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Spatial and temporal scales of marine connectivity in bivalves : insights from a multidisciplinary perspective
No full textUnderstanding larval dispersal of marine organisms is important for designing effective marine protected areas and informing sustainable fisheries management. Larval exchange among populations has been assessed using a variety of techniques that include biophysical modeling, genetic markers, and geochemical analysis. Although these methods are increasingly applied to study connectivity in sedentary species such as marine bivalves, the physical and biological factors affecting their resolution are often overlooked. This study analyzed 100 articles that examined connectivity patterns of 54 bivalve species across local, regional, basin, and global scales to evaluate the spatial and temporal resolution of these methods. The findings indicated that geochemical markers have been most successfully used to estimate connectivity at spatial scales of 30–39 km, biophysical models at spatial scales of 29–210 km, and genetic markers at the largest spatial scales of 185–1,675 km. No significant correlation was found between pelagic larval duration and the extent of measured connectivity. Instead, local oceanographic currents, environmental gradients, and physical barriers emerged as principal determinants of connectivity at spatial scales of 30–250 km. Additionally, 37% of the studies examined multiple years or generations, highlighting the importance of interannually and seasonally variable oceanographic currents in influencing the extent of larval dispersal. This synthesis provides quantifiable connectivity estimates across different methods and spatial scales, offering valuable insights for integrating marine bivalve connectivity into effective area-based management
Reconstruction of the Spatial Physical and Bio-Geochemical Fields based on of earth observations, numerical modeling and AI methods within the framework of 4DBaltDyn ESA project
No full textModern satellite data offer powerful and unprecedented tools for monitoring the marine environment on a global scale. However, due to their inherent nature, these observations are predominantly limited to the sea surface, thus providing only a partial understanding of the marine ecosystem. This limitation can be addressed by integrating numerical models (NMs), which represent the physical processes in the marine environment through mathematical equations.
The 4D BaltDyn project aims to develop four-dimensional physical and bio-geochemical parameters by merging advanced satellite earth observation data with numerical models and AI methods. Firstly, the project will develop new SSH, SSS and ocean color products that will be later used in the assimilation and development of 4D (x,y,z,t) fields. In this study, we employ three principal models together with novel ML and AI methods used for the 4D reconstruction of ocean currents, temperature, salinity, oxygen, chlorophyll-a and nutrients:
The Coupled Sea Ice-Ocean Model of the Baltic Sea (BSIOM - GEOMAR): Utilized to improve the general representation of salinity distribution by nudging a new product in the coupled model.
The 3D Coupled Ecosystem Model of the Baltic Sea (CEMBS - IOPAN): Based on the Community Earth System Model (CESM), this model will be adapted for assimilating sea surface temperature and chlorophyll-a data.
Recently developed Climate and Environmental Modelling System (CEMS - IOPAN, current version consists of coupled Community Ice CodE (CICE) to Regional Ocean Modelling System (ROMS)): Applied to enhance the barotropic components of numerical models.
SOCA- Artificial intelligence method adapted for merging satellite observations and BGC-Argo floats for estimation of the vertical structure of particulate backscattering coefficient
All these models will incorporate satellite data developed within the framework of the project consortium. By integrating satellite and modeling data, we aim to create one of the most accurate reanalyzed datasets to date, surpassing the quality of currently available datasets.
The poster will present preliminary results, focusing on the adapted methodologies. Given the well-known advantages and limitations of both satellite data and numerical model outputs, we anticipate significant improvements, which will be showcased in this work
The age and early evolution of the Moon revealed by the Rb-Sr systematics of lunar ferroan anorthosites
No full textThe formation of the Moon by a giant impact of an object called Theia onto proto-Earth marks the end of the main stage of Earth's accretion. However, the timing of this event is controversial, with estimates ranging between ∼50 and ∼220 million years (Ma) after solar system formation. The 87Rb-87Sr system has the potential to resolve this debate, as formation of the Moon resulted in strong fractionation of rubidium from strontium. To better determine the initial 87Sr/86Sr of the Moon, we obtained Rb-Sr isotope data for several lunar ferroan anorthosites, which define an initial 87Sr/86Sr of 0.6990608±0.0000005 (2 s.e.) at 4.360±0.003 Ga. Modeling the pre-giant impact Rb-Sr isotopic evolution of Theia and the proto-Earth reveals that while in the canonical giant impact model no Rb-Sr model age can be determined, all other current impact models yield a Moon formation age of 4.502±0.020 Ga, or 65±20 Ma after solar system formation. When compared to the chronology of lunar samples, this age implies that solidication of the lunar magma ocean took ∼70 Ma, and that the Moon underwent a global re-melting event ∼150 Ma after its formation
Seismological characterization of the March 3, 2018, Maceió (Brazil) earthquake and its link to subsidence
No full textGround subsidence processes, both natural and human-induced, influence metropolitan areas worldwide. Maceió, Brazil, has seen an increase in sinkhole development and infrastructure damage since a magnitude 2.4 earthquake occurred on March 3, 2018. This seismic event occurred near a deep salt mining operation. We relocated the earthquake using data from the Brazilian Seismographic Network, with station distances ranging from 58-289 km, and processed seismic records with a Wiener and a 4-8 Hz band-pass filter. The HYPO71 code from the SeisComP package estimated the earthquake's location, utilising P and S wave arrivals from the four closest stations. We estimated the focus depth at 1 km near Mundaú Lagoon, where over 200 cm of accumulated subsidence occurred. The epicentre and depth uncertainties were 3 km and 4 km, respectively. Using P-wave polarities and amplitude ratios to perform a focal mechanism inversion with the FOCMEC package, we found that the solutions indicate normal faulting along NE-oriented fault planes. We also inverted for the full moment tensor with the ISOLA package for three stations with good surface wave records, with the best-fitting results also indicating a normal faulting mechanism at 0.7 km depth with a small DC component of 4.7, high CLVD of -66.2, and VOL (=ISO) of -29.1. These results suggest that this main event is associated with subsidence primarily linked to removing localised, deep-seated material where salt is mined. This work contributes to Project TSHAPS (REF 541685934) supported by Program FCT - Aga Khan
Bathymetry-constrained impact of relative sea-level change on basal melting in Antarctica
No full textRelative sea level (local water depth) on the Antarctic continent is changing through the complex interplay of processes associated with glacial isostatic adjustment (GIA). This involves near-field viscoelastic bedrock displacement and gravitational effects in response to changes in Antarctic ice load but also far-field interhemispheric effects on the sea-level pattern. On glacial timescales, these changes can be of the order of several hundred meters, potentially affecting the access of ocean water masses at different depths to Antarctic grounding lines and ice-sheet margins. Due to strong vertical gradients in ocean temperature and salinity at the continental-shelf margin, basal melt rates of ice shelves have the potential to change just by variations in relative sea level alone. Based on simulated relative sea-level change from coupled ice-sheet–GIA model experiments and the analysis of topographic features such as troughs and sills that regulate the access of open-ocean water masses onto the continental shelf, we derive maximum estimates of Antarctic basal melt rate changes, solely driven by relative sea-level variations. Our results suggest that the effect of relative sea-level changes on basal melting is limited, especially compared to transient changes in the climate forcing
The Role of Submesoscale Processes in the Decay of Agulhas Rings
No full textFine-scale ocean processes (1–100 km) are central to global ocean circulation, water mass transformation, and the long-range transport of tracers such as heat and carbon. The Agulhas Current system and the Cape Basin are hotspots for such dynamics, where mesoscale and submesoscale flows interact strongly. Among the most prominent features in this region are anticyclonic Agulhas rings that are shed from the Agulhas retroflection as well as cyclonic eddies, which both decay while transporting relatively warm and saline waters into the South Atlantic. In this study, we investigate how submesoscale dynamics influence the decay of these eddies and the associated redistribution of heat and salt. To isolate the role of the submesoscale, we compare two global ocean model configurations with high-resolution in the focus region achieved through nesting: one with 1/20° resolution that is strongly eddying but does not represent submesoscale flows, and another with 1/60° resolution and modified tracer and momentum advection schemes, allowing for realistic submesoscale motions throughout the Agulhas region. We use Lagrangian simulations with the OceanParcels tool with virtual particles representing small amounts of water masses. Coherent eddies, both anticyclonic and cyclonic, are identified horizontally and vertically using automated eddy-detection algorithms. Over an 8-year period, large numbers of particles are seeded in 3D within eddies intersecting the GoodHope section and tracked to assess retention times within the eddies and the spatiotemporal patterns of mixing. Our results reveal distinct differences in eddy decay rates and mixing behaviour between the two configurations, pointing to the critical role of submesoscale flows in controlling eddy lifetimes and tracer dispersal in the Cape Basin
Characterizing the Interannual Variability of North Atlantic Subpolar Overturning
No full textVariability of the Atlantic Meridional Overturning Circulation (MOC) has drawn extensive attention due to its impact on the global redistribution of heat and freshwater. Here we present the latest time series (2014-2022) of the Overturning in the Subpolar North Atlantic Program and characterize MOC interannual variability. We find that any single boundary current captures similar to 30% of subpolar MOC interannual variability. However, to fully resolve MOC variability, a wide swath across the eastern subpolar basin is needed; in the Labrador Sea both boundaries are needed. Through a volume budget analysis for the subpolar basins' lower limbs, we estimate the magnitude of unresolved processes (e.g., diapycnal mixing) required to close the mean budget (similar to 2 Sv). We find that in the eastern subpolar basin surface-forced transformation variability is linked to lower limb volume variability, which translates to MOC changes within the same year. In contrast, this linkage is weak in the Labrador Sea