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Novel oxygen optode sensor with fast response time: an in-depth characterization and assessment of the HydroFlash O2, applicable for several ocean observing platforms
No full textOptics-based sensors, called optodes, for oxygen are used for routine operations on autonomous instrumentation and profiling platforms with great success. Observations of oxygen gradients with high spatial and temporal resolution become increasingly important, while shortcomings still exist, namely, time constant problems, stability issues, or accuracy levels, that limit leveraging their full scientific and operational potential. Here, we demonstrate the utility of a novel, although currently not commercially available optode, the HydroFlash O2. It was manufactured by Kongsberg Maritime Contros GmbH between 2014 and 2019, and peer-reviewed studies illustrate its use until today. Our work comprises its first integrated characterization with data from 13 HydroFlash O2 optodes assessing oxygen, temperature, salinity and hydrostatic pressure dependence, long-term stability and drift, response time, and air-calibration compatibility. We multi-point calibrated this optode up to a root mean square error (RMSE) of <1 µmol L-1 (mean RMSE: 1.79 ± 0.50 µmol L-1), depending on the fit model type. Our laboratory setup yielded a temperature-dependent response time of τ63% = 3.31 ± 0.58 s, showing no significant difference between a weakly turbulent and turbulent flow, and was at least 50 % faster compared to the two most common optodes in oceanography, i.e., 4330 (Aanderaa) and SBE 63 (Sea-Bird Scientific). We assessed its pressure dependence between 0–5797 dbar, yielding an overall factor of 2.372 ± 0.409 % per 1,000 dbar based on three multi-point calibrated, drift-corrected optodes and five CTD (conductivity - temperature - depth) profiles. Ship-underway, mooring, and CTD-cast applications promise high-quality observations, including fast oxygen level changes. The optode revealed a strong sensitivity of the sensor spot, causing erroneous oxygen measurements when exposed to direct solar irradiation during an Argo float test profile. The drift assessment covering a maximum time span of approximately 3 years is based on two optodes and yielded linear (R2 = 0.98) and exponential (τ = 2.35 ± 0.30 yr, 95 % CI) drift behaviors. The HydroFlash O2 is applicable in low to high oxygen, pressure, and temperature conditions, yet we do not call for additional performance studies unless the manufacturer reactivates its production and reduces sensor spot issues. In an ocean affected by climate change, reliable oxygen optodes will contribute crucial information about the global oxygen and carbon budget, e.g., through observations in the mixed layer, thermocline, or deep sea, and require assessments of existing and promising instrumentation
Meeting Carbon Dioxide Removal Demand in 2030: The Potential of Macroalgae Cultivation and Harvest
No full textA growing number of countries have announced net-zero and net-negative emissions targets, but only a few countries provide incentives for carbon dioxide removal (CDR). We derive estimates of countries' hypothetical demand for CDR in 2030 based on their emissions reduction targets under the Paris Agreement. The aggregated average global demand for CDR in the compliance year 2030 is 1064 MtCO2, 353 MtCO2, and 124 MtCO2 for the low, medium, and high-cost CDR scenarios, respectively. This demand comes exclusively from countries and regions with relatively high GDP per capita, relatively high abatement costs and a limited supply of removals from afforestation. In a scenario with full international emissions trading, CDR demand until 2030 would drop to zero. Thus, the near-term demand for CDR is primarily driven by fragmented, inefficient climate policies. As there will be no functioning system of international emissions trading in the near future, regions with ambitious climate targets and high abatement costs, such as Canada, Japan, the United Kingdom, and the European Union, will already have significant CDR demand in 2030. Marine CDR methods such as macroalgae cultivation and harvesting could make a small but relevant contribution to meeting this demand. However, given the lead time required to achieve reasonable carbon sequestration efficiencies, a forward-looking climate policy would begin to incentivize and develop such methods now, so that areas within countries' exclusive economic zones can be developed for this purpose
Impact of ice sheet dynamics and short-lived climate oscillations on the late Quaternary stratigraphy and paleo-environments of the Gulf of St. Lawrence off Prince Edward Island (Canada
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Effects of ocean alkalinity enhancement on plankton in the Equatorial Pacific
No full textOcean alkalinity enhancement is a potential strategy for gigatonne-scale atmospheric carbon dioxide removal. It uses alkaline substances to convert seawater carbon dioxide into (bi)carbonate, enabling uptake of additional carbon dioxide from the atmosphere. A critical knowledge gap is how ocean alkalinity enhancement could influence marine plankton communities. Here we conducted 19 ship-based experiments in the Equatorial Pacific, examining three prevalent alkaline substances (sodium hydroxide, olivine, and steel slag) and their effects on natural phytoplankton populations under realistic and moderate alkalinity enhancements (16–29 μmol kg−1). Results demonstrate that sodium hydroxide had a negligible effect on phytoplankton while providing predictable alkalinity. Conversely, olivine disrupted plankton, especially cyanobacteria, heterotrophic bacteria, and picoeukaryotes while only providing 0.06 mmol alkalinity g−1 olivine. Steel slag moderately changed phytoplankton communities and fertilized growth while delivering 8 mmol alkalinity g−1 slag. Our study helps to determine which alkaline substance could be suitable for application in the Equatorial Pacific
Wildfires Induced by Volcanic Activity at Stromboli Island during the 2019 Summer through Satellite and Drone Data
No full textActive volcanic areas with intense explosive activity are often affected by secondary hazardous phenomena, such as wildfires triggered by incandescent ballistic material that hits vegetated zones. A testimony of this was the wildfire induced by the 3rd of July 2019 paroxysm at Stromboli Island (Aeolian Archipelago, Italy). This wildfire involved significant portions of territory and caused the loss of a human life. In order to produce an accurate mapping and quantification of the burnt areas during the 2019 summer, the spectral indexes NDVI and NBR were derived from Landsat-8, Sentinel-2 and Pléiades data. The maps of difference in NDVI and NBR, between pre- and post- paroxysm of 3 July, were compared with the burnt areas map obtained by a very high spatial resolution drone imagery. Sentinel-2 dNDVI map results the most accurate and identifies 3.60 km 2 of burnt areas covering 29.5% of the entire island. New investigations on 4 July–5 September period allowed, for the first time, to distinguish 12 outbreaks and map the burnt areas related to the intra-paroxysms volcanic activity (from 4 July to 27 August) and those generated by the second paroxysm (28 August), resulting in 1.76 km 2 and 0.11 km 2 , respectively. Overall, during the 2019 summer, the wildfires induced by volcanic activity burned a total area of 5.47 km 2 (43.5% of the island), affecting mainly the southwest and southeast flanks. Finally, evidences on the wildfire vegetation resilience has arisen, and hazard evaluations indicated that all touristic pathways were involved by the wildfires except the northern one positioned at elevations < 300 m a.s.l
Pattern scaling of simulated vegetation change in northern Africa during glacial cycles
No full textOver the last hundreds of millennia, natural rhythms in Earth's astronomical motions triggered large-scale climate changes and led periodically to humid conditions in much of northern Africa. Known as African Humid Periods (AHPs), such times sustained vast river networks, vegetation, wildlife, and prehistoric settlements. The mechanisms, extent, and timing of the changes remain poorly constrained. Although AHPs along glacial cycles are recognizable in marine sediment records, the related land cover changes are difficult to reconstruct due to the scarcity of proxy data over the continent. Moreover, most available information covers only the latest AHP during the Holocene. Here we use a comprehensive Earth system model to look at additional, much earlier, possible cases of AHPs. We simulate the full last glacial cycle, aiming to reproduce the last four AHPs as seen in available proxies. The simulated AHPs seem in broad agreement with geological records, especially in terms of timing and relative strength. We focus on the simulated vegetation coverage in northern Africa, and we detect a dominant change pattern that seems to scale linearly with known climate forcing variables. We use such scaling to approximate northern African vegetation fractions over the last eight glacial cycles. Although the simple linear estimation is based on a single mode of vegetation variability (that explains about 70 % of the variance), it helps to discuss some broad-scale spatial features that had only been considered for the Holocene AHP. Extending the climate simulation several millennia into the future reveals that such (palaeo-based) pattern scaling breaks when greenhouse gases (GHGs) become a stronger climate change driver
Open science for the ocean. Recommendations from the perspective of marine carbon observations in Germany, Brazil, and beyond
No full textThe ocean plays an essential role in regulating the global climate, absorbing around 25 % of global CO2 emissions. Scientific knowledge of the ocean's capacity as a carbon sink is therefore essential for policy-making at the national and international level. However, the capacity of the existing marine science system to deliver this information at sufficiently high quality, without geographical and temporal gaps, and with equitable contributions by and access for less affluent national science systems, is far from assured. This contribution applies the six guiding principles of Open Science as a yardstick for science in the service of society to assess the current state of marine (carbon) science, pointing out strengths and shortcomings, and deriving specific recommendations for science policy. This contribution results from a three-year interdisciplinary research project with researchers from Brazil and Germany and was discussed within the UN Ocean Decade Program Ocean Acidification Research for Sustainability (OARS) to validate the applicability of insights and recommendations beyond these particular contexts
1. Wochenbericht Reise SO312
No full textForschungsschiff SONNE Reise SO312, BRASS Brothers Volcano Seismic Structure, Auckland, 04.05.2025 - 31.05.2025.
1. Wochenbericht (04. - 11.05.2025
Identification and source provenance of jadeite‐bearing jade axes from Ulucak Höyük, Western Anatolia
No full textThe jades from Ulucak Höyük (İzmir, Turkey) are green‐colored in hand specimen, and combined petrographic, XRD, and whole‐rock analyses indicate that they mainly comprise jadeitic clinopyroxene, characterizing them as jadeite‐bearing jades. Primitive mantle (PM)‐normalized multi‐element patterns reveal two distinct chemical groups. Both groups display depletion in Th and U; however, Group 1 shows a narrower elemental range and marked positive Pb anomaly. The second group, on the other hand, displays a wide elemental range in most elements and strong negative anomalies in Zr and Hf ([Nd/Zr] PM = 1.6–4.2; [Sm/Hf] PM = 1.8–3.5). Regarding REE systematics, both groups are characterized by weak positive slopes ([La/Yb] Ch = 1.7–5.3). However, whereas Group 1 shows coherent LREE‐enriched trends, Group 2 displays flat‐ to LREE‐enriched patterns with a wide range in Eu. When the geochemical features of Ulucak jades are compared with the high‐pressure (HP) metamorphic rocks from Turkey and Greece, the similar multi‐element patterns of Syros eclogites (Greece) to Group 2 Ulucak jades make Syros a possible source area for the Ulucak artefacts. On the other hand, the geochemical resemblance of the Sifnos jadeite‐bearing gneisses to Group 1 Ulucak jades may raise the possibility of this island being another source for the Ulucak jades