scholarly journals Utilizing sponge spicules in taxonomic, ecological and environmental reconstructions: a review

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e10601
Author(s):  
Magdalena Łukowiak
Keyword(s):  
Ocean Circulation ◽  
Environmental Data ◽  
Silicon Isotope ◽  
Structural Elements ◽  
Climate Conditions ◽  
The Past ◽  
Sponge Spicules ◽  
Silica Cycle ◽  
Taxonomic Assignments ◽  
Water Depths

Most sponges produce skeletons formed by spicules, structural elements that develop in a wide variety of sizes and tridimensional shapes. The morphologies of spicules are often unique to clade- or even species-level taxa which makes them particularly useful in taxonomic assignments. When dead sponge bodies disintegrate, spicules become incorporated into sediments and sometimes accumulate into enormous agglomerations called spicule mats or beds, or fossilize to form special type of rocks called the spiculites. The record of fossil and subfossil sponge spicules is extraordinarily rich and often serves as a basis for far-reaching reconstructions of sponge communities, though spicules are also bearers of significant ecological and environmental information. Specific requirements and preferences of sponges can be used to interpret the environment in which they lived, and reconstruct oscillations in water depths, pH, temperatures, and other parameters, providing snapshots of past climate conditions. In turn, the silicon isotope compositions in spicules (δ30Si) are being increasingly often used to estimate the level of silicic acid in the marine settings throughout the geological history, which enables to reconstruct the past silica cycle and ocean circulation. This contribution provides a review of the use of sponge spicules in reconstructions of sponge communities, their ecology, and environments, and aims to detect the pertinent gaps in their utilization. Even though spicules are well known for their significance as bearers of taxonomic, ecological, and environmental data, their potential remains to be fully exploited.

Toward an improved characterisation of climate and environmental changes during warm periods of the past: First results from the MOPGA HOTCLIM project 

2021 ◽  
Author(s):  
Etienne Legrain ◽  
Emilie Capron ◽  
Frederic Parrenin
Keyword(s):  
Carbon Cycle ◽  
Ocean Circulation ◽  
Environmental Changes ◽  
Temporal Structure ◽  
Ice Cores ◽  
Environmental Data ◽  
Interglacial Period ◽  
Climate Projections ◽  
The Past ◽  
First Results

<p>The current and future anthropogenic-induced high-latitude warming will have global climatic implications due to polar ice mass loss, sea level rise and ocean circulation changes. However, uncertainty remains on future climate projections mainly due to an incomplete understanding of climate, cryosphere and carbon cycle feedback processes occurring at centennial to millennial- timescales. Progress can be achieved by exploring climate and environmental changes that occurred in the past. In the HOTCLIM project, we are studying past warm periods, also referred to as interglacials, which exhibit a polar warming comparable to that projected by 2100 due to specific combinations of orbital and CO<sub>2</sub> forcing. Especially, we are investigating the link between the carbon cycle dynamics and climate changes. To do so, we are combining (i) new analyses on the air trapped in Antarctic deep ice cores to inform on past changes in Antarctic climate and atmospheric CO2 concentrations (ii) climate and environmental data synthesis looking into the lower latitudes using terrestrial and oceanic archives (sea surface temperature, hydrological cycles, ocean circulation) (iii) an evaluation of outputs from climate models using the new comparison of the paleoclimatic datasynthesis and models output. The HOTCLIM project will improve our understanding of the natural climate variability and the processes involved during past periods associated with temperature changes comparable to projected future warming, hence helping improve climate projections</p><p>Here, we present the first results from the HOTCLIM project which is a multi-archive synthesis focused on the warm interval occurring between 190 and 243 ka BP, also refered to as Marine Isotopic Stage 7 (MIS 7). This warm period is of special interest because it follows the fastest transition between a cold (glacial) and a hot (interglacial) period of the last 800 000 ka, with a polar warming of 10 degrees in less than 5ka. We have compiled more than 30 oceanic cores, 9 speleothems and 3 ice cores covering the MIS 7 period. To compare them, we are now building a common chronology to these records. The use of combined continental (ice cores, speleothems) and oceanic (sediment cores) archives located on the whole surface of the Earth will allows to characterize (i) the amplitude and the temporal structure of the surface warming across the globe (ii) the contrast between oceanic and continental warming.</p>

Iceland-Faroe Ridge overflow dynamics, 55-6 ka BP

2020 ◽  
Author(s):  
Maryam Mirzaloo ◽  
Dirk Nürnberg ◽  
Markus Kienast ◽  
Jeroen van der Lubbe
Keyword(s):  
Grain Size ◽  
Ocean Circulation ◽  
Academic Career ◽  
Meridional Overturning Circulation ◽  
Bottom Current ◽  
Oceanic Circulation ◽  
Climate Conditions ◽  
Bottom Currents ◽  
The Past ◽  
Bulk Chemistry

<p>The understanding of the past changes in this critical area of oceanic circulation will be beneficial to predict future climate conditions and their related socio-economic impacts. Sediment cores recovered from the western flank of the Iceland-Faroe Ridge (IFR; P457-905 and -909) provide unique archives to reconstruct changes in the Iceland-Scotland overflow water (ISOW), an important component of the Atlantic Meridional Overturning Circulation (AMOC) over the last 55-6 ka BP. We provide high-resolution records of lithogenic grain-size and XRF bulk chemistry on millennial timescales. The age models of both cores have been constrained by radiocarbon datings of planktonic foraminifera and distinct tephra layers, which include the well-known Faroe-Marine-Ash-Zones (FMAZ) II and III. Both grain-size and XRF bulk chemistry (Zr/Rb and Ti/K) reveal prominent Dansgaard-Oeschger sedimentary cycles, which reflect considerable changes in near-bottom current strength and sediment transport/deposition. The transition between cold Greenland Stadials (GSs) and warm Greenland Interstadials (GIs) occur in typical, recurring sedimentation patterns. The GIs are characterized by relatively strong bottom currents and the transport/deposition of basaltic (Ti-rich) silts from local volcanic sources resembling the modern ocean circulation pattern. In contrast, fine grained felsic (K-rich) sediments were deposited during GSs, when the ISOW was weak. In particular, the Heinrich (like) Stadials HS1 and HS2 stand out as intervals of very fine felsic sediment deposition and hence, slackened bottom currents. The bottom currents appear to progressively strengthen throughout the GIs, and sharply decline towards the GSs. This pattern contrasts with records from north of the IFR, which might be explained by a diminishing contribution of the flow cascading over the IFR. Together, these new records show strong changes in bottom current dynamics related to the Iceland-Scotland overflow, which has a strong influence on the past and modern climate of the North Atlantic Region. However, climate change is an interdisciplinary field of research. HOSST-TOSST transatlantic interdisciplinary research program provides the unique opportunity for constructive communication and collaboration among scientists with different skills filling knowledge gaps and bridging the earth sciences with social and economic disciplines. Such interdisciplinary programs at early stages in an academic career is necessary to move and encourage the new generation of the scientific community toward a tradition of broad‐scale interactions.</p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p><p> </p>

The Role of Diagenesis in the Apparent Rise of Diatoms

2021 ◽  
Author(s):  
Sophie Westacott ◽  
Noah Planavsky ◽  
Ming-Yu Zhao ◽  
Pincelli Hull
Keyword(s):  
Silicon Isotope ◽  
Sedimentation Rates ◽  
Bottom Water Temperature ◽  
Baleen Whales ◽  
The Past ◽  
Isotope Evidence ◽  
Silica Cycle ◽  
Fossil Data ◽  
Burial Efficiency

<p><span>Diatoms are one of the most dominant primary producers in the ocean today and largely control the modern marine silica cycle. Their ecological expansion in the Cenozoic is thought to have lowered silica concentrations by two orders of magnitude and has been linked to the rise of grasslands and baleen whales. According to the fossil record much of diatoms' rise to dominance occurred in the past 20 m.y.; however, silicon isotope evidence suggests an earlier expansion. Using a diagenetic model and collated deep sea drill core data, we examine how changes in bottom-water temperature and sedimentation rates over the past 65 m.y. affected the burial efficiency of biogenic silica. We find that once taphonomic potential is taken into account there is no support for the traditionally recognized ~5-20 Ma increase in diatom abundance. These results help reconcile interpretations based on geochemical and fossil data, and add to mounting evidence pushing back the evolution of the modern silica cycle to before 20 Ma and possibly earlier than 40 Ma.</span></p>

scholarly journals EXTREME WAVE PRESSURES AND LOADS ON A PILE-SUPPORTED WHARF DECK - INFLUENCES OF AIR GAP AND WAVE DIRECTION

2018 ◽  
pp. 5
Author(s):  
Andrew Cornett
Keyword(s):  
Offshore Structures ◽  
Model Tests ◽  
Scale Model ◽  
Extreme Waves ◽  
Wave Direction ◽  
Coastal Structures ◽  
Extreme Wave ◽  
Wave Impact ◽  
The Past ◽  
Water Depths

Many deck-on-pile structures are located in shallow water depths at elevations low enough to be inundated by large waves during intense storms or tsunami. Many researchers have studied wave-in-deck loads over the past decade using a variety of theoretical, experimental, and numerical methods. Wave-in-deck loads on various pile supported coastal structures such as jetties, piers, wharves and bridges have been studied by Tirindelli et al. (2003), Cuomo et al. (2007, 2009), Murali et al. (2009), and Meng et al. (2010). All these authors analyzed data from scale model tests to investigate the pressures and loads on beam and deck elements subject to wave impact under various conditions. Wavein- deck loads on fixed offshore structures have been studied by Murray et al. (1997), Finnigan et al. (1997), Bea et al. (1999, 2001), Baarholm et al. (2004, 2009), and Raaij et al. (2007). These authors have studied both simplified and realistic deck structures using a mixture of theoretical analysis and model tests. Other researchers, including Kendon et al. (2010), Schellin et al. (2009), Lande et al. (2011) and Wemmenhove et al. (2011) have demonstrated that various CFD methods can be used to simulate the interaction of extreme waves with both simple and more realistic deck structures, and predict wave-in-deck pressures and loads.

Response of Siberian trees to climatic changes over the past 1500 years

2021 ◽  
Author(s):  
Olga Churakova (Sidorova) ◽  
Marina Fonti ◽  
Rolf Siegwolf ◽  
Tatyana Trushkina ◽  
Eugene Vaganov ◽  
...  
Keyword(s):  
Tree Ring ◽  
Ice Core ◽  
Climatic Changes ◽  
Medieval Warm Period ◽  
Warm Period ◽  
Taimyr Peninsula ◽  
Climate Conditions ◽  
Northeastern Part ◽  
The Past ◽  
Tree Ring Cellulose

<p>We use an interdisciplinary approach combining stable isotopes in tree rings, pollen data, ice cores from temperature-limited environment in the Siberian north and developed a comprehensive description of the climatic changes over the past 1500 years. We found that the Climatic Optimum Period was warmer and drier compared to the Medieval one, but rather similar to the recent period. Our results indicate that the Medieval Warm period in the Taimyr Peninsula started earlier and was wetter compared to the northeastern part of Siberia (northeastern Yakutia). Summer precipitation reconstruction obtained from carbon isotopes in tree-ring cellulose from Taimyr Peninsula significantly correlated with the pollen data of the Lama Lake (Andreev et al. 2004) and oxygen isotopes of the ice core from Severnaya Zemlya (Opel et al. 2013) recording wetter climate conditions during the Medieval Warm period compared to the northeastern part of Siberia. Common large-scale climate variability was confirmed by significant relationship between oxygen isotope data in tree-ring cellulose from the Taimyr Peninsula and northeastern Yakutia, and oxygen isotope ice core data from Severnaya Zemlja during the Medieval Warm period and the recent one. Finally, we showed that the recent warming on the Taimyr Peninsula is not unprecedented in the Siberian north. Similar climate conditions were recorded by stable isotopes in tree rings, pollen, and ice core data 6000 years ago. On the northeastern part of Siberia newly developed a 1500-year summer vapor pressure deficit (VPD) reconstruction showed, that VPD increased recently, but does not yet exceed the maximum values reconstructed during the Medieval Warm period. The most humid conditions in the northeastern part of Siberia were recorded in the Early Medieval period and during the Little Ice Age. However, the increasing VPD under elevated air temperature in the last decades affects the hydrological regime of these sensitive ecosystems by greater evapotranspiration rates. Further VPD increase will significantly affect Siberian forests most likely leading to drought even under additional access of thawed permafrost water.</p><p>This work was supported by the FP7-PEOPLE-IIF-2008 - Marie Curie Action: "International Incoming Fellowships" 235122 and "Reintegration Fellowships" 909122 “Climatic and environmental changes in the Eurasian Subarctic inferred from tree-ring and stable isotope chronologies for the past and recent periods” and the Government of Krasnoyarsk Kray and Russian Foundation for Basic Research and Krasnoyarsk Foundation 20-44-240001 “Adaptation of conifer forests on the north of the Krasnoyarsk region (Taimyr Peninsula) to climatic changes after extreme events over the past 1500 years“ awarded to Olga V. Churakova (Sidorova).</p>

An old bridge transformed into a new one: possible, recommendable?

2019 ◽  
Author(s):  
Diego Carro-López ◽  
Ignasi Fernandez ◽  
Natalie Williams Portal
Keyword(s):  
Environmental Issues ◽  
Quality Standards ◽  
Structural Effect ◽  
Coarse Fraction ◽  
Concrete Bridges ◽  
Recycled Aggregates ◽  
Structural Elements ◽  
The Past ◽  
Reinforced Concrete Bridges ◽  
Natural Aggregates

<p>There is an extensive network of reinforced concrete bridges that give service to roads, highways and railways. These structures where constructed with quality standards of the past, and they suffer of severe problems. Now we consider the idea of substituting them with structural elements with much longer service life. However, there is an important question to be addressed in this area: what to do with the existing infrastructure that would be demolished. Even more if we consider environmental issues.</p><p>One good example of this recurrent problem could be found in the case of the Gullspång bridge (Sweden). It was constructed in 1935 and it was severely damaged with corrosion. The administration decided in the 2016 that no further repair would be done and that the bridge would be demolished and a new erected in substitution. A fraction of the concrete from the old bridge was crushed and processed to produce new aggregate. With this aggregate, using the coarse fraction, it was analyzed the structural effect of replacing natural aggregates with these recycled aggregates. The performance of the new structural elements was positive, and it seems that a high percentage of the natural aggregates could be replaced with recycled ones.</p>

scholarly journals Fingerprints of changes in the terrestrial carbon cycle in response to large reorganizations in ocean circulation

2010 ◽  
Vol 6 (5) ◽  
pp. 1811-1852 ◽  
Author(s):  
A. Bozbiyik ◽  
M. Steinacher ◽  
F. Joos ◽  
T. F. Stocker
Keyword(s):  
Carbon Cycle ◽  
Ocean Circulation ◽  
North Atlantic ◽  
Climate Model ◽  
Carbon Stocks ◽  
Meridional Overturning Circulation ◽  
Climate Conditions ◽  
Tropical Regions ◽  
The North ◽  
Northern Latitudes

Abstract. CO2 and carbon cycle changes in the land, ocean and atmosphere are investigated using the comprehensive carbon cycle-climate model NCAR CSM1.4-carbon. Ensemble simulations are forced with freshwater perturbations applied at the North Atlantic and Southern Ocean deep water formation sites under pre-industrial climate conditions. As a result, the Atlantic Meridional Overturning Circulation reduces in each experiment to varying degrees. The physical climate fields show changes that are well documented in the literature but there is a clear distinction between northern and southern perturbations. Changes in the physical variables affect, in return, the land and ocean biogeochemical cycles and cause a reduction, or an increase, in the atmospheric CO2 by up to 20 ppmv, depending on the location of the perturbation. In the case of a North Atlantic perturbation, the land biosphere reacts with a strong reduction in carbon stocks in some tropical locations and in high northern latitudes. In contrast, land carbon stocks tend to increase in response to a southern perturbation. The ocean is generally a sink of carbon although large re-organizations occur throughout various basins. The response of the land biosphere is strongest in the tropical regions due to a shift of the Intertropical Convergence Zone. The carbon fingerprints of this shift, either to the south or to the north depending on where the freshwater is applied, can be found most clearly in South America. For this reason, a compilation of various paleoclimate proxy records of Younger Dryas precipitation changes are compared with our model results.

scholarly journals 'Critical Study Of Konkan Territory Of Maharashtra State w.s.r. To The Concept Of Desha ln Ayurveda'

2021 ◽  
Vol 5 (04) ◽  
Author(s):  
Dr. Pranali A. Nagdeve ◽  
Dr. Ravi k. Golghate
Keyword(s):  
The State ◽  
Critical Study ◽  
Present Climate ◽  
Web Portals ◽  
Research Papers ◽  
Food Treatment ◽  
Climate Conditions ◽  
Etiological Factors ◽  
The Past

Background- Desha Pariksha (examination) has been mentioned in the Charaka Samhita (cha.vi.8/84) which is considered as the oldest and the most authentic treatise of Ayurveda. Ayurveda has described three types of Desha viz. Jangl , Anup and Sadharan. Desha also known as Bhumi refers to the natural  inhabitant of an individual. Desha is one of the factors which have to be assessed in ascertaining the Hetu (etiological factors) and also in deciding the treatment. Climate, diseases, food, treatment and so many factors may vary according to desh (habitat). An attempt has been made to critically analyse the konkan region of the state Maharashtra considering present climate conditions and geography in comparison to the concept of Ayurvedic desha description.  Methods- Authentic government web portals of this region have been visited to know the present climatic situations. Various research papers were also reviewed to discern the territory from other parts of the state.  Conclusion- After scrutinizing the facts over the past few years; it has been found that most of the regions of konkan fall under excess rainfall terrain. Flora and fauna is similar to that of wetland. The Konkan region of the Maharashtra State can be compared with Anup desha in Ayurveda.

Advanced Bridge Automation

1993 ◽  
Vol 30 (04) ◽  
pp. 276-285
Author(s):  
Edward Denham
Keyword(s):  
Human Error ◽  
Environmental Data ◽  
Management Systems ◽  
Propulsion Systems ◽  
The Past ◽  
Key Technologies ◽  
Routine Tasks ◽  
Information Management Systems ◽  
Better Than ◽  
Do So

The past thirty years have seen great advances in many areas of the technologies used in naval vessels. Propulsion systems, machinery automation, and information management systems have all undergone revolutionary changes. The bridges of these ships have similarly seen the advent of many new sources of navigational and environmental data. The process of correlating and interpreting all of this information has until now remained very labor-intensive, subject to human error at many stages of the process. In response to this challenge, a suite of new equipment has been developed for distributing, displaying, correlating, and logging shipboard data. This equipment automates most of the low-level, routine tasks involved in navigating a vessel at sea, significantly reducing the stress and workload of bridge personnel. This gives the humans on the bridge more time for doing the job that they do so much better than machines: making decisions. This paper focuses on the key technologies that are used in these new products and the advances in bridge design and automation they make possible. The benefits of these new capabilities to system designers, to shipbuilders, and to ship operators are also explored.

An Evaluation and Comparison of Models for Maximum Deflection of Stiffened Plates Using Finite Element Analysis

2007 ◽  
Vol 44 (04) ◽  
pp. 212-225
Author(s):  
Lior Banai ◽  
Omri Pedatzur
Keyword(s):  
Finite Element ◽  
Orthotropic Plate ◽  
Lateral Pressure ◽  
Stiffened Plates ◽  
Maximum Deflection ◽  
Structural Elements ◽  
The Finite Element Method ◽  
Element Analysis ◽  
The Past ◽  
Different Types

Stiffened plates form the backbone of most of a ship's structure. Today, finite element (FE) models are used to analyze the behavior of such structural elements for different types of loads. In the past, when usage of computers and FE models were not used very much, analytical analysis methods were required. Two well-known methods have been developed for analyses of stiffened plates under lateral loading (uniform pressure), based on two different models, namely, the orthotropic plate model and the grillage model. Both models can give estimations for the maximum plate deflection under uniform lateral pressure. The objective of this paper is to present the two methods, evaluate and compare the methods using the finite element method, and finally implement the methods as a computer program for quick estimations of the maximum deflection of stiffened plates. The degree of accuracy of the two methods when compared to FE is discussed in some detail.

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