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The Red Sea : in search of lost space
\"The Red Sea has, from time immemorial, been one of the world's most navigated spaces, in the pursuit of trade, pilgrimage and conquest. Yet this multidimensional history remains largely unrevealed by its successive protagonists. Intrigued by the absence of a holistic portrayal of this body of water and inspired by Fernand Braudel's famous work on the Mediterranean, this book brings alive a dynamic Red Sea world across time, revealing the particular features of a unique historical actor. In capturing this heretofore lost space, it also presents a critical, conceptual history of the sea, leading the reader into the heart of Eurocentrism. The Sea, it is shown, is a vital element of the modern philosophy of history. Alexis Wick is not satisfied with this inclusion of the Red Sea into history and attendant critique of Eurocentrism. Contrapuntally, he explores how the world and the sea were imagined differently before imperial European hegemony. Searching for the lost space of Ottoman visions of the sea, The Red Sea makes a deeper argument about the discipline of history and the historian's craft\"--Provided by publisher.
Book
Self-powered soft robot in the Mariana Trench
The deep sea remains the largest unknown territory on Earth because it is so difficult to explore
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–
4
. Owing to the extremely high pressure in the deep sea, rigid vessels
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and pressure-compensation systems
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are typically required to protect mechatronic systems. However, deep-sea creatures that lack bulky or heavy pressure-tolerant systems can thrive at extreme depths
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–
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. Here, inspired by the structure of a deep-sea snailfish
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, we develop an untethered soft robot for deep-sea exploration, with onboard power, control and actuation protected from pressure by integrating electronics in a silicone matrix. This self-powered robot eliminates the requirement for any rigid vessel. To reduce shear stress at the interfaces between electronic components, we decentralize the electronics by increasing the distance between components or separating them from the printed circuit board. Careful design of the dielectric elastomer material used for the robot’s flapping fins allowed the robot to be actuated successfully in a field test in the Mariana Trench down to a depth of 10,900 metres and to swim freely in the South China Sea at a depth of 3,224 metres. We validate the pressure resilience of the electronic components and soft actuators through systematic experiments and theoretical analyses. Our work highlights the potential of designing soft, lightweight devices for use in extreme conditions.
A free-swimming soft robot inspired by deep-sea creatures, with artificial muscle, power and control electronics spread across a polymer matrix, successfully adapts to high pressure and operates in the deep ocean.
Journal Article
A global inventory of small floating plastic debris
Microplastic debris floating at the ocean surface can harm marine life. Understanding the severity of this harm requires knowledge of plastic abundance and distributions. Dozens of expeditions measuring microplastics have been carried out since the 1970s, but they have primarily focused on the North Atlantic and North Pacific accumulation zones, with much sparser coverage elsewhere. Here, we use the largest dataset of microplastic measurements assembled to date to assess the confidence we can have in global estimates of microplastic abundance and mass. We use a rigorous statistical framework to standardize a global dataset of plastic marine debris measured using surface-trawling plankton nets and coupled this with three different ocean circulation models to spatially interpolate the observations. Our estimates show that the accumulated number of microplastic particles in 2014 ranges from 15 to 51 trillion particles, weighing between 93 and 236 thousand metric tons, which is only approximately 1% of global plastic waste estimated to enter the ocean in the year 2010. These estimates are larger than previous global estimates, but vary widely because the scarcity of data in most of the world ocean, differences in model formulations, and fundamental knowledge gaps in the sources, transformations and fates of microplastics in the ocean.
Journal Article
Summertime increases in upper-ocean stratification and mixed-layer depth
The surface mixed layer of the world ocean regulates global climate by controlling heat and carbon exchange between the atmosphere and the oceanic interior
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3
. The mixed layer also shapes marine ecosystems by hosting most of the ocean’s primary production
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and providing the conduit for oxygenation of deep oceanic layers. Despite these important climatic and life-supporting roles, possible changes in the mixed layer during an era of global climate change remain uncertain. Here we use oceanographic observations to show that from 1970 to 2018 the density contrast across the base of the mixed layer increased and that the mixed layer itself became deeper. Using a physically based definition of upper-ocean stability that follows different dynamical regimes across the global ocean, we find that the summertime density contrast increased by 8.9 ± 2.7 per cent per decade (10
−5
–10
−4
per second squared per decade, depending on region), more than six times greater than previous estimates. Whereas prior work has suggested that a thinner mixed layer should accompany a more stratified upper ocean
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, we find instead that the summertime mixed layer deepened by 2.9 ± 0.5 per cent per decade, or several metres per decade (typically 5–10 metres per decade, depending on region). A detailed mechanistic interpretation is challenging, but the concurrent stratification and deepening of the mixed layer are related to an increase in stability associated with surface warming and high-latitude surface freshening
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,
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, accompanied by a wind-driven intensification of upper-ocean turbulence
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,
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. Our findings are based on a complex dataset with incomplete coverage of a vast area. Although our results are robust within a wide range of sensitivity analyses, important uncertainties remain, such as those related to sparse coverage in the early years of the 1970–2018 period. Nonetheless, our work calls for reconsideration of the drivers of ongoing shifts in marine primary production, and reveals stark changes in the world’s upper ocean over the past five decades.
Oceanographic observations from 1970–2018 reveal substantial changes in the summer upper-ocean structure, showing a thickening of the mixed layer and a density gradient increase at its base.
Journal Article
Metabolic trait diversity shapes marine biogeography
Climate and physiology shape biogeography, yet the range limits of species can rarely be ascribed to the quantitative traits of organisms
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. Here we evaluate whether the geographical range boundaries of species coincide with ecophysiological limits to acquisition of aerobic energy
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for a global cross-section of the biodiversity of marine animals. We observe a tight correlation between the metabolic rate and the efficacy of oxygen supply, and between the temperature sensitivities of these traits, which suggests that marine animals are under strong selection for the tolerance of low O
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(hypoxia)
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. The breadth of the resulting physiological tolerances of marine animals predicts a variety of geographical niches—from the tropics to high latitudes and from shallow to deep water—which better align with species distributions than do models based on either temperature or oxygen alone. For all studied species, thermal and hypoxic limits are substantially reduced by the energetic demands of ecological activity, a trait that varies similarly among marine and terrestrial taxa. Active temperature-dependent hypoxia thus links the biogeography of diverse marine species to fundamental energetic requirements that are shared across the animal kingdom.
A tight coupling between metabolic rate, efficacy of oxygen supply and the temperature sensitivities of marine animals predicts a variety of geographical niches that better aligns with the distributions of species than models of either temperature or oxygen alone.
Journal Article
Two-step closure of the Miocene Indian Ocean Gateway to the Mediterranean
The Tethys Ocean was compartmentalized into the Mediterranean Sea and Indian Ocean during the early Miocene, yet the exact nature and timing of this disconnection are not well understood. Here we present two new neodymium isotope records from isolated carbonate platforms on both sides of the closing seaway, Malta (outcrop sampling) and the Maldives (IODP Site U1468), to constrain the evolution of past water mass exchange between the present day Mediterranean Sea and Indian Ocean via the Mesopotamian Seaway. Combining these data with box modeling results indicates that water mass exchange was reduced by ~90% in a first step at ca. 20 Ma. The terminal closure of the seaway then coincided with the sea level drop caused by the onset of permanent glaciation of Antarctica at ca. 13.8 Ma. The termination of meridional water mass exchange through the Tethyan Seaway resulted in a global reorganization of currents, paved the way to the development of upwelling in the Arabian Sea and possibly led to a strengthening of South Asian Monsoon.
Journal Article
Sea ice impact on naval operations
This paper highlights the icing regime and its impact on the primary naval operations conducted in the Black Sea basin. The article analyzes seawater's phenomenon freezing through the perspective of merchant shipping operations and underlines the impact on undersea or surface warfare. The article figures out the impact on the ship hull, weapons systems, personnel, as well as the tactics aspects of operations or de-icing strategies when ice accrues on ship hull and equipment. The article points out associated meteorological phenomena and brings in attention the importance of meteorological and oceanographic observations in situ or by satellites as a condition for the success of the operation. In the end, the article concludes regarding shortfalls faced during icing periods and give some directions meant to curb the adversary effects of unfavorable icing environment.
Journal Article