ALBERT

Description: Highlights • Development of an autonomous DIC analyzer based on Conductometric technique using a cell with 4 hollow brass electrodes. • CO2 extraction from seawater using a gas diffusion cell with a “Tube In A Tube” configuration and a gas permeable membrane. • Formulation of mathematical temperature and salinity correction to determine accurate DIC concentration. • Demonstration of the analyzer performance in the southwest Baltic Sea. Abstract Background The increase in anthropogenic CO2 concentrations in the Earth's atmosphere since the industrial revolution has resulted in an increased uptake of CO2 by the oceans, leading to ocean acidification. Dissolved Inorganic Carbon (DIC) is one of the key variables to characterize the seawater carbonate system. High quality DIC observations at a high spatial-temporal resolution is required to improve our understanding of the marine carbonate system. To meet the requirements, autonomous DIC analyzers are needed which offer a high sampling frequency, are cost-effective and have a low reagent and power consumption. Results We present the development and validation of a novel analyzer for autonomous measurements of DIC in seawater using conductometric detection. The analyzer employs a gas diffusion sequential injection approach in a “Tube In A Tube” configuration that facilitates diffusion of gaseous CO2 from an acidified sample through a gas permeable membrane into a stream of an alkaline solution. The change in conductivity in the alkaline medium is proportional to the DIC concentration of the sample and is measured using a detection cell constructed of 4 hollow brass electrodes. Physical and chemical optimizations of the analyzer yielded a sampling frequency of 4 samples h−1 using sub mL reagent volumes for each measurement. Temperature and salinity effects on DIC measurements were mathematically corrected to increase accuracy. Analytical precision of ±4.9 μmol kg−1 and ±9.7 μmol kg−1 were achieved from measurements of a DIC reference material in the laboratory and during a field deployment in the southwest Baltic Sea, respectively. Significance This study describes a simple, cost-effective, autonomous, on-site benchtop DIC analyzer capable of measuring DIC in seawater at a high temporal resolution as a step towards an underwater DIC sensor. The analyzer is able to measure a wide range of DIC concentrations in both fresh and marine waters. The achieved accuracy and precision offer an excellent opportunity to employ the analyzer for ocean acidification studies and CO2 leakage detection in the context of Carbon Capture and Storage operations.

Description: Marine Neurotoxins, Volume Five provides comprehensive information on marine toxins present in the human food chain and the affecting targets relevant for the functioning of the brain and our nervous system, covering all the information ...

Description: Marine Neurotoxins, Volume Five provides comprehensive information on marine toxins present in the human food chain and the affecting targets relevant for the functioning of the brain and our nervous system, covering all the information ...

Description: While the influence of precession on monsoon at low latitudes through insolation forcing is well-known, the role of obliquity is still debated since its influence on the distribution of incoming solar radiation is small in these regions. In southern Africa, long marine and terrestrial sedimentary records attest of a precessional influence on the South African monsoon at orbital time scale. The obliquity signal is occasionally observed in the geological records although modeling results suggest an influence of precession and obliquity on summer monsoon. Here, we present a record of microscopic charcoal from core MD96-2098 located off Namibia covering the past 184,000 years. Our record of fire activity reveals cyclic changes at frequencies of 23, 58 and 12 kyr−1 and lacks the obliquity signal at 41 kyr−1. Changes in fire over southern Africa are interpreted as shifts in large and intense fires spreading in open-grassland savanna as a result of orbitally-driven changes in rainfall intensity associated with the South African monsoon. We show that, despite the absence of a 41 kyr obliquity imprint, the presence of 23, 58 and 12 kyr−1 frequencies likely stems from a nonlinear response of fire to precipitation controlled by a combination of precession and obliquity frequencies, supporting the influence of obliquity on the South African monsoon.

Description: Preface of a special issue.

Description: Published

Description: 3365-3366

Description: OSA3: Climatologia e meteorologia spaziale

Description: JCR Journal

Description: Highlights: • The interactions between vortices in a four-vortex flow field using a rotating water tank. • Driven by the strain field, non-ideal vortices stretch along the centerline, and manifest an asymmetric stretching pattern. • Non-ideal vortices disperse vorticity, accumulate filaments, and exhibit distinctive variations in anti-symmetric vorticity distribution, impacting respective merging efficiency. Abstract: Oceanic vortex merging is an important physical process for the vortex evolution and its impact on marine environment. However, limitation of the in-situ oceanic observational data of vortex merging inhabits its better understanding. This study investigates the interactions between non-ideal vortices in a four-vortex flow field in a rotating tank. We examine the merging stages of anticyclonic vortices, influenced by two other cyclonic vortices and their respective dynamical behaviors and quantify the effects of merging on vortex characteristics. The results indicate a strong shear flow between two counter-rotating vortices, which accelerates the motion of the anticyclonic vortex, while cyclonic ones exhibit greater stability. Subsequently, different stages of non-ideal vortex merging in a co-rotating framework are defined, primarily the encircling stage, rapid approaching stage, and merging vortex stage. In addition, we quantify and compare variations in morphological parameters and anti-symmetric vorticity distribution of non-ideal vortices across these stages. The stretching of vortices primarily occurs along the line connecting their centers due to the strain field exerted by neighboring vortices, resulting in an asymmetric stretching pattern in the interactions among non-ideal vortices. Furthermore, during the merging process, non-ideal vortices disperse vorticity outward and accumulate vortex filaments in the surrounding environment, leading to distinctive variations in anti-symmetric vorticity distribution, affecting their respective merging efficiency.

Description: In the past three decades, altimeter-based remote sensing has been a widely used system to estimate ocean surface currents. However, it remains a great challenge to effectively resolve scales below ∼100 km at high latitudes and ∼ 300 km at mid-latitudes. In this study, we propose a scheme that utilizes geostrophic equilibrium and surface quasigeostrophy theory (SQG) to improve surface current resolution by incorporating remote sensing sea surface temperature (SST), sea surface height (SSH), and sea surface salinity (SSS) observations. The scheme separately characterizes the larger-scale flows and smaller-scale motions of surface currents. A case study encompassing the Agulhas surface current demonstrates that the smaller-scale motions associated with temperature fronts are well captured by introducing high spatial-temporal resolution SST data. Furthermore, the reconstructed surface current is systemically evaluated by using surface drogued drifters and a Lagrangian synthetic particle tracking tool throughout the South Indian Ocean (SIO) for 2011–2015. Notably, the reconstructed zonal velocity component is closer to the drifter observations than the meridional counterpart and corresponding velocity phase. Regionally, the Antarctic Circumpolar Current (ACC) showcases superior reconstruction performance, with higher skill scores and lower Lagrangian separation distances. However, a relatively large uncertainty is observed around the Agulhas Retroflection (AR) and Greater Agulhas System (GAS), which are linked to complicated regional dynamic regimes. We finally conduct four simulation experiments to explore the effect of different SST products on surface current reconstruction within the subdomain AR. The results indicate the varying potentials of the four evaluated SST products for informing surface current applications. Specifically, the MWIRSST enhances the likelihood of particles reaching the target field, while DMI OI shortens the average deviation distance of the arrived particles.

Description: Marine imaging studies have unique constraints on the data collected requiring a tool for defining the biological scope to facilitate data discovery, quality evaluation, sharing and reuse. Defining the ‘target population’ is way of scoping biological sampling or observations by setting the pool of organisms to be observed or sampled. It is used in survey design and planning, to determine statistical inference, and is critical for data interpretation and reuse (both images and derived data). We designed a set of attributes for defining and recording the target population in biological studies using marine photography, incorporating ecological and environmental delineation and marine imaging method constraints. We describe how this definition may be altered and recorded at different phases of a project. The set of attributes records the definition of the target population in a structured metadata format to enhance data FAIRness. It is designed as an extension to the image FAIR Digital Objects metadata standard, and we map terms to other biological data standards where possible. This set of attributes serves a need to update ecological metadata to align with new remotely-sensed data, and can be applied to other remotely-sensed ecological image data.

Description: The Arctic is greatly impacted by climate change. The increase in air temperature drives the thawing of permafrost and an increase in coastal erosion and river discharge. This leads to a greater input of sediment and organic matter into coastal waters, which substantially impacts the ecosystems by reducing light transmission through the water column and altering the biogeochemistry, but also the subsistence economy of local people, and changes in climate because of the transformation of organic matter into greenhouse gases. Yet, the quantification of suspended sediment in Arctic coastal and nearshore waters remains unsatisfactory due to the absence of dedicated algorithms to resolve the high loads occurring in the close vicinity of the shoreline. In this study we present the Arctic Nearshore Turbidity Algorithm (ANTA), the first reflectance-turbidity relationship specifically targeted towards Arctic nearshore waters that is tuned with in-situ measurements from the nearshore waters of Herschel Island Qikiqtaruk in the western Canadian Arctic. A semi-empirical model was calibrated for several relevant sensors in ocean color remote sensing, including MODIS, Sentinel 3 (OLCI), Landsat 8 (OLI), and Sentinel 2 (MSI), as well as the older Landsat sensors TM and ETM+. The ANTA performed better with Landsat 8 than with Sentinel 2 and Sentinel 3. The application of the ANTA to Sentinel 2 imagery that matches in-situ turbidity samples taken in Adventfjorden, Svalbard, shows transferability to nearshore areas beyond Herschel Island Qikiqtaruk.

Description: Tundra is primarily a habitat for shrub growth, not trees, but growth of prostrate forms of trees has been reported occasionally from the subarctic tundra region. In the light of on-going climate change, climate sensitivity studies of these unique trees are essential to predict vegetation dynamics and potential northward expansion of boreal forest tree species into tundra. Here we studied one of the northernmost Larix Mill. trees and Betula nana L. shrubs (72°N) from the Siberian tundra for the common period 1980-2017. We took advantage of the discovery of a single cohort of prostrate Larix trees within a tundra ecosystem, i.e., ca. 60 km northwards from the northern treeline, and compared climate-growth relationships of the two species. Both woody plants were sensitive to the July temperature, however this relationship was stable across the entire study period (1980-2017) only for Betula nana chronology. Additionally, radial growth of Larix trees became negatively correlated to temperatures during the previous summer. In recent period moisture sensitivity between Larix trees and Betula nana shrubs was contrasting, with generally wetter soil conditions favoring Larix trees growth and dryer conditions promoting Betula nana growth. Our study indicates that Larix trees radial growth in recent years is more sensitive to moisture than to summer air temperatures, whereas temperature sensitivity of Betula nana shrub is stable over time. We provide first detailed insight into the annual resolution on Larix tree growth sensitivity to climate in the heart of the tundra. The potentially higher Betula nana shrub resistance to warmer and drier climate versus Larix trees on a tundra revealed in our study needs to be further examined across habitats of various soil, moisture and permafrost status.