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CDRmare Insights: Neues Wissen zur CO2-Entnahme durch die Erhöhung der Alkalinität des Meeres: Die sieben wichtigsten Erkenntnisse aus der RETAKE-Forschung
No full textIm CDRmare-Forschungsverbund RETAKE untersuchen Wissenschaftler*innen verschiedene
Verfahren zur Erhöhung des Säurebindungsvermögens (Alkalinität) des Ozeans daraufhin, ob
sie die natürliche Kohlendioxid-Aufnahme des Meerwassers verstärken und welche Risiken
oder positiven Effekte sie möglicherweise nach sich ziehen. Sieben ihrer relevantesten
Forschungsergebnisse stellen wir an dieser Stelle vor
Assessment of the 11-year solar cycle signals in the middle atmosphere in 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 large ensemble 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 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, and this reliance becomes more complex when the solar cycle amplitude exceeds a certain threshold. 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
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 textQuantifying the mean state and temporal change of seawater age is crucial for understanding the role of ocean circulation and its change in the climate system. One commonly used technique to estimate the water age is the Inverse Gaussian Transit Time Distribution method (IG-TTD), which applies measurements of transient abiotic tracers like chlorofluorocarbon 12 (CFC-12). Here we use an Earth system model to evaluate how accurately the IG-TTD method infers the mean state and temporal change of true water age from 1981 to 2015 in the tropical thermocline (on isopycnal layer σ0=25.5 kg ⋅ m-3). To this end, we compared the mean age of IG-TTD (Γ) derived from simulated CFC-12 with the model "truth", the simulated ideal age. Results show that Γ underestimates the ideal age of 46.0 years by up to 50 %. We suggest that this discrepancy can be attributed to imperfect assumptions about the shapes of transit-time distribution of water parcels in the tropics and the short atmospheric history of CFC-12. As for the temporal change of seawater age, when only one transient tracer (CFC-12) is available, Γ might be an unreliable indicator and may even be of opposite sign to trends of it due to uncertainties of mixing ratio. The disparity between Γ and ideal age temporal trends can be significantly reduced by incorporating an additional abiotic tracer with a different temporal evolution, which we show by constraining Γ with sulfur hexafluoride (SF6) in addition to CFC-12
Management and rhizosphere microbial associations modulate genetic-driven nitrogen fate
No full textHighlights:
• NILs rhizosphere N modulated by microbial association, and management.
• NIL 1 and NIL 2 differed in N content but had similar nitrification inhibition.
• Elevated N triggered BNI capacity of BNI-NILs.
• BNI trait and diazotroph inoculation synergistically enhanced NILs' NUE.
• Archangium plays a crucial role in NIL2 N uptake and availability.
The interplay between plant genotype and nutrient management affects rhizodeposition, which in turn modulates the rhizosphere-microbiome and microbe-mediated functions. Substituting mineral nitrogen (N) with an N-fixing inoculant reduces reliance on N fertilizer while supplying N to crops. We evaluated the effectiveness of integrating maize near-isogenic lines (NIL 1 and NIL 2) with the biological nitrification inhibition (BNI) trait into management practices aimed at optimizing N provisioning. Management strategies included mineral N inputs (0 and 67 kg ha⁻¹) with and without an N-fixing inoculant. Our approach synthesized insights from amplicon sequencing data and evaluated nitrification rates, rhizosphere N content, maize N uptake, and N use efficiency (NUE). Genotypes and management structured prokaryotic communities, while the developmental stages of genotypes further refined both fungal and prokaryotic communities. The N-fixing inoculant increased N availability, triggering the BNI capacity without increasing the nitrification rate. This was reflected in lower NO₃⁻ and higher NH₄⁺ levels in BNI-NIL leachate compared to B73, suggesting improved N retention. NIL2, characterized by distinct fungal biomarkers, exhibited higher N content (72.3 kg ha⁻¹) and superior NUE compared to NIL1 (65.0 kg ha⁻¹). NIL2’s enhanced N uptake was associated with a robust microbial network, featuring Archangium (prokaryote) and Trichoderma (eukaryote) as keystone taxa. Notably, Archangium was linked to rhizosphere N dynamics Synergizing BNI with diazotroph inoculants reduces N fertilizer reliance and increases maize N supply for sustainable agroecosystems
First findings of late pleistocene tephras of Avachinsky volcano (Southern Kamchatka) (in Russian)
No full textIn the Nikolaevka-1 quarry (53 degrees 05 ' 17.45 '' N, 158 degrees 21 ' 26.28 '' E), in lake sediments formed about 100 000 years ago, we found buried ash layers. Geochemical analysis of the volcanic glass from these ash layers allowed, for the first time, the identification of three Late Pleistocene tephras from the Avachinsky volcano labeled 21/23, 21/4, and 21/10. In addition, we found a tephra labeled DS7 from one of the centers of the Karymsky volcanic area, dated to similar to 107 ka. The stratigraphic position of Avachinsky ash relative to the DS7 tephra suggests that tephra 21/10 is slightly younger than 100 ka, whereas the other two (21/4 and 21/23) are older than 100 ka. Estimates of the minimum volumes of material ejected during these eruptions make them comparable to most historical eruptive events at this volcano, and eruption 21/4 to the 1945 eruption - the most powerful eruption of the 20th century
Varying organic content in fish otoliths: Effects on SIMS-based δ18O measurements and possible corrections
No full textVarying organic contents in otoliths have complex and sometimes counterintuitive effects on intra-otolith δ18O measurements. This is often addressed by roasting otoliths or applying fixed corrections, however, the underlying chemical and physiological mechanisms involved are poorly understood and have not been tested in a quantitative manner, potentially rendering such corrections unreliable. Using high-resolution secondary ion mass spectrometry (SIMS) measurements of δ18O values paired with OH/16O ion ratios as organic proxy, we derived quantitative relationships of these measurements over the entire life of a large sample of northern pike (Esox lucius) otoliths from freshwater and brackish habitats. We assessed OH/16O ion count ratio as an organic tracer, and estimated its relationship with δ18O determinations. We developed a pointwise correction approach that accounted for variations in otolith organic contents. OH/16O ion ratio profiles agreed with other organic proxies, confirming them as reliable tracer of organic content. We detected an inverse relationship between δ18O values and OH/16O ion ratio, with elevated OH/16O ion ratios near otolith cores. OH/16O ratios decreased with distance to the core. Pairwise corrections for the effect of OH/16O ratios on δ18O values resulted in a mean offset between uncorrected and corrected values of 0.52 ‰, suggesting an approximately 2°C bias towards warmer temperature if uncorrected data were to be used for δ18O thermometry. Simultaneous determination on organic- and inorganic-bound oxygen resulted in a negative offset of δ18O, which varies with the life history of individual fish. Varying offsets in δ18O values within individual life histories could be accounted for using our correction. We recommend future SIMS-based δ18O thermometry studies to estimate the local organic content to assess whether correction is warranted. We further offer more general recommendations on how future studies may assess whether corrections for organics are necessary
The major role of riverine outflows in shaping the current and future habitats of Harmful Algal Blooms: the case of the North Sea
No full textThis study investigates the extension of the potential habitat of Harmful Algal Blooms (HABs) in the North Sea using observational data and model experiments under current and future climate scenarios. We assess the combined effects of temperature, salinity, and nutrient availability, particularly the nitrogen-to-phosphorus ratio, on HABs in the region. Climate change projections indicate a decrease in salinity concomitant with an increase in surface temperature, potentially leading to an offshore extension of HAB habitat. Reducing nitrogen and phosphorus loads in rivers differentially affects dissolved inorganic nitrogen (DIN) and phosphorus (DIP) levels, with DIN being more sensitive to load reduction, thereby constraining HAB habitat extension. We underscore the importance of considering both physical and biogeochemical factors in assessing HAB habitat dynamics and the potential impacts of climate change and nutrient reduction measures on HAB expansion in the North Sea. These findings have significant implications for environmental policy and management
Carbon dioxide storage in geological formations below the German North Sea - Version 4
No full textFactsheet:
Carbon dioxide storage in the deep subsurface of the North Sea is technically feasible and has been practiced for decades beneath Norwegian waters. Under the German North Sea, there are rock formations in which large quantities of carbon dioxide could presumably be stored, too. However, important questions remain, which are to be addressed and answered in the CDRmare research mission – with the aim of enabling a demonstration project for carbon dioxide storage in the geological subsurface of the German North Sea
Northern Scandinavian mountains supported by a low-grade eclogitic crustal keel
No full textPlate tectonics predicts that mountain ranges form by tectono-magmatic processes at plate boundaries, but high topography is often observed along passive margins far from any plate boundary. The high topography of the Scandes range at the Atlantic coast of Fennoscandia is traditionally assumed isostatically supported by variation in crustal density and thickness. Here we demonstrate, by our Silverroad seismic profile, that the constantly ~44 km thick crust instead is homogenous above the Moho, and Pn-velocity abruptly change from 7.6 km s−1 below the Scandes to >8.2 km s−1 below the Proterozoic shield. By modelling gravity anomalies and topography, based on the seismic model, we demonstrate that this change corresponds to an increase in metamorphic eclogitic grade from 35% below the high-topography Scandes to 70% below the low-topography shield. The sharp contrast between the low-grade, reduced-density and the high-grade, high-density eclogitic bodies below the uniform seismological Moho explains the enigmatic topography of the mountain range without a crustal root
