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Quantifying Self-Noise of the Seaglider AUV Using a Passive Acoustic Monitor
No full textThe Seaglider, a type of underwater glider, is a relatively quiet vehicle in comparison with propelled autonomous underwater vehicles, making it a desirable acoustic receiving platform. Vehicle operations, such as pumping/bleeding oil to change buoyancy, shifting/rotating the battery to change pitch/roll, and oceanographic data collection, do, however, produce some self-noise. This system performance study analyzes the prevalence, frequency content, duration, and levels of self-noise associated with vehicle operations using data collected with a passive acoustic monitoring system mounted on the body of a Seaglider vehicle. Guidance and control functions, including pitch, roll, and buoyancy changes, were the major source of platform noise, producing broadband noise ranging from less than a second to over 3 min in duration, with sound pressure levels of 120–145.5 dB re 1μPa. Frequencies below 10 kHz were the most impacted by self-noise, with a maximum 1/3 octave level of 137.5 dB re 1μPa in the 2.5 kHz band caused by the pumping of oil in the variable buoyancy device. Guidance and control changes occurred during 4%–13% of the dive for dives greater than 500 m. The bulk of these operations, however, were performed near the surface and apogee of the dive and typically affected only about 6% of the dive cycle duration for deep dives
Multi-annual and multi-decadal evolution of sediment accretion in a saltmarsh of the French Atlantic coast: Implications for carbon sequestration
No full textCoastal marshes offer natural solutions for adapting to and mitigating the effects of climate change and sea level rise. However, the resilience of the marsh physical system and, with it, the ecosystem services that it provides, is largely site specific. This calls for the increase in the spatial cover of coastal marsh studies in order to assess the controlling factors of marsh evolution, and their long-term carbon storage capacities. Here, we study the spatio-temporal variations in sedimentation rates and organic carbon (OC) sequestration capacity of the macrotidal minerogenic saltmarshes in Aiguillon Bay, belonging to one of the largest French coastal marshes. Supported by aerial photographs and satellite image analysis, we first show that saltmarshes of the Aiguillon Bay have prograded at very high rates, up to 14 m yr−1 since 1950. Sediment accumulation rates (SAR) were estimated at both multi-annual to multi-decadal scales based on two approaches: (i) LiDAR-based digital elevation models from multiple acquisition dates (2010–2021); and (ii) depth profiles of 210Pb in excess and 137Cs in sediment cores collected along cross-shore transects in the saltmarshes. Long-term SAR range from 0.8 to 2.2 cm yr−1 and are among the highest reported worldwide for equivalent systems. The positive accretion balance (accretion rate minus local sea-level rise rate) provides important clues on marsh resilience suggesting that the Aiguillon Bay is currently able to adapt to rising sea level. Despite relatively low organic carbon content (1.3–6.0%), high SAR leads to high carbon sequestration rates (99–345 gC m−2 yr−1; or a mean value of 2.5 Mg C ha−1 yr−1). The isotopic signature of sediment OC reveals a significant and rapid decomposition of organic material in surface cores, while allochthonous sediment of marine origin dominates the signature of chemically-stable OC of marsh sediments. This implies that the carbon sequestration capacity of minerogenic saltmarshes, such as those of the Pertuis Charentais, also depends upon the wealth of adjacent coastal environments through high sediment supply and primary productivity
REINFORCING ECOSYSTEM ENGINEERS WITH ENHANCED VEGETATION AND AN ARTIFICIAL REEF ALONG THE US RHODE ISLAND COASTAL BARRIER SYSTEMS
No full textBeach barrier systems (BBS) act as “ecosystem engi-neers” (EE), protecting the mainland and back bays from direct wave impact and reducing storm surge and flow passing through their inlets. BBS naturally adapt to slowly evolving wave climates by regressing or transgressing. However, observations show that BBS have been destabilized during past periods of fast changes in sea level or wave climate, potentially leading to drowning of the barrier. In this respect, current predictions of large changes in future Sea Level Rise (SLR) and wave climate, combined with anthropogenic effects, are concerning as these could challenge the natural adaptability of BBS. This raises the following questions: (1) can the future protective ability of local EE be predicted? (2) can the added benefits of implementing selected Nature Based Solutions (NbS) to enhance this natural protective ability be quantified, as well as their potentially negative feedback effects? In this study, these questions are considered for the south shore of Rhode Island (RI) through numerical modeling, in part based on earlier regional storm hazard assessment (Grilli et al., 2020). Specifically, here, as part of a NOAA project (“Effects of Sea-Level Rise 2021, Coastal Resilience” program), we assess the efficiency of NbS in changing climate conditions, while integrating local concerns, observed trends, and supporting local ecosystem and people’s way of life
A marine plastic cloud - Global mass balance assessment of oceanic plastic pollution
Get PDFTo improve our understanding and management of marine plastic pollution of the ocean, a total plastic budget is needed which quantifies the sources and sinks, as well as inputs and removal of plastic per unit time. The current state of knowledge indicates that the coastal zone and ocean water column are major locations for plastic pollution, but the fate of much of this must ultimately be the deep ocean floor. We reviewed 23 journal articles that provide 280 observations of deep-sea sediment microplastic concentration across six different off-shelf environments. We calculate the following mean concentrations of microplastic particles (number) per kg of sediment: continental slope 502; submarine canyons 784; submarine fans and continental rise 714; abyssal plains 217; trenches and troughs 2782; and abyssal hills, mountains and other ocean floor 165 particles kg−1. These figures are alarming because several exceed one estimate of ‘safe’ levels of microplastic concentration for benthic marine life (540 particles kg−1). Monitoring of the concentration of plastic particles in sediments of submarine canyons, fans and continental rise environments and in trenches and troughs should be a priority to ensure efficacy of policies and actions taken to curb ocean plastic pollution at both the national and global level. We estimate 3.05 million tonnes of microplastic resides in deep ocean sediments but acknowledge the uncertainties of this figure. If correct, this figure implies that the ocean water column (which may contain as much as 90 million tonnes of microplastic) is a major, transitory sink for MP, forming a suspended, marine plastic cloud. In addition to particle concentrations, further measurements of the size and mass of microplastic in deep-sea sediments and in the water column are needed to advance development of mass balance budgets for marine plastic pollution
A Conversation with Pulitzer Prize-Winner Elizabeth Kolbert
No full textElizabeth Kolbert has been a staff writer for The New Yorker since 1999 and written dozens of pieces for the magazine. Her series on global warming, “The Climate of Man,” appeared in The New Yorker in the spring of 2005 and won the American Association for the Advancement of Science’s magazine award.
Her second book, Field Notes from a Catastrophe: Man, Nature, and Climate Change grew out of a groundbreaking three-part series on global warming for The New Yorker. The book brings the environment into the consciousness of the American people and asks what, if anything, can be done, and how we can save our planet. She explains the science and the studies, draws frightening parallels to lost ancient civilizations, unpacks the politics, and presents the personal tales of those who are being affected most—the people who make their homes near the poles and, in an eerie foreshadowing, are watching their worlds disappear.
Kolbert’s 2014 book, The Sixth Extinction: An Unnatural History, won the Pulitzer Prize for general non-fiction. This work, which began as an article for The New Yorker, is a study about mass extinctions that weaves intellectual and natural history with reporting in the field. Kolbert’s latest book, Under a White Sky: The Nature of the Future, was a national bestseller and was named one of the best books of the year by the Washington Post, Time, Esquire, Smithsonian Magazine, Publishers Weekly, Kirkus Reviews, and Library Journal. This latest text follows many of the same themes Kolbert explored in The Sixth Extinction.
Kolbert has won numerous accolades, most recently being voted into the American Academy of Arts and Letters. Prior to joining the staff at The New Yorker, Kolbert was a political journalist at The New York Times
A reassessment of the sulfur, chlorine and fluorine atmospheric loading during the 1815 Tambora eruption
No full textThe 1815 eruption of Mount Tambora (Sumbawa Island, Indonesia), largest known explosive eruption in recorded history, was cataclysmic. It was responsible for a strong short-term global atmospheric cooling the following year, known as “the year without a summer”. To evaluate the climatic impact, an accurate quantification of volatile elements degassed during this eruption is crucial. In this study, we re- evaluate the atmospheric release of sulfur, chlorine and fluorine during the 1815 eruption using the petrological approach based on plagioclase-hosted melt inclusions. The pre-eruptive (melt inclusions) and post-eruptive (matrix glass) volatile element concentrations of the magma are measured by electron microprobe. We discuss three different outgassing scenarios and conclude that 147 ± 17 Tg of SO2, 49 ± 5 Tg of Cl and 20 ± 2 Tg of F were degassed during the eruption, considering closed system ascent and degassing. The SO2 results take into account the dissolution of sulfides which are present in melt inclusions and plagioclase crystals but not in matrix glasses. Our new estimates are higher than previous estimations from petrological methods or derived from ice cores but are consistent with atmospheric optical depth observations from 1816. The 1815 eruption of Tambora ranks in first place in terms of volcanic SO2 emission in the last 2000 years, higher than the 1257 Samalas eruption (Lombok Island, Indonesia) if equal methodologies are applied. These estimates remain nonetheless minima as they do not account for the possible additional contribution of a pre-existing gas phase in the magma reservoir