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Air-sea gas exchange measurements helped derive in-situ organic and inorganic carbon fixation in response to Ocean Alkalinity Enhancement in a temperate plankton community
No full textOcean Alkalinity Enhancement (OAE) is a carbon dioxide removal strategy that aims to chemically sequester atmospheric CO2 in the ocean while potentially alleviating localized effects of ocean acidification. Depending on the implementation approach, OAE can considerably alter seawater carbonate chemistry, resulting in reduced CO2 partial pressures (pCO2) and high pH. To investigate the effects of OAE on biogeochemical processes and organisms under close-to-natural conditions, a large-scale mesocosm experiment was conducted in the temperate fjord ecosystem near Bergen, Norway during late spring. A non-CO2-equilibrated approach was chosen, simulating OAE with calcium- and silicon-based minerals. A gradient of five OAE levels was achieved by increasing total alkalinity (TA) by 0–600 µmol kg-1. The added TA remained relatively stable over the 47-day experimental period and the measured CO2 gas exchange rate was comparable to what would be expected for large oceanic regions. We estimated that full equilibration (95 %) for a ∆TA of 600 µmol kg-1 would take ~1050 days. Furthermore, there were a number of mineral-type and pCO2/pH effects, with cumulative coccolithophore calcification showing an optimum curve response to decreasing pCO2, consistent with findings from single-species laboratory cultures, while no mineral-type effect was observed. In contrast, in-situ net community production was higher in the silicate treatments but there was no pCO2 effect. Zooplankton respiration, estimated from in-situ net community production and in-vitro net community production incubations, was lower for the silicate treatments and negatively correlated with pCO2. These complex findings suggest both direct and indirect effects of mineral type and OAE level and provide a valuable foundation for designing future OAE field trials
Antarctic Intermediate Water Variability in the South Atlantic Over the Last 600,000 years
No full textDespite its importance as a key component of the Atlantic Meridional Overturning Circulation, the long-term variability of Antarctic Intermediate Water (AAIW) remains poorly constrained due to the lack of adequate proxy records. To address this, we present the longest reconstruction of AAIW variability in the South Atlantic using authigenic (foraminifera and sediment leachates) neodymium (Nd) isotopes complemented with a benthic foraminiferal δ13C record from Deep Sea Drilling Project (DSDP) Site 516 on the Rio Grande Rise from 1,313 m water depth within the core of AAIW today. By comparison of DSDP Site 516 detrital and authigenic Nd isotope records with those from neighboring DSDP Site 517 bathed in North Atlantic Deep Water (NADW), we demonstrate that the Nd isotope signals obtained from mixed planktonic foraminifera from this open ocean pelagic setting reliably recorded past intermediate water mass mixing. The authigenic Nd isotope record and the benthic δ13C data show consistent glacial-interglacial variability over the last 600 kyr. More radiogenic Nd isotope values and lower benthic δ13C signatures during glacial periods point to the reduced admixture of unradiogenic NADW into Circumpolar Deep Water during glacials. The glacial-interglacial variability seen in our Nd isotope record is consistent with other AAIW records from the Southeast Atlantic, Indian and the Southwest Pacific Oceans suggesting an essentially uniform southern-sourced AAIW signal transported northwards at intermediate depth through the three major Ocean basins. The new record shows AAIW shifted to more radiogenic values during the MIS 14 glacial in contrast to Nd isotope records of NADW
Insights into mesoscale eddy dynamics: a three-dimensional perspective on potential density anomalies
No full textMesoscale eddies are fundamental components of the global ocean circulation. In situ observations and Lagrangian analyses have shown that some eddies are materially coherent, transporting within their cores a water mass distinct from the surrounding environment. Additionally, laboratory experiments indicate that eddies locally deflect isopycnal surfaces in accordance with thermal wind balance, regardless of whether they trap a water mass. These two mechanisms drive spiciness mode anomalies and heaving mode anomalies, respectively, associated with mesoscale eddies. In this study, we quantitatively assess the physical processes governing mesoscale eddy dynamics by introducing a novel theoretical decomposition of the potential density field within eddy cores that accounts for both effects. We apply this framework to six anticyclonic eddies sampled during the EUREC4A-OA, METEOR 124, and Physindien 2011 oceanographic campaigns. Unlike previous studies, we evaluate not only the amplitude of these anomalies but also their vertical structure. Our results confirm that heaving mode anomalies dominate the total density anomaly. However, contrary to previous assumptions, we demonstrate that their vertical structure is dictated by the local background stratification and often exhibits a nearly Gaussian profile. In contrast, spiciness anomalies provide only a second-order contribution to the total potential density anomaly, making them negligible for most dynamical processes governing mesoscale eddies. By bridging experimental results with observational eddy datasets, our study refines the understanding of the mesoscale eddy vertical structure, providing a more accurate predictive framework for their shape and role in the transport of oceanic properties
Cruise Report R/V Littorina, Cruise No. L25-16 Investigation of circular structures near Sønderborg (Denmark)
No full textDates of Cruise: 10.11.2025 – 13.11.2025
Areas of Research: Marine Geophysics, Geology, Archaeology
Port Calls: Kiel – Sønderborg (DK) – Kiel
Institutes: Institute of Geoscience (CAU), Institute for Baltic Sea Research Warnemünde (IOW), Langelands Museum (Denmark) Universtität Rostock (URos)
Chief Scientist: Dr. Jens Schneider von Deimling
Number of Scientists: 10
Projects: SEASCAP
Earth system climate-carbon response to pulses and continuous negative emissions
No full textCarbon Dioxide Removal (CDR) encompasses a wide range of anthropogenic activities to remove CO2 from the atmosphere to reduce its climate warming effect. The implementation of CDR technologies is necessary to achieve global climate-temperature goals. Commonly, negative emissions effects on the climate and carbon cycle have been thought to be nearly equal but opposite to those of positive emissions. This assumption was challenged recently, with results showing an asymmetric response of the Earth system to positive and negative emissions over a 1000-year timescale (Zickfeld et al. 2021). Positive emissions showed a more potent effect at increasing atmospheric CO2 concentration than negative emissions at reducing it. Yet, positive emissions had a less potent effect at increasing atmospheric temperature than negative emissions at decreasing it. Here we aim to re-evaluate the asymmetric climate-carbon response of the Earth system to negative emissions in a shorter-immediate timescale using an emissions-driven approach. Starting from a preindustrial spin-up the University of Victoria Earth system climate model (version 2.10) was forced with 10 PgC/yr emitted to the atmosphere until the cumulative carbon emission budget reached 1000 PgC (esmflat-10-1000PgC). Thereafter, pulses of positive and negative CO2 emissions ranging from ±50 to ±750 PgC were emitted or removed instantly. To assess the transient climate response to cumulative negative CO2 emissions a -10 PgC/yr was carried. Finally, a zero emission simulation from pre-industrial served as a control. Our results show agreement with the temperature and carbon asymmetry shown in previous studies. However, we only observed relative large differences with regards to atmospheric temperature and carbon redistribution in the first 40 years of simulations. Later responses (>50 years) show much small differences between the mirrored atmospheric CO2 concentrations and temperatures to negative and positive emissions. The transient climate response to cumulative CO2 emissions and cumulative CO2 removal was found to be 1.81 and -1.79 K/EgC, respectively. These findings suggest that, while temperature asymmetry may remain undetectable in the first century of negative emissions deployment, carbon cycle dynamics could deviate significantly from symmetric assumptions. This highlights the importance of accounting for asymmetric carbon redistribution when designing negative emission strategies
Assessment of the 11-year solar cycle signals in the middle atmosphere during boreal winter with multiple-model ensemble simulations
No full textTo better understand possible reasons for the diverse modeling results and large discrepancies of the detected solar fingerprints, we took one step back and assessed the "initial" solar signals in the middle atmosphere based on a set of ensemble historical simulations with multiple climate models FOCI, EMAC, and MPI-ESM-HR. Consistent with previous work, we find that the 11-year solar cycle signals in the short wave heating rate (SWHR) and ozone anomalies are robust and statistically significant in all three models. These initial solar cycle signals in the SWHR, ozone, and temperature anomalies are sensitive to the strength of the solar forcing. Correlation coefficients of the solar cycle with the SWHR, ozone, and temperature anomalies linearly increase along with the enhancement of the solar cycle amplitude. This reliance becomes more complex when the solar cycle amplitude indicated by the standard deviation of the December-January-February mean F10.7 is larger than 40. In addition, the cold bias in the tropical stratopause of EMAC dampens the subsequent results of the initial solar signal. The warm pole bias in MPI-ESM-HR leads to a weak polar night jet (PNJ), which may limit the top-down propagation of the initial solar signal. Although FOCI simulated a so-called top-down response as revealed in previous studies in a period with large solar cycle amplitudes, its warm bias in the tropical upper stratosphere results in a positive bias in PNJ and can lead to a "reversed" response in some extreme cases. We suggest a careful interpretation of the single model result and further re-examination of the solar signal based on more climate models
3. Wochenbericht SO316 CAVA Tephras
No full textFS SONNE Ausfahrt SO316 - CAVA Tephras,
21.11. – 26.12.2025, Balboa (Panama) – San Diego (USA
Multidisciplinary Teaching Cruise MNF-bioc-301 Plankton Along the Baltic Sea Salinity Gradient AL601
No full text29.8.2023 – 9.9.2023,
Kiel (Germany) – Kiel (Germany)
BiOc SeaPrac22-2
Supplementary Data to "Dual-tracer constraints on the Inverse-Gaussian Transit-time distribution improve the estimation of watermass ages and their temporal trends in the tropical thermocline"
No full textNative S from seafloor hydrothermal sites: Messenger for magmatic degassing of metals into submarine hydrothermal systems
No full textNative S-0 precipitates in form of little chimneys, submarine crater lakes, stains and crusts on sediments, and as crack and vesicle fillings in rocks at the seafloor hydrothermal sites. Unlike the biogenic native S-0 precipitated in anoxic and euxinic seafloor environment, the seafloor hydrothermal native S-0 is a result of either disproportionation of magmatic SO2 (delta S-34(sample) delta S-34(terrestrial mantle sulfide)). Using it as a proxy for magmatic volatile flux we found out that it carried isotopic signal for magmatic degassing of Zn (delta Zn-66(sample) < delta Zn-66(bulk silicate Earth)). Thus, the seafloor hydrothermal native S-0 provides new isotopic evidence for direct magmatic contribution of metals to seafloor hydrothermal systems and appears to be a messenger for magmatic volatile metal discharge in the ocean