Enhance Ocean Carbon Observations: Successful Implementation of a Novel Autonomous Total Alkalinity Analyzer on a Ship of Opportunity

Over recent decades, observations based on merchant vessels (Ships of Opportunity—SOOP) equipped with sensors measuring the CO2 partial pressure (pCO2) in the surface seawater formed the backbone of the global ocean carbon observation system. However, the restriction to pCO2 measurements alone is one severe shortcoming of the current SOOP observatory. Full insight into the marine inorganic carbon system requires the measurement of at least two of the four measurable variables which are pCO2, total alkalinity (TA), dissolved inorganic carbon (DIC), and pH. One workaround is to estimate TA values based on established temperature-salinity parameterizations, but this leads to higher uncertainties and the possibility of regional and/or seasonal biases. Therefore, autonomous SOOP-based TA measurements are of great interest. Our study describes the implementation of a novel autonomous analyzer for seawater TA, the CONTROS HydroFIAⓇ TA system (-4H-JENA engineering GmbH, Germany) for unattended routine TA measurements on a SOOP line operating in the North Atlantic. We present the installation in detail and address major issues encountered with autonomous measurements using this analyzer, e.g., automated cleaning and stabilization routines, and waste handling. Another issue during long-term deployments is the provision of reference seawater in large-volume containers for quality assurance measurements and drift correction. Hence, a stable large-volume seawater storage had to be found. We tested several container types with respect to their suitability to store seawater over a time period of 30 days without significant changes in TA. Only one gas sampling bag made of polyvinylidene fluoride (PVDF) satisfied the high stability requirement. In order to prove the performance of the entire setup, we compared the autonomous TA measurements with TA from discrete samples taken during the first two trans-Atlantic crossings. Although the measurement accuracy in unattended mode (about ± 5 μmol kg^-1) slightly deteriorated compared to our previous system characterization, its overall uncertainty fulfilled requirements for autonomous TA measurements on SOOP lines. A comparison with predicted TA values based on an established and often used parameterization pointed at regional and seasonal limitations of such TA predictions. Consequently, TA observations with better coverage of spatiotemporal variability are needed, which is now possible with the method described here

Novel Optical Oxygen Sensor for Profiling Observation Platforms: Fast Response Time Enables Higher Spatial and Temporal Data Resolution

Ocean warming has a severe impact on oxygen distribution because it reduces oxygen solubility and increases stratification in the upper ocean. Models predict a decline of the global oxygen inventory of about 1-7% over the next century and data show a decrease of more than 2% since 1960 (Schmidtko et al., Nature, 2017). Quantifying global as well as regional changes of oxygen will improve the understanding of chemical, biological and physical processes, especially in Oxygen Minimum Zones (OMZ) where consistent trends of intensification and spatial expansion exit (e.g., Stramma et al., Science, 2008). Although optical sensors, so-called optodes, are available to accurately measure changes in ocean oxygen levels, users still wish to obtain better spatial and temporal resolution on profiling observation platforms than can be currently achieved. Here we demonstrate the utility of a novel and fast, commerciallyavailable optode for in-situ and autonomous oxygen measurements, potentially closing this gap. This novel oxygen optode shows a temperature-dependent response time (t63%) of about 4 seconds and is thereby at least 50% faster compared to other optical oxygen sensors. We aim to fully characterize this optode with regard to accuracy, precision, pressure dependence, long-term stability and drift, response time as well as aircalibration compatibility. Results build on data from extensive laboratory experiments and field deployments in the Tropical North, South and Southern Atlantic (underway, mooring, float and CTD-cast applications). This promises high quality observations for detecting oxygen level changes on small and fast-changing scales in this ocean region. This novel optode could be used on a wide range of autonomous observation platforms such as ships for Repeat Hydrography, time-series stations and wave gliders, yet is especially promising on floats, gliders and fast-moving ships. In a changing ocean those applications eventually will contribute valuable information to the global oxygen budget

Novel Oxygen Optode Sensor for Profiling Ocean Observation Platforms: Extensive Characterization and In-Depth Assessment of its Fast Response Time

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

Validation of sensor and instrumentation innovations

Validated prototypes of new and enhanced biogeochemical and biological sensors and instruments. Validation will be undertaken in the laboratory, in test scenarios, and by deployment in operational condition

Terrestrial Very-Long-Baseline Atom Interferometry:Workshop Summary

This document presents a summary of the 2023 Terrestrial Very-Long-Baseline Atom Interferometry Workshop hosted by CERN. The workshop brought together experts from around the world to discuss the exciting developments in large-scale atom interferometer (AI) prototypes and their potential for detecting ultralight dark matter and gravitational waves. The primary objective of the workshop was to lay the groundwork for an international TVLBAI proto-collaboration. This collaboration aims to unite researchers from different institutions to strategize and secure funding for terrestrial large-scale AI projects. The ultimate goal is to create a roadmap detailing the design and technology choices for one or more km-scale detectors, which will be operational in the mid-2030s. The key sections of this report present the physics case and technical challenges, together with a comprehensive overview of the discussions at the workshop together with the main conclusions

Light-pulse atom interferometry with entangled atom-optical elements

The analogs of optical elements in light-pulse atom interferometers are generated from the interaction of matter waves with light fields. As such, these fields possess quantum properties, which fundamentally lead to a reduced visibility in the observed interference. This loss is a consequence of the encoded information about the atom's path. However, the quantum nature of the atom-optical elements also gives an additional degree of freedom to reduce such effects: We demonstrate that entanglement between all light fields can be used to erase information about the atom's path and by that to partially recover the visibility. Thus, our work highlights the role of complementarity on atom-interferometric experiments

Analysis of person-situation interactions in educational settings via cross-classified multilevel longitudinal modeling : illustrated with the example of students' stress experience

The investigation of learning processes by assessing students’ experience along with objective characteristics within a classroom context has a long tradition in empirical learning process research (e.g. Sembill, 1984 et passim; Wild & Krapp, 1996). However, most of the existing studies confine themselves to psychological variables that seem to be too narrowly considered, as there is theoretical and empirical evidence proving the involvement of somatic and psychological processes in learning and in stress reactions. Furthermore there is a lack of studies that investigate situation-related experience (states) as an outcome of interactions between relatively stable characteristics (traits) and continuously changing “objective” context conditions. Against this background, we will present an approach for cross-classified multilevel longitudinal modelling of person-situation interactions in naturalistic educational settings. We illustrated our model with the example of students’ stress experience referring to empirical data that we measured within a multidisciplinary research project (pedagogy, psychology, adolescent medicine). 53 students at a public German vocational school were investigated during 9 lessons. There are up to 38 state measurements per person, resulting in 2,014 measurements in total. Taking into account that states are nested within persons and within situations we applied a cross-classified multilevel model to analyse effects on students’ stress experience. The analysis shows significant person-situation interactions between academic self-concept and classroom demands and between baseline cortisol concentration and classroom demands: the relation between classroom demands and stress experience depends on relatively stable person-related characteristics. A deeper knowledge about the complex interrelations between traits, states, and continuously changing context conditions seems to be essential for a more holistic understanding of learning at school and for the identification of crucial aspects for an evidence-based design and implementation of teaching and learning arrangements.publishe

Atom interferometry with quantized light pulses

The far-field patterns of atoms diffracted from a classical light field or from a quantum one in a photon-number state are identical. On the other hand, diffraction from a field in a coherent state, which shares many properties with classical light, displays a completely different behavior. We show that in contrast to the diffraction patterns, the interference signal of an atom interferometer with light-pulse beam splitters and mirrors in intense coherent states does approach the limit of classical fields. However, low photon numbers reveal the granular structure of light, leading to a reduced visibility since welcher-Weg (which-way) information is encoded into the field. We discuss this effect for a single photon-number state as well as a superposition of two such states

Evaluation of the thermal stability of a low-coherence interferometer for precision surface profilometry

Manufacturing of precise structures in MEMS, semiconductors, optics and other fields requires high standards in manufacturing and quality control. Appropriate surface topography measurement technologies should therefore deliver nm accuracy in the axial dimension under typical industrial conditions. This work shows the characterization of a dispersion-encoded low-coherence interferometer for the purpose of fast and robust surface topography measurements. The key component of the interferometer is an element with known dispersion. This dispersive element delivers a controlled phase variation in relation to the surface height variation which can be detected in the spectral domain. A laboratory setup equipped with a broadband light source (200 - 1100 nm) was established. Experiments have been carried out on a silicon-based standard with height steps of 100 nm under different thermal conditions such as 293.15 K and 303.15 K. Additionally, the stability of the setup was studied over periods of 5 hours (with constant temperature) and 15 hours (with linear increasing temperature). The analyzed data showed that a height measurement of 97:99 +/- 4:9nm for 293.15 K and of 101:43 +/- 3:3nm for 303.15 K was possible. The time-resolved measurements revealed that the developed setup is highly stable against small thermal fluctuations and shows a linear behaviour under increasing thermal load. Calibration data for the mathmatical corrections under different thermal conditions was obtained