Volcanic Activity and Associated Landslides Offshore Martinique (Lesser Antilles): Sites U1397 and U1399 of IODP 340 Expedition

The products of eruptive and mass-wasting processes that built island arc volcanoes are better preserved in marine deposits than on land. Holes U1397A and U1399A drilled during IODP Expedition 340 provide a 1.5 Ma record of the volcanic history of Martinique. 14C dating and δ18O patterns are used to reconstitute the chronostratigraphy of tephra, volcaniclastic turbidites, and mass-wasting events (traced by debris avalanches, debrites, and duplication and deformation of pre-existing sediments), leading to a new volcanic history of Montagne Pelée and Pitons du Carbet volcanoes. The top 50 m of core U1397A provides a continuous high-resolution sedimentation record over the last ∼130 ka. The sedimentation record deeper than 50 m in core U1397A and in the whole core U1399A is discontinuous because of the numerous sliding and deformation events triggered by debris avalanches related to flank collapses. Three successive activity periods are identified since ∼190 ka: the “Old Pelée” until 50 ka, the “Grand Rivière” (50–20 ka), and the “Recent Pelée” (20 ka—present day). The first two periods have the highest volcanic deposition rates offshore but very little outcrop on land. The whole magmatic activity of Mt Pelée comprises silicic andesites, but mafic andesites were also emitted during the whole “Grand Rivière.” At ∼115 ka, a major flank collapse (“Le Prêcheur”) produced a debris avalanche and submarine landslide that affected sea floor sediments by erosion and deformation up to ∼70 km from the shore. The Pitons du Carbet volcano was active from 1.2 Ma to 260 ka with numerous large flank collapses at a mean rate of 1 event every 100 ka. The average deposition rate of tephra fall offshore is much less than that at Mt Pelée. Our data show that correlations between the timing of large landslides or emission of mafic magmas and rapid sea level rise or lowstands suggested by previous studies are not systematic. The reconstituted chronostratigraphy of cores U1397A and U1399A provides the framework necessary for further studies of the magma petrology and production rates and timing of the mechanisms triggering flank collapses and related submarine landslides of Mt Pelée and Pitons du Carbet.

Sea level rise and climate change acting as interactive stressors on development and dynamics of tropical peatlands in coastal Sumatra and South Borneo since the Last Glacial Maximum.

Southeast Asian peatlands, along with their various important ecosystem services, are mainly distributed in the coastal areas of Sumatra and Borneo. These ecosystems are threatened by coastal development, global warming and sea level rise (SLR). Despite receiving growing attention for their biodiversity and as massive carbon stores, there is still a lack of knowledge on how they initiated and evolved over time, and how they responded to past environmental change, that is, precipitation, sea level and early anthropogenic activities. To improve our understanding thereof, we conducted multi-proxy paleoecological studies in the Kampar Peninsula and Katingan peatlands in the coastal area of Riau and Central Kalimantan, Indonesia. The results indicate that the initiation timing and environment of both peatlands are very distinct, suggesting that peat could form under various vegetation as soon as there is sufficient moisture to limit organic matter decomposition. The past dynamics of both peatlands were mainly attributable to natural drivers, while anthropogenic activities were hardly relevant. Changes in precipitation and sea level led to shifts in peat swamp forest vegetation, peat accumulation rates and fire regimes at both sites. We infer that the simultaneous occurrence of El Niño-Southern Oscillation (ENSO) events and SLR resulted in synergistic effects which led to the occurrence of severe fires in a pristine coastal peatland ecosystem; however, it did not interrupt peat accretion. In the future, SLR, combined with the projected increase in frequency and intensity of ENSO, can potentially amplify the negative effects of anthropogenic peatland fires. This prospectively stimulates massive carbon release, thus could, in turn, contribute to worsening the global climate crisis especially once an as yet unknown threshold is crossed and peat accretion is halted, that is, peatlands lose their carbon sink function. Given the current rapid SLR, coastal peatland managements should start develop fire risk reduction or mitigation strategies.

Aerial surveys reveal biotic drivers of mangrove expansion along a Thai salt flat ecotone

Rapid sea level rise (SLR) could overwhelm the adaptive capacity of many mangrove forests. The conservation of functional mangrove ecosystems will rely on their expansion into upper intertidal areas, including salt marshes and salt flats, in advance of SLR. The development of new mangrove habitats could be accelerated by amplifying positive biotic interactions among herbaceous plants, macrofauna, and mangrove trees, such as trapping of hydrochorous propagules or site amelioration. It was investigated how biotic and abiotic factors influenced the expansion of mixed‐species mangrove stands along a mangrove‐salt flat ecotone. Multi‐temporal unmanned aerial vehicle (UAV) imagery (< 1 cm/pixel) was used to monitor seedlings of Avicennia alba, Bruguiera cylindrica, and Lumnitzera racemosa in three sample plots (0.7–0.9 ha) over 2 years. The aerial images were used to map mangrove crowns, sedges (Fimbristylis tetragona), substrate elevation, and microtopography. The spatial distribution of seedlings was modeled using point pattern processes; mixed‐effects models were used to analyze how environmental factors influenced seedling survival and growth. The spatio‐temporal patterns of mangrove regeneration revealed that sedges and macrofauna facilitated the regeneration of mangroves into higher‐elevated areas of low tree density. Sedges not only trapped seeds but also increased the likelihood of survival among seedlings of all species. Large‐sized propagules established in undulating microtopography created through the bioturbation of macrofauna. Herbaceous vegetation expanded the range of macrofauna in the absence of trees. Thus, the migration of mangroves into hypersaline retreat areas may be accelerated by enhancing the growth of herbaceous vegetation and promoting burrowing macrofauna.

The response of foraminifera to rapid sea-level rise from tidal restoration of Ni-les'tun marsh, Oregon, U.S.A

Foraminifera preserved in saltmarshes are widely used to reconstruct relative sea-level change (RSL), and inferred from this, coseismic vertical coastal motions following an earthquake. However, how quickly foraminifera respond to rapid changes in RSL is poorly understood. Here, we present a six-year foraminiferal study of the tidal restoration of Ni-les'tun marsh and a comparison of modern and fossil assemblages. We installed eight stations on the marsh and sampled these stations for live foraminifera prior to and during the first six years after tidal restoration (2011–2017), and we extruded one short core at station 1 in 2016. At stations 1 to 7, tidal flat/low marsh assemblages, dominated by Miliammina fusca, colonized 10 months to 2.5 years after tidal restoration. At station 8, the first living mixed assemblage of foraminifera, dominated by Haplophragmoides wilberti, was found 2 years after tidal restoration. Our observations suggest that M. fusca, and to some extent H. wilberti, are opportunistic species (r-strategists), able to increase their standing crop rapidly after invading a new habitat (to up to ~3600 specimens per 10 cm3 sediment volume). Potential causes for the delay in foraminifera colonization include their reproductive cycle and/or limited food availability due to the slow response of the vegetation community and soil development to tidal restoration. However, the similarity among assemblages and concentrations of agglutinated foraminifera between the fossil and modern sediments, indicate that post-depositional taphonomic processes have minimal influence when incorporated in the stratigraphic record. Although foraminifera have shown a delayed response to tidal restoration in the Ni-les'tun marsh, the similarities between the modern and fossil assemblages indicate that the delayed response of foraminifera to tidal restoration is undetectable in study areas with low sedimentation rates (in this case 3.3 mm/yr) after tidal restoration. In the case of high post-earthquake sedimentation rates, sampling a few cm higher rather than immediately above an earthquake contact could avoid uncertainties of coseismic vertical motions when foraminifera have a delayed colonization.

Petrographical and geochemical characterization of the Upper Permian Longtan formation and Dalong Formation in the Lower Yangtze region, South China: Implications for provenance, paleoclimate, paleoenvironment and organic matter accumulation mechanisms

The Upper Permian Longtan and Dalong Formations are considered prospective targets for shale gas exploration and production in the Lower Yangtze region, South China. However, the paleoclimate change and the mechanism of organic matter accumulation in the shales are rarely reported. In this study, the varying provenance, paleoclimate, paleoenvironment, primary productivity, and the mechanism of organic matter accumulation of the Longtan and Dalong Formations were investigated using X-ray diffraction (XRD), polished section and scanning electron microscope (SEM), pyrite morphology, and elemental geochemical data.Multiple geochemical proxies indicate that the Longtan Formation was deposited in marine–continental transitional facies under a highly humid climate and intermediate-to-strong weathering conditions. The water column was oxic with low paleoproductivity and high terrigenous influx. The rapid rise in sea level during the deposition of the lower Dalong Formation resulted in an anoxic water column, high productivity, and low terrigenous input under a semiarid–semihumid climate and weak-to-moderate weathering conditions. The oceanic upwelling elevated primary productivity and was crucial in the organic matter accumulation. Therefore, the total organic carbon (TOC) is high in the lower Dalong Formation. However, the later sea level fall at the upper Dalong Formation led to a dramatic change in the sedimentary environment, which is characterized by a moderately humid climate, intermediate weathering conditions, decreased productivity, a dysoxic–oxic water column, and enhanced detrital flux.The correlations between TOC content and geochemical proxies suggest that the enrichment of organic matter in the Longtan Formation was mainly affected by terrigenous influx and sedimentation rate. The high TOC enrichment in the lower Dalong Formation was because of oxygen-deficit water column, high productivity, and low terrigenous influx. In the upper Dalong Formation, a combined effect of the decrease in primary productivity and relatively oxygen-enriched conditions was not conducive to the organic matter accumulation. They gave rise to low concentration of organic matter. However, the positive correlations of TOC vs. Cu/Al and TOC vs. Ni/Al indicate that paleoproductivity was nevertheless the most critical factor controlling the enrichment of organic matter.

Revised chronology of northwest Laurentide ice-sheet deglaciation from 10Be exposure ages on boulder erratics

We present new 10Be surface exposure ages from boulders on bedrock to directly date northwest Laurentide ice-sheet deglaciation through a wide swath of the western Canadian Shield that had no previous reliable temporal constraints on ice-margin retreat. Uplift-corrected boulder 10Be surface exposure ages are 13.9 ± 0.2 ka (n = 6) at a site on the western edge of the Slave Craton and 12.4 ± 0.2 ka (n = 5, 1 outlier) at a second site ∼110 km up-ice to the east. These direct 10Be ages for ice-margin retreat are ∼2.4 kyr and ∼1.6 kyr older, respectively, than the canonical deglacial chronology for the northwest Laurentide ice sheet that is based on minimum-limiting 14C dates. We infer an ice-margin retreat rate of 60–100 m yr−1 between the two sites over an interval spanning the transition from the Allerød warm period into the Younger Dryas cold period. This is significantly slower than the rapid >800 m yr−1 retreat rate for the northwest Laurentide ice sheet inferred from earlier deglacial chronologies, which has been hypothesized as a potential source of meltwater forcing for the Younger Dryas cold period. These first direct ages on spatio-temporal patterns of deglaciation in this data-poor region suggest that additional refinement of the deglacial chronology is needed to test hypotheses on the relation between ice-sheet retreat, associated meltwater discharge, abrupt climate change, and rapid sea-level rise.

A stepwise approach for identifying climate change induced socio-economic tipping points

Climate change may cause socio-economic tipping points (SETPs), where the state of a socio-economic system abruptly changes to a fundamentally different state. While their potential existence is recognized, a systematic method for policy-relevant research on SETPs is lacking. This study introduces a stepwise approach for identification of SETPs that supports decision making under uncertain climate and socio-economic conditions. The approach is demonstrated with a stylized case study on the collapse of house prices (a SETP) in a coastal city, due to increasing flood risk from sea level rise. We explore four dynamic adaptive management strategies under a wide range of possible futures. We find that under scenarios with very high and rapid sea level rise, tipping points in real estate prices occur if the market responds to sudden changes in perceived flood risk rather than gradually adjusting prices to changes in flood risk in a rational manner. Such SETPs can only be avoided with a proactive strategy and when flood protection measures are implemented rapidly. Our approach can guide future studies on SETPs and seeks to move the study of SETPs towards a concept that provides perspective of action for policy makers.

Seismic Attributes Aided Characterization of Margin Backstepping and Advance along Isolated Carbonate Sequences, Sirt Basin, Libya

Isolated carbonate platforms are common and contain significant hydrocarbon accumulations, particularly in the tectonically complex Sirt Basin in Libya. This study investigates the margin cyclicity of two carbonate stratigraphic sequences developed on an isolated carbonate platform in the NW Sirt Basin using 3-D post-stack seismic volume and wireline log data. The two sequences (sequences 4 and 5) are bounded by unconformity surfaces from the base and top. Seismic attributes show that each sequence displays a cycle of margin backstepping followed by margin advance for several hundred meters. This study concludes that the margin backstepping and advance are mainly influenced by sea-level changes. A rapid sea-level rise caused the backstepping, whereas slow sea-level rise caused the margin advance.

Coralline algal assemblages record Miocene sea-level changes in the South China Sea

We have previously shown that the coralline algal assemblages (CAAs) of the South China Sea may indicate post-Pliocene paleo-water depth changes; however, the pre-Pliocene coralline algal compositions and related sea-level significance remain to be elucidated. In the present study, we explore the Miocene coralline algal compositions and their role in recording the sea level, and show the distribution, classification, type, abundance, and diversity of Miocene coralline algae from 213 petrologic thin sections using a coral-reef carbonate sequence from the northern South China Sea. The diversity and abundance of coralline algae in the early and late Miocene are higher than those in the middle Miocene. Eleven genera were identified and grouped into seven CAAs, showing a water depth range from <5 m to >25 m. At 18.67–17.98 Ma, the coral reef was in a stagnation/drowning stage, with rising sea levels exceeding the development of the coral reef. At 17.98–16.78 Ma, the coral reef was in a rapid development during a rapid rise in sea level. Additionally, at 16.78–14.79 Ma, low coralline algal abundance was observed, and the corals were sporadically distributed at a relatively stable sedimentation rate, suggesting a decline in coral reef development. At 14.79–10 Ma, the coral reef development was remarkably slow or stagnant. Furthermore, at 10–5.3 Ma, the coral reefs developed slowly, indicating a gradual rise in the sea level. The sea-level changes indicated by coral reef development are consistent with the long-term global sea-level changes, indicating that the composition and assemblage of Miocene coralline algae can be used to accurately relay the sea-level history. • Eleven coralline algal genera were identified in a Miocene carbonate sequence. • Miocene coralline algae were divided into 7 coralline algal assemblages (CAAs). • Sea-level changes due to coral reef development were consistent with global values.

Chronostratigraphic and palaeogeographic interpretation of Nakdong deltaic sequences in the south-eastern Korean Peninsula

We investigated the chronostratigraphy of six boreholes in the Nakdong River delta area in South Korea based on optically stimulated luminescence (OSL) and 14C dating. The standardised growth curves (SGCs) produced from single and multiple boreholes performed well in determining low equivalent dose (De; < 40 Gy). 14C dates from shell and wood fragments were mostly representative of depositional time. Based on 14C and OSL ages, the lowermost fluvial sediments showed relatively low sediment accumulation rates (0.1–0.8 m/kyr−1) prior to 12 ka. A hiatal discontinuity ranging from 12 to a maximum of 50 ka resulted in a break in sedimentation between the Last Glacial Maximum and the Holocene. A thick fluvio-estuarine unit in the lower part indicated relatively high accumulation rates (3.3–9.4 m/kyr−1) from 12 to 9 ka, which corresponded to rapid sea level rise. In the middle part, decreased accumulation rates (1.7–5.5 m/kyr−1) from approximately 9 to 6 ka were interpreted as transgressive deepening. Lower accumulation rates (0.9–3.2 m/kyr−1) during the middle to late Holocene were caused by relative sea level fall and a horizontally extended sedimentation area. In the upper part, the highest sediment accumulation rates (3.5–8.3 m/kyr−1) and rapid delta progradation during the last 2.0 ka might have been caused by widespread human influence and monsoonal climatic change. Isochrons of 1-kyr scale were identified based on the lithologic boundary and age results for each borehole, which represent palaeoshoreline positions during the transgressive cycle and boundaries of considerable delta progradation.

Millennial-Scale Carbon Storage in Natural Pine Forests of the North Carolina Lower Coastal Plain: Effects of Artificial Drainage in a Time of Rapid Sea Level Rise

Coastal forested wetlands provide important ecosystem services along the southeastern region of the United States, but are threatened by anthropogenic and natural disturbances. Here, we examined the species composition, mortality, aboveground biomass, and carbon content of vegetation and soils in natural pine forests of the lower coastal plain in eastern North Carolina, USA. We compared a forest clearly in decline (termed “ghost forest”) adjacent to a roadside canal that had been installed as drainage for a road next to an adjacent forest subject to “natural” hydrology, unaltered by human modification (termed “healthy forest”). We also assessed how soil organic carbon (SOC) accumulation changed over time using 14C radiocarbon dating of wood sampled at different depths within the peat profile. Our results showed that the ghost forest had a higher tree density at 687 trees ha−1, and was dominated by swamp bays (Persea palustric), compared to the healthy forest, which had 265 trees ha−1 dominated by pond pine (Pinus serotina Michx). Overstory tree mortality of the ghost forest was nearly ten times greater than the healthy forest (p &lt; 0.05), which actually contributed to higher total aboveground biomass (55.9 ± 12.6 Mg C ha−1 vs. 27.9 ± 8.7 Mg ha−1 in healthy forest), as the dead standing tree biomass (snags) added to that of an encroaching woody shrub layer during ecosystem transition. Therefore, the total aboveground C content of the ghost forest, 33.98 ± 14.8 Mg C ha−1, was higher than the healthy forest, 24.7 ± 5.2 Mg C ha−1 (p &lt; 0.05). The total SOC stock down to a 2.3 m depth in the ghost forest was 824.1 ± 46.2 Mg C ha−1, while that of the healthy forest was 749.0 ± 170.5 Mg C ha−1 (p &gt; 0.05). Carbon dating of organic sediments indicated that, as the sample age approaches modern times (surface layer year 2015), the organic soil accumulation rate (1.11 to 1.13 mm year−1) is unable to keep pace with the estimated rate of recent sea level rise (2.1 to 2.4 mm year−1), suggesting a causative relationship with the ecosystem transition occurring at the site. Increasing hydrologic stress over recent decades appears to have been a major driver of ecosystem transition, that is, ghost forest formation and woody shrub encroachment, as indicated by the far higher overstory tree mortality adjacent to the drainage ditch, which allows the inland propagation of hydrologic/salinity forcing due to SLR and extreme storms. Our study documents C accumulation in a coastal wetland over the past two millennia, which is now threatened due to the recent increase in the rate of SLR exceeding the natural peat accumulation rate, causing an ecosystem transition with unknown consequences for the stored C; however, much of it will eventually be returned to the atmosphere. More studies are needed to determine the causes and consequences of coastal ecosystem transition to inform the modeling of future coastal wetland responses to environmental change and the estimation of regional terrestrial C stocks and flux.

Recrystallization of ice enhances the creep and vulnerability to fracture of ice shelves

The initiation of fractures and fast flow in floating regions of Antarctica have the potential to destabilize large regions of the grounded ice sheet, leading to rapid sea-level rise. While observations have shown rapid, localized deformation and damage in the margins of fast-flowing glaciers, there remain gaps in our understanding of how rapid deformation affects the viscosity and toughness of ice. Here we derive a model for dynamic recrystallization of ice that includes a novel representation of migration recrystallization. This mechanism is absent from existing models and is likely dominant in warm areas undergoing rapid deformation, such as shear margins in ice sheets. While solid earth studies find fine-grained rock in shear zones, here we find elevated ice grain sizes (>10 mm) due to warmer temperatures and high strain rates activating migration recrystallization. Large grain sizes imply that ice in shear margins deforms primarily by dislocation creep, suggesting a flow-law stress exponent of n≈4 rather than the canonical n=3. Further, we find that this increase in grain size results in a decrease in tensile strength of ice by ∼75% in the margins of glaciers. Thus, this increase in grain size softens the margins of fast-flowing glaciers and makes ice shelf margins more vulnerable to fracture than previously supposed. These results also suggest the need to consider the effects of dynamic recrystallization in large-scale ice-sheet modeling.

Rapid Sea-Level Rise in the Southern-Hemisphere Subtropical Oceans

AbstractThe subtropical oceans between 35°-20°S in the Southern Hemisphere (SH) have exhibited prevailingly rapid sea-level rise (SLR) rates since the mid-20th century, amplifying damages of coastal hazards and exerting increasing threats to South America, Africa, and Australia. Yet, mechanisms of the observed SLR have not been firmly established, and its representation in climate models has not been examined. By analyzing observational sea-level estimates, ocean reanalysis products, and ocean model hindcasts, we show that the steric SLR of the SH subtropical oceans between 35°-20°S is faster than the global mean rate by 18.2%±9.9% during 1958-2014. However, present climate models—the fundamental bases for future climate projections—generally fail to reproduce this feature. Further analysis suggests that the rapid SLR in the SH subtropical oceans is primarily attributable to the persistent upward trend of the Southern Annular Mode (SAM). Physically, this trend in SAM leads to the strengthening of the SH subtropical highs, with the strongest signatures observed in the southern Indian Ocean. These changes in atmospheric circulation promote regional SLR in the SH subtropics by driving upper-ocean convergence. Climate models show systematic biases in the simulated structure and trend magnitude of SAM and significantly underestimate the enhancement of subtropical highs. These biases lead to the inability of models to correctly simulate the observed subtropical SLR. This work highlights the paramount necessity of reducing model biases to provide reliable regional sea-level projections.

As Inland Becomes Coastal: Shifting Equity and Flood Risk in the Amite River Basin (USA)

Abstract Coastal Louisiana is experiencing the most rapid relative sea-level rise in the US due to a combination of a subsiding delta and rising coastal waters. Consequently, the influences of extreme coastal weather are reaching farther inland and impacting urban areas where traditional environmental policy, organised at the parish (county) level, is unable to address this changing flood risks. This situation is most prominent in the metro Baton Rouge region with the largest city situated upstream from two small, but rapidly growing, parishes. Following a massive flood in 2016, the upstream parishes have undertaken policy adjustments to facilitate the expulsion of water toward downstream neighbors and foster redevelopment in the floodplain. The lower parish has expressed concerns about the anticipated increases in discharge to be sent its way. Although the state is concerned with rising sea levels, it has not merged coastal and inland flood policy considerations. Downstream residents have little voice in upstream policy making and the absence of basin-wide management strategy perpetuates emergent risks and environmental injustices. As climate change drives coastal conditions inland, the misalignment between locally based governance and regional environmental realities will become more pronounced and exacerbate social injustices.

Post-tsunami adjustment of coral reef platform and other morphometric changes in Landfall Island, North Andaman—An integrated field and remote sensing-based approach

Coral reefs are active areas of scientific interest. Globally, coral reefs are declining due to enhanced sea surface temperature, rapid sea-level rise and other tectonic-climatic factors. In this paper, we have presented tectonic control for coral reef morphodynamics over the northern part of Andaman, Landfall Island. The 2004 Sumatra earthquake of Mw 9.1 posed essential changes on the overriding plate. Consequently, the Landfall Island changed its pattern of neotectonic movements. Here, we collected multi-temporal regional proxies like shoreline change rate, reef upliftment rate, and coral reef geomorphology for systematic tracking of earthquake-induced changes for various short-term [inter-seismic (1987–2004), co-seismic (2004–2006), early post-seismic (2006–2009), post-seismic (2009–2014)] and long-term [inter-seismic to post-seismic (1987–2014)] durations. Maximum upliftment rates (0.24 m/yr) and shoreline change rates (108.2 m/yr) with comparable geomorphic variations were noticed in co-seismic time. Other short-term changes are primarily related to earthquakes, wave actions and local geomorphology change. Additionally, we have reported new zones of adaptation for live corals. Our field survey and geodetic study verified remotely-derived morphologic adjustment of coral reefs.

Changes in organic carbon source and storage with sea level rise-induced transgression in a Chesapeake Bay marsh

Organic matter (OM) accumulation in marsh soils affects marsh survival under rapid sea-level rise (SLR). This work describes the changing organic geochemistry of a salt marsh located in the Blackwater National Wildlife Refuge on the eastern shore of Chesapeake Bay that has transgressed inland with SLR over the past 35–75 years. Marsh soils and vegetation were sampled along an elevation gradient from the intertidal zone to the adjacent forest, representing a space-for-time substitution of the process of marsh transgression. Stable carbon isotope analysis of bulk OM gives evidence for a transition from C3 upland-sourced OM to C4-dominated marsh vegetation over time. The vegetative source of the OM changes along a marsh-upland mixing line from herbaceous angiosperm-sourced lignin in the lower elevation marsh to a woody gymnosperm signature at the upper border of the marsh. The results of stable isotope and lignin analyses illustrate that landward encroachment of marsh grasses results in deposition of herbaceous tissues exhibiting relatively little decay. This presents a possible mechanism for OM stabilization as marshes migrate inland. Regional index termsUSA, Maryland, Chesapeake Bay, Blackwater National Wildlife Refuge.

Homo Sapiens Sapiens Progressive Defaunation During The Great Acceleration: The Cli-Fi Apocalypse Hypothesis

Homo Sapiens Sapiens Progressive Defaunation During The Great Acceleration: The Cli-Fi Apocalypse Hypothesis