ALBERT

Description: The Arctic is greatly impacted by climate change. The increase in air temperature drives the thawing of permafrost and an increase in coastal erosion and river discharge. This leads to a greater input of sediment and organic matter into coastal waters, which substantially impacts the ecosystems by reducing light transmission through the water column and altering the biogeochemistry, but also the subsistence economy of local people, and changes in climate because of the transformation of organic matter into greenhouse gases. Yet, the quantification of suspended sediment in Arctic coastal and nearshore waters remains unsatisfactory due to the absence of dedicated algorithms to resolve the high loads occurring in the close vicinity of the shoreline. In this study we present the Arctic Nearshore Turbidity Algorithm (ANTA), the first reflectance-turbidity relationship specifically targeted towards Arctic nearshore waters that is tuned with in-situ measurements from the nearshore waters of Herschel Island Qikiqtaruk in the western Canadian Arctic. A semi-empirical model was calibrated for several relevant sensors in ocean color remote sensing, including MODIS, Sentinel 3 (OLCI), Landsat 8 (OLI), and Sentinel 2 (MSI), as well as the older Landsat sensors TM and ETM+. The ANTA performed better with Landsat 8 than with Sentinel 2 and Sentinel 3. The application of the ANTA to Sentinel 2 imagery that matches in-situ turbidity samples taken in Adventfjorden, Svalbard, shows transferability to nearshore areas beyond Herschel Island Qikiqtaruk.

Description: Vor etwa 10 Jahren startet die Stadt Potsdam ein ehrgeiziges Programm zur Verringerung der Klimaauswirkungen. Dies beinhaltet die Substitution fossiler Energieträger durch erneuerbare Energien für die Bereitstellung von grüner Fernwärme. Die unterirdische Erkundung des geothermischen Potenzials im Stadtgebiet ist ein wichtiger und anspruchsvoller Bestandteil dieser Strategie. Im Potsdamer Stadtgebiet weisen mehrere tiefe salzwasserführende Aquifere ein Potenzial für die geothermische Nutzung auf, von denen der Aalener Sandstein (Mittlerer Jura) für die weitere Erschließung ausgewählt wurde. Hier wird über die Erkundungsergebnisse, die Dublettenbohrung, die Bewertung der Reservoirformation und die wissenschaftliche Auswertung des Aalener Speichersandsteins berichtet. Die Ergebnisse werden im Hinblick auf die künftige Nutzung in der Fernwärmeversorgung der umliegenden Wohngebäude und auf die Bedeutung für die erweiterte geothermische Feldesentwicklung in Potsdam diskutiert.

Description: Im Weltwärmestrom-Datenbank Projekt wird eine neue Forschungsdateninfrastruktur für terrestrische Wärmestromdaten aufgebaut. Zentraler Aspekt ist die Einhaltung der FAIR und OPEN Datenpolitik. Unter anderem werden webbasierte fachbezogene Explorations- und Analysewerkzeuge angeboten, womit sich Nutzende bereits im Browser einen ersten Überblick über die Daten verschaffen können. Fokus dieser Präsentation ist die technische Umsetzung dieser Explorationswerkzeuge. Das Weltwärmestrom Datenbank Projekt setzt sich als Ziel eine neue Forschungsdateninfrastruktur (Web Portal) für terrestrische Wärmestromdaten zu entwickeln. Über die letzten Jahrzehnte ist eine umfangreiche, globale Datensammlung zum Thema Wärmestrom entstanden, welche über eine zentrale Anlaufstelle im Internet durch Einhaltung der FAIR und OPEN Datenpolitik zur Verfügung gestellt werden soll. Neben den Daten selbst, bietet die Anwendung eine integrierte Literaturdatenbank, einen internen Bereich für registrierte Nutzende, eine API und fachbezogene Explorationswerkzeuge, welche hier detaillierter beschrieben werden. Das Paper beschäftigt sich mit den Funktionalitäten des Web Portals, welche durch eine Anforderungsanalyse erfasst wurden, und beschreibt die für die Umsetzung verwendeten Komponenten. Die Explorationswerkzeuge sind hierbei ein separates Modul, welche in VueJS implementiert wurden und über npm in die Projekthomepage eingebunden werden. Als Input benötigt die Anwendung Punktdaten und eine Schema Datei für die Datenbeschreibung. Zentral für die Datenexploration ist ein auf MapLibre basierender Kartenviewer, der die georeferenzierten Punktdaten auf einer Weltkarte darstellt. Damit soll Nutzen-den bereits im Browser die Möglichkeit geboten werden, sich einen ersten Überblick über die Daten zu verschaffen.

Description: Vertical phytoplankton distribution, temperol fluctuations and sedimentation rates were studied in the central Baltic Sea during the "Baltic Sea Patchiness Experiment 1986" (PEX'86). Vertical particle flux was measured with free sediment traps deployed at 30 and 60m depth for ten April/May 1986 within the PEX grid (20 x 40 nautical drifting days in miles). In the vicinity of one drifting trap water samples were collected in 10-12 depths down to 70m and vertical profiles of temperature, salinity, beam attenuation and light intensity were measured at three hour intervals. Water samples were analyzed for Chl.a, POC and PON content, dry weight and nutrients. Particulate parameters including the activity of 137 Cs were measured in trap samples. Suspended and sedimented particulates were counted under an inverted microscope. Precision and accuracy of the microscopical counts are discussed and confidence limits are calculated for different spec1es and applied counting schemes. Errors in all cases were smaller than the observed in situ variability. A general description of spring blooms in the central Baltic is given and the particular situation of spring 1986 is summarized. Within the station grid of PEX'86 an anticyclonic eddy was observed in which this study was conducted. Here the phytoplankton had reached peak concentrations and mass sedimentation of diatoms was about to start. The bloom was dominated by Thalassiosira levanderi and Chaetoceros spp. (lOµm size). Achnantes taeniata, Mesodinium rubrum, Gonyaulax catenata and an autotrophic Gymnodinium species (26-30µm) were also abundant. Horizontal patchiness and advection caused greater variability in the distribution of phytoplankton biomass blooms as well as temperature and attenuation during the first days than during the latter half of the investigation period. In four different areas within the PEX grid different developed independently. On still smaller time and space scales, the phytoplankton species composition also changed. The degree of patchiness was different for different species. General concepts explaining vertical distribution patterns of phytoplankton by physical and biological mechanisms are discussed. The species-specific distribution of selected diatoms, dinoflagellates and of the funktionally autotrophic ciliate M.rubrum are described. None of the species were homogeneously distributed although no vertical density stratification was observed. Whereas the diatoms and M.rubrum were present within the whole trophogenic layer, the dinoflagellates were only found in the upper 30m. The vertical distribution was different for concentrations were encountered each at species and different maximum depths respectively. Mechanisms affecting species-specific distribution of mobile and non-mobile phytoplankters in isopycnal layers are discussed in light of the particular situation of this study. Diurnal vertical migration is shown for two dinoflagellates and the phytociliate and triggering factors are discussed. All three species migrated upwards during the day and downwards at night. In its detail, however, the migratory behaviour differed between species and also within single populations. Different strategies of adaptation of phytoplankton to changing environmental conditions are suggested: Wheras diatoms adapt to fluctuations of the light climate by physiological adaptations, mobile organisms have the possibility to stay in an isolume layer. The significance of turbulence, of chainformation and of resting stages in the life cycles of phytoplankton is also evaluated. Trap deployments reveiled that only T.levanderi and Chaetoceros spp. sedimented. Their daily relative sedimentation rates (losses as % of standing stocks) increased over time and were species-specific (for T.levanderi max. 50%). Since part of the T.levanderi population was actively dividing (20% of the standing stock was found as paired cells) their suspended concentration decreased slower than that of Chaetoceros spp., although the daily sedimentation of the latter species was only about 30% of the standing stock. T.levanderi occured in chains in the water column but only single cells were found in sedimented material and paired cells were never found in the trap samples. Chaetoceros spores were rare in the water column and only sporadically collected by the sediment traps. The relative sedimentation rate of all other species was less than 5% per day. The settling velocity of the cells was estimated in different independent ways to be about 40-60m/d. This high sinking speed was attributed to aggregate formation. The results indicate that aggregate formation is not only species-specific but also differs between life-stages within one species. Variability of sedimentation rates on a timescale of hours was high, suggesting a diurnal pattern. Sedimentation did not change the vertical distribution patterns, indicating that cells were sinking with similar rates from all depths. The advantages of a Lagrangian sampling strategy (time series measurements 1n the vicinity of a free drifting buoy) for investigating phytoplankton development in time are evaluated and compared to a sampling at a moored station (Eulerian approach). In an environment that exhibits an intense patchiness even at spatial scales of lOOm, as encountered in this study, the influence of advection and patchiness on a time-series with a resolution of hours to days can not be neglected even if the Lagrangian approach is followed. Furthermore, in this study the variability of var1ous parameters measured in an Eulerian mode was not generally higher than that following the Lagrangian one, as one would have expected.

Description: Highlights • δ13C and δ18O profiles increase from exterior to interior until reaching a plateau. • Primary Layer δ13C reflects the δ13C of the Dissolved Inorganic Carbon. • In high pCO2 experiments, δ13C and δ18O closer to equilibrium fields. • Brachiopods grow according to an incremental growth model. Abstract Brachiopod shells are ubiquitous since the Early Cambrian up to now. As they secrete a shell made of low-magnesium calcite, more resistant to diagenesis than biocarbonates richer in Mg, their geochemical signatures are generally considered a powerful tool for paleo-environmental and paleo-climatic reconstructions. However, gaps in knowledge still remain on the underlying controls of the shell chemistry, in particular at a high spatial resolution. In this study, in situ oxygen and carbon isotope measurements by SIMS (Secondary Ion Mass Spectrometry) were performed in brachiopod shells of the cold-temperate water species Magellania venosa, constituted of a primary and a secondary layer. The individual specimens studied here grew under controlled conditions mimicking the natural environment and in experiments under low-pH (high pCO2) and high-temperature conditions. Transversal carbon and oxygen profiles showed a “brachiopod pattern” typical of extant two-layered brachiopods, with the primary layer depleted in 18O and 13C relative to equilibrium and the secondary layer showing a gradual increasing trend until reaching a near-equilibrium plateau. Overall, shells cultured at low pH were found to have δ18O and δ13C values closer to equilibrium when compared to shells from the control experiment. These near-equilibrium values may reflect a decrease in shell precipitation rate, leading to less kinetic effects, and/or a more rapid kinetics for the equilibration between DIC species and water. By close pairing of seawater δ18O and δ13C to that of shell microstructure, our study enables us to derive layer-specific C and O enrichment factors, which show the extent of pH and temperature effects superimposed on the seawater δ18O and DIC δ13C signal inherited. Finally, we show that during brachiopod shell growth, newly precipitated calcite is added to the calcite already existing, thus empirically validating the conceptual accretionary growth model proposed by Ackerly (1989).

Description: Highlights: • Huidobria chilensis is an endemic shrub distributed in the south of the Atacama Desert with a disjunct population at the northern coast. • Population and genetic structure correlate with geographic distance and geological factors. • Rain fall and fog, as well as ground water, must be regarded as important factors for populations at the coast and the Andean valleys, respectively. • A combination of different software tool to analyze GBS data allowed a good understanding of the population structure and genetic diversity. Abstract: Survival in hyperarid deserts is a major challenge for life in general and for plants in particular. The Atacama Desert presents harsh conditions such as limited rainfall, crusted soils, high soil salinity, high altitude, and intense solar radiation. These conditions, together with paleoclimatic variations over the last 10 million years, have influenced the genetic structure and connectivity of plant populations, resulting in a diverse flora with high endemism. However, the diversification of most lineages appears to be relatively recent, in contrast to the reported age of the Atacama Desert and the onset and expansion of hyperarid conditions since the late Oligocene and early Miocene. A prominent exception is Huidobria chilensis (Loasaceae), which is thought to be endemic to the Atacama since the Eocene. However, it is still not understood why this plant has been successful in adapting to the harshening environmental conditions. To investigate its genetic structure in relation to the history of the Atacama Desert, we studied 186 individuals from 11 populations using genotyping-by-sequencing (GBS). A total of nearly 56 k genome-wide single nucleotide polymorphisms (SNPs) were analyzed for population structure and genetic diversity. We identified four genetic clusters corresponding to geographic regions: the coastal region south of Tocopilla, the Cordillera de la Costa around Chañaral, and the Copiapó catchment 1 and 2. Genetic diversity within and between these clusters was analyzed along with rainfall, altitude, and landscape data. Although the genetic data support `isolation by distance’ as a major factor for genetic divergence between populations, the study also reveals the influence of topography on the distribution of H. chilensis and highlights the role of hydrologically connected watersheds and rivers in plant migration and colonization. This shapes the species' evolutionary trajectory and genetic diversity. Understanding these patterns in H chilensis lets one draw general conclusions about adaptation and survival strategies of plants in extreme desert environments such as the Atacama.

Description: Freshwater input from Greenland ice sheet melt has been increasing in the past decades from warming temperatures. To identify the impacts from enhanced meltwater input into the subpolar North Atlantic from 1997 to 2021, we use output from two nearly identical simulations in the eddy-rich model VIKING20X (1/20°) only differing in the freshwater input from Greenland: one with realistic interannually varying runoff increasing in the early 2000s and the other with climatologically (1961–2000) continued runoff. The majority of the additional freshwater remains within the boundary current enhancing the density gradient toward the warm and salty interior waters yielding increased current velocities. The accelerated boundary current shows a tendency to enhanced, upstream shifted eddy shedding into the Labrador Sea interior. Further, the experiments allow to attribute higher stratification and shallower mixed layers southwest of Greenland and deeper mixed layers in the Irminger Sea, particularly in 2015–2018, to the runoff increase in the early 2000s. Key Points The West Greenland Current (WGC) freshens and cools with the observed recent increase in meltwater runoff from Greenland The density gradient across the boundary current intensifies, strengthening the WGC and increasing local eddy formation Enhanced meltwater runoff contributed to an eastward shift in deep convection towards the Irminger Sea (2015–2018) Plain Language Summary Global warming has accelerated the melting of the Greenland ice sheet over the past few decades resulting in enhanced freshwater input into the North Atlantic. The additional freshwater can potentially inhibit deep water formation and have future implications on ocean circulation. To determine the influence from Greenland melt, we compare two high-resolution model experiments all with the same forcing but differing input of Greenland freshwater fluxes from 1997 to 2021. We find that in the experiment with realistically increasing Greenland meltwater, the water becomes fresher and cooler along the continental shelf and boundary of the subpolar gyre. The density difference between the shelf and interior increases with more freshwater, resulting in faster West Greenland Current speeds and enhanced eddy formation. Deeper mixed layers are found in the eastern Irminger Sea, particularly in 2015–2018. From 2009 to 2013, there were shallower mixed layers in the Labrador Sea where less Greenland meltwater was mixed downwards and spread eastward, causing mixed layers to deepen in the Irminger Sea.