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Asymmetric bubble-mediated gas transfer enhances global ocean CO2 uptake
No full textSea-air carbon dioxide (CO2) flux is typically estimated from the product of the gas transfer velocity (K) and the CO2 fugacity difference between the ocean surface and atmosphere. Total gas exchange comprises interfacial transfer across the unbroken surface and bubble-mediated transfer from wave breaking. While interfacial transfer is symmetric for invasion and evasion, bubble-mediated transfer theoretically favours invasion due to hydrostatic pressure, though field evidence has been lacking. Here we provide direct field evidence of this asymmetry and develop an asymmetric flux equation. Applying the asymmetric equation reduces bias in K, and increases global oceanic CO2 uptake by 0.3-0.4 Pg C yr-1 (~15% on average from 1991 to 2020) relative to conventional estimates. Further evasion data are needed to better quantify the asymmetry factor. Our study suggests that the ocean may have absorbed more CO2 than previously thought, and the asymmetric equation should be used for future CO2 flux assessments
A roadmap for designing a virtual interface to explore a digital twin of the oceans for marine ecosystems monitoring
No full textMany marine monitoring infrastructures continuously collect biological and abiotic data, yet user-friendly interfaces for visualizing and translating this knowledge remain limited. This gap persists due to challenges associated with effective frameworks and tools for processing and analysing biological data in real-time. In this paper, we outline a roadmap for developing a Graphical User Interface (GUI) tailored to the continuous monitoring of ecological data with a focus on supporting marine scientists and engineers. To guide this process, we reviewed existing GUIs for visualizing marine ecological data and surveyed 43 experts to identify current gaps and key priorities. Our findings revealed a key dichotomy: GUIs either represent diverse array of biological data or perform inadequately when attempting to transfer qualitative observations to quantitative insights. Finally, we propose a stepwise roadmap for GUI development within the Digital Twin of the Ocean framework by starting from spatial mapping and progressing to data navigation. Ultimately, this study outlines critical considerations for integrating complex ecological data from diverse sources into an effective GUI. This GUI aims to support realtime monitoring, control remote monitoring for data collection, inform policymakers, and enhance public engagement in marine science
The ocean flows downhill near the seafloor and recirculates upward above
No full textThe ocean’s circulation redistributes heat, salt, biota, dissolved gases, microplastics, and sediments on Earth. The abyssal ocean, in the lowest 1000 m above the seafloor, moves on average with the deeper seafloor to its left in the Northern Hemisphere and to its right in the Southern Hemisphere. This finding has received little attention and its consequences for the abyssal vertical circulation have remained largely unexplored. Here, we show, using current-meter measurements and numerical simulations, that the interior flow, (100 m) - (1000 m) above the seafloor, is deflected within the bottom boundary layer, the lowest (10 m), into a widespread downhill flow. This flow intensifies with the steepness of the seafloor. We further reveal that typical local changes in seafloor steepness lead to a shallow divergence and a deep convergence of this downhill flow. These are connected by an overlying upward recirculation forming closed overturning cells that extend on average over the lowest 1000 m of the ocean. Our study improves the understanding of the oceanic abyssal circulation and the climate-relevant overturning. Future research should focus on quantifying the transports of heat, particles, and dissolved chemicals associated with these abyssal slope overturning cells
Strain and fault evolution during gravitational volcano collapse: Experiments with different substrata geometries
No full textMany volcanoes on Earth show evidence of gravitational collapse of their entire structure or a sector at
rates ranging from a few millimetres or centimetres per year to catastrophic collapse. While deformation
at the surface of volcanoes can be measured using geodetic methods, its origin and relation to the
structures inside the volcanic edifice and its basement are complex to explore.
This study uses analogue models to experimentally investigate how the geometry of a volcano’s basement controls the deformation under gravitational loading. The models are composed of a viscous layer
(the d´ecollement) overlain by a brittle layer (the brittle sedimentary basement) and a cohesive conical
edifice (the volcano). The surface deformation is monitored in 3D by high-resolution cameras and digital
image correlation techniques.
Gravitation can cause the stable edifice to sink into the substratum - a process called sagging - while
it can also cause destabilisation of the edifice. Then, the edifice flattens on the substratum and generates
faults - a process called spreading. It is well established that an increase of brittle layer thickness
stabilises the volcano. Spatial variations in brittle layer thickness can therefore be expected to control
sectorial collapse. Here, I present analogue models to test this hypothesis and further refine models
of sector collapse. To identify the sagging-to-spreading threshold in my specific experimental setup, I
systematically varied the thickness of the brittle layer. In further series of models, I then vary the angle
of an implemented slope in the brittle layer, connecting the spreading and the sagging regime, and the
distance between the slope and the edifice.
Transtensional faults develop mainly on that half of the edifice that is facing the basement slope.
Grabens narrow from the peak toward the edifice base and bent folds form around it in the basement.
Up until a 5° brittle layer slope, the displacement rates and expression of faults and grabens increase with
increasing slope angle, while the change of slope angle >5° has less influence. If the edifice is located at
a distance from the slope break, it can still develop a sector collapse, although the brittle layer directly
beneath it supports a sagging mechanism. Here, the sectoral spreading starts to decrease when the centre
of the edifice is two radii away from the slope break. Mechanisms that cause different surface features
are discussed. Finally, the models show a general decrease in deformation rates over time with a distinct
phase in which the faults are activated in a stick-slip manner. The study demonstrates that an inclined
sedimentary basement (e.g. as present below Etna) contributes to a flank collapse and the emergence of
distinct faults at the surface. The surface deformation observed at Mount Etna was best approximated
by a model with 5° brittle layer slope and 10 cm (corresponding to 30 km) distance between slope and
edifice. This suggests that the sedimentary basement beneath Etna continues with a slope beneath the
widely unexplored submarine flank. As the high rates of horizontal displacement in my models continue
down the basement slope, Etna’s mobile flank is likely to continue into the sea. Submarine parts may
drag the upper parts of the flank
HELCOM Thematic assessment on hazardous submerged objects in the Baltic Sea (volume 2) Potentially polluting shipwrecks in the Baltic Sea
No full textiqa - image quality analysis
No full textShort description of the research software : A C++ library to analyze image quality. Detect e.g. if an image is over-/underexposed, blurry or contains little information. iqa is based on OpenVC and can utilize your GPU for a great performance boost. To do so you only need OpenCV built with Cuda support. Everything else is handled by iqa - no need for your code to change
Robustness and mechanisms of the atmospheric response over the Southern Ocean to idealized freshwater input around Antarctica
No full textEnhanced Antarctic ice sheet mass loss yields ocean surface freshening, cooling and sea ice expansion, which result in changes in the atmospheric conditions. Using the Southern Ocean Freshwater Input from Antarctica (SOFIA) multi-model ensemble, we study the atmospheric response to a 100-year idealized freshwater release of 0.1 Sv. All models simulate a surface-intensified tropospheric cooling and lower-stratospheric warming south of 35°S. Tropospheric cooling is attributed to sea ice expansion and the associated albedo enhancement in winter and a colder sea surface in summer. This cooling yields a downward displacement of the tropopause, reduced stratospheric water vapor content and ultimately warming around 200 hPa. An enhanced southward eddy heat flux explains warming at 10–100 hPa during austral winter. Despite a temporally (and spatially) uniform prescribed freshwater flux, a prominent sea ice seasonal cycle and atmosphere dynamics result in a distinct seasonal pattern in the occurrence and magnitude of the temperature responses.
Key Points:
- Tropospheric cooling and stratosphere warming south of 35°S are robust responses to Southern Ocean freshwater input in a multi-model ensemble
- The tropospheric cooling is driven by enhanced surface albedo in winter and colder sea surface temperature in summer
- Two types of stratospheric warming, one caused by a lowering of the tropopause and reduced water vapor content in the lower stratosphere, another by an enhanced poleward eddy heat flu
Spatial and temporal patterns of zooplankton trophic interactions and carbon sources in the eutrophic Elbe estuary (Germany)
No full textZooplankton in estuaries encounter complex physical and biogeochemical processes that affect the quantity, quality, and origin of their food sources. The knowledge about how zooplankton deal with highly variable organic matter sources is sparse. Here, we investigated the spatial and temporal patterns of zooplankton trophic dynamics and carbon sources in the intensively dredged, eutrophic Elbe estuary. For this purpose, we applied elemental and stable isotope analysis (delta 13C and delta 15N) on particulate organic matter (POM) and dominant meso- and macrozooplankton species, including ichthyoplankton, from five stations along the entire salinity gradient of the estuary in 2022. The delta 13C values of POM (-29.2 to -23.0 parts per thousand) indicated a mixture of riverine, terrestrial, and coastal carbon sources used by most taxa for their diet. Eurytemora affinis (-34.0 to -23.3 parts per thousand) and Mesopodopsis slabberi (-22.2 to -20.0 parts per thousand) exhibited a broader range in delta 13C than POM, suggesting selective feeding on single POM components depending on the season. In winter and autumn, under high suspended matter loads and limited availability of high-quality autochthonous phytoplankton, zooplankton showed increased tendency for carnivory (higher delta 15N values). Our study revealed a high trophic plasticity of estuarine Elbe zooplankton to buffer hydrological-related alterations in their food source by dietary niche partitioning and a flexible switch in their feeding behaviour
