Cold Ocean Water Research Articles

Potential of Cold-Water Agriculture (ColdAg) in Mexico: Challenges and Opportunities for Sustainable Food Production

To guarantee sustainable development at a global level, humanity currently faces serious challenges related to a greater demand and better distribution of food to meet the needs of the growing population in environments affected by global climate change (GCC), and in limiting conditions with respect to natural, genetic, financial, and technological resources. Therefore, there is a dire need to implement technologies that can guarantee food security and sovereignty around the world, enabling sustainable development for all nations. Cold-Water Agriculture (ColdAg) is an available technology that offers an alternative to conventional food production in coastal areas and islands of the tropical and subtropical belts worldwide, making use of cold deep ocean water. Mexico has places with the optimal environmental conditions to adapt this technology, mainly in coastal areas and islands, which can contribute to ensuring access to food and drinking water. Initial tests have shown its viability, while production costs need to be adjusted to make this technology accessible to the poorest populations, so that it can contribute to their sustainable development and wealth. In this review article, we aimed to critically analyze some of the most salient literature on the ColdAg technology and outline the feasibility of this technology to be implemented and exploited in Mexico to contribute to alternative food production in a sustainable manner.

Reducing Biases in Thermal Infrared Surface Radiance Calculations Over Global Oceans

Thermal infrared (IR) environmental satellite data assimilation and remote sensing of the surface and lower troposphere depend on accurate specification of the spectral surface emissivity within clear-sky forward calculations. Over ocean surfaces, accurate modeling of surface-leaving radiances over the sensor scanning swaths is complicated by a quasi-specular bidirectional reflectance distribution function (BRDF). Recent findings at the Joint Center for Satellite Data Assimilation (JCSDA) have also revealed significant zonally varying systematic biases (≈ |0.5| K) on a global scale over cold ocean waters, these the result of temperature dependence in the thermal IR optical constants. This paper proposes practical solutions to these problems by modeling thermal IR “effective emissivity” in a manner that accounts for both surface emission and quasi-specular reflectance, along with temperature dependence, while meeting the latency and computational constraints of operational global data assimilation and retrieval systems. We overview the theoretical basis of the model and validate it against ship-based Marine Atmospheric Emitted Radiance Interferometer (MAERI) spectra obtained from cold and warm water ocean campaigns.

Combining hydro-acoustic sources and bathymetric differences to track the vent evolution of the Mayotte eruption, Mozambique Channel

The majority of Earth volcanism takes place in the deep ocean. Deep-sea volcanoes are particularly complicated to study due to their remoteness. Very different methods can be used and their combination can lead to crucial information about submarine volcanoes behavior. In Mayotte, Comoros archipelago, efforts have been made to study and monitor the deep volcanic activity (∼3000 m) currently occurring east of Mayotte through various methods and campaigns on land and at sea. In October 2020, a line of 10 Ocean Bottom Seismometers was deployed during 10 days, leading to a hand-picked catalog of more than a thousand of hydro-acoustic signals, which have been associated with reactions between hot lava and deep cold ocean waters. During the same period, repeated swath bathymetry surveys were performed over an active lava flow field. We compare the time evolution of the hydro-acoustic events locations and bathymetry differences observed between each survey. While bathymetric information gives absolute location of new lava flows, hydro-acoustic events give detailed relative time variations leading to short-term spatial evolution. Bathymetric information thus provides snapshots of the eruptive area evolution at specific times, when hydro-acoustic signals show its continuous evolution. By combining both complementary analyses we are able to clearly define the detailed evolution of the lava flows pattern in the short time period of 10 days. Applied to the data already acquired on Mayotte since 2019, this method could allow us to estimate more precisely the volcano effusion rate and its evolution, giving further insights on the feeding system.

Quantifying the potential future contribution to global mean sea level from the Filchner–Ronne basin, Antarctica

Abstract. The future of the Antarctic Ice Sheet in response to climate warming is one of the largest sources of uncertainty in estimates of future changes in global mean sea level (ΔGMSL). Mass loss is currently concentrated in regions of warm circumpolar deep water, but it is unclear how ice shelves currently surrounded by relatively cold ocean waters will respond to climatic changes in the future. Studies suggest that warm water could flush the Filchner–Ronne (FR) ice shelf cavity during the 21st century, but the inland ice sheet response to a drastic increase in ice shelf melt rates is poorly known. Here, we use an ice flow model and uncertainty quantification approach to project the GMSL contribution of the FR basin under RCP emissions scenarios, and we assess the forward propagation and proportional contribution of uncertainties in model parameters (related to ice dynamics and atmospheric/oceanic forcing) on these projections. Our probabilistic projections, derived from an extensive sample of the parameter space using a surrogate model, reveal that the FR basin is unlikely to contribute positively to sea level rise by the 23rd century. This is primarily due to the mitigating effect of increased accumulation with warming, which is capable of suppressing ice loss associated with ocean-driven increases in sub-shelf melt. Mass gain (negative ΔGMSL) from the FR basin increases with warming, but uncertainties in these projections also become larger. In the highest emission scenario RCP8.5, ΔGMSL is likely to range from −103 to 26 mm, and this large spread can be apportioned predominantly to uncertainties in parameters driving increases in precipitation (30 %) and sub-shelf melting (44 %). There is potential, within the bounds of our input parameter space, for major collapse and retreat of ice streams feeding the FR ice shelf, and a substantial positive contribution to GMSL (up to approx. 300 mm), but we consider such a scenario to be very unlikely. Adopting uncertainty quantification techniques in future studies will help to provide robust estimates of potential sea level rise and further identify target areas for constraining projections.

Experimental characterization of hydrate formation in non-emulsifying systems upon shut-in and restart conditions

In offshore oil production, scheduled or emergency shutdowns of the production system may occur due to maintenance, equipment failure, production issues, and weather-related events. During the shut-in, the fluids may enter into the hydrate zone because of the thermal energy transfer to the cold ocean waters, increasing the risk of hydrate formation during the shut-in period and upon the restart of the production system. This work is focused on identifying some parameters that influence the hydrate formation in shut-in and restart conditions. Using a rock-flow cell with visual capabilities, the hydrate formation and the phenomena involved upon the restart were investigated. The main results of the experiments showed that the high shear conditions applied at the restart promoted water dispersion into the oil phase and contributed to the dispersion of hydrates. In addition, the low shear rate favored the formation of hydrate deposits while hydrate agglomerate was formed at high shear rate. Besides the shear rate, the subcooling proved to be an important parameter that favors the hydrate formation under sheared conditions. Conditions with high subcooling and low water cut promoted the formation of small hydrate particles (~2 mm) that can be dispersed in the oil-phase even without the anti-agglomerant. A high subcooling promoted the formation of “dry” hydrates, preventing the particles to stick with each other (agglomerates). The results indicated that subcooling is an important parameter to ensure a safe restart in the pipeline. Lastly, the addition of an anti-agglomerant reduced the water–oil interfacial tension, which promoted the water/hydrate dispersion; the effectiveness of the anti-agglomerant was clearly affected by the shear and the water cut.

Ocean‐Driven and Topography‐Controlled Nonlinear Glacier Retreat During the Holocene: Southwestern Ross Sea, Antarctica

AbstractRecent ice sheet mass loss in Antarctica has been attributed to an influx of warm ocean waters, which drove grounding‐line retreat and ice thinning. Episodic retreat and rapid thinning also occurred in the southwestern Ross Sea during the Holocene, which today accommodates cold ocean waters. We applied finite element ice‐flow modeling to investigate the roles of ocean temperature and bed topography in the deglaciation of this region. First, our experiments demonstrate that bed topography controlled the spatial pattern of grounding‐line retreat. Topographic pinning points limited the rate of ice loss until retreat progressed beyond a bathymetric threshold. Second, ocean thermal forcing determined the timing of this ice loss. Enhanced ocean‐driven melt is required during the Early‐to‐Mid Holocene to replicate geological records of deglaciation, possibly indicating that warm ocean waters were once present in this region. On multi‐centennial timescales, ocean temperature drove, while bed topography controlled, nonlinear rates of ice mass loss.

Extensive use of the high seas by Vulnerable Fiordland Penguins across non-breeding stages

Migratory seabirds experience varying levels of both protection and threats as they travel across marine regions and countries’ jurisdictions. Studying their seasonal distribution provides insights into the full range of exploited habitats and potential gaps in conservation policy existing in the visited areas. Here we used light-based geolocation to examine the seasonal at-sea distribution of an endemic seabird from New Zealand, the Fiordland Penguin Eudyptes pachyrhynchus, with respect to Economic Exclusive Zones (EEZs). We show that the five birds successfully tracked from the remote Open Bay Islands exploited vast areas in the South Pacific Ocean and used contrasted habitats across seasons. During extensive periods at-sea before and after moulting, Fiordland Penguins reached cold oceanic waters across the Subantarctic Front (Subantarctic and Polar Frontal zones, 2–10 °C), ranging 1500–2000 km in the southwest of their colony. Across both these trips, all birds distributed extensively outside New Zealand’s EEZ (nearly 50% of time), into areas beyond national jurisdiction providing little tangible protection, and some temporarily entered Australia’s EEZ. This contrasted with previous results from the breeding season, when the Penguins distributed exclusively within New Zealand’s EEZ, in relatively shallow and warm (c. 12–20 °C) waters north of the Southern Subtropical Front. Annually, the tracked Penguins spent 102 days outside New Zealand waters, of which 79 days in the high seas. Our results provide new perspectives on pertinent conservation strategies for migratory “endemic” Penguins. Year-round approach on the at-sea ecology of species seems fundamental for adequate management of threatened marine biodiversity.

Semi-Automatic Versus Manual Mapping of Cold-Water Coral Carbonate Mounds Located Offshore Norway

Cold-water coral reefs are hotspots of biological diversity and play an important role as carbonate factories in the global carbon cycle. Reef-building corals can be found in cold oceanic waters around the world. Detailed knowledge on the spatial location and distribution of coral reefs is of importance for spatial management, conservation and science. Carbonate mounds (reefs) are readily identifiable in high-resolution multibeam echosounder data but systematic mapping programs have relied mostly on visual interpretation and manual digitizing so far. Developing more automated methods will help to reduce the time spent on this laborious task and will additionally lead to more objective and reproducible results. In this paper, we present an attempt at testing whether rule-based classification can replace manual mapping when mapping cold-water coral carbonate mounds. To that end, we have estimated and compared the accuracies of manual mapping, pixel-based terrain analysis and object-based image analysis. To verify the mapping results, we created a reference dataset of presence/absence points agreed upon by three mapping experts. There were no statistically significant differences in the overall accuracies of the maps produced by the three approaches. We conclude that semi-automated rule-based methods might be a viable option for mapping carbonate mounds with high spatial detail over large areas.

Repeated turnovers in Late Jurassic faunal assemblages of the Gulf of Mexico: Correlation with cold ocean water

Our research on Late Jurassic–earliest Cretaceous (Kimmeridgian–earliest Berriasian) marine shelf to bathyal sediments in northeastern Mexico reveals significant repeated oceanic and biotic turnovers in the northwestern Proto-Gulf of Mexico. We here document these environmental changes based on alternating cold and warm water mollusk assemblages, element concentrations and organofacies, as well as associated changes in sea level. We hypothesize that oscillations in the oceanic current system of the Gulf of Mexico were responsible for appearance of cold-water assemblages of Boreal and possibly Austral origins, situated in specific horizons which were previously described as poor in fossil content or even as fossil-free. In addition, these specific horizons show significant changes in element concentrations and organofacies and correlate to relative sea-level changes.

Techno-economic analysis of multipurpose OTEC power plants

Ocean Thermal Energy Conversion (OTEC) is a promising technology to provide sustainable and dispatchable energy supply to oceanic coastal areas and islands. It exploits the temperature difference between deep cold ocean water and warm tropical surface water in an Organic RankineCycle (ORC), guaranteeing a continuous and dispatchable electric production, overcoming one ofthe most critical issue of renewable generators such as PV or wind turbines. Despite the technological maturity of ORC application to OTEC systems, it still presents technical and economicbarriers mainly related to their economic feasibility, large initial investments as well as heavy and time demanding civil installation works. To overcome such issues, multipurpose OTEC plants are proposed, producing electrical power as well as other products, such as useful thermal power (e.g. ambient cooling) and desalinated water. Since OTEC engineering is still at a lowdegree of maturity, there are no widespread and established tools to facilitate OTEC feasibility studies and to allow performance and cost optimization. Therefore, in this paper, a new tool for techno-economic analysis and optimization of multipurpose OTEC plants is presented. Starting from a detailed database of local water temperature and depth, the approach allows to provide a quantitative insight on the achievable performance, required investment, and expected economic returns, allowing for a preliminary but robust assessment of site potential as well as plant size. After the description of the techno-economic approach and related performance and cost functions, the tool is applied to an OTEC power plant case study in the range of 1 MW gross electrical power, including a preliminary assessment of scaling-up effects.

Analysis of Ocean Thermal Energy Conversion Power Plant using Isobutane as the Working Fluid

The use of organic isobutane will be investigated for a closed-cycle Ocean Thermal Energy Conversion (OTEC) onshore plant that delivers 110 MW electric powers. This paper will cover concept, process, energy calculations, cost factoids and environmental aspects. In isobutane cycle, hot ocean surface water is used to vaporize and to superheat isobutane in a heat exchanger. Isobutane vapor then expands through a turbine to generate useful power. The exhaust vapor is condensed afterwards, using the cold deeper ocean water, and pumped to a heat exchanger to complete a cycle. Results show the major design characteristics and equipment's of the OTEC plant along with cycle efficiency and cycle improvement techniques.

Ocean thermal energy conversion and open ocean mariculture: The prospect of Mainland-Taiwan collaborative research and development

Ocean thermal energy conversion (OTEC) is an energy generation technology that uses cold deep ocean water (DOW) and warm surface water to produce electricity. Active development of OTEC was started in the 1970s with Hawaii as a major research and development center. In the following several decades, small pilot-scale closed-cycle and open-cycle OTEC plants were successfully designed, constructed, and tested. An open-cycle OTEC plant produces both electricity and freshwater. Besides its low temperature, DOW is also nutrient-rich and free from pathogenic bacteria. DOW-enhanced open ocean mariculture can significantly increase the world fish catch and induce an air to water transfer of greenhouse gas CO2. Therefore, an integrated development of DOW as a natural resource is the center of a “blue revolution” that has the potential to solve four of the most urgent world problems: energy, freshwater, food, and global warming. This paper will review technological development of OTEC and open ocean mariculture, followed by a discussion of the prospect of Mainland-Taiwan research collaboration on the technological development and application of DOW resources.

Dinoflagelados del Eoceno medio a superior de las cuencas Punta Del Este y Colorado, latitudes medias del Atlántico sudoccidental

The analysis of middle Eocene dinoflagellate cyst assemblages from sites at Punta del Este (~36°S, Uruguay) and Colorado (~38°S, Argentina) basins allows to interpret ocean circulation patterns on the South American Shelf prior to the opening of the Drake Passage. The assemblages contain endemic-Antarctic taxa such as Enneadocysta, Deflandrea, Vozzhennikovia and Spinidinium, which are also dominant in several circum-Antarctic sites, located southern 45°S. Enneadocysta dictyostila is the most abundant species recorded from the studied sites and the unique member of the endemic assemblage apparently tolerant to warm surface waters. The presence of endemic taxa at mid latitudes has been related to a strong clockwise subpolar gyre favoured by the partial continental blockage of the Tasmanian Gateways and the Drake Passage. The distribution of the dinoflagellate cyst assemblages along the South Atlantic Ocean Shelf can be explained by a similar dynamical mechanism induced by a cyclonic subpolar gyre on the South Atlantic Ocean. The western boundary current of this gyre, starting on the west Antarctic continental slope, would follow a similar path to the present Malvinas Current on the Patagonian slope, which introduce cold oceanic waters to the shelf and intensifies the northward shelf transport. In the same way, during the middle Eocene the western boundary current of a proto-Weddell Gyre transported the circum-Antarctic waters and the endemic taxa northward along the Southwestern Atlantic Shelf. The opening and deepening of the Tasmanian Gateway and Drake Passage and the development of an incipient Antarctic Circumpolar Current during the latest Eocene-Oligocene disrupted the subpolar gyres and promoted the extinction of the endemic species. © 2016 by the Sociedade Brasileira de Paleontologia.

Drivers of exceptionally cold North Atlantic Ocean temperatures and their link to the 2015 European heat wave

The North Atlantic and Europe experienced two extreme climate events in 2015: exceptionally cold ocean surface temperatures and a summer heat wave ranked in the top ten over the past 65 years. Here, we show that the cold ocean temperatures were the most extreme in the modern record over much of the mid-high latitude North-East Atlantic. Further, by considering surface heat loss, ocean heat content and wind driven upwelling we explain for the first time the genesis of this cold ocean anomaly. We find that it is primarily due to extreme ocean heat loss driven by atmospheric circulation changes in the preceding two winters combined with the re-emergence of cold ocean water masses. Furthermore, we reveal that a similar cold Atlantic anomaly was also present prior to the most extreme European heat waves since the 1980s indicating that it is a common factor in the development of these events. For the specific case of 2015, we show that the ocean anomaly is linked to a stationary position of the Jet Stream that favours the development of high surface temperatures over Central Europe during the heat wave. Our study calls for an urgent assessment of the impact of ocean drivers on major European summer temperature extremes in order to provide better advance warning measures of these high societal impact events.

Coexistence of urban uses and shellfish production in an upwelling-driven, highly productive marine environment: The case of the Ría de Vigo (Galicia, Spain)

The Ría de Vigo, located at the northern border of the Iberia-NW Africa eastern boundary upwelling ecosystem, is an incised deep (45 m maxim depth) valley originated by the combined action of tectonic and erosive processes. Upwelling events promote a quick renewal (3–4 days) of the volume of water in the Ría, which is replaced by cold, oxygenated and nutrient-rich subsurface oceanic water, giving rise to nutrient fertilization of the embayment that translates into high primary production rates (ca. 3 g C m−2 d−1). This high productivity allows the development of an important shellfish exploitation activity. The Ría de Vigo has 529 rafts where 37000 tons of mussels are produced annually. This territory has been subjected to an increasing human pressure since the early XX century deriving in an intense landscape transformation. The city of Vigo showed a six-fold increase in the number of inhabitants from 1900 to 2001 and more than 21% of the land in the study area is currently artificial. Therefore, urban and industrial activities coexist with local fisheries and shellfish mariculture that accounts for ca. 7% of the income and employment in this urban region. Incomplete depuration of wastewater in treatment plants, explain the relatively high contribution (22%) of sewage-derived nutrients to the total allochthonous fertilization in the Ría. Furthermore, and given the importance of shellfish production, microbial pollution originated from urban wastewater is considered as the main environmental threat of the Ría de Vigo. The dependence of the local economy on marine renewable resources together with the limitation of the natural productivity of the Rías imposed by anthropogenic pressure lies behind a significant fraction of the conflicts occurring in the region during the past two decades. The characteristics of Ría de Vigo, described in this review, confer this coastal ecosystem unique, conditions as a natural laboratory where the interaction between human activity and marine ecological processes can be studied within the framework of the World Harbour Project.

Research progress in artificial upwelling and its potential environmental effects

Artificial upwelling, as a geoengineering tool, has received worldwide attention because it may actualize ocean fertilization in a sustainable way, which could potentially alleviate the pressures on the fish stocks and human-driven climate change in the ocean. We reviewed the current knowledge on the development of an artificial upwelling system and its potential environmental effects. Special attention was given to the research progress on the air-lift concept artificial upwelling by Zhejiang University. The research on artificial upwelling over the past few decades has generated a range of devices that have been successfully applied in the field for months. Based on field experiments and the associated modeling results, part of them reported positive effects on increasing primary production and enhancing CO2 sequestration. However, as a significant disturbance to the environment, especially for large-scale applications, the uncertainties related to the potential effects on ecosystem remain unsolved. Zhejiang University has overcome the technical challenges in designing and fabricating a robust and high efficiency artificial upwelling device which has been examined in two field experiments in Qiandao Lake and one sea trial in the East China Sea. It was investigated that cold and hypoxic deep ocean water (DOW) could be uplifted to the euphotic layer, which could potentially change the nutrient distribution and adjust the N/P ratio. Both simulation and field experiments results confirmed that utilizing self-powered energy to inject compressed air to uplift DOW was a valid and efficient method. Therefore, further field-based research on artificial upwelling, especially for long-term field research is required to test the scientific hypothesis.

Microbial ecology of Antarctic aquatic systems.

The Earth's biosphere is dominated by cold environments, and the cold biosphere is dominated by microorganisms. Microorganisms in cold Southern Ocean waters are recognized for having crucial roles in global biogeochemical cycles, including carbon sequestration, whereas microorganisms in other Antarctic aquatic biomes are not as well understood. In this Review, I consider what has been learned about Antarctic aquatic microbial ecology from 'omic' studies. I assess the factors that shape the biogeography of Antarctic microorganisms, reflect on some of the unusual biogeochemical cycles that they are associated with and discuss the important roles that viruses have in controlling ecosystem function.

Chemical profiles in otoliths from 3 fish species along the Moroccan coast: accumulation and migration patterns

Event Abstract Back to Event Chemical profiles in otoliths from 3 fish species along the Moroccan coast: accumulation and migration patterns Maylis Labonne1, Hicham Masski2*, Raymond Lae1, Sophia Talba2, Claire Bassoulet3, Eric Dabas1, Imane Tai2, Jean Marie Munaron1 and Luis Tito De Morais1 1 UMR 6539 IRD/CNRS/UBO LEMAR, IUEM,, France 2 INRH, Morocco 3 UMS 3113, PSO, IUEM, France The Canary Current Large Ecosystem is characterized by a major, nutrient-rich up-welling of deep, cold oceanic waters, which stimulates high biological productivity that results in an abundance of both pelagic and demersal fishery resources. In this area, the Moroccan coast is also under direct anthropogenic activities influences such as phosphates industries. Several observations indicate that variations of the upwelling activities observed in the recent years would generate the remobilization of the contaminants. Our study deals with the metallic concentrations in the otoliths of 3 fish species of economic interest ( Merlucius merlucius, Pagellus acarne, Sardina pilchardus) along the Moroccan coast. The fishes were collected in markets in june 2012 for the northern part of Morocco (during the maximum of the upwelling activity) and in November 2012 for the southern part. Concentrations were measured by ICP-MS on transects from nucleus to the edge of otoliths to characterize environmental variations or accumulations linked to ecophases and growth. For each species, 5 fishes were analyzed in 7 locations from North to south of the Moroccan Atlantic coast. First results indicate that the concentrations are highly variable in hake transects, and on the other hand, transects in seabreams seem very stable regardless of location. Transects in sardines indicate different patterns depending on the locations and, some of them, clearly show the upwelling signature. Keywords: Otolith microchemistry, Sardine, hake, Pagellus acarne, Morocco Conference: XV European Congress of Ichthyology, Porto, Portugal, 7 Sep - 11 Sep, 2015. Presentation Type: Oral Presentation Topic: Otoliths as a tool to study fish life cycles Citation: Labonne M, Masski H, Lae R, Talba S, Bassoulet C, Dabas E, Tai I, Munaron J and Tito De Morais L (2015). Chemical profiles in otoliths from 3 fish species along the Moroccan coast: accumulation and migration patterns. Front. Mar. Sci. Conference Abstract: XV European Congress of Ichthyology. doi: 10.3389/conf.fmars.2015.03.00126 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 23 Nov 2015; Published Online: 24 Nov 2015. * Correspondence: Dr. Hicham Masski, INRH, Casablanca, Morocco, hmasski@protonmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Maylis Labonne Hicham Masski Raymond Lae Sophia Talba Claire Bassoulet Eric Dabas Imane Tai Jean Marie Munaron Luis Tito De Morais Google Maylis Labonne Hicham Masski Raymond Lae Sophia Talba Claire Bassoulet Eric Dabas Imane Tai Jean Marie Munaron Luis Tito De Morais Google Scholar Maylis Labonne Hicham Masski Raymond Lae Sophia Talba Claire Bassoulet Eric Dabas Imane Tai Jean Marie Munaron Luis Tito De Morais PubMed Maylis Labonne Hicham Masski Raymond Lae Sophia Talba Claire Bassoulet Eric Dabas Imane Tai Jean Marie Munaron Luis Tito De Morais Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Identifying hazards associated with lava deltas

Lava deltas, formed where lava enters the ocean and builds a shelf of new land extending from the coastline, represent a significant local hazard, especially on populated ocean island volcanoes. Such structures are unstable and prone to collapse—events that are often accompanied by small explosions that can deposit boulders and cobbles hundreds of meters inland. Explosions that coincide with collapses of the East Lae ‘Apuki lava delta at Kīlauea Volcano, Hawai‘i, during 2005–2007 followed an evolutionary progression mirroring that of the delta itself. A collapse that occurred when the lava–ocean entry was active was associated with a blast of lithic blocks and dispersal of spatter and fine, glassy tephra. Shortly after delta growth ceased, a collapse exposed hot rock to cold ocean water, resulting in an explosion composed entirely of lithic blocks and lapilli. Further collapse of the delta after several months of inactivity, by which time it had cooled significantly, resulted in no recognizable explosion deposit. Seaward displacement and subsidence of the coastline immediately inland of the delta was measured by both satellite and ground-based sensors and occurred at rates of several centimeters per month even after the lava–ocean entry had ceased. The anomalous deformation ended only after complete collapse of the delta. Monitoring of ground deformation may therefore provide an indication of the potential for delta collapse, while the hazard associated with collapse can be inferred from the level of activity, or the time since the last activity, on the delta.

Links between southwestern tropical Indian Ocean SST and precipitation over southeastern Africa over the last 17 kyr

Time series of Mg/Ca, Ba/Ca, and δ18O analyzed in tests of surface-dwelling planktonic foraminifer Globigerinoides ruber from two marine sediment cores recovered in the Mozambique Channel off the Zambezi River, southwestern tropical Indian Ocean, reveal climate variability over the last 17kyr. Analysis of samples collected from the water column of the Mozambique Channel validates that Mg/Ca in G. ruber reflects calcification temperatures at 0–30m water depth and that the surface water of the southwestern Indian Ocean is very sensitive to dissolved Ba input from adjacent rivers. Foraminiferal Ba/Ca and Mg/Ca time series are used to reconstruct hydrological and thermal changes over southeastern African and southwestern tropical oceans. The Mg/Ca-based sea surface temperature (SST) estimates indicate that the thermal evolution of the tropical southwestern Indian Ocean followed, within age model uncertainties, climate changes over Antarctica. The trend of the SST record is marked by a gradual warming from 24.7±0.6°C at 17.0±0.2kyr BP to 26.4±0.3°C at 10–11kyr BP interrupted by two prominent coolings of ~1.5±0.2°C and ~1°C centered at 15±0.1kyr BP and 13.4±0.2kyr BP, respectively. Declining SSTs in the early Holocene reach their minimum (25°C) at 8.7±0.2kyr BP and give way to stable thermal conditions over the Middle and Late Holocene. The Ba/Ca record indicates that the Zambezi basin experienced relatively wet conditions during the early phase of the last deglaciation, Bølling–Allerød, and the early Holocene. These wet phases coincide with an increase of SST in the Mozambique Channel. In contrast, relatively dry conditions throughout the middle and late Holocene epoch are accompanied by relatively cold Mozambique Channel surface water. These shifts likely reflect a response to meridional shifts of the austral westerlies and subtropical front. These hypothesized shifts would have modulated the advection of cold Southern Ocean water into the Mozambique Channel. Changes in SST in the Mozambique Channel, and possible resultant changes in the zonal gradient in the tropical Indian Ocean, in turn, had a strong impact on the precipitation over southeastern Africa.