The driving mechanisms of the carbon cycle perturbations in the late Pliensbachian (Early Jurassic)

AbstractThe Early Jurassic (late Pliensbachian to early Toarcian) was a period marked by extinctions, climate fluctuations, and oceanic anoxia. Although the causes of the early Toarcian Oceanic Anoxia Event (OAE) have been fairly well studied, the events that lead to the Toarcian OAE, i.e. the events in the late Pliensbachian, have not been well constrained. Scenarios of the driving mechanism of biotic and environmental changes of the late Pliensbachian have ranged from LIP volcanism (the Karoo-Ferrar LIP), ocean stagnation, and changing ocean circulation, to orbital forcing. The temporal relationship between the Karoo LIP and the late Pliensbachian (Kunae-Carlottense ammonite Zones) are investigated in an effort to evaluate a causal relationship. We present the first absolute timescale on the Kunae and Carlottense Zones based on precise high-precision U-Pb geochronology, and additional geochemical proxies, for a range of environmental proxies such as bulk organic carbon isotope compositions, Hg concentration, and Hg/TOC ratios, and Re-Os isotopes to further explore their causal relationship. The data presented here show that causality between the Karoo LIP and the late Pliensbachian events cannot be maintained.

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Shifting ocean circulation warms the Subpolar North Atlantic since 2016

10.5194/egusphere-egu21-940 ◽

2021 ◽

Author(s):

Damien Desbruyères ◽

Léon Chafik ◽

Guillaume Maze

Keyword(s):

Ocean Circulation ◽

North Atlantic ◽

Large Scale ◽

Deep Ocean ◽

Ocean Heat Uptake ◽

Driving Mechanisms ◽

Temperature Trends ◽

Meridional Overturning ◽

Ocean Observing

The Subpolar North Atlantic (SPNA) is known for rapid reversals of decadal temperature trends, with ramifications encompassing the large-scale meridional overturning and gyre circulations, Arctic heat and mass balances, or extreme continental weather. Here, we combine datasets derived from sustained ocean observing systems (satellite and in situ), and idealized observation-based modelling (advection-diffusion of a passive tracer) and machine learning technique (ocean profile clustering) to document and explain the most-recent and ongoing cooling-to-warming transition of the SPNA. Following a gradual cooling of the region that was persisting since 2006, a surface-intensified and large-scale warming sharply emerged in 2016 following an ocean circulation shift that enhanced the northeastward penetration of warm and saline waters from the western subtropics. Driving mechanisms and ramification for deep ocean heat uptake will be discussed.

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No signal of a plume push force in Indo-Atlantic plate speeds before, during, or after Deccan plume arrival

10.5194/egusphere-egu21-8496 ◽

2021 ◽

Author(s):

Graeme Eagles ◽

Lucía Pérez Díaz ◽

Karin Sigloch

Keyword(s):

Late Cretaceous ◽

Upper Mantle ◽

Plate Boundary ◽

Plate Motion ◽

Driving Mechanism ◽

African Plate ◽

Plate Motions ◽

Driving Mechanisms ◽

High Resolution Models ◽

Spreading Rates

Observations of the apparent links between plate speeds and the global distribution of plate boundary types have led to the suggestion that subduction may provide the largest component in the balance of torques maintaining plate motions. This would imply that plate speeds should not exceed the sinking rates of slabs into the upper mantle. Instances of this &#8216;speed limit&#8217; having been broken may thus hint at the existence of driving mechanisms additional to those resulting from plate boundary forces. The arrival and emplacement of the Deccan-R&#233;union mantle plume beneath the Indian-African plate boundary in the 67-62 Ma period has been discussed in terms of one such additional driving mechanism, leading to the establishment of &#8220;plume-push&#8221; hypothesis, which in recent years has gained significant traction. We challenge the model-based observations that form the principal evidence in favour of plume-push: a late Cretaceous pulse of anticorrelating accelerations and decelerations in seafloor spreading rates around the African and Indian plates. Using existing and newly-calculated high-resolution models of plate motion, we instead document an increase in divergence rates at 67-64 Ma. Because of its ubiquity, we consider this increase to be the artefact of a timescale error affecting chrons 29-28. Corrected for this artefact, the evolution of plate speeds resembles a smooth continuation of pre-existing late Cretaceous trends, consistent with the idea that the arrival of the R&#233;union plume did not substantially affect the existing balance of plate boundary forces on the Indian and African plates.&#160;

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Driving Mechanisms, Motion, and Mechanics of Screw Drive In-Pipe Robots: A Review

Applied Sciences ◽

10.3390/app9122514 ◽

2019 ◽

Vol 9 (12) ◽

pp. 2514 ◽

Cited By ~ 2

Author(s):

Tao Ren ◽

Yin Zhang ◽

Yujia Li ◽

Yonghua Chen ◽

Qingyou Liu

Keyword(s):

Mechanism Design ◽

Driving Mechanism ◽

Mechanical Behaviors ◽

Pipe Inspection ◽

Advantages And Disadvantages ◽

Screw Drive ◽

Driving Mechanisms ◽

Pipe Networks ◽

Design Requirements ◽

Inspection Tasks

In recent years, interest in in-pipe robot research has been steadily increasing. This phenomenon reflects the necessity and urgency of pipe inspection and rehabilitation as several pipe networks have become outdated around the globe. In-pipe robots can be divided into several groups in accordance with their locomotion principles, each with its own advantages and best suited application scope. Research on the screw drive in-pipe robot (SDIR) has had a rising trend due to the robot’s simple driving mechanism design and numerous advantages. This study compares and analyzes the characteristics of various SDIRs from the aspects of mechanism design, driving principle, and motion and mechanical behaviors. Each SDIR has its own advantages and disadvantages depending on its design requirements and intended applications. A number of prototypes have been fabricated to verify their functionality and efficiency in inspection tasks. This study can provide an up-to-date reference for researchers to conduct further analysis on SDIRs.

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Enhanced 20th-century heat transfer to the Arctic simulated in the context of climate variations over the last millennium

Climate of the Past ◽

10.5194/cp-10-2201-2014 ◽

2014 ◽

Vol 10 (6) ◽

pp. 2201-2213 ◽

Cited By ~ 44

Author(s):

J. H. Jungclaus ◽

K. Lohmann ◽

D. Zanchettin

Keyword(s):

Heat Transfer ◽

20Th Century ◽

Ocean Circulation ◽

Internal Variability ◽

Atlantic Water ◽

Arctic Sea Ice ◽

The Arctic ◽

Driving Mechanism ◽

Last Millennium ◽

Fram Strait

Abstract. Oceanic heat transport variations, carried by the northward-flowing Atlantic Water, strongly influence Arctic sea-ice distribution, ocean–atmosphere exchanges, and pan-Arctic temperatures. Palaeoceanographic reconstructions from marine sediments near Fram Strait have documented a dramatic increase in Atlantic Water temperatures over the 20th century, unprecedented in the last millennium. Here we present results from Earth system model simulations that reproduce and explain the reconstructed exceptional Atlantic Water warming in Fram Strait in the 20th century in the context of natural variability during the last millennium. The associated increase in ocean heat transfer to the Arctic can be traced back to changes in the ocean circulation in the subpolar North Atlantic. An interplay between a weakening overturning circulation and a strengthening subpolar gyre as a consequence of 20th-century global warming is identified as the driving mechanism for the pronounced warming along the Atlantic Water path toward the Arctic. Simulations covering the late Holocene provide a reference frame that allows us to conclude that the changes during the last century are unprecedented in the last 1150 years and that they cannot be explained by internal variability or natural forcing alone.

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Substantial vegetation response to Early Jurassic global warming with impacts on oceanic anoxia

Nature Geoscience ◽

10.1038/s41561-019-0349-z ◽

2019 ◽

Vol 12 (6) ◽

pp. 462-467 ◽

Cited By ~ 28

Author(s):

Sam M. Slater ◽

Richard J. Twitchett ◽

Silvia Danise ◽

Vivi Vajda

Keyword(s):

Global Warming ◽

Early Jurassic ◽

Vegetation Response ◽

Oceanic Anoxia

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First satellite tracks of South Atlantic sea turtle ‘lost years’: seasonal variation in trans-equatorial movement

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2017.1730 ◽

2017 ◽

Vol 284 (1868) ◽

pp. 20171730 ◽

Cited By ~ 17

Author(s):

Katherine L. Mansfield ◽

Milagros L. Mendilaharsu ◽

Nathan F. Putman ◽

Maria A. G. dei Marcovaldi ◽

Alexander E. Sacco ◽

...

Keyword(s):

Ocean Circulation ◽

Environmental Changes ◽

Circulation Model ◽

Sea Turtle ◽

South Atlantic ◽

Swimming Velocity ◽

The South ◽

Frontal Zones ◽

Few Data ◽

Passive Drift

In the South Atlantic Ocean, few data exist regarding the dispersal of young oceanic sea turtles. We characterized the movements of laboratory-reared yearling loggerhead turtles from Brazilian rookeries using novel telemetry techniques, testing for differences in dispersal during different periods of the sea turtle hatching season that correspond to seasonal changes in ocean currents. Oceanographic drifters deployed alongside satellite-tagged turtles allowed us to explore the mechanisms of dispersal (passive drift or active swimming). Early in the hatching season turtles transited south with strong southward currents. Late in the hatching season, when currents flowed in the opposite direction, turtles uniformly moved northwards across the Equator. However, the movement of individuals differed from what was predicted by surface currents alone. Swimming velocity inferred from track data and an ocean circulation model strongly suggest that turtles' swimming plays a role in maintaining their position within frontal zones seaward of the continental shelf. The long nesting season of adults and behaviour of post-hatchlings exposes young turtles to seasonally varying ocean conditions that lead some individuals further into the South Atlantic and others into the Northern Hemisphere. Such migratory route diversity may ultimately buffer the population against environmental changes or anthropologic threats, fostering population resiliency.

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An Optimal Design of Driving Mechanism in a 1 Degree of Freedom (d.o.f.) Anthropomorphic Finger

Applied Bionics and Biomechanics ◽

10.1155/2005/897687 ◽

2005 ◽

Vol 2 (2) ◽

pp. 103-110 ◽

Cited By ~ 1

Author(s):

M. Ceccarelli ◽

N. E. N. Rodríguez ◽

G. Carbone ◽

C. Lopez-Cajùn

Keyword(s):

Optimization Problem ◽

Evaluation Criteria ◽

Design Procedure ◽

Degree Of Freedom ◽

Driving Mechanism ◽

Multi Objective Optimization ◽

Force Transmission ◽

Driving Mechanisms ◽

Finger Motion ◽

Actuation Systems

Mechanisms can be used in finger design to obtain suitable actuation systems and to give stiff robust behavior in grasping tasks. The design of driving mechanisms for fingers has been attached at LARM in Cassino with the aim to obtain one degree of freedom actuation for an anthropomorphic finger. The dimensional design of a finger-driving mechanism has been formulated as a multi-objective optimization problem by using evaluation criteria for fundamental characteristics regarding with finger motion, grasping equilibrium and force transmission. The feasibility of the herein proposed optimum design procedure for a finger-driving mechanism has been tested by numerical examples that have been also used to enhance a prototype previously built at LARM in Cassino.

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Reconstruction of anthropogenic environmental changes from a Cuban coral over the last 175 years

10.5194/egusphere-egu2020-19578 ◽

2020 ◽

Author(s):

Marie Harbott ◽

Henry C. Wu ◽

Henning Kuhnert ◽

Simone A. Kasemann ◽

Carlos Jimenez ◽

...

Keyword(s):

Climate Variability ◽

Ocean Circulation ◽

Environmental Changes ◽

Anthropogenic Activities ◽

Regional Climate ◽

Florida Current ◽

Loop Current ◽

Carbonate Chemistry ◽

Important Region ◽

Warm Surface Water

Ocean warming and ocean acidification (OA) are increasingly influencing marine life. Parts of the increasing amount of CO2 in the atmosphere will eventually get absorbed by the ocean, which changes the oceans carbonate chemistry and threatens the ecological competitiveness of calcareous marine organisms. Currently,&#160; the global coverage of studies on the development of pH since preindustrial times is sparse. An important region to study environmental and climate variations is the northwestern coastal part of Cuba where the Loop Current (LC) joins the Florida Current and contributes to the Gulf Stream. The tropical Atlantic is a primary region for the formation of warm surface water of the thermohaline ocean circulation and the Caribbean in particular as a habitat for coral reefs in the Atlantic making them susceptible to changes in water temperatures and carbonate chemistry. This provides a unique chance to study multiple aspects of the implications of anthropogenic activities such as changes in SST, ocean pH, and carbonate chemistry using the coral skeletal geochemistry as an archive of climate and environmental changes. Here we present results from a multi-proxy approach for the reconstruction of environmental change and natural climate variability from a North Cuban Siderastrea siderea coral. The sub-seasonally resolved records indicate interannual to decadal changes in SST and seawater carbonate chemistry since 1830 CE. The comparison with pH will provide clues on whether the regional climate variability has been directly affected by atmospheric CO2 forcing.

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A perspective on the future of physical oceanography

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2012.0400 ◽

2012 ◽

Vol 370 (1980) ◽

pp. 5480-5511 ◽

Cited By ~ 8

Author(s):

Alberto C. Naveira Garabato

Keyword(s):

Ocean Circulation ◽

Focal Point ◽

Research Priorities ◽

Ocean Dynamics ◽

Dynamical Response ◽

Physical Oceanography ◽

Driving Mechanisms ◽

Main Challenge ◽

The Future ◽

Fundamental Research

The ocean flows because it is forced by winds, tides and exchanges of heat and freshwater with the overlying atmosphere and cryosphere. To achieve a state where the defining properties of the ocean (such as its energy and momentum) do not continuously increase, some form of dissipation or damping is required to balance the forcing. The ocean circulation is thought to be forced primarily at the large scales characteristic of ocean basins, yet to be damped at much smaller scales down to those of centimetre-sized turbulence. For decades, physical oceanographers have sought to comprehend the fundamentals of this fractal puzzle: how the ocean circulation is driven, how it is damped and how ocean dynamics connects the very different scales of forcing and dissipation. While in the last two decades significant advances have taken place on all these three fronts, the thrust of progress has been in understanding the driving mechanisms of ocean circulation and the ocean's ensuing dynamical response, with issues surrounding dissipation receiving comparatively little attention. This choice of research priorities stems not only from logistical and technological difficulties in observing and modelling the physical processes responsible for damping the circulation, but also from the untested assumption that the evolution of the ocean's state over time scales of concern to humankind is largely independent of dissipative processes. In this article, I illustrate some of the key advances in our understanding of ocean circulation that have been achieved in the last 20 years and, based on a range of evidence, contend that the field will soon reach a stage in which uncertainties surrounding the arrest of ocean circulation will pose the main challenge to further progress. It is argued that the role of the circulation in the coupled climate system will stand as a further focal point of major advances in understanding within the next two decades, supported by the drive of physical oceanography towards a more operational enterprise by contextual factors. The basic elements that a strategy for the future must have to foster progress in these two areas are discussed, with an overarching emphasis on the promotion of curiosity-driven fundamental research against opposing external pressures and on the importance of upholding fundamental research as the apex of education in the field.

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Degree of Achievability of Omnidirectional Motion in Various Mobile Robot Designs: A Review

IAES International Journal of Robotics and Automation (IJRA) ◽

10.11591/ijra.v5i1.pp17-28 ◽

2016 ◽

Vol 5 (1) ◽

pp. 17

Author(s):

Ajju Raja Justus

Keyword(s):

Mobile Robot ◽

Control Mechanism ◽

Operating Conditions ◽

Driving Mechanism ◽

Functional Requirement ◽

Current Field ◽

Driving Mechanisms ◽

And Control ◽

Comprehensive Study

In the current field of robotics, many new robots are being developed based on different working principles. Each robot has its own strengths and weaknesses. Omnidirectional mobility is a major functional requirement for performing more complex actions. This article is a comprehensive study of some of the robots developed by different people with distinctive driving mechanisms. The actuation, driving method, operating conditions and control mechanism of all the selected robots is studied. Then finally, all the considered robots are compared based on various parameters to gauge the efficiency and degree of achievability of omnidirectional motion in each robot. Therefore, by the end of this article, we can have an understanding of how much effective each driving mechanism is in producing omnidirectional mobility.

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