Climate variation affects surface ocean processes and the production of organic carbon, which ultimately comprises the primary food supply to the deep-sea ecosystems that occupy ≈60% of the Earth's ...surface. Warming trends in atmospheric and upper ocean temperatures, attributed to anthropogenic influence, have occurred over the past four decades. Changes in upper ocean temperature influence stratification and can affect the availability of nutrients for phytoplankton production. Global warming has been predicted to intensify stratification and reduce vertical mixing. Research also suggests that such reduced mixing will enhance variability in primary production and carbon export flux to the deep sea. The dependence of deep-sea communities on surface water production has raised important questions about how climate change will affect carbon cycling and deep-ocean ecosystem function. Recently, unprecedented time-series studies conducted over the past two decades in the North Pacific and the North Atlantic at >4,000-m depth have revealed unexpectedly large changes in deep-ocean ecosystems significantly correlated to climate-driven changes in the surface ocean that can impact the global carbon cycle. Climate-driven variation affects oceanic communities from surface waters to the much-overlooked deep sea and will have impacts on the global carbon cycle. Data from these two widely separated areas of the deep ocean provide compelling evidence that changes in climate can readily influence deep-sea processes. However, the limited geographic coverage of these existing time-series studies stresses the importance of developing a more global effort to monitor deep-sea ecosystems under modern conditions of rapidly changing climate.
The Mesozoic Era featured emplacement of a number of Large Igneous Provinces (LIPs), formed by the outpouring of millions of cubic kilometres of basaltic magma. The radiometric ages of several ...Mesozoic LIPs coincide with the dates of Oceanic Anoxic Events (OAEs). As a result of these coincidences, a causal link has been suggested, but never conclusively proven. This study explores the use of mercury as a possible direct link between the Karoo–Ferrar LIP and the coeval Toarcian OAE (T-OAE). Mercury is emitted to the atmosphere as a trace constituent of volcanic gas, and may be distributed globally before being deposited in sediments. Modern marine deposits show a strong linear correlation between mercury and organic-matter content. Results presented here indicate departures from such a simple linear relationship in sediments deposited during the T-OAE, and also during the Pliensbachian–Toarcian transition (an event that saw elevated benthic extinctions and carbon-cycle perturbations prior to the T-OAE). A number of depositional settings illustrate an increased mercury concentration in sediments that record one or both events, suggesting a rise in the depositional flux of this element. Complications to this relationship may arise from very organic-rich sediments potentially overprinting any Hg/TOC signal, whereas environments preserving negligible organic matter may leave no record of mercury deposition. However, the global distribution of coevally elevated Hg-rich levels suggests enhanced atmospheric mercury availability during the Early Toarcian, potentially aided by the apparent affinity of Hg for terrestrial organic matter, although the relative importance of aquatic vs terrestrial fixation of Hg in governing these enrichments remains uncertain. A perturbation in atmospheric Hg is most easily explained by enhanced volcanic output. It is suggested that extrusive igneous activity caused increased mercury flux to the Early Toarcian sedimentary realm, supporting the potential of this element as a proxy for ancient volcanism. This interpretation is consistent with a relationship between LIP formation and a perturbed carbon cycle during the Pliensbachian–Toarcian transition and T-OAE. The recording of these two distinct Hg excursions may also indicate that the Karoo–Ferrar LIP released volatiles in temporally distinct episodes, due either to multiple phases of magmatic emplacement or sporadic release of thermogenic gaseous products from intrusion of igneous material into volatile-rich lithologies.
•Analysis of seven Toarcian stratigraphic sections for Hg concentrations and Hg/TOC ratios.•Control analysis of an upper Jurassic section not associated with volcanism for comparison.•Evidence for two pulses of increased atmospheric mercury levels during the Early Toarcian.•Hg/TOC spikes coincide with record of Pliensbachian–Toarcian extinction and Toarcian OAE.•A global perturbation of volcanic mercury is inferred, but with locally derived complexities.
The inclusion of behavioral components in the analysis of a community can be of paramount importance in marine ecology. Diel (i.e., 24-h based), seasonal activity rhythms, or longer durational in ...behavioral responses can result in shifts in populations, and therefore on measurable abundances. Here, we review the value of developing cabled video observatory technology for the remote, long-term, and high-frequency monitoring of fish and their environments in coastal temperate areas. We provide details on the methodological requirements and constraints for the appropriate measurement of fish behavior over various seasonal scales (24 h, seasonal, annual) with camera systems mounted at fixed observatory locations. We highlight the importance of using marine sensors to simultaneously collect relevant environmental data in parallel to image data acquisition. Here we present multiparametric video, oceanographic, and meteorological data collected from the Mediterranean observatory platform, OBSEA (www.obsea.es ; 20 m water depth). These data are reviewed in relation to ongoing and future developments of cabled observatory science. Two key approaches for the future improvement of cabled observatory technology are: (1) the application of Artificial Intelligence to aid in the analysis of increasingly large, complex, and highly interrelated biological and environmental data sets, and (2) the development of geographical observational networks to enable the reliable spatial analysis of observed populations over extended distances.
A large bloom of Salpa spp. in the northeastern Pacific during the spring of 2012 resulted in a major deposition of tunics and fecal pellets on the seafloor at ~ 4000 m depth (Sta. M) over a period ...of 6 months. Continuous monitoring of this food pulse was recorded using autonomous instruments: sequencing sediment traps, a timelapse camera on the seafloor, and a bottom-transiting vehicle measuring sediment community oxygen consumption (SCOC). These deep-sea measurements were complemented by sampling of salps in the epipelagic zone by California Cooperative Ocean Fisheries Investigations. The particulate organic carbon (POC) flux increased sharply beginning in early March, reaching a peak of 38 mg C m−2 d−1 in mid-April at 3400 m depth. Salp detritus started appearing in images of the seafloor taken in March and covered a daily maximum of 98% of the seafloor from late June to early July. Concurrently, the SCOC rose with increased salp deposition, reaching a high of 31 mg C m−2 d−1 in late June. A dominant megafauna species, Peniagone sp. A, increased 7-fold in density beginning 7 weeks after the peak in salp deposition. Estimated food supply from salp detritus was 97–327% of the SCOC demand integrated over the 6-month period starting in March 2012. Such large episodic pulses of food sustain abyssal communities over extended periods of time.
The end-Triassic environmental crisis with major extinctions in the marine realm is followed by successive recovery in the lower Jurassic Hettangian Stage. Accurate timing of events is however still ...poorly constrained. In this study, combined field observations and physical and chemical proxy records, covering the uppermost Triassic and lower Jurassic marine successions of St Audrie's Bay and East Quantoxhead (UK), have been used to construct a floating astronomical time-scale of ∼2.5Myr in length. This time-scale is based on the recognition of meters thick cycles in limestone and (black) shale predominance and concurrent variability in physical and chemical proxy records. Three to five individual black-shale beds occur within these meter-scale sedimentary bundles and are interpreted to reflect precession-controlled changes in monsoon intensity, while the bundles are interpreted as forced by the ∼100-kyr eccentricity cycle. On the basis of these findings, we propose an astronomically constrained duration of the Hettangian stage of 1.8Myr in the UK and unequal duration of Hettangian ammonite zones (Psilocerasplanorbis zone: ∼250kyr; Alsatitesliasicus zone: ∼750kyr; Schlotheimiaangulata zone: ∼800kyr). Within this astronomical framework, the extinction interval and coinciding negative CIE represent 1 to 2 precession cycles (∼20–40kyr). The amount of time succeeding the end-Triassic negative carbon isotope excursion (CIE) and preceding the first Jurassic ammonite occurrence (in the UK) is constrained to 6 climatic precession cycles (∼120kyr). Cyclostratigraphic correlation to the astronomically-tuned sedimentary record of the continental Newark basin (USA) allows to locate the stratigraphic position of the marine defined Triassic–Jurassic and Hettangian–Sinemurian boundary in the continental realm. Continuous low δ13CTOC values throughout the Hettangian and early Sinemurian, succeeding volcanic activity in the Central Atlantic Magmatic Province (CAMP), may suggest a long-term change in Earth's global biogeochemical cycles, which do not fully recover for several million years.
In the past decade, our understanding of galaxy evolution has been revolutionized by the discovery that luminous, dusty starburst galaxies were 1,000 times more abundant in the early Universe than at ...present. It has, however, been difficult to measure the complete redshift distribution of these objects, especially at the highest redshifts (z > 4). Here we report a redshift survey at a wavelength of three millimetres, targeting carbon monoxide line emission from the star-forming molecular gas in the direction of extraordinarily bright millimetre-wave-selected sources. High-resolution imaging demonstrates that these sources are strongly gravitationally lensed by foreground galaxies. We detect spectral lines in 23 out of 26 sources and multiple lines in 12 of those 23 sources, from which we obtain robust, unambiguous redshifts. At least 10 of the sources are found to lie at z > 4, indicating that the fraction of dusty starburst galaxies at high redshifts is greater than previously thought. Models of lens geometries in the sample indicate that the background objects are ultra-luminous infrared galaxies, powered by extreme bursts of star formation.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Little is known about the fate of subsurface hydrocarbon plumes from deep-sea oil well blowouts and their effects on processes and communities. As deepwater drilling expands in the Faroe–Shetland ...Channel (FSC), oil well blowouts are a possibility, and the unusual ocean circulation of this region presents challenges to understanding possible subsurface oil pathways in the event of a spill. Here, an ocean general circulation model was used with a particle tracking algorithm to assess temporal variability of the oil-plume distribution from a deep-sea oil well blowout in the FSC. The drift of particles was first tracked for one year following release. Then, ambient model temperatures were used to simulate temperature-mediated biodegradation, truncating the trajectories of particles accordingly. Release depth of the modeled subsurface plumes affected both their direction of transport and distance travelled from their release location, and there was considerable interannual variability in transport.
•Advective pathways in the model allowed detailed visualisation of the potential impact scenarios.•Faroe–Shetland Channel circulation would strongly affect direction of transport depending on depth.•Timing of an oil spill could have a critical effect on its severity.•Deep waters of the FSC and Iceland basin could be more impacted than those further north.•Pathways and transport extent are strongly determined by oil decay rate and subsurface plume depth.
In this work, we present measurements of the E-mode (EE) polarization power spectrum and temperature-E-mode (TE) cross-power spectrum of the cosmic microwave background using data collected by ...SPT-3G, the latest instrument installed on the South Pole Telescope. This analysis uses observations of a 1500 deg2 region at 95, 150, and 220 GHz taken over a four-month period in 2018. We report binned values of the EE and TE power spectra over the angular multipole range 300≤ℓ<3000, using the multifrequency data to construct six semi-independent estimates of each power spectrum and their minimum-variance combination. These measurements improve upon the previous results of SPTpol across the multipole ranges 300 ≤ ℓ ≤ 1400 for EE and 300 ≤ ℓ ≤ 1700 for TE, resulting in constraints on cosmological parameters comparable to those from other current leading ground-based experiments. We find that the SPT-3G data set is well fit by a ΛCDM cosmological model with parameter constraints consistent with those from Planck and SPTpol data. From SPT-3G data alone, we find H0=68.8±1.5 km s-1 Mpc-1 and σ8=0.789±0.016, with a gravitational lensing amplitude consistent with the ΛCDM prediction (AL=0.98±0.12). We combine the SPT-3G and the Planck data sets and obtain joint constraints on the ΛCDM model. The volume of the 68% confidence region in six-dimensional ΛCDM parameter space is reduced by a factor of 1.5 compared to Planck-only constraints, with no significant shifts in central values. We note that the results presented here are obtained from data collected during just half of a typical observing season with only part of the focal plane operable, and that the active detector count has since nearly doubled for observations made with SPT-3G after 2018.
Long time-series studies are critical to assessing impacts of climate change on the marine carbon cycle. A 27-year time-series study in the abyssal northeast Pacific (Sta. M, 4000 m depth) has ...provided the first concurrent measurements of sinking particulate organic carbon supply (POC flux) and remineralization by the benthic community. Sediment community oxygen consumption (SCOC), an estimate of organic carbon remineralization, was measured in situ over daily to interannual periods with four different instruments. Daily averages of SCOC ranged from a low of 5.0 mg C m
−2
day
−1
in February 1991 to a high of 31.0 mg C m
−2
day
−1
in June 2012. POC flux estimated from sediment trap collections at 600 and 50 m above bottom ranged from 0.3 mg C m
−2
day
−1
in October 2013 to 32.0 mg C m
−2
day
−1
in June 2011. Monthly averages of SCOC and POC flux correlated significantly with no time lag. Over the long time series, yearly average POC flux accounted for 63 % of the estimated carbon demand of the benthic community. Long time-series studies of sediment community processes, particularly SCOC, have shown similar fluctuations with the flux of POC reaching the abyssal seafloor. SCOC quickly responds to changes in food supply and tracks POC flux. Yet, SCOC consistently exceeds POC flux as measured by sediment traps alone. The shortfall of ~37 % could be explained by sediment trap sampling artifacts over decadal scales including undersampling of large sinking particles. High-resolution measurements of SCOC are critical to developing a realistic carbon cycle model for the open ocean. Such input is essential to evaluate the impact of climate change on the oceanic carbon cycle, and the long-term influences on the sedimentation record.
ABSTRACT We present cosmological parameter constraints obtained from galaxy clusters identified by their Sunyaev-Zel'dovich effect signature in the 2500 square-degree South Pole Telescope Sunyaev ...Zel'dovich (SPT-SZ) survey. We consider the 377 cluster candidates identified at with a detection significance greater than five, corresponding to the 95% purity threshold for the survey. We compute constraints on cosmological models using the measured cluster abundance as a function of mass and redshift. We include additional constraints from multi-wavelength observations, including Chandra X-ray data for 82 clusters and a weak lensing-based prior on the normalization of the mass-observable scaling relations. Assuming a spatially flat ΛCDM cosmology, we combine the cluster data with a prior on H0 and find and , with the parameter combination . These results are in good agreement with constraints from the cosmic microwave background (CMB) from SPT, WMAP, and Planck, as well as with constraints from other cluster data sets. We also consider several extensions to ΛCDM, including models in which the equation of state of dark energy w, the species-summed neutrino mass, and/or the effective number of relativistic species ( ) are free parameters. When combined with constraints from the Planck CMB, H0, baryon acoustic oscillation, and SNe, adding the SPT cluster data improves the w constraint by 14%, to .
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