Rate Of Sea-level Rise Research Articles

COASTAL INUNDATION SIMULATION DUE TO SEA LEVEL RISE IN TERENGGANU, MALAYSIA

Abstract. Coastal Inundation is the amount of water levels that reach above normal level due to flooding in coastal areas. This natural phenomenon is due to the rising of local sea level. This study aims to develop a coastal inundation simulation along the coastline of Terengganu. To ensure the success of this study, the rate and magnitude of sea level rise are calculated using Radar Altimetry Database System (RADS) from multi-mission satellite altimetry data. The rate of sea level rise is computed using robust fit regression technique and overlaid with global Digital Elevation Model (DEM) data, known as TanDEM-X. The overlaid data are utilised to simulate the probable areas to be affected by inundation from year 2040 to 2100 using ArcGIS software. The results obtained from the period of 1993 to 2015 show that the average rate of sea level rise along the Terengganu shoreline is 4.84 mm/year with a standard deviation of 0.49 mm/year. By 2100, the estimated average regional sea level rise is projected to increase by 0.412 m. This study could help coastal development planning, defence, and safety monitoring.

ASSESSMENT OF SEA LEVEL RISE IMPACT ON PENINSULAR MALAYSIA GEODETIC VERTICAL DATUM

Abstract. Sea level is the height of the ocean surface in relation to a benchmark or vertical control point. The rising of sea level has become a crucial topic, which frequently discussed among professionals, government, non-government, and researchers upon their devastating impacts on daily human life and human survival. Nevertheless, there is a great deal of ambiguity around the rates, ranges, and time frame of sea levels rise. It is importance to study the variation of present-day sea level rise to understand its impact, particularly on our National Geodetic Vertical Datum (NGVD). This study focuses on quantifying the rate and magnitude of sea level rise over Peninsular Malaysia using in-situ tide gauge and multi-mission satellite altimeter. The time period for tide gauge data used is 35 years (1984–2018) consisting 12 tide gauges in Peninsular Malaysia. Meanwhile, the period of satellite altimetry data is 26 years (1993–2018). This study uses robust fit regression (Iterative Re-weighted Least-Squares) for both tide gauge and satellite altimetry data to calculate the rate of sea level rise. The outcomes of this study show that the rate of sea level rise at Pelabuhan Kelang tide gauge station is the lowest among 12 other tide gauges with a rate of 2.36 ± 0.35 mm/year and slightly affected by sea level rise. Besides, the rate of sea level rise in Peninsular Malaysia is on an upward trend with an average of 3.20 ± 0.27 mm/year from tide gauge data and 4.14 ± 0.32 mm/year from satellite altimetry data. The sea level rise study provides insights to the rate and magnitude of sea level rise at tide gauge stations, particularly at Pelabuhan Kelang station for further study. Last but not least, this study would also benefit authorities in preparing mitigation plans to secure and improve our Peninsular Malaysia Geodetic Vertical Datum (PMGVD) for various applications.

Resisting-accepting-directing sea level rise on the Chesapeake Bay: Agricultural producers’ motivations and actions

As relative rates of sea level rise accelerate in the Mid-Atlantic region of the United States, the frequency of flooding and saltwater intrusion on coastal lands also increases, prompting ecological transformation which can conflict with existing coastal land use such as agriculture. We performed an exploratory study of coastal farmers and woodlot managers in Maryland and Virginia to understand how these producers make land management decisions within the context of sea level rise. Specifically, we used a mixed-methods approach to identify and understand 1) the producer-observed impacts of sea level rise and flooding on coastal lands; 2) the range of actions producers may take in response to sea level rise and flooding; 3) producers' intentions for managing their land in the short- and long-term; 4) producers' motivations for selecting a particular response; and 5) the additional support coastal producers need to successfully adapt to sea level rise. We used the Resist-Accept-Direct framework as an analytical tool to understand how producers’ actions and motivations align with 1) prevention or removal of impacts from flooding and saltwater intrusion, 2) accommodation for wetter or saltier conditions as they naturally occur, or 3) facilitation of specific changes toward a new desired outcome. We found that while most producers in our study plan to resist or accept changes over the next five years, over the longer term a majority of participating producers plan to transition land to a use that is compatible with increased saltwater intrusion and flooding. Most producers in our study would prefer to continue farming yet face a lack of effective and/or affordable management options to resist ecological changes. Flexible mechanisms that support producers in resisting sea level rise impacts in the short term, while supporting them in directing the transition of their land to another productive use in the long term, are needed to support coastal farmers as they adapt to a changing climate.

Hazard Assessment and Modeling of Erosion and Sea Level Rise under Global Climate Change Conditions for Coastal City Management

Sea-level rise in response to climate change and global warming severely impacts coastal cities through increased soil erosion and other hazards. Therefore, simulating threats in coastal locations is critical for coastal city management and planning. The Nonlinear Autoregressive Exogenous-Neural Network (NARX-NN) was used in conjunction with the Bruun model and GIS methods to estimate the rate of sea-level rise, develop a coastal erosion model and coastal hazards maps, and simulate a sea-level increase with a maximum speed of 79.26 mm/year, and an average of about 25.34 mm/year, with a 1.48 m/year average erosion rate simulated from 2013 to 2020 along Merang kechil to Kuala Marang in Terengganu state coastal areas. According to the Bruun model, the areas most vulnerable to shoreline erosion are Kuala Nerus, Pendagan Buluh, and Kuala Ibai. Batu Rakit (Reach 1) has the highest rate of coastal erosion, at 28.16%, compared to 16.5 percent in Kuala Nerus (Reach 2) and 19.1% in Pengadang Buluh (Reach 3). The findings of this study might be utilized to build new coastal hazard erosion maps in a GIS framework, which could then be used as part of Malaysia’s East Coast zone vulnerability assessment. The findings may also aid in the prioritization of conservation efforts in afflicted areas or the decision to adapt to the effects of coastal erosion. This article presents a methodological framework and an erosion management prioritization system to help coastal managers, planners, and developers identify hazardous zones and improve coastal management plans using geospatial models.

Resolving Uncertainties in Foraminifera-Based Relative Sea-Level Reconstruction: a Case Study from Southern New Zealand

Abstract Since the pioneering work of David Scott and others in the 1970s and 1980s, foraminifera have been used to develop precise sea-level reconstructions from salt marshes around the world. In New Zealand, reconstructions feature rapid rates of sea-level rise during the early to mid-20th century. Here, we test whether infaunality, taphonomy, and sediment compaction influence these reconstructions. We find that surface (0–1 cm) and subsurface (3–4 cm) foraminiferal assemblages show a high degree of similarity. A landward shift in assemblage zones is consistent with recent sea-level rise and transgression. Changes associated with infaunality and taphonomy do not affect transfer function-based sea-level reconstructions. Applying a geotechnical modelling approach to the core from which sea-level changes were reconstructed, we demonstrate compaction is also negligible, resulting in maximum post-depositional lowering of 2.5 mm. We conclude that salt-marsh foraminifera are indeed highly accurate and precise indicators of past sea levels.

Anthropogenic impacts on tidal creek sedimentation since 1900.

Land cover and use around the margins of estuaries has shifted since 1950 at many sites in North America due to development pressures from higher population densities. Small coastal watersheds are ubiquitous along estuarine margins and most of this coastal land-cover change occurred in these tidal creek watersheds. A change in land cover could modify the contribution of sediments from tidal creek watersheds to downstream areas and affect estuarine habitats that rely on sediments to persist or are adversely impacted by sediment loading. The resilience of wetlands to accelerating relative sea-level rise depends, in part, on the supply of lithogenic sediment to support accretion and maintain elevation; however, subtidal habitats such as oyster reefs and seagrass beds are stressed under conditions of high turbidity and sedimentation. Here we compare sediment accumulation rates before and after 1950 using 210Pb in 12 tidal creeks across two distinct regions in North Carolina, one region of low relief tidal-creek watersheds where land cover change since 1959 was dominated by fluctuations in forest, silviculture, and agriculture, and another region of relatively high relief tidal-creek watersheds where land-use change was dominated by increasing suburban development. At eight of the creeks, mass accumulation rates (g cm-2 y-1) measured at the outlet of the creeks increased contemporaneously with the largest shift in land cover, within the resolution of the land-cover data set (~5-years). All but two creek sites experienced a doubling or more in sediment accumulation rates (cm yr-1) after 1950 and most sites experienced sediment accumulation rates that exceeded the rate of local relative sea-level rise, suggesting that there is an excess of sediment being delivered to these tidal creeks and that they may slowly be infilling. After 1950, land cover within one creek watershed changed little, as did mass accumulation rates at the coring location, and another creek coring site did not record an increase in mass accumulation rates at the creek outlet despite a massive increase in development in the watershed that included the construction of retention ponds. These abundant tidal-creek watersheds have little relief, area, and flow, but they are impacted by changes in land cover more, in terms of percent area, than their larger riverine counterparts, and down-stream areas are highly connected to their associated watersheds. This work expands the scientific understanding of connectivity between lower coastal plain watersheds and estuaries and provides important information for coastal zone managers seeking to balance development pressures and environmental protections.

Coastal switching of dominant depositional processes driven by decreasing rates of Holocene sea-level rise along the macrotidal coast of Gochang, SW Korea

ABSTRACTDecreasing rates of eustatic sea-level rise during the Holocene accompanied the deposition of transgressive coastal deposits worldwide. However, unraveling how transgressive deposition varies in response to different rates of relative sea-level (RSL) rise is limited by the scarcity of long (10+ m) well-dated cores spanning the entire middle to late Holocene record along macrotidal coasts. To investigate the sedimentary response of this macrotidal coast to decreasing rates of RSL rise, we acquired four cores up to 32 m in length and Chirp seismic profiles along the west coast of Korea. Core sediments were analyzed in terms of sedimentary texture, structure, and facies. Nineteen optically stimulated luminescence (OSL) and fourteen 14C accelerated mass spectrometry (AMS) ages constrain the timing of deposition of the sandy sediments. This relatively dense distribution of ages is used to determine how deposition rates changed through time. We also use a compilation of previously published RSL indices for the southwestern Korean coast in order to better constrain RSL changes through time. Results show that the evolution of the Gochang coastline switched from a tide-dominated environment to a wave-dominated environment during the latter stage of transgression as the rate of the sea-level rise decreased. Rugged antecedent topography likely led to the development of tidal currents and the formation of a tide-dominated tidal flat during rapid RSL rise from 10 to 6 ka. As the tidal channels filled with fine-grained sediments from 6 to 1 ka, tidal amplification likely waned leading to a greater role of wave energy in shaping the formation of the sandy open-coast tidal flat. Since 1 ka, wave-dominated environments formed sand-rich tidal beaches and flats. Decreasing changes in rates of the RSL rise resulted in changes in depositional environments from a tide-dominated intertidal flat to an open-coast tidal flat and finally a wave-dominated tidal beach. This study highlights the important role that rates of RSL rise play on not only sedimentation rates in a shelf setting but also playing a role in the switch from a tide-dominated to a wave-dominated setting.

Novel luminescence diagnosis of storm deposition across intertidal environments

Salt marshes provide valuable nature-based, low-cost defences protecting against coastal flooding and erosion. Storm sedimentation can improve the resilience of salt marshes to accelerating rates of sea-level rise, which poses a threat to salt marsh survival worldwide. It is therefore important to be able to accurately detect the frequency of storm activity in longer-term sediment records to quantify how storms contribute to salt marsh resilience. Luminescence is able to infer how long mineral grains were exposed to sunlight prior to burial (e.g., the presence or absence of sediment processing). This study used sediment cores collected from the Ribble Estuary, North West England, to show that luminescence properties of sand-sized K-feldspar grains can diagnose the differential modes of deposition across intertidal settings (i.e., sandflat, mudflat and salt marsh) in longer-term sediment records by detecting the variability in sediment bleaching potential between settings (i.e., sediment exposure to sunlight), thus establishing a framework for the interpretation of luminescence properties of intertidal sediments. It then used modern sediment samples collected before and after a storm event to show how such properties can diagnose changes in sediment processing (i.e., bleaching potential) of mudflat sediments caused by storm activity, despite no changes in sediment composition being recorded by geochemical and particle size distribution analyses. This new luminescence approach can be applied to longer-term sediment records to reveal (and date) changes in the environment of deposition and/or depositional dynamics where there is no obvious stratigraphic evidence of such.

Climate adaptation in Coastal Virginia: an analysis of existing policies and main stakeholders

ABSTRACT The impacts of climate change have sparked policy responses at different governance levels. Studying the central adaptation policies and understanding the interactions and complexities of governmental and non-governmental stakeholders is essential in guiding policymakers at different levels of government to formulate policies and make investment decisions. With strategic and economic significance on the national level, Coastal Virginia has one of the highest rates of sea-level rise in the United States, instigating intensified and more frequent climate hazards such as flooding and storms. This paper strives to characterize the status of adaptation policymaking in this region through a novel keyword analysis method and a thematic analysis of interviews with the main adaptation decision-makers and stakeholders. We identify the central adaptation policies and programmes at the local, regional, state, and federal level, as well as the major relevant players. This provides a comprehensible narrative of adaptation policymaking, which could be exploited to further analyze governance gaps and adaptation challenges. The approach and methodologies of this research could be implemented in similar studies for other areas of the U.S. that are at high climate risk, possibly facilitating an informed national adaptation policy, long overdue by the federal government. The research is also relevant for other jurisdictions at risk of sea-level rise. Key policy insights Coastal adaptation policymaking in Virginia has been a bottom-up and fragmented process initiated by most affected localities, exhibiting the importance of local initiatives in higher-level adaptation policies. The long-lasting impacts of 100 Resilient cities and Dutch Dialogues in the City of Norfolk highlight the value of fostering cross-geographic coordination and capacity-building programmes, confirming the importance of informal policy networks in learning and innovation for adaptation. There is a vast difference among localities in adaptation planning and implementation, creating the need for coordinating state leadership. Adaptation policymaking in Virginia has been influenced by political cycles with priorities drastically altered by each administration change, introducing significant uncertainty for continuation of policies. National policies and programmes, such as the Inflation Reduction Act of 2022, can significantly affect local-level policies and decision-making.

Adaptability of Common Coastal Wetland Plant Populations to Future Sea Level Rise

An accelerating rate of sea level rise (SLR) is causing huge inundation pressure on coastal wetlands worldwide. Vegetation of coastal wetlands plays a key role in stabilizing the coast and accreting sediment in order to mitigate the negative impact of SLR. The ability to accrete sediment is influenced by individual species traits; however, there are insufficient information and indicators to identify differences in the adaptability of various coastal vegetations to SLR at a regional or global scale. Here, the potential adaptation of 27 plant populations in coastal wetlands subject to SLR was evaluated using a compiled global dataset and a marsh equilibrium model. Sediment accretion efficiency differed among plant populations, but most coastal marsh populations and a few mangrove populations had relatively high accretion rates; habitats with high accretion rates will have a better potential to deal with the threat of SLR. These results showed that latitude and efficiency shared a nonlinear relationship, and plant stem density and root structure were among the important factors that influenced the efficiency. Fibrous root plant populations had a greater sediment accretion efficiency than tap root plant populations, and perennial populations had a greater sediment accretion efficiency than annual plant populations. These findings can provide key parameters relating to the sediment accretion efficiency of hydrological and geomorphic models on a global scale. This study offers some novel insights into the dynamic changes in coastal wetlands following SLR that will be particularly useful in devising appropriate strategies for the protection and management of coastal wetlands.

Transformative Sea-level Rise Research and Planning: Establishing a University, Tribal, and Community Partnership for a Resilient California North Coast

Sea-level rise (SLR) is and will continue to be a pressing issue in the rural, North Coast region of California, especially since nearby Wigi (or Humboldt Bay) is experiencing one of the fastest rates of relative SLR on the U.S. West Coast. In this paper, we argue that SLR presents a transformative opportunity to rekindle environmental relationships and reshape the future of the California North Coast and beyond. As the preeminent higher education institution of the region, Cal Poly Humboldt has the responsibility to be a leader in education, research, and planning for climate resilience. We describe efforts of the Cal Poly Humboldt Sea Level Rise Institute to establish a university-Tribal-community partnership that braids together different approaches and ways of knowing to develop research and planning that supports a resilient California North Coast. Since Wigi is projected to experience the effects of SLR sooner than the rest of the state, the North Coast region is poised to act as an incubator for new ideas and solutions, including Indigenous knowledge systems, and to play a role in influencing equitable, resilient, and transformative SLR adaptation processes in other parts of the state and the world. This will require developing programming and expertise in specific disciplinary areas, but, more importantly, will require the development of opportunities and spaces for various disciplines, ways of knowing, and sectors (e.g. Tribal nations, academia, government, NGOs, private companies, and community groups) to converge and bring the best of what they have to address climate-induced challenges and opportunities.

Salt Marsh Response to Inlet Switch‐Induced Increases in Tidal Inundation

AbstractThere is widespread concern that rapidly rising sea levels may drown salt marshes by exceeding the rate at which these important ecosystems can build elevation. A significant fraction of marshes reside within backbarrier estuaries, yet little attention has been paid to how changes in inlet geometry influences estuarine tides and marshes. In 1898, a coastal storm eroded a new inlet through the barrier beach that fronts the North‐South Rivers Estuary in Massachusetts, USA. The new inlet shortened the North River by 5.6 km and lengthened the South River channel by the same amount. Modern measurements of tidal attenuation suggest that channel shortening abruptly increased mean high tide along the North River by at least 30 cm. Foraminifera communities within North River marsh sediments indicated an environmental change from infrequent to frequent inundation at the time of the 1898 switch in inlet location, which supports this hypothesis. Increased mineral sediment deposition after the inlet switch played a dominant role in allowing marshes along the North River channel to adjust to greater inundation. Following the inlet switch, sediment accreted in North River marshes at 2–5 times the rate of sea level rise (SLR). The North River channel widened by an average of 18% relative to pre‐1898 conditions to accommodate the increased tidal prism. The role of mineral sediment accretion in making this marsh resilient to an abrupt increase in inundation depth highlights the importance of maintaining adequate sediment supplies in coastal regions as SLR accelerates.

Tidal marsh restoration on Sapelo Island: A legacy of R.J. Reynolds, Jr., Eugene Odum and the University of Georgia Marine Institute

Restoration of tidal marshes throughout the 20th century have attempted to bring back important functions of natural tidal systems. In this study, vertical accretion, organic carbon (C) sequestration, and nitrogen burial were compared between a natural, never diked tidal salt marsh and a hydrologically restored tidal salt marsh on Sapelo Island, Georgia to examine the impacts of restoration years later. 64 years after hydrologic restoration in 1956, the restored marsh studied had higher rates of accretion based on 137Cs and 210Pb (4.8–5.1 mm/yr), C sequestration (118–125 g C/m2/yr) and N burial (8.3–8.8.g N/m2/yr) than the never diked marsh (2.9–3.4 mm/yr, 75–85 g C/m2/yr, 4.8–5.6 g N/m2/yr).Since maximum 137Cs deposition in 1964, approximately 30 cm of accretion has occurred in the restored marsh while the never diked marsh had approximately 10–30 cm of new soil deposited. The accumulated soil in the restored marsh was comparable to the natural marsh soil in terms of bulk density, percent C and N. However, below this depth, legacy effects from diking could be found through the higher soil bulk density and lower percent organic C and N relative to soils of the natural marsh.Vertical accretion in the natural marsh appears to be keeping pace with the current rate of sea level rise (SLR) (3.4 mm/yr) while accretion in the restored marsh exceeds SLR as the marsh compensates for subsidence that occurred when it was diked. Under current SLR and accretion rates, ecosystem functions of continual sequestration of C and burial of N will be supported. However, as SLR accelerates, the ability of both marshes to sequester C and bury N will depend on their ability to keep pace. If not, the marshes will eventually convert to mudflats or open water with a concurrent loss of these and other ecosystem services.

Episodic postglacial deltaic pulses in the Gulf of Cadiz: Implications for the development of a transgressive shelf and driving environmental conditions

Abstract The postglacial sea-level rise after the Last Glacial Maximum provided ideal conditions to study the transgressive sedimentary response to sudden shelf flooding driven by different rates of sea-level rise. In this study, a high-resolution seismic stratigraphic interpretation and sedimentological analysis were conducted on data from the northern Gulf of Cadiz continental shelf (SW Iberian Peninsula), in order to: 1) understand the succession of sedimentary processes during each shelf flooding episode and 2) explore the significance of variable rates of sea-level rise, sediment fluxes, and climatic conditions on the development of postglacial deposits. Four backstepping seismic postglacial transgressive units (PTUs; 4 to 1 from oldest to youngest) that are linked to the retreating mouth of the Guadiana River were interpreted. Together, these seismic units display a wedge-shape geometry, are located over the inner to middle shelf, and overlie a regional unconformity formed during the Last Glacial Maximum. Each PTU can be divided into several sub-units with distinctive seismic facies that have a similar stratigraphic organization. Each PTU contains lower sub-units that are composed of low-angle tangential-oblique clinoforms. The clinoforms are locally topped by a channelized sub-unit. The distal and/or lateral parts of the clinoforms are occasionally buried by sheet-like semitransparent subunits. The uppermost sub-units are present over the proximal and central parts of each seismic unit and are also sheet-like. PTUs can also be subdivided and described sedimentologically. Fine-grained sands with intercalated silty layers dominate the lower part of each PTU (lower clinoform sub-units). The upper part of each PTU (upper sheet-like sub-units) is characterized by reworked facies, composed of highly fragmented bioclasts within a mixture of silt and coarse to medium sand. Finally, mud deposits occur as a sediment drape over the PTUs. The internal structure of each PTU reveals several phases of development under a general process of transgressive submergence in which both coastal and marine deposits were formed and eventually preserved. The initial phase involved the development of coarse-grained deltas in shallow water, which were locally eroded by a network of distributary channels. In a transitional phase, the infilling of distributary channels and the offshore export of fine-grained sediments is related to a change in sediment sources, possibly triggered by enhanced hydrodynamic processes. The final phase involved the reworking of fluvio-deltaic sediments by shoreface processes to generate a sediment sheet. Age correlation with a suite of postglacial sea-level curves indicates that the formation of the postglacial transgressive deposits is bracketed between 14 ka and 9 ka. The studied deposits are related to a period of reduced sea-level rise, culminating in the Younger Dryas event (two oldest PTUs), and to phases of enhanced sea-level rise, such as Meltwater Pulse (MWP) 1B (two youngest PTUs). In spite of high rates of sea-level rise over MWP-1B, each PTU exhibits progradation and preservation of much of the delta. The preservation of progradational deltaic units is likely caused by increased sediment supply during progradational pulses. We suggest that those pulses of enhanced sediment fluxes during MWP-1B were strongly driven by the overall climatic conditions in the southwest of the Iberian Peninsula, probably resulting from enhanced rainfall runoff during humid periods and scarce land vegetation cover.

Improved mapping of coastal salt marsh habitat change at Barnegat Bay (NJ, USA) using object-based image analysis of high-resolution aerial imagery

Tidal wetlands are valued for the ecosystem services they provide yet are vulnerable to loss due to anthropogenic disturbances such as land conversion, hydrologic modifications, and the impacts of climate change, especially accelerating rates of sea level rise. To effectively manage tidal wetlands in face of multiple stressors, accurate studies of wetland extent and trends based on high-resolution imagery are needed. We provide salt marsh delineations for Barnegat Bay, New Jersey, by means of object-based image analysis of high-resolution aerial imagery and digital elevation models. We performed trends analyses of salt marsh extent from 1995 to 2015 and estimated drivers of marsh area change. We found that in 1995, 8830 ± 390 ha were covered with marsh vegetation, while in 2015 only 8180 ± 380 ha of salt marsh habitat remained. The resulting net loss rate of 0.37% yr−1 is equivalent to historic loss rates since the 1970s, indicating that despite regionally accelerating relative sea level rise and purported eutrophication, salt marsh loss rates at Barnegat Bay remain steady. The main drivers of salt marsh loss are excavations for mosquito control (409 ha), edge erosion (303 ha) and ponding (240 ha). Upland migration of salt marsh did not completely mitigate these losses but accounted for a gain of 147 ha of tidal marsh habitat. The methodology presented herein yielded accurate salt marsh delineations (>90%) and trend detection (85%), outperforming low-resolution wetland delineations used in coastal management. This study demonstrates the suitability of high-resolution imagery for the detection of open water features. For the purposes of salt marsh change detection and the identification of change drivers, management and conservation agencies should make use of high-resolution imagery whenever feasible.

Toward Collaborative Adaptation: Assessing Impacts of Coastal Flooding at the Watershed Scale.

The U.S. Mid-Atlantic coastal region is experiencing higher rates of SLR than the global average, especially in Hampton Roads, Virginia, where this acceleration is primarily driven by land subsidence. The adaptation plans for coastal flooding are generally developed at the municipal level, ignoring the broader spatial implications of flooding outside the individual administrative boundaries. Flood impact assessments at the watershed scale would provide a more holistic perspective on what is needed to synchronize the adaptation efforts between the neighboring administrative units. This paper evaluates flooding impacts from sea level rise (SLR) and storm surge among watersheds in Hampton Roads to identify those most at risk of coastal flooding over different time horizons. It also explores the implications of flooding on the municipalities, the land uses, and land covers throughout this region within the case study watershed. The 2% Annual Exceedance Probability (AEP) storm surge flood hazard data and NOAA's intermediate SLR projections were used to develop flooding scenarios for 2030, 2060, and 2090 and delineate land areas at risk of combined flooding. Findings show that five out of 98 watersheds will substantially increase in inundation, with two intersecting multiple municipalities. They also indicate significant inundation of military, commercial, and industrial land uses and wetland land covers. Flooding will also impact residential land use in urban areas along the Elizabeth River and Hampton city, supporting the need for collaborative adaptation planning on hydrologically influenced spatial scales.

Through an Ice Sheet, Darkly

Through an Ice Sheet, Darkly

Vertical deformation and residual altimeter systematic errors around continental Australia inferred from a Kalman-based approach

HighlightsWe further developed a method to investigate time-variability of vertical land motion (VLM) and regionally-correlated altimeter systematic errors around Australia.Our approach confirms widespread subsidence of the Australian region, and this is not explained by glacial isostatic adjustment alone.We identified noise driven by likely different oceanographic signals between tide gauge and offshore locations as a limit to resolving time-variable VLM signals.The addition of non-reference missions improves spatial sampling and reduces the impact of differential oceanic signals.The average rate of absolute sea-level rise is higher than previously published estimates, suggesting an acceleration in sea-level.

Reef growth history at intermediate to mesophotic depths since the end of the Last Glacial period along the Great Barrier Reef shelf edge

Reef communities at intermediate (10 to 30 m) and mesophotic (~ 30 to 150 m) depths occupy large areas of sea floor but little is known about their potential to accrete vertically, their response to sea-level change and other environmental perturbations. In this study, the authors have examined cores from two holes, M0040A and M0041A, drilled by the International Ocean Drilling Program Expedition 325 along the shelf edge of the modern GBR at 131 m water depth. The objective was to investigate reef growth history at palaeo-water depths > 20 m over a time period spanning 30,000 years, from the end of the Last Glacial period through the last deglaciation. Based on changes in lithologies and biotic components, and a robust chronostratigraphic framework supported by 47 radiometric ages, the authors have identified two episodes of reef growth, one during Marine Isotope Stage (MIS) 2 and the other at the onset of the deglaciation, both characterised by abundant microbialite crusts and distinct coral assemblages. Palaeo-water depths range from 30 to 60 m and from 20 to 30 m for the MIS 2 and early deglacial reef sections, respectively. The first episode of reef growth documented in the cores initiated at 27 to 25 ka, possibly in response to increased light availability and change in sedimentation resulting from falling sea-level between 32 and 29 ka from MIS 3 and also to low atmospheric pCO2 at the end of the Last Glacial period. Reef accretion was reduced or ceased sometime between 24 and 19 ka, coinciding with the rapid 20 m sea-level fall of the peak Last Glacial Maximum and minima of SSTs. Reef growth resumed at 19.5 to 18.5 ka, influenced by a period of moderate sea-level rise and increasing sea surface temperatures at the onset of the deglaciation. Reef growth termination at ca. 17 ka correlates with a major episode of reef demise previously identified in adjacent mid and outer terrace cores and linked to reduced water quality combined with rapid deglacial sea-level rise. Vertical accretion (VA) rates were calculated based on two methods: linear visual fitting and Bayesian modelling. The findings show that the highest VA rates are associated with microbialite boundstone. Reef ecosystems dominated by microbialite and corals developed at intermediate and mesophotic depths, and grew vertically at maximum rates of 2 to 5 mm yr-1 depending on the method used, over a period of rapid environmental change during the transition from MIS 3 to MIS 1. Further study needs to explore the potential of modern-type deep coralgal communities to cope with higher rates of sea-level rise predicted this century.

Late Pleistocene-Holocene Evolution of Malé Island (North Malé Atoll Rim, Republic of Maldives)

Malé, the capital of the Republic of Maldives, is established on an island of about 6.8 square kilometres, with a maximum relief of 2.7 m and a population of 236,000 inhabitants. It is amongst the most densely populated areas on Earth and located virtually at sea-level. This study focuses on the late Pleistocene-Holocene evolution of Malé island that recently formed as part of the discontinuous North Malé Atoll rim. Understanding the formation of Malé Island is relevant in predicting its future in the context of accelerating rates of sea-level rise in the next centuries due to anthropogenic global warming. Analyses of two boreholes up to 35 m-long, published information from additional boreholes drilled on Malé Island and a high-resolution multi-beam bathymetric survey acquired along its upper slopes and deep surroundings were available for this study. Two distinct sedimentary units were recovered from the boreholes. Facies analyses of the lower unit reveal an overall deepening coralgal reef that accumulated probably during the previous interglacial (Marine Isotope Stage = MIS 5e) and which was subsequently altered by meteoric diagenesis during a 100 kyr-long time of exposure. The upper unit consists of Holocene unconsolidated coralgal accumulation, unconformably overlying the lower karstified coralgal MIS 5e unit. The upper unit, protected behind a karstified late Pleistocene reef, was initiated at ~8200 yr BP and vertically grew 25 m-high until 6510 yr BP in the northern part of the Malé Island area, which at the time was a karstified limestone island with a central geomorphological depression. The narrow, 30 to 35 m-deep, newly formed central faro lagoon started to fill ~ 5500 yr BP, when a reef initiated on top of the southern highest Pleistocene karstified reef and sea-level rise stalled. The infilling of the faro lagoon was completed ~ 4500 yr BP. An island formed that was flanked on its south side by a shallow lagoon and surrounded by a reef flat. Through several phases of land reclamation since the 1950s, the shallow lagoon was infilled and the reef flat buried with sand and rubble to form Malé Island as it is known today.