Search

Polar research is an interdisciplinary and multi-faceted field of research ranging from history to geology and geophysics to social sciences and education. Thus, several different universities and institutions within Germany participate in polar research. The seminar series POLARSTUNDE, organized by the German Society for Polar Research (Deutsche Gesellschaft für Polarforschung) and the German National Committee of the Association of Polar Early Career Scientists (APECS Germany) regularly features different topics of German polar research. Although initially a "pandemic solution", the seminar series has established itself as a valuable and highly successful part of the German polar research landscape. The seminar series was held in German and was aimed at both scientists and the general public. This article addresses the first season of POLARSTUNDE and provides (1) comprehensive summaries of the talks and (2) insight into the planning and execution from an organizational point of view.

Studies of the upper 447 m of the DEEP site sediment succession from central Lake Ohrid, Balkan Peninsula, North Macedonia and Albania provided important insights into the regional climate history and evolutionary dynamics since permanent lacustrine conditions established at 1.36 million years ago (Ma). This paper focuses on the entire 584-m-long DEEP sediment succession and a comparison to a 197-m-long sediment succession from the Pestani site ~5 km to the east in the lake, where drilling ended close to the bedrock, to unravel the earliest history of Lake Ohrid and its basin development. 26Al/10Be dating of clasts from the base of the DEEP sediment succession implies that the sedimentation in the modern basin started at c. 2 Ma. Geophysical, sedimentological and micropalaeontological data allow for chronological information to be transposed from the DEEP to the Pestani succession. Fluvial conditions, slack water conditions, peat formation and/or complete desiccation prevailed at the DEEP and Pestani sites until 1.36 and 1.21 Ma, respectively, before a larger lake extended over both sites. Activation of karst aquifers to the east probably by tectonic activity and a potential existence of neighbouring Lake Prespa supported filling of Lake Ohrid. The lake deepened gradually, with a relatively constant vertical displacement rate of ~0.2 mm a−1 between the central and the eastern lateral basin and with greater water depth presumably during interglacial periods. Although the dynamic environment characterized by local processes and the fragmentary chronology of the basal sediment successions from both sites hamper palaeoclimatic significance prior to the existence of a larger lake, the new data provide an unprecedented and detailed picture of the geodynamic evolution of the basin and lake that is Europe’s presumed oldest extant freshwater lake.

Gezeitenbewegungen auf Eisschelfen werden schon seit den 90er-Jahren mit globalen Navigationssatellitensystemen (GNSS) gemessen. Kürzlich wurden an der Neumayer-Station III auf dem Ekström-Eisschelf mit Seismologie und GNSS unerwartet große drittel- und vierteltägige Gezeitensignale in der horizontalen Bewegung beobachtet. Es wurde die Hypothese aufgestellt, dass diese hochfrequenten Gezeitensignale ihren Ursprung an der Aufsetzzone des Ekström-Eisschelfs haben. Deshalb wurden im Laufe der letzten zwei Jahre weitere seismologische und GNSS-Messungen an der Aufsetzzone durchgeführt. Diese Arbeit verfolgt die Forschungsfragen, mit welcher Genauigkeit epochenweise geschätzte Koordinaten der GNSS-Messungen an der Aufsetzzone bestimmt werden können und welche Gezeitensignale signifikant auf geophysikalische oder glaziologische Prozesse zurückzuführen sind. Dafür wurden sowohl mit den Grundgestein verbundene GNSS-Stationen als auch die GNSS-Stationen an der Aufsetzzone mit der Bernese GNSS Software ausgewertet. Die stationären mit dem Grundgestein verbundenen GNSS-Stationen wurden dabei zur Abschätzung der erreichbaren Genauigkeit genutzt und als Referenzstation für die differentielle GNSS-Auswertung verwendet. Die Koordinatenzeitreihen wurden anschließend im Zeit- sowie Frequenzbereich analysiert. Die Ergebnisse zeigen, dass mit differentiellem GNSS kinematische Koordinaten in Nordrichtung auf 6,0 mm, in Ostrichtung auf 5,4 mm und vertikal auf 17,7 mm genau bestimmt werden können. Dabei handelt es sich aber um eine Genauigkeit zu einem zeitlichen Mittel. Die absolute Position wird eventuell weniger genau bestimmt. Die Signifikanz geophysikalischer und glaziologischer Signale ist abhängig vom Messrauschen in den Zeitreihen. Die dadurch entstehenden Unsicherheiten konnten in dieser Arbeit akkurat abgeschätzt werden. Zusätzlich wird die Signifikanz einzelner Signale stark von Artefakten aus den GNSS-Orbits beeinflusst. Konkret betrifft das Frequenzen, die nahe den ganzzahli

This paper was initiated by a multidisciplinary Topic Workshop in the frame of the Deutsche Forschungsgemeinschaft Priority Program 1158 “Antarctic Research with Comparative Investigations in Arctic Ice Areas”, and hence it represents only the national view without claiming to be complete but is intended to provide awareness and suggestions for the current discussion on so-called big data in many scientific fields. The importance of the polar regions and their essential role for the Earth system are both undoubtedly recognized. However, dramatic changes in the climate and environment have been observed first in the Arctic and later in Antarctica over the past few decades. While important data have been collected and observation networks have been built in Antarctica and the Southern Ocean, this is a relatively data-scarce region due to the challenges of remote data acquisition, expensive labor, and harsh environmental conditions. There are many approaches crossing multiple scientific disciplines to better understand Antarctic processes; to evaluate ongoing climatic and environmental changes and their manifold ecological, physical, chemical, and geological consequences; and to make (improved) predictions. Together, these approaches generate very large, multivariate data sets, which can be broadly classified as “Antarctic big data”. For these large data sets, there is a pressing need for improved data acquisition, curation, integration, service, and application to support fundamental scientific research. Based on deficiencies in crossing disciplines and to attract further interest in big data in Antarctic sciences, this article will (i) describe and evaluate the current status of big data in various Antarctic-related scientific disciplines, (ii) identify current gaps, (iii) and provide solutions to fill these gaps. How to cite. Graiff, A., Braun, M., Driemel, A., Ebbing, J., Grossart, H.-P., Harder, T., Hoffman, J. I., Koch, B., Leese, F., Piontek, J., Scheinert, M.

Geodynamic processes in Antarctica such as glacial isostatic adjustment (GIA) and post-seismic deformation are measured by geo-detic observations such as global navigation satellite systems (GNSS) and satellite gravimetry. GNSS measurements have comprised both continuous measurements and episodic measurements since the mid-1990s. The estimated velocities typically reach an accuracy of 1 mm a−1 for horizontal velocities and 2 mm a−1 for vertical velocities. However, the elastic deformation due to present-day ice-load change needs to be considered accordingly. Space gravimetry derives mass changes from small variations in the inter-satellite distance of a pair of satellites, starting with the GRACE (Gravity Recovery and Climate Experiment) satellite mission in 2002 and continuing with the GRACE-FO (GRACE Follow-On) mission launched in 2018. The spatial resolution of the measurements is low (about 300 km) but the measurement error is homogeneous across Ant-arctica. The estimated trends contain signals from ice-mass change, and local and global GIA signals. To combine the strengths of the individual datasets, statistical combinations of GNSS, GRACE and satellite altimetry data have been developed. These combinations rely on realistic error estimates and assumptions of snow density. Nevertheless, they capture signals that are missing from geodynamic forward models such as the large uplift in the Amundsen Sea sector caused by a low-viscous response to century-scale ice-mass changes., Physical and Space Geodesy, Astrodynamics & Space Missions

Lake Vostok, East Antarctica, represents an extensive water surface at the base of the ice sheet. Snow, ice and atmospheric pressure loads applied anywhere within the lake area produce a hydrostatic response, involving deformations of the ice surface, ice–water interface and particle horizons. A modelling scheme is developed to derive height changes of these surfaces for a given load pattern. It is applied to a series of load scenarios, and predictions based on load fields derived from a regional climate model are compared to observational datasets. Our results show that surface height changes due to snow-buildup anomalies are damped over the lake area, reducing the spatial standard deviation by one-third. The response to air pressure variations, in turn, adds surface height variability. Atmospheric pressure loads may produce height changes of up to 4 cm at daily resolution, but decay rapidly with integration time. The hydrostatic load response has no significant impact neither on ICESat laser campaign biases determined over the lake area nor on vertical particle movements derived from GNSS observations.

The Arctic is warming two times faster than the global mean, and a phenomenon known as the ‘Atlantification of the Arctic’ via the Fram Strait is having growing influences on both biological and physical processes in the region. Changes to community composition and function are already underway and these environmental changes will continue to rapidly alter Arctic ecosystems. Greater understanding of how this impacting local marine biodiversity is crucial for formulating accurate predictions of future Arctic marine ecosystems and management decisions. Gelatinous zooplankton (GZP) is a highly diverse group of taxa, including cnidarians, ctenophores and tunicates. Very little is currently known about GZP ecology, particularly in the Arctic Ocean, and even less about how they are being impacted by climate-related changes. Not only are they often actively left out of zooplankton surveys, but GZP are notoriously difficult to catch in good condition because their fragile bodies are easily destroyed by traditional sampling methods. These challenges contribute to GZP taxa regularly being underestimated in biodiversity, distribution and abundance, which has led to a lack of reliable and comprehensive baseline data available, especially in the Arctic. The aim of this study is to apply non-invasive environmental DNA (eDNA) metabarcoding methods to investigate GZP biodiversity and distribution across the Fram Strait. COI mitochondrial and 18s rRNA amplicons from water and sediment samples will be sequenced with Next Generation Sequencing (NGS) and validated with depth-stratified net-catch data. Net-caught specimens will be barcoded where possible, to complement existing reference databases. Oceanographic data will then be incorporated in order to form a holistic baseline dataset of GZP biodiversity across the region. Such data would be a valuable contribution to future research into the deviations in Arctic GZP biodiversity, community composition and distribution over time, as a

Gelatinous zooplankton (GZP) comprising ctenophores, cnidarians and tunicates, gained more interest in recent years. During favorable conditions GZP is known to rapidly increase in biomass and several dominant species are able to exploit the zooplankton standing stock. It is assumed that GZP will increase in biomass with the ongoing warming and Atlantification of the Arctic Ocean. Hence, it is crucial to gain insights into the role of gelatinous zooplankton in the current and future Arctic marine food web . This study targets both the benthic and pelagic components of the Arctic marine food web . First, we aim to determine the role of so-called “jellyfalls”, or jelly carcasses on the seafloor, as a food source for the benthic community. To do so, we investigate the stomach content of benthic scavenging amphipods in Kongsfjorden sampled during Polar night with DNA metabarcoding. By doing so,. Second, we look at the role of jellyfish as predators in the pelagic system. We focus on a widely distributed boreal-Arctic hydrozoan species, Aglantha digitale, which is also assumed to be a climate-change winner in an “Atlantified” Arctic. Its feeding ecology is scarcely studied, in particular in the Arctic region? This jellyfish is believed to feed on a wide range of zooplankton including copepods. Due to its high abundances in the Arctic regions, both in summer and in winter, it is crucial to investigate spatio-temporal patterns in its diet. Hence, we use DNA metabarcoding of Aglantha’s stomach content to reveal its prey composition in different seasons and regions in order to better predict its future role in an ice-free and Atlantified Arctic.

Rapid warming in the Arctic is drastically impacting marine ecosystems, affecting pelagic communities and food web structure. Themisto amphipods are dominant in the Arctic zooplankton community and represent a key link between secondary producers and higher trophic levels. In the Arctic seas, two coexisting species are found in high biomass: Themisto libellula, considered a true Arctic species and Themisto abyssorum, a sub-Arctic, boreal species. Many aspects of the ecology and genetic structure of these two species are not well studied, despite their importance in the food web. First, we tested both species for levels of genetic diversity and then assessed their diet spectrum with molecular methods, with a regional focus on the Greenland shelf, Fram Strait and Svalbard. Spatial genetic structure was evaluated using the mitochondrial cytochrome c oxidase subunit 1 gene (COI). Our results revealed strikingly different levels of genetic diversity: low levels in T. libellula contrasted with higher diversity in T. abyssorum. No spatial genetic structure was found, and both species exhibited high levels of connectivity and evidence of historic demographic expansion. The observed low genetic diversity, in combination with cold adaptations, could cause T. libellula to be more susceptible to the warming Arctic. In contrast, high diversity likely increases adaptive potential in T. abyssorum. In order to comprehensively characterize the prey spectrum of both Themisto species, we also applied DNA metabarcoding, also using COI, on gut contents. Both species showed a regional variation in prey spectrum. T. abyssorum’s diet showed a clear dominance of reads identified as chaetognath species, whereas T. libellula had a broader prey spectrum, including ice-associated taxa such as polar cod. Calanoid copepods did not appear as important as prey as assumed from previous (morphological) studies. Several previously overlooked jellyfish taxa were found in the stomachs of both species. T

The Southern Ocean, in particular the southwest Atlantic sector, is experiencing rapid environmental changes. A long-term trend of density changes of key pelagic species has been noted over the last decades: Antarctic krill populations are declining whilst salps are on the rise and shifting their distribution poleward. A similar poleward expansion is anticipated for a third key player, the hyperiid amphipod crustacean Themisto gaudichaudii, leading to an increasing overlap of the distributions of these three species. Due to major knowledge gaps in the ecology, and genetic connectivity of T. gaudichaudii, the likelihood of this shift and its consequences for the pelagic food web structure remain largely unexplored. In this context, Themisto’s genetic and trophic connectivity as well as thermal response were investigated with state-of-the-art molecular methods. Phylogeographic analyses showed genetic homogeneity between localities in the Southern Ocean and Atlantic waters combined with high degree of phenotypic plasticity enabling different lineages to thrive in regions further south. Diet analyses using DNA metabarcoding were applied to characterize regional variation in diet. These analyses showed a diet predominantly composed of krill, in particular in the Antarctic Peninsula region, showing that Themisto’s poleward range expansion can further impact the already declining krill stocks. It also unexpectedly revealed ctenophores to be an important prey, despite their reputation as “trophic dead-end”. Transcriptome analyses were used to study the thermal response of Themisto individuals from different geographic populations that were experimentally exposed to heat and cold treatments. The analysis of differentially expressed genes showed that genetic lineages differ in thermal tolerances. It also revealed a wide range of molecular mechanisms in Themisto amphipods to cope with thermal stress. These findings contribute to better predict the impact of climate-driven rang