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Bermuda is an intraplate ocean swell that does not conform to traditional mantle plume theory. Unlike other prominent bathymetric swells, such as Hawaii, it lacks age‐progressive volcanism, a deeply rooted mantle plume, and modern volcanism. High‐frequency receiver‐function imaging of the shallow lithosphere beneath the Bermuda swell reveals two prominent interfaces interpreted as the fossil oceanic Moho and the bottom of an underplated layer. This underplated layer is ∼20 km thick, ∼2x greater than observations at many other intraplate ocean islands. Based on the topography of the Bermuda swell, this layer could be rock that is ∼50 kg/m3 less dense than the lithospheric mantle it has replaced. We suggest that the Bermuda swell is supported by a ∼20 km thick layer of modified lithospheric mantle, not a hot thermal anomaly from a mantle plume.

A proper understanding on the local wind-wave climate is essential and of great importance for sustainable developments in the offshore and coastal waters. This study investigates the response of distant swells at various locations along coastal regions that is generated thousands of kilometers away. Utilizing the ESTELA (Evaluating the Source and Travel-time of the wave Energy reaching a Local Area) method, this study investigated the travel time for swell wave energy to arrive at the Indian coast, including Lakshadweep archipelago and the Andaman Islands. Based on historical data of 42 years, the study revealed that extreme wave energy generated in the western regions of the extratropical south Indian Ocean reaches the North Indian Ocean (NIO) with an average travel time of 7–8 days during all the seasons. The study defines a peculiar directional feature of the northeast monsoonal winds and associated swells that move southwards parallel to the west coast of India, and reaching the mid-Kerala coast. It is seen that southwest monsoonal wave field dominates the extratropical swells in the NIO during June-September, when both are at their maximum potential. The presence of Sri Lanka and Lakshadweep Islands are paramount in attenuating and redistributing the wave energy along the Tamil Nadu and Kerala coasts. During the non-monsoon months, the northwesterly swells ( Shamal and Makran ), northeast monsoon swells, Southern Ocean swells, and cyclone generated swells significantly modify the NIO wind-wave climate. The study demonstrates the long-term analysis of swell systems signifying their dominance on the local wave system, persistence, and variability in the NIO region.

Dramé, A.-B.; Burningham, H., and Sall, M., 2024. Ocean and wave climate variability in West Africa, and implications for alongshore sediment transport on the Senegal-Mauritania coast. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 670-674. Charlotte (North Carolina), ISSN 0749-0208. The east Atlantic wave climate in the region of West Africa is dominated by north-northwesterly high energy swell. Wave conditions are variably modified inshore, but a strong obliquity in wave approach remains, leading to a predominance of north-south sediment transport. Implications for coastal sediment movement in the event of deviations or progressive shifts in offshore wave climate are important in driving change in patterns of erosion and deposition. Here, ERA5 wave data covering the last 6 decades (1940-2023) is analysed at annual and seasonal scales to understand the variability in wave climate over time and to explore the association with key climate drivers such as ENSO, NAO, and AMO. The winter season is considered in more detail to investigate extreme wave parameters. Results show that wave height (>2.5m), period (14s) and were more frequent in the 1950s and over the 2000-2018 period, with extreme wave height (3.92m) being associated with a direction of 335.60°. Wave direction increased by 4.08° between 1940 and 2023, which influences sediment transport direction patterns along the coast. NAO has a greater influence on winter swell wave height and direction than ENSO, which only moderately affects the local wave climate.

Highly susceptible to moisture changes, expansive soils are widely recognized as problematic soils. Swelling-induced damages to overlying engineering structures result in financial loss and billions of dollars in repair costs annually worldwide. Therefore, to mitigate swelling potential, various soil amendment approaches have been investigated to date. Sustainable soil treatment techniques such as microbially induced carbonate precipitation, although enjoying a low CO2 footprint, suffer from challenges pertinent to the use of living microorganisms at field scale treatments. Hence, the current study aims to explore the feasibility and efficiency of using enzyme-induced calcium carbonate precipitation (EICP) as an alternative eco-friendly method, yet to be examined for improving swelling characteristics of clayey soil. For this purpose, a series of laboratory experiments from macro- to microstructural scales involving free swell tests, swell pressure, pH measurement, X-ray powder diffraction, Bernard calcimeter, confocal Raman spectroscopy, and scanning electron microscopy have been conducted on the EICP-treated expansive samples. The experimental program focuses on the influence of constituent concentrations used in the EICP treatment on the swelling potential to obtain the optimal EICP solution. The study reveals that EICP can result in more than 60% reduction in the free swell index compared to untreated soil conditions. The results indicate that the EICP technique can double calcium carbonate content within expansive soil, increasing it by as much as 220%. Finally, it is demonstrated that there is a strong correlation between the amount of precipitated calcite and enhancement in the free swell index.

Ocean swell activities excite body‐wave microseisms that contain information on the Earth's internal structure. Although seismic interferometry is feasible for exploring structures, it faces the problem of spurious phases stemming from an inhomogeneous source distribution. This paper proposes a new method for inferring seismic discontinuity structures beneath receivers using body‐wave microseisms. This method considers the excitation sources of body‐wave microseisms to be spatially localized and persistent over time. To detect the P‐s conversion beneath the receivers, we generalize the receiver function analysis for earthquakes to body‐wave microseisms. The resultant receiver functions are migrated to the depth section. The detected 410‐ and 660‐km mantle discontinuities are consistent with the results obtained using earthquakes, thereby demonstrating the feasibility of our method for exploring deep‐earth interiors. This study is a significant step toward body‐wave exploration considering the sources of P‐wave microseisms to be isolated events. Plain Language Summary The ocean waves excite persistent and random ground motions called microseisms. Since this excitation is independent of seismic activities, this wavefield has information about seismic structures that earthquakes never have. For the deep structure, such as the mantle and core, body‐wave microseisms are more suitable than surface‐wave microseisms because body‐wave microseisms have better sensitivity. Previous studies using body‐wave microseisms mainly adopted the cross‐correlation analysis known as seismic interferometry. This method assumes that the microseisms are excited everywhere. However, the inhomogeneous source distribution of body‐wave microseisms causes artifacts for exploration by seismic interferometry. We developed a new method which circumvents this problem. Assuming that the body‐wave microseisms are spatially isolated, this method extracted the P‐s converted waves beneath receivers from body‐wave microseisms. The 3‐Dimensional imaging result of extracted P‐s converted waves shows both 410‐ and 660‐km mantle discontinuities, consistent with results using earthquakes. This study shows the potential of body‐wave microseisms for exploring the deep earth structure. Key Points The P‐S waves at mantle discontinuities were extracted from the ambient noise excited by the ocean swells We developed the source deconvolution method to generalize a receiver function method to P‐wave microseisms The migration result of P‐S waves was consistent with previous studies, showing the potential of P‐wave microseisms to seismic structures

In late March 2011, landfast sea ice (hereafter, “fast ice”) formed in the northern Larsen B embayment and persisted continuously as multi-year fast ice until January 2022. In the 11 years of fast-ice presence, the northern Larsen B glaciers slowed significantly, thickened in their lower reaches, and developed extensive mélange areas, leading to the formation of ice tongues that extended up to 16 km from the 2011 ice fronts. In situ measurements of ice speed on adjacent ice shelf areas spanning 2011 to 2017 show that the fast ice provided significant resistive stress to ice flow. Fast-ice breakout began in late January 2022 and was closely followed by retreat and breakup of both the fast-ice mélange and the glacier ice tongues. We investigate the probable triggers for the loss of fast ice and document the initial upstream glacier responses. The fast-ice breakup is linked to the arrival of a strong ocean swell event (>1.5 m amplitude; wave period waves >5 s) originating from the northeast. Wave propagation to the ice front was facilitated by a 12-year low in sea ice concentration in the northwestern Weddell Sea, creating a near-ice-free corridor to the open ocean. Remote sensing data in the months following the fast-ice breakout reveals an initial ice flow speed increase (>2-fold), elevation loss (9 to 11 m), and rapid calving of floating and grounded ice for the three main embayment glaciers Crane (11 km), Hektoria (25 km), and Green (18 km).

A high-resolution third-generation wave model based on unstructured grids, WAVEWATCH III (WW3), was used to study the projected future wave climate of Bass Strait and south-east Australia under two different greenhouse gas emission scenarios (SSP1-2.6 and SSP5-8.5). The wave model, forced with winds from the Australian ACCESS-CM2 Global Climate Model, shows good agreement with coastal long-term buoy observations and an independent WW3 hindcast dataset over the historical period 1985–2014. The projected mean significant wave height ( H s ) for SSP5-8.5 by the end of the twenty-first century (2071–2100) shows a robust increase for the majority of the domain, but a decrease in nearshore regions, mainly due to projected decreases in local wind speed. The increase in H s for SSP1-2.6 is relatively small. Seasonal variations show that H s (SSP5-8.5) is primarily influenced by Southern Ocean swell in spring and winter and local winds prevail in summer and autumn. H s percentiles show a stronger increase in extreme wave climate for SSP5-8.5 than for SSP1-2.6. Extreme value H s for SSP1-2.6 shows a projected decrease in western regions of the domain and an increase in the east. Extreme value H s for SSP5-8.5 shows a decrease in the nearshore areas of Victoria. This study shows that projected wave climate changes in south-east Australia may have potential implications for Tasmanian and Victorian coastline stability.

Remotely generated swell waves are the dominant contributor of the coastal wind-wave climate along most of the world coastlines. In this work we describe the characteristics of swells from a coastal perspective. We identify the main regions of formation of swell waves at present and during the late twenty-first century under the RCP8.5 emissions/climate change scenario. We have applied an algorithm that allows one to unequivocally differentiate the swell component from the local wind-waves for a global wave hindcast and for eight CMIP5 state-of-the-art wave model climate projections. We have identified four different regions of swell formation, two in each hemisphere, with the Southern Ocean being by far the main region of swell generation. By the end of this century, the number of swell events generated in the Northern Hemisphere is expected to decrease while the opposite is projected to occur in the Southern Hemisphere. The increase in the Southern Hemisphere is directly associated with a poleward movement and intensification of the wind belts projected by atmospheric climate models.

Bentonite pellets are recognized as good buffer/backfill materials for sealing technological voids in high-level radioactive waste (HLW) repository. Compared to that of a traditional compacted bentonite block, one of the most important particularities of this material is the initially discrete pellets and the inevitable heterogeneous porosity formed, leading to a distinctive water retention behaviour. In this paper, water retention and mercury intrusion porosimetry (MIP) tests were conducted on pellet mixture (constant volume), single pellet (free swelling) and compacted block (constant volume) of GMZ bentonite, water retention properties and pore structure evolutions of the specimens were comparatively investigated. Results show that the water retention properties of the three specimens are almost similar to each other in the high suction range (> 10 MPa), while the water retention capacity of pellet mixture is lower than those of the compacted block and single pellet in the low suction range (< 10 MPa). Based on the capillary water retention theory (the Young–Laplace equation), a new concept ‘saturated void ratio’ that was positively related to water content and dependent on pore size distribution of the specimen was defined. Then, according to the product of saturated void ratio and water density in saturated void, differences of water retention properties for the three specimens at low suctions were explained. Meanwhile, MIP tests indicate that as suction decreases, the micro- and macrovoid ratios of pellet mixture and compacted block decrease as the mesovoid ratio increases, while all the void ratios of single pellets increase. This could be explained that upon wetting, water is successively adsorbed into the inter-layer, inter-particle and inter-pellet voids, leading to the subdivision of particles and swelling of aggregates and pellets. Under constant volume condition, aggregates and pellets tend to swell and fill into the inter-aggregates or inter-pellets voids. While under free swelling condition, the particles and aggregates in a single pellet tend to swell outward rather than squeezing into the inter-aggregate voids, leading to the expansion of the pores and even formation of cracks. Results including the effects of initial conditions (initial dry density and fabric) and constraint conditions (constant volume or free swelling) on the water retention capacity and pore structure evolution reached in this work are of great importance in designing of engineering barrier systems for the HLW repository.

Various methods have been reported in the literature to measure the swelling pressure of clayey soils. These methods generally include experimental measurements of the swelling pressure of the soil using indirect methods by conventional oedometer apparatus; while the measurement of swelling pressure of compacted samples using direct method has been less considered. Direct methods involve constant volume swell method with initial vertical stress and without applying vertical stress. Indirect methods consist of swell-consolidation (Free-swell and Restricted-swell) and zero swell experiments. In the present study, in addition to using conventional oedometer, an experimental technique using a modified loading frame was employed to directly measure the swelling pressure. It is observed that the swelling pressure measured by direct method is greatly affected by the vertical stress at which the sample is inundated. The measured swelling pressures obtained from direct and indirect methods are compared with each other. The results indicate that zero swell method slightly overestimates swelling pressure compared to the direct method of constant volume swell without initial vertical stress. Furthermore, the methods of free swell-consolidation and restricted swell-consolidation excessively overestimate the swelling pressure. Regarding the actual conditions of the soil in practical works, it seems that the swelling pressure measured by the method of constant volume swell with initial vertical stress is closer to the true value. The effects of initial conditions such as dry unit weight and initial water content on the swelling pressure are also evaluated in all methods.