Atmospheric CO2 concentrations present a repetitive pattern of gradual decline and rapid increase during the last climate cycles, closely related to temperature and sea level change. During the Last Glacial Maximum (LGM; 23-19 kyr BP), when sea level was ca. 120 m below present, the ocean must have stored additionally about 750 Gt carbon. There is consensus that the Southern Ocean represents a key area governing past and present CO2 change. The latter is not only of high scientific but also of socio-economic and political concern since the Southern Ocean provides the potential for an efficient sink of anthropogenic carbon. However, the sensitivity of this carbon sink to climate-change induced reorganizations in wind patterns, ocean circulation, stratification, sea ice extent and biological production remains under debate. Models were not yet able to reproduce the necessary mechanisms involved, potentially due to a lack of the dynamic representation/resolution of atmospheric and oceanic circulation as well as missing carbon cycling. Data on past Southern Ocean hydrography and productivity are mainly from the Atlantic sector, thus do not adequately document conditions in the Pacific sector. This sector is not only the largest part of the Southern Ocean, but it also represents the main drainage area of the marine-based West Antarctic Ice Sheet (WAIS). In the proposed study we aim to generate paleo-data sets with a newly established proxy method from sediment core transects across the Pacific Southern Ocean. This will enhance the baselines for the understanding and modeling of the Southern Ocean's role in carbon cyling, i.e. ocean/atmosphere CO2 exchange and carbon sequestration. It will also allow insight into the response of the WAIS to past warmer than present conditions. Paired isotope measurements (oxygen, silicon) will be made on purified diatoms and radiolarians to describe glacial/interglacial contrasts in physical and nutrient properties at surface and subsurface water depth. This will be used to test (i) the impact of yet unconsidered dust-borne micronutrient deposition on the glacial South Pacific on shifts of primary productivity, Si-uptake rates and carbon export, (ii) the 'silicic-acid leakage' hypothesis (SALH) and (iii) the formation and extent of surface water stratification. Diatom and radiolarian oxygen isotopes will provide information on the timing of surface ocean salinity anomalies resulting from WAIS melt water. Climate model simulations using a complex coupled atmosphere ocean general circulation model (AOGCM) in combination with a sophisticated ocean biogeochemical model including Si-isotopes will be used for comparison with the paleo records. The analysis will cover spatial as well as temporal variability patterns of Southern Ocean hydrography, nutrient cycling and air-sea CO2-exchange. With the help of the climate model we aim to better separate and statistically analyse the individual impacts of ocean circulation and bio
The Jacupiranga carbonatite (Brazil) was investigated to better understand how modal proportions and mineral chemistry control the fO2 recorded by a natural carbonatite rock. Mineral compositions were determined using SEM-EDS, EPMA-WDS and Raman microspectroscopy building upon detailed petrography. Based on magnetite-ilmenite oxythermobarometry, rock-forming temperatures range from 505 to 732 °C, with a wide span of fO2 values (∆FMQ –1.21 to +4.56). In each sample, ilmenite grains and lamellae are distinguishable, with the latter recording higher temperature–fO2 conditions. Consistently, independently determined homogenization temperatures of apatite-hosted fluid inclusions show a similar range between 550 and 685 °C. From the wall-rock contact toward the carbonatite body, samples exhibit a decrease in the modal abundance of olivine, phlogopite, magnetite, ilmenite, and dolomite, alongside an increase in Mg-calcite. Over the same spatial gradient, temperature, fO2, and the magnesioferrite (in magnetite) and geikielite (in ilmenite) components decrease. During the antiskarn reaction, silica and mafic components (Mg, FeT, Al, and Ti) derived from the ultramafic wall-rock were incorporated into olivine, phlogopite, magnetite-ilmenite, and dolomite. Calcite-rich samples, which were less influenced by the wall-rock, preserved ephemeral alkali components of the carbonatite melts within burbankite. Apatite-hosted fluid inclusions represent coeval fluid modified by antiskarn reactions. Adjacent to equilibrium magnetite-ilmenite pairs, olivine and phlogopite exhibit high mg# (93–97 and 88–95, respectively). Despite the broad span of ∆FMQ values recorded by the oxide pairs, we found only a weak positive correlation between the recorded fO2 and mg#. Consequently, we suggest that the high mg# (>88–90) of carbonatitic olivine is primarily controlled by the low (<0.2) 〖K_D〗_(Fe^(2+)-Mg)^(olivine-carbonatite melt) (Fe2+/Mg exchange partition coefficient between olivine and the carbonatite melt) at crustal conditions. The exceptionally high mg# of olivine and phlogopite, compared to the adjacent dunite cumulates (mg# 84–88), combined with their negligible Ni and Cr contents, indicate an in situ antiskarn process. This study demonstrates that carbonatite systems can be characterized by dynamic redox conditions, spanning the range from Fe3O4 ̶ Fe2O3 to Fe2SiO4 ̶ Fe3O4 ̶ SiO2 during their evolution and emplacement.
Diatoms account for up to 40% of marine primary production and require silicic acid to grow and build their opal shell. On the physiological and ecological level, diatoms are thought to be resistant to, or even benefit from, ocean acidification. Yet, global-scale responses and implications for biogeochemical cycles in the future ocean remain largely unknown. Here we conducted five in situ mesocosm experiments with natural plankton communities in different biomes and find that ocean acidification increases the elemental ratio of silicon (Si) to nitrogen (N) of sinking biogenic matter by 17 ± 6 per cent under pCO2 conditions projected for the year 2100. This shift in Si:N seems to be caused by slower chemical dissolution of silica at decreasing seawater pH. We test this finding with global sediment trap data, which confirm a widespread influence of pH on Si:N in the oceanic water column. Earth system model simulations show that a future pH-driven decrease in silica dissolution of sinking material reduces the availability of silicic acid in the surface ocean, triggering a global decline of diatoms by 13–26 per cent due to ocean acidification by the year 2200. This outcome contrasts sharply with the conclusions of previous experimental studies, thereby illustrating how our current understanding of biological impacts of ocean change can be considerably altered at the global scale through unexpected feedback mechanisms in the Earth system.
The data presented herein originates from a mesocosm study conducted as part of the BMBF CDRmare, Retake project (grant agreement no. 03F0895A), aimed at investigating the ecological ramifications of ocean alkalinity enhancement (OAE). Twelve mesocosms were deployed in Helgoland South Harbor, Germany, and systematically sampled using integrated water samplers over the period spanning from March 12th to April 20th, 2023. Six alkalinity levels under two dilution scenarios were established to differentiate between localized and uniform OAE additions. Alkalinity was increased stepwise to ΔTAmax = 1250 μmol kg-1 (250 μmol TA kg-1 increments) using sodium hydroxide (NaOH) with calcium chloride (CaCl2) to simulate cation release during calcium-based mineral dissolution, causing strong carbonate chemistry perturbations (e.g., pHT > 9.25). The dataset encompasses a spectrum of sediment trap particle flux data, water column biogeochemistry including pigment variables, inorganic nutrients, carbonate chemistry parameters. The study and data set offer insights into impacts of alkalinity enhancement on marine ecosystems and their associated biogeochemistry.
In the context of global change, marine organisms are subjected not only to gradual changes in abiotic parameters, but also to an increasing number of extreme events, such as heatwaves. However, we still know little about the influence of heatwaves on the structure of marine communities, and experimental studies are needed to test the impact of heatwaves alone, and in combination with other environmental drivers. Here, we conducted a mesocosm experiment and applied an integrated multiple driver design to assess the potential impact of heatwaves under ambient and future environmental conditions on natural coastal plankton communities. To represent future environmental conditions, temperature and pH were manipulated based on the Representative Concentration Pathway 8.5 proposed by the IPCC for 2100, and dissolved N:P ratios were increased to simulate the conditions expected in European coastal zones. Throughout the experiment, we measured abiotic conditions as well as the abundance of bacterioplankton, phytoplankton, and microzooplankton.
Das Projekt hat die Entwicklung und Untersuchung eines hinreichend aktiven sowie langzeitstabilen Katalysators zur Oxidation von Methan im Abgas von Biogas-Blockheizkraftwerken (BHKW) zum Ziel. Die Basis dafür bildet pulverförmiges biogenes Silica, welches aus der energetischen Verwertung von biogenen Rest- und Abfallstoffen gewonnen wird. Zusammen mit den aktiven Komponenten wird dies einerseits als Washcoat auf a-Aluminiumoxid Hohlkugeln aufgebracht. Andererseits werden Hohlkugeln aus dem pulverförmigen Katalysator gefertigt. Im Projektverlauf wird die Katalysatorentwicklung ausgehend vom Labormaßstab nach Upscaling auch unter realen Bedingungen abgebildet. Die Untersuchungen sollen unter Praxisbedingungen durchgeführt werden. Dabei soll unter Verwendung einer mobilen Katalysatortestapparatur mit Realabgas und nachfolgend direkt im BHKW-Abgasstrang der Nachweis der Praxistauglichkeit geführt werden.
The 11.8 m-long composite sediment record from the hardwater lake of Sacrower See, located near the city of Potsdam (north-eastern Germany), has been characterised by a range of analytical techniques. These include magnetic susceptibility, chemical parameters (XRF core scanning, CNS analysis, biogenic silica) and stable isotopes (13C, 15N). The chronology covers the entire Holocene and the concluding Lateglacial (Alleröd, Younger Dryas) and is based on age-depth modelling using radiocarbon dates refined by the onset of the local varve chronology in 1870 CE (Lüder et al., 2006) and by the Laacher See Tephra, an isochrone dated to 13,000 cal. BP. It offers a detailed environmental reconstruction providing insights into depositional processes influenced by both natural climatic variations and human activities (Enters et al., 2009; Kirilova et al., 2009). The Lateglacial and Early Holocene are distinguished by the stabilisation of natural landscapes characterised by the presence of pine-birch (Alleröd) and mixed oak forests (Early Holocene). This development was interrupted by the climatic deterioration of the Younger Dryas, which resulted in a destabilisation of vegetation and increased natural soil erosion. It is evident that, for the first time around 5500 cal. BP, anthropogenic forest clearing became a factor, which subsequently led to increasing cultural soil erosion further accelerating during the Bronze Age (3600-3200 cal. BP), the Early Iron Age (2800-2600 cal. BP) and the Middle Ages (900-600 cal. BP). In the course of industrialisation since the 19th century, human impact underwent a transition from the destabilisation of soils to the phenomenon of eutrophication. This transition resulted in the occurrence of hypolimnetic anoxia, accompanied by the formation of carbonaceous varves.
This database expands the Poulton et al., 2018 (doi:10.1594/PANGAEA.888182) database of pelagic calcium carbonate (CP) rate measurements from isotopic tracer uptake in incubated discrete water samples, as discussed in Daniels et al., 2018 (doi:10.5194/essd-10-1859-2018), and accompanies Marsh et al. (in prep.). The database now includes more CP (new data n = 400; complete database n = 3165), net primary production rate (PP) (new data n = 399; complete database n = 3150), total coccolithophore cell counts (new data n = 240; complete database n = 1512), and Emiliania huxleyi cell counts (new data n = 27; complete database n = 612). This expanded database maintains the record of data, including the principal investigator, expedition, OS region, doi reference (where available), collection date and year, sample ID, latitude, longitude, sampling and light depth, and method of measuring CP. We further expand the Poulton et al. (2018) data collection by including ancillary and environmental data, including: optical depth (OD, n = 3165), pHtotal (hereinafter referred to as pHT, n = 398), temperature (n = 1160), salinity (n = 1161), and the concentrations of chlorophyll a (n = 1363), NOx (NO3 or the sum of NO3 + NO2, n = 1161), silicic acid (Si(OH)4, n= 1156), phosphate (PO4, n = 1232), dissolved inorganic carbon (DIC, n = 318), total alkalinity (TA, n = 307), bicarbonate ion concentration (n = 349), and carbonate ion concentration (n = 352). All data was matched to CP, sample bottle identifiers (Niskin bottle numbers), and/or sampling depth values. This global database (81 °N - 64 °S, 132 °E - 174 °W) now covers expeditions and upper ocean measurements (0 - 193 m) from 1989 to 2024. Global in-situ geolocated data spanning time is valuable for modelling, satellite algorithms, and capturing calcium carbonate production in the global ocean. This expanded database, including the environmental, nutrient, chlorophyll a, and carbonate chemistry data, also allows for analysis of factors influencing calcium carbonate production on a global scale. This data amalgamation contributes to understanding the biogeochemistry of the oceans, global carbon cycle, and ocean acidification.
Die Elementkarte stellt die räumliche Verteilung der klassifizierten Gehalte des 90. Perzentils von Siliziumdioxid (in Gew.-%) innerhalb der 184 geochemischen Gesteinseinheiten in Bayern dar. In die Auswertung gehen dabei nur die Daten der ersten (von maximal drei) Lithologien einer geochemischen Gesteinseinheit ein. Für Informationen im Hinblick auf die Auswertung der Daten sowie auf die kartenmäßige Darstellung wird auf die Metadaten der digitalen Lithogeochemischen Karte 1:25 000 von Bayern (dLGK25) verwiesen.
Die Elementkarte stellt die räumliche Verteilung der klassifizierten Gehalte des 50. Perzentils von Siliziumdioxid (in Gew.-%) innerhalb der 184 geochemischen Gesteinseinheiten in Bayern dar. In die Auswertung gehen dabei nur die Daten der ersten (von maximal drei) Lithologien einer geochemischen Gesteinseinheit ein. Für Informationen im Hinblick auf die Auswertung der Daten sowie auf die kartenmäßige Darstellung wird auf die Metadaten der digitalen Lithogeochemischen Karte 1:25 000 von Bayern (dLGK25) verwiesen.
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