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  • 1
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    In:  [Poster] In: 1. International AtlantOS Symposium. Session 4: Sensors Development and Best Practices, 25.-29.03.2019, Paris, France .
    Publication Date: 2019-05-21
    Description: Ocean warming severely impacts oxygen distribution, because it reduces oxygen solubility and increases stratification in the upper ocean. Quantifying changes of oxygen levels will improve the understanding of chemical, biological and physical processes, especially in Oxygen Minimum Zones characterized by intensification and spatial expansion. Despite existing optical sensors (optodes) that accurately measure ocean oxygen levels, users wish for an improved spatial and temporal measurement resolution from profiling platforms. We demonstrate the utility of a novel, commercially-available optode that shows a temperature-dependent response time (t63%) of about 4 seconds, which is significantly faster compared to other optical oxygen sensors. This optode can be used on a wide range of observation platforms such as ships, time-series stations, unmanned surface vehicles and autonomous underwater platforms such as floats and gliders. We aim to characterize this optode regarding oxygen, temperature, salinity and pressure dependence, long-term stability and drift, response time and air-calibration compatibility. Results build on data from laboratory experiments and field deployments in the Tropical and Southern Atlantic. Underway, mooring, float and CTD-cast applications promise high quality observations including fast oxygen level changes on small scales. We will conclude with a status update on our general optode technology developments.
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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  • 2
    Publication Date: 2024-02-07
    Description: Highlights • Real-time monitoring of CO2 release. • Measurements of water column pH and pCO2 via towed Video-CTD system. • Assessment of towed sensors capacity to detect potential CO2 leakage in the water column. • Estimation of thresholds for the detection of anomalous pCO2. Within the framework of the STEMM-CCS project, a controlled CO2 release experiment was conducted under real-life conditions in the Goldeneye complex area, a depleted gas field located in the UK sector of the North Sea. Here, the viability of water column monitoring for the detection of the injected CO2 is evaluated. Real-time pH and pCO2 measurements were taken in the water column during the CO2 release experiment. Monitoring was carried out throughout the full water column, from the near-seafloor to the sea surface, in order to assess the spatial extent of the CO2 release. The dispersion of the CO2 plume was strongly influenced by tidal circulation in the area. The strongest signals were detected within 8 m of the bubble stream during low tide. The lowest pH and highest pCO2 values were 7.965 and 942.1 µatm, respectively, corresponding to variations of 16.4% [H+] and 125.6% from baseline values. The pCO2 baseline dynamics of Goldeneye area were assessed by the evaluation of the natural pCO2-O2 covariance. The estimation of seasonal thresholds for anomalous pCO2 (pCO2:O2 ratio May= 1.63 ± 0.04) allowed us to assess with confidence the non-biological origin of the detected CO2 during the release experiment.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 3
    Publication Date: 2024-02-07
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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  • 4
    Publication Date: 2019-07-17
    Description: Over the past 50 years, warming of the Antarctic Peninsula has been accompanied by accelerating glacier mass loss and the retreat and collapse of ice shelves. A key driver of ice loss is summer melting; however, it is not usually possible to specifically reconstruct the summer conditions that are critical for determining ice melt in Antarctic. Here we reconstruct changes in ice-melt intensity and mean temperature on the northern Antarctic Peninsula since AD 1000 based on the identification of visible melt layers in the James Ross Island ice core and local mean annual temperature estimates from the deuterium content of the ice. During the past millennium, the coolest conditions and lowest melt occurred from about AD 1410 to 1460, when mean temperature was 1:6 �C lower than that of 1981–2000. Since the late 1400s, there has been a nearly tenfold increase in melt intensity from 0.5 to 4.9%. The warming has occurred in progressive phases since about AD 1460, but intensification of melt is nonlinear, and has largely occurred since the mid-twentieth century. Summer melting is now at a level that is unprecedented over the past 1,000 years.We conclude that ice on the Antarctic Peninsula is now particularly susceptible to rapid increases in melting and loss in response to relatively small increases in mean temperature.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 5
    Publication Date: 2021-07-05
    Description: The partial pressure of carbon dioxide (pCO2) in surface seawater is an important biogeochemical variable because, together with the pCO2 in the atmosphere, it determines the direction of air–sea carbon dioxide exchange. Large‐scale observations of pCO2 are facilitated by Ships‐of‐Opportunity (SOOP‐CO2) equipped with underway measuring instruments. The need for expanding the observation capacity and the challenges involving the sustainability and maintenance of traditional equilibrator systems led the community toward developing simpler and more autonomous systems. Here we performed a comparison between a membrane‐based sensor and a showerhead equilibration sensor installed on two SOOP‐CO2 between 2013 and 2018. We identified time‐ and space‐adequate crossovers in the Skagerrak Strait, where the two ship routes often crossed. We found a mean total difference of 1.5 ± 10.6 μatm and a root mean square error of 11 μatm. The pCO2 values recorded by the two instruments showed a strong linear correlation with a coefficient of 0.91 and a slope of 1.07 (± 0.14), despite the dynamic nature of the environment and the difficulty of comparing measurements from two different vessels. The membrane‐based sensor was integrated with a FerryBox system on a ship with a high sampling frequency in the study area. We showed the strength of having a sensor‐based network with a high spatial coverage that can be validated against conventional SOOP‐CO2 methods. Proving the validity of membrane‐based sensors in coastal and continental shelf seas and using the higher frequency measurements they provide can enable a thorough characterization of pCO2 variability in these dynamic environments.
    Keywords: 551.46 ; surface seawater ; carbon dioxide ; partial pressure ; measurements
    Type: article
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  • 6
    Publication Date: 2021-12-15
    Description: Carbon capture and storage (CCS) is a key technology to reduce carbon dioxide (CO2) emissions from industrial processes in a feasible, substantial, and timely manner. For geological CO2 storage to be safe, reliable, and accepted by society, robust strategies for CO2 leakage detection, quantification and management are crucial. The STEMM-CCS (Strategies for Environmental Monitoring of Marine Carbon Capture and Storage) project aimed to provide techniques and understanding to enable and inform cost-effective monitoring of CCS sites in the marine environment. A controlled CO2 release experiment was carried out in the central North Sea, designed to mimic an unintended emission of CO2 from a subsurface CO2 storage site to the seafloor. A total of 675 kg of CO2 were released into the shallow sediments (~3 m below seafloor), at flow rates between 6 and 143 kg/d. A combination of novel techniques, adapted versions of existing techniques, and well-proven standard techniques were used to detect, characterise and quantify gaseous and dissolved CO2 in the sediments and the overlying seawater. This paper provides an overview of this ambitious field experiment. We describe the preparatory work prior to the release experiment, the experimental layout and procedures, the methods tested, and summarise the main results and the lessons learnt.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
    Format: application/pdf
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