scholarly journals Coral reef islands can accrete vertically in response to sea level rise

2020 ◽  
Vol 6 (24) ◽  
pp. eaay3656 ◽  
Author(s):  
Gerd Masselink ◽  
Eddie Beetham ◽  
Paul Kench
Keyword(s):  
Coral Reef ◽  
Sea Level Rise ◽  
Sea Level ◽  
Sediment Supply ◽  
Carbonate Sediment ◽  
Full Characterization ◽  
Alternative Future ◽  
Reef Islands ◽  
Near Term

Increased flooding due to sea level rise (SLR) is expected to render reef islands, defined as sandy or gravel islands on top of coral reef platforms, uninhabitable within decades. Such projections generally assume that reef islands are geologically inert landforms unable to adjust morphologically. We present numerical modeling results that show reef islands composed of gravel material are morphodynamically resilient landforms that evolve under SLR by accreting to maintain positive freeboard while retreating lagoonward. Such island adjustment is driven by wave overtopping processes transferring sediment from the beachface to the island surface. Our results indicate that such natural adaptation of reef islands may provide an alternative future trajectory that can potentially support near-term habitability on some islands, albeit with additional management challenges. Full characterization of SLR vulnerability at a given reef island should combine morphodynamic models with assessments of climate-related impacts on freshwater supplies, carbonate sediment supply, and future wave regimes.

scholarly journals Role of Future Reef Growth on Morphological Response of Coral Reef Islands to Sea-Level Rise

2020 ◽  
Author(s):  
Gerhard Masselink ◽  
Robert McCall ◽  
Edward Beetham ◽  
Paul Simon Kench ◽  
Curt D. Storlazzi
Keyword(s):  
Coral Reef ◽  
Sea Level Rise ◽  
Sea Level ◽  
Reef Growth ◽  
Morphological Response ◽  
Reef Islands

scholarly journals Role of Future Reef Growth on Morphological Response of Coral Reef Islands to Sea‐Level Rise

2021 ◽  
Vol 126 (2) ◽  
Author(s):  
G. Masselink ◽  
R. McCall ◽  
E. Beetham ◽  
P. Kench ◽  
C. Storlazzi
Keyword(s):  
Coral Reef ◽  
Sea Level Rise ◽  
Sea Level ◽  
Reef Growth ◽  
Morphological Response ◽  
Reef Islands

scholarly journals Sediment supply dampens the erosive effects of sea-level rise on reef islands

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Megan E. Tuck ◽  
Murray R. Ford ◽  
Paul S. Kench ◽  
Gerd Masselink
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Physical Stability ◽  
Physical Modelling ◽  
Sediment Supply ◽  
Ecological Processes ◽  
Geomorphic Response ◽  
The Future ◽  
Reef Islands ◽  
The Impact

AbstractLarge uncertainty surrounds the future physical stability of low-lying coral reef islands due to a limited understanding of the geomorphic response of islands to changing environmental conditions. Physical and numerical modelling efforts have improved understanding of the modes and styles of island change in response to increasing wave and water level conditions. However, the impact of sediment supply on island morphodynamics has not been addressed and remains poorly understood. Here we present evidence from the first physical modelling experiments to explore the effect of storm-derived sediment supply on the geomorphic response of islands to changes in sea level and energetic wave conditions. Results demonstrate that a sediment supply has a substantial influence on island adjustments in response to sea-level rise, promoting the increase of the elevation of the island while dampening island migration and subaerial volume reduction. The implications of sediment supply are significant as it improves the potential of islands to offset the impacts of future flood events, increasing the future physical persistence of reef islands. Results emphasize the urgent need to incorporate the physical response of islands to both physical and ecological processes in future flood risk models.

scholarly journals Can coral reef islands survive sea level rise?

2020 ◽  
Vol 06 (04) ◽  
Author(s):  
Eddie Beetham ◽  
Gerd Masselink ◽  
Paul Kench
Keyword(s):  
Coral Reef ◽  
Sea Level Rise ◽  
Sea Level ◽  
Reef Islands

scholarly journals EVIDENCE OF RESILIENCE IN REEF ISLANDS IN RESPONSE TO RISING SEA LEVEL ON HUVADHOO ATOLL, MALDIVES

2020 ◽  
pp. 43
Author(s):  
Christine Yiqing Liang ◽  
Paul S. Kench ◽  
Murray R. Ford ◽  
Holly K. East
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Textural Properties ◽  
Growth Strategy ◽  
Sediment Supply ◽  
Coralline Algae ◽  
Turnover Rates ◽  
Crustose Coralline Algae ◽  
High Turnover ◽  
Reef Islands

Reef islands are at the forefront of concern for future accelerating sea-level rise since their low-lying and isolated nature puts them at higher risk of marine inundation compared to continental coastlines. However, the perceived threat of complete submersion as implied by projected future sea-level rise and current island elevations do not consider the morphologically resilient nature of reef island systems. In particular, the role of sediment supply in the resilience of these islands is still relatively poorly studied. This study presents detailed descriptions of the sedimentary characteristics and stratigraphy of two lagoonal platform islands in Huvadhoo Atoll, Maldives, that formed during periods of Holocene sea-level rise. Island subsurface stratigraphy was reconstructed by analysing the skeletal composition and textural properties of 306 sediment samples from 37 cores extracted across the islands. Island sediments were dominated by coral sands with varied proportions of secondary constituents (molluscs, Halimeda, foraminifera, and crustose coralline algae). Downcore variations in composition show that the proportion of coral sands decrease with depth and the proportion of molluscs and Halimeda increase with depth (with the exception of cores that terminated on lagoon infill). The increased proportion of Halimeda and molluscs in these early island deposits may have resulted from the catch-up growth strategy of the reef during the mid-Holocene highstand as both organisms have high turnover rates and directly contribute to sediment production after death. The sedimentological response of increased Halimeda and molluscs highlights the resilient and dynamic nature of reef islands and the ability of reefs to adjust ecologically to changing sea levels.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/gy3zhqocMGw

scholarly journals Physical modelling of the response of reef islands to sea-level rise

Geology ◽  
2019 ◽  
Vol 47 (9) ◽  
pp. 803-806 ◽  
Author(s):  
Megan E. Tuck ◽  
Paul S. Kench ◽  
Murray R. Ford ◽  
Gerd Masselink
Keyword(s):  
Coral Reef ◽  
Sea Level Rise ◽  
Physical Model ◽  
Sea Level ◽  
Predictive Models ◽  
Physical Modelling ◽  
Present Evidence ◽  
Flood Impacts ◽  
Reef Islands ◽  
Rising Sea Level

Abstract Sea-level rise and increased storminess are expected to destabilize low-lying reef islands formed on coral reef platforms, and increased flooding is expected to render them uninhabitable within the coming decades. Such projections are founded on the assumption that islands are geologically static landforms that will simply drown as sea-level rises. Here, we present evidence from physical model experiments of a reef island that demonstrates islands have the capability to morphodynamically respond to rising sea level through island accretion. Challenging outputs from existing models based on the assumption that islands are geomorphologically inert, results demonstrate that islands not only move laterally on reef platforms, but overwash processes provide a mechanism to build and maintain the freeboard of islands above sea level. Implications of island building are profound, as it will offset existing scenarios of dramatic increases in island flooding. Future predictive models must include the morphodynamic behavior of islands to better resolve flood impacts and future island vulnerability.

scholarly journals Contributions of Organic and Mineral Matter to Vertical Accretion in Tidal Wetlands across a Chesapeake Bay Subestuary

2021 ◽  
Vol 9 (7) ◽  
pp. 751
Author(s):  
Jenny R. Allen ◽  
Jeffrey C. Cornwell ◽  
Andrew H. Baldwin
Keyword(s):  
Organic Matter ◽  
Sea Level Rise ◽  
Chesapeake Bay ◽  
Sea Level ◽  
210Pb Dating ◽  
Sediment Supply ◽  
Mineral Matter ◽  
Tidal Wetlands ◽  
Vertical Accretion ◽  
Inorganic Matter

Persistence of tidal wetlands under conditions of sea level rise depends on vertical accretion of organic and inorganic matter, which vary in their relative abundance across estuarine gradients. We examined the relative contribution of organic and inorganic matter to vertical soil accretion using lead-210 (210Pb) dating of soil cores collected in tidal wetlands spanning a tidal freshwater to brackish gradient across a Chesapeake Bay subestuary. Only 8 out of the 15 subsites had accretion rates higher than relative sea level rise for the area, with the lowest rates of accretion found in oligohaline marshes in the middle of the subestuary. The mass accumulation of organic and inorganic matter was similar and related (R2 = 0.37). However, owing to its lower density, organic matter contributed 1.5–3 times more toward vertical accretion than inorganic matter. Furthermore, water/porespace associated with organic matter accounted for 82%–94% of the total vertical accretion. These findings demonstrate the key role of organic matter in the persistence of coastal wetlands with low mineral sediment supply, particularly mid-estuary oligohaline marshes.

Feasibility of sedimentation strategies for the Mekong delta to counterbalance relative sea-level rise

2021 ◽  
Author(s):  
Frances E. Dunn ◽  
Philip S. J. Minderhoud
Keyword(s):  
Land Use ◽  
Sea Level Rise ◽  
Sea Level ◽  
Mekong Delta ◽  
Sediment Deposition ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Relative Sea Level ◽  
Fluvial Sediment ◽  
Relative Sea Level Rise

<p>As one of the largest deltas in the world, the Mekong delta is home to over 17 million people and supports internationally important agriculture. Recently deposited sediment compacts and causes subsidence in deltas, so they require regular sediment input to maintain elevation relative to sea level. These processes are complicated by human activities, which prevent sediment deposition indirectly through reducing fluvial sediment supply and directly through the construction of flood defence infrastructure on deltas, impeding floods which deliver sediment to the land. Additionally, anthropogenic activities increase the rate of subsidence through the extraction of groundwater and other land-use practices.</p><p>This research shows the potential for fluvial sediment delivery to compensate for sea-level rise and subsidence in the Mekong delta over the 21st century. We use detailed elevation data and subsidence scenarios in combination with regional sea-level rise and fluvial sediment flux projections to quantify the potential for maintaining elevation relative to sea level in the Mekong delta. We present four examples of localised sedimentation scenarios in specific areas, for which we quantified the potential effectiveness of fluvial sediment deposition for offsetting relative sea-level rise. The presented sediment-based adaptation strategies are complicated by existing land use, therefore a change in water and sediment management is required to effectively use natural resources and employ these adaptation methods. The presented approach could be an exemplar to assess sedimentation strategy feasibility in other delta systems worldwide that are under threat from sea-level rise.</p>

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