Alfred Wegener Institute for Polar and Marine Research
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Spatial and temporal changes in surface mass balance derived from airborne radio sounding for the plateau area in Dronning Maud Land
Get PDFContrary to the rest of the Antarctic ice sheet, East Antarctica currently gains mass due to an increase in snow accumulation over the last decades. How or if this increase is linked to anthropogenic warming is not yet clear and requires better understanding of the surface mass balance history over the last centuries, and also the dependency of snow accumulation with the local surface slopes across different spatial scales.
Here, we present a novel airborne dataset using the multichannel ultra-wideband radar system from the Alfred Wegener Institute in Germany with a decadal vertical resolution for the plateau area in Dronning Maud Land. We assess the spatial and temporal variability of surface mass balance and snow accumulation for the past centuries for an area of ~200,000 km2. With this contribution, we aim to (1) show the potential to use ultra-wideband radar systems to reconstruct the recent surface mass balance and accumulation rates in low-accumulation regions, (2) present information on large spatial scales, and (3) discuss potential overlap of interests and/or data in this and/or other areas on the plateau of East Antarctica
Adaptive cycles of a phyto-zooplankton community under human pressure
Get PDFHuman activities, such as global warming and nutrient pollution, are posing significant threats to the ecological interactions and biodiversity in aquatic environments [1]. The German Bight, a highly dynamic coastal region of the North Sea, has been subject to considerable warming and nutrient fluctuations over recent decades. These changes have had profound impacts on the plankton communities in this area, leading to a swift reorganization of both phyto- [2] and zooplankton functional structures [3].
While the effects of these changes on individual phyto- and zooplankton levels have been well-documented, our understanding of how plankton interactions respond to these environmental stressors remains limited. In this study, we hypothesize that the synergy of warming and nutrient limitation will alter plankton network interactions, resulting in a shift towards consumers being controlled by resources.
We approach this hypothesis from the perspective of Gunderson and Holling’s adaptive cycle metaphor [4]. The metaphor describes ecosystem development as alternating phases of stability and reorganization, being shaped by three systemic properties: the system’s potential available for future change, the connectedness among its internal variables, and its resilience in the light of perturbations.
For the quantification of the adaptive cycle, we use a method developed by zu Castell and Schrenk [5,6]. Based on the most comprehensive timeseries available in marine environments, we infer a dynamic network of information transfer, which allows us to study the evolving interaction pattern between phyto-and zooplankton. We discuss this pattern in the context of the adaptive cycle phases and alternative measures of system resilience.
To our knowledge, our study is the first to provide a holistic analysis of plankton network interactions in marine environments, considering both phyto- and zooplankton species. This approach offers a deeper understanding of how human-induced impacts affect the foundation of marine food webs.
 
[1] E. Merz, E. Saberski, L. J. Gilarranz, P. D. F. Isles, G. Sugihara, C. Berger, and F. Pomati, Disruption of ecological networks in lakes by climate change and nutrient fluctuations, Nature Climate Change (2023).
[2] J. Di Pane, K. H. Wiltshire, M. McLean, M. Boersma, and C. L. Meunier, Environmentally induced functional shifts in phytoplankton and their potential consequences for ecosystem functioning. Global Change Biology, 28, 2804–2819 (2022).
[3] M. M. Deschamps, M. Boersma, C. L. Meunier, I. V. Kirstein, K. H. Wiltshire, and J. Di Pane, Major shift in the copepod functional community of the southern North Sea and potential environmental drivers. ICES Journal of Marine Science, 0, 1–13 (2023).
[4] L. H. Gunderson and C. S. Holling. Panarchy: understanding transformations in human and natural systems (Island, Washington, D.C., 2002).
[5] W. zu Castell, and H. Schrenk, Computing the adaptive cycle, Scientific Reports 2020(10):18175 (2020).
[6] H. Schrenk, C. Garcia-Perez, N. Schreiber, and W. zu Castell, QtAC: an R-package for analyzing complex systems development in the framework of the adaptive cycle metaphor, Ecological Modelling 466:109860 (2022).</jats:p
Discrepancies in lacustrine bacterial lipid temperature reconstructions explained by microbial ecology
Get PDFBacterial lipid branched glycerol dialkyl glycerol tetraethers (brGDGTs) are a valuable tool for reconstructing past temperatures. However, a gap remains regarding the influence of bacterial communities on brGDGT profiles. Here, we identified two distinct patterns of brGDGTs from the surface sediments of 38 Tibetan Plateau lakes using an unsupervised clustering technique. Further investigation revealed that salinity and pH significantly change bacterial community composition, affecting brGDGT profiles and causing brGDGT-based temperatures to be overestimated by up to 2.7 ± 0.7 °C in haloalkaline environments. We subsequently used the trained clustering model to examine the patterns of bacterial assemblages in the global lacustrine brGDGT dataset, confirming the global applicability of our approach. We finally applied our approach to Holocene brGDGT records from the Tibetan Plateau, showing that shifts in bacterial clusters amplified temperature variations over timescales. Our findings demonstrate that microbial ecology can robustly diagnose and constrain site-specific discrepancies in temperature reconstruction
Developments in Permafrost Science and Engineering in Response to Climate Warming in Circumpolar and High Mountain Regions, 2019–2024
Get PDFResearch in geocryology is currently principally concerned with the effects of climate change on permafrost terrain. The motivations for most of the research are (1) quantification of the anticipated net emissions of CO2 and CH4 from warming and thaw of near-surface permafrost and (2) mitigation of effects on infrastructure of such warming and thaw. Some of the effects, such as increases in ground temperature or active-layer thickness, have been observed for several decades. Landforms that are sensitive to creep deformation are moving more quickly as a result, and Rock Glacier Velocity is now part of the Essential Climate Variable Permafrost of the Global Climate Observing System. Other effects, for example, the occurrence of physical disturbances associated with thawing permafrost, particularly the development of thaw slumps, have noticeably increased since 2010. Still, others, such as erosion of sedimentary permafrost coasts, have accelerated. Geochemical effects in groundwater from trace elements, including contaminants, and those that issue from the release of sediment particles during mass wasting have become evident since 2020. Net release of CO2 and CH4 from thawing permafrost is anticipated within two decades and, worldwide, may reach emissions that are equivalent to a large industrial economy. The most immediate local concerns are for waste disposal pits that were constructed on the premise that permafrost would be an effective and permanent containment medium. This assumption is no longer valid at many contaminated sites. The role of ground ice in conditioning responses to changes in the thermal or hydrological regimes of permafrost has re-emphasized the importance of regional conditions, particularly landscape history, when applying research results to practical problems
Permafrost and Active Layer Temperature and Freeze/Thaw Timing Reflect Climatic Trends at Bayelva, Svalbard
No full textPermafrost warming has been observed all around the Arctic, however, variations in temperature trends and their drivers remain poorly understood. We present a comprehensive analysis of climatic changes spanning 25 years (1998–2023) at Bayelva (78.92094°N, 11.83333°E) on Spitzbergen, Svalbard. The quality controlled hourly data set includes air temperature, radiation fluxes, snow depth, rainfall, active layer temperature and moisture, and, since 2009, permafrost temperature. Our Bayesian trend analysis reveals an annual air temperature increase of 0.9 ± 0.5°C/decade and strongest warming in September and October. We observed a significant shortening of the snow cover by −14 ± 8 days/decade, coupled with reduced winter snow depth. The active layer simultaneously warmed by 0.6 ± 0.7°C/decade at the top and 0.8 ± 0.5°C/decade at the bottom. While the soil surface got drier, in particular during summer, soil moisture below increased in accordance with the longer unfrozen period and higher winter temperatures. The thawed period prolonged by 10–15 days/decade at different depths. In contrast to earlier top-soil warming, we observed stable temperatures since 2010 and only little permafrost warming (0.14 ± 0.13°C/decade). This is likely due to recently stable winter air temperature and continuously decreasing winter snow depth. This recent development highlights a complex interplay among climate and soil variables. Our distinctive long-term data set underscores (a) the changes in seasonal warming patterns, (b) the influential role of snow cover decline, and (c) that air temperature alone is not a sufficient indicator of change in permafrost environments, thereby highlighting the importance of investigating a wider range of parameters, such as soil moisture and snow characteristics
Multiple Pleistocene refugia for Arctic Bell‐Heather revealed with genomic analyses of modern and historic plants
Get PDFAim: Arctic plants survived the Pleistocene glaciations in unglaciated refugia. The number, ages, and locations of these refugia are often unclear. We use high-resolution genomic data from present-day and Little-Ice-Age populations of Arctic Bell-Heather to re-evaluate the biogeography of this species and determine whether it had multiple independent refugia or a single refugium in Beringia. Location: Circumpolar Arctic and Coastal British Columbia (BC) alpine. Taxon: Cassiope tetragona L., subspecies saximontana and tetragona, outgroup C. mertensiana (Ericaceae). Methods: We built genotyping-by-sequencing (GBS) libraries using Cassiope tetragona tissue from 36 Arctic locations, including two ~250- to 500-year-old populations collected under glacial ice on Ellesmere Island, Canada. We assembled a de novo GBS reference to call variants. Population structure, genetic diversity and demography were inferred from PCA, ADMIXTURE, fastsimcoal2, SplitsTree, and several population genomics statistics. Results: Population structure analyses identified 4–5 clusters that align with geographic locations. Nucleotide diversity was highest in Beringia and decreased eastwards across Canada. Demographic coalescent analyses dated the following splits with Alaska: BC subspecies saximontana (5 mya), Russia (~1.4 mya), Europe (>200–600 kya), and Greenland (~60 kya). Northern Canada populations appear to have formed during the current interglacial (7–9 kya). Admixture analyses show genetic variants from Alaska appear more frequently in present-day than historic plants on Ellesmere Island. Conclusions: Population and demographic analyses support BC, Alaska, Russia, Europe and Greenland as all having had independent Pleistocene refugia. Northern Canadian populations appear to be founded during the current interglacial with genetic contributions from Alaska, Europe and Greenland. We found evidence, on Ellesmere Island, for continued recent gene flow in the last 250–500 years. These results suggest that a re-analysis of other Arctic species with shallow population structure using higher resolution genomic markers and demographic analyses may help reveal deeper structure and other circumpolar glacial refugia
Tracing Recent Large Herbivore Influence on Soil Carbon in Permafrost and Seasonally Frozen Arctic Ground Using Lipid Biomarkers: a Pilot Study
Get PDFThis study investigates the impact of large herbivores on soil organic matter (OM) stability in Arctic permafrost and seasonally frozen ground ecosystems, focusing on the potential preservation effect of grazing. Soil samples were collected from Siberian and Finnish permafrost and non-permafrost areas and organic carbon content, carbon-to-nitrogen ratio, stable carbon isotopes as well as the content of n-alkanes and n-alcohols were analysed to assess OM stability. The results suggest that grazing activity, particularly in permafrost environments, preserves soil OM by reducing decomposition. Permafrost soils exhibit higher functionalized to non-functionalized biomarker ratios, indicating in general better preservation under frozen conditions. While differences in grazing intensities had minor effects, the data also showed variability due to soil heterogeneity, especially in seasonally frozen ground ecosystems. Nevertheless, there are slight trends towards enhanced OM preservation with increasing grazing intensity, especially in permafrost, emphasising the potential role of grazing in locally preserving Arctic soil OM. This pilot study offers initial insights into the impact of large herbivores on OM stability in cold-region ecosystems, suggesting that significant effects may require prolonged, intensive grazing pressure
Removal of existing and legacy plastic pollution
Get PDFIt is important to recognize that removal efforts alone cannot solve the plastic problem and that they fail to address the scale or wider issues of plastic pollution. The only sustainable, safe, long-term, and effective solution to the global plastics crisis is to significantly reduce, simplify and detoxify plastic polymers and products, and to establish and implement measures to prevent their release to the environment along their full life cycle. In the transition towards this goal, targeted removal of existing plastic pollution and remediation of environments contaminated with legacy plastics and associated chemicals is necessary to mitigate the detrimental impacts on ecosystems, biodiversity, and human health, and to restore natural habitats and their functions.
This policy brief outlines key environmental, economic, social and transparency factors to consider in the removal of existing and legacy plastic pollution
Overture for the Mandara and Vasuki Plates
Get PDFModels of past plate motions in the Indian Ocean help map the supercontinent Gondwana and investigate how mantle plumes influence plate tectonics. Reducing confidence in this, however, the range of available models all produce large pre-94 Ma movements, in various kinematic senses, between India and Madagascar. There is no observational evidence for any of these motions, suggesting along with their diversity that they are artefacts stemming from contrasting resolutions of techniques used for reconstructing India and Madagascar to Antarctica. A higher resolution approach to India–Antarctica reconstruction concentrates on geophysical records of relative plate motion azimuths. Applying its results regionally eliminates Indo-Malagasy motions before 94 Ma, and prompts new hypotheses of two small tectonic plates. The early Cretaceous Mandara plate, in the Enderby Basin off East Antarctica, may have initiated and rotated at a mid-ocean ridge that was supplied by excess melt from the Kerguelen plume. The late Cretaceous Vasuki plate may have conveyed Sri Lanka southwards across the western Bay of Bengal. The 85°E and Comorin ridges may have formed at active transform fault zones along Vasuki’s margins that were supplied with excess melt from the Crozet and Marion plumes. The model confidently implies the presence of 500,000 km2 of continental crust beneath the Kerguelen Plateau, places Sri Lanka 1000 km further east within Gondwana than previous reconstructions, and casts doubt on the existence of plate kinematic signals that have previously been attributed to the arrival and spread of the Marion plume beneath India and Madagascar at ~105 Ma.</jats:p
Eiskalt vereint – Die Geschichte der letzten DDR-Antarktis-Expedition
Get PDFIm Oktober 1989 machen sich unabhängig voneinander zehn DDR-Forscher und neun BRDForscherinnen
auf den Weg in die Antarktis und erleben den deutschen Vereinigungsprozess zehntausende
Kilometer von Berlin entfernt. Sie nehmen Funkkontakt auf und teilen fortan die Freude, die Furcht
und die Fassungslosigkeit über die Ereignisse. Das erste Mal bestreiten Frauen den Betrieb der westdeutschen
Forschungsstation, das letzte Mal weht die Flagge der DDR in der Antarktis. Der Film von Anna
Schmidt und Ernst-Michael Brandt rekonstruiert in Originalaufnahmen, Amateurvideos, Tagebuchaufzeichnungen,
in Dokumenten und Zeitzeugenberichten die Wochen und Monate zwischen der Ankunft
der ostdeutschen Forscher im Herbst 1989 und der westdeutschen Forscherinnen im Januar 1990 und
ihrer Abfahrt im Frühjahr 1991.
In Kooperation mit dem Alfred-Wegener-Institut zum Wissenschaftsjahr 2024, Thema: Freiheit.
Estella Weigelt wird über ihre Erfahrungen der ersten weiblichen Antarktis-Überwinterung erzählen und
dazu Fragen aus dem Publikum beantworten. Hier gibt es mehr Infos: www.helmholtz-klima.de