Polar regions are some of the most sensitive and vulnerable regions on Earth. In particular, the long-term interactions between climate, ecosystems and humans in polar continental areas are still poorly understood. The “Polar Terrestrial Environmental Systems” research group investigates past climate dynamics, high-latitude vegetation change, arctic lake system dynamics and biodiversity change in high latitudes. As the time-period covered by direct observations is short, the analysis of long-term changes requires the use of indirect proxy data extracted from environmental archives such as lake sediments. Therefore, proxy development and proxy data synthesis are also key research interests of the group. From these, a better understanding of the polar continental areas and their interactions with the global Earth system can be gained.
Analysing the krummholz form of Larix cajanderi in the Russian Arctic (Photo: Julius Schröder)
'Glacial legacy on the establishment of evergreen vs summergreen boreal forests'
Ecosystem services of boreal forests are of critical importance for humanity and differ markedly between evergreen and summergreen needle‐leaf forests. GlacialLegacy will address the timely questions “Why is northern Asia dominated by summergreen boreal forests?" and “How will these larch forests change in the future?” with a coherent empirical and modelling approach integrating pollen data synthesis, sedimentary ancient DNA analyses, vegetation and biophysical surveys and vegetation modelling.
The hypothesis is that summergreen and evergreen needle‐leaf forests represent alternative quasi‐stable states occurring under similar climates today but which came about because of the different (genetic) characteristics of the northern tree refugia – a legacy of the preceding glacial stage. Once established Asian larch forests stabilised because of their unique vegetation–fire–permafrost–climate system that inhibits the invasion of evergreen taxa. However, the long‐term vegetation trajectory causes the irreversible transition of summergreen into evergreen needle‐leaf forests. This is mainly because larch is a poor competitor compared to evergreen spruce and pine when growing in mixed stands. Asian larch forest would only be able to re‐establish after a new forest‐free glacial stage. As both boreal forest types are only stable across a certain climate range, a future warmer and drier climate may cause their transition into steppe, which is irreversible for Asian larch forests.
Funding: European Research Council Consolidator Grant 2018-2023
Cooperation:
Prof. Dr. Luidmila A. Pestryakova (NEFU, University Yakutsk)
Further reading:
Herzschuh, U., Birks, H.J.B., Laepple, T., Andreev, A., Melles, M., & Brigham-Grette, J. (2016). Glacial legacies on interglacial vegetation at the Pliocene-Pleistocene transition in NE Asia. Nature Communications.7, 1–11. doi:10.1038/ncomms11967, https://www.nature.com/articles/ncomms11967.pdf
Illustration of the concept of “Boreal forest bi‐stability and glacial legacy“. (Photo: Alfred-Wegener-Institut)
Web-based visualisation of past environmental change in permafrost regions
This project brings together stakeholders from the economy, research and educational sectors to shape the future of our scientific goals towards their relevance for the German and international society. The overall objective of PAST PERMAFROST is the development of a web-tool that allows the user to visualise AWI environmental data sets in space and time in permafrost areas (including interactive maps of past and present vegetation). The sites can be used to compare the millennial scale climate history in the area to the present thermal state of permafrost. Our vision is to link palaeoclimate findings to direct consequences of recent environmental change in the Arctic.
The northern foreland of the Tibetan Plateau with its endorheic basins plays a key role in the geological and palaeoenvironmental development of central Asia. The depositional environment is characterized by aeolian, fluvial, and lacustrine conditions. Sediment supply is also controlled by glacial dynamics and periglacial processes in the mountainous hinterland of the Qilian Shan. The mountains are important sources for water supply to the agriculture belt of the adjacent Hexi Corridor and the endorheic basins. The sediments in the basins are repositories for dust transported over central Asia and northern China and are directly connected with the Chinese Loess Plateau.
The seasonal extent and properties of arctic ice on land and in the ocean determine the efficacy of the albedo feedback mechanism causing arctic climate amplification. Various ice types are inhabited by specific ice algae that across taxonomic boundaries share similar mechanisms to survive in these extreme environments. This project explores the potential of sedimentary DNA as a proxy for ice cover changes on millennial time-scales by analysing community functional composition in ice, water column and sediment-surface samples, and in marine and lake sediment cores from the Fram Strait, Northwest Pacific, and Siberia (Samoylov, Central Yakutia) covering about the last 6000 years.
Sampling and analytical strategy to investigate taxonomic and functional ice algae composition in the ocean and lakes. (Photo: Alfred-Wegener-Institut)
The interdisciplinary German-Russian project 'KoPf-Kohlenstoff im PermafrostKohlenstoffumsatz und Treibhaugasfreisetzung aus tauendem Permafrost Nordostsibiriens unter sich ändernden Umwelt- und Klimabedingungenprojekt' (Carbon in permafrost: Carbon turnover and greenhouse gas release from thawing permafrost in northeast Siberia under changing environmental and climatic conditions) is funded by the German Federal Ministry of Education and Research (BMBF). Polar ecosystems on continents are habitats for northern communities and provide indispensable ecosystem services. KoPf will investigate the status, formation, turnover and release of organic carbon in eastern Siberian permafrost landscapes to gain increased understanding of how permafrost-affected landscapes will respond to global warming and how this response will influence the local, regional and global carbon balance. Rising arctic temperatures will result in increased permafrost thawing, landscape disturbance, vegetation biomass changes and increased fire frequency in taiga and tundra.
Scientists from Russia and Germany work together at different key sites in the Siberian Arctic that are characterised by different disturbance regimes. Key sites are the long-term research sites of the Lena Delta and Chukotka with large data collections of below-ground carbon in permafrost soils and permafrost and a detailled characterisation of the vegetation. Vegetation will also be analysed for the Taymyr, Omoloy, and Kolyma regions. This in situ data collection from Russian-German expeditions will be used for upscaling of vegetation, biomass and below and above ground carbon.
Funding: BMBF - Federal Ministry of Education and Research (2017-2020)
Cooperation:
Uni Hamburg (PI): Prof. Pfeiffer, Prof. Kutzbach
Helmholtz-Zentrum Potsdam – Deutsches Geoforschungszentrum GFZ, Prof. Sachs
Max-Planck-Institut für Meteorologie Hamburg, Prof. Brovkin
Max-Planck-Institut für Biogeochemie, Jena, Dr. Göckede
University of Cologne: Prof. Rethmeyer
NEFU Yaktusk, Prof. Pestryakova
AARI St. Petersburg: Prof. D. Bolshiyanov
Uni St. Petersburg: Prof. I. Fedorova
Melnikov Permafrost Institute Yakutsk, Dr. Grigoriev
SPbSU Dr. Abakumov
RAS/SB Dr. Barsukov
Formation, turnover and release of carbon in the ground-ice rich lowland permafrost landscape of the Lena River Delta. (Photo: Alfred-Wegener-Institut)
The German-Russian ‘Paleolimnological Transect’ (PLOT) project funded by the German Ministry for Education and Research (BMBF) aims at the investigation of the Late Quaternary climate and environmental history along a more than 6000 km long transect crossing northern Eurasia, focusing on the potentially old lakes of Ladoga, Bolshoye Shuchye, Levinson-Lessing, Taymyr and Emanda.
Within the project, AWI Potsdam (PI H. Meyer) is responsible for analysing the stable isotope geochemistry for climate and environmental research. The lakes are being investigated for stable oxygen isotopes in diatoms derived from lacustrine sediments and for stable water isotopes to reconstruct past climate, environment and hydrology changes. For a quantitative reconstruction, these measured environmental variations are then combined with climate model outputs with explicit isotope diagnostics (AWI Bremerhaven, M Werner).
High-resolution reconstruction of regional climate changes in Antarctica
- Glaciological and isotope-geochemical studies on the Antarctic Peninsula and the West Antarctic Ice Sheet
This project is investigating the recent and past climate variability of two high-accumulation regions in West Antarctica - the northern Antarctic Peninsula and the Union Glacier region in the Ellsworth Mountains on the West Antarctic Ice Sheet - will determine the potential forcing factors for observed changes. To do so, newly collected firn cores from both regions are used as natural climate archives and analysed at high (sub-annual) resolution for density, stable water isotopes and various chemical parameters. New data on accumulation rates and meteorological parameters (e.g. air temperature) as well as information on moisture source regions and transport paths of precipitating air masses will be collected.
Interdisciplinary research projects at the interface between natural science and data science
Topic A: "Arctic Environmental Data Analytics"– Gregor Pfalz
Topic B: "Data fusion using remote sensing data and machine/deep learning techniques to better understand present, past and future vegetation dynamics in Central Yakutia" – Femke van Geffen
The Helmholtz Einstein International Research School in Data Science (HEIBRiDS) is a cooperation project with the Einstein Center Digital Future (ECDF), Berlin’s universities and the six Helmholtz Centers in the capital region.
The different doctoral theses focus on topics from the fields of imaging, machine learning, modeling, innovative hardware concepts, visualization and sequencing. The interdisciplinary topics are formulated and supervised by a team consisting of two professors, one of whom is a member of the Helmholtz Association and one an ECDF member
HEIBRiDS can therefore rely on a unique environment that enables research, from different perspectives, into the core methods, algorithms and processes of digitalization, while at the same time transporting knowledge between different disciplines.
Topic A tries to reconstruct past and present relationships between climate change in the Arctic and ecosystem dynamics in northern lake systems, by developing a data analysis system designed for multivariate statistics on lake sediment core parameters.
The goal of Topic B, is to employ machine learning and deep learning methods to analyse data to gain better insights into the dynamics of the vegetation species and how these change over time. In order to accomplish this goal, various types of remote sensing data are used such as Sentinel-2 and Landsat 7/8 as well as drone data collected in the field. The ultimate goal is to develop a fusion method that can use the available data to create a comprehensive overview of vegetation dynamics of the past, present and future. .
