Sommersemester 2023

Vast amounts of organic carbon and ground ice that accumulated during past cold climates in northern high latitudes are still preserved as permafrost today. However, with amplified warming of the Arctic climate, permafrost landscapes are rapidly transforming, with serious consequences for both local ecosystems and the global climate. Thus, permafrost loss has been suggested as a tipping point for Earth's climate. In this talk, I will provide an overview of the role of Arctic permafrost for Earth's climate where it not only acts as a source of carbon but also as a sink for heat. I will discuss whether permafrost loss is indeed a tipping process and highlight how climate models have to improve in order to accurately represent high latitude land systems.

Global scale ecological catastrophes such as mass extinctions have occurred several times in the past and study of these provide important lessons for the present and future, particularly during the ongoing deforestations and climate change. We focussed on fluvial Gondwana sediments from eastern India to study biodiversity loss of terrestrial flora and the palaeoenvironmental conditions during the transition from late Permian to early Triassic. Our study using hydrocarbon biomarkers and palynomorphs demonstrates massive deforestation of coal-forming vegetation and a sharp decline in vascular plant diversity during early Triassic. In the talk, I will also present the molecular signatures that indicate occurrence of intense wildfires during the late Permian-Early Triassic and implications of the presence of a hydrogen sulfide-rich bottom waters in the palaeo-floodplains.

Biosphärenreservate sind Modellregionen einer ökologischen, ökonomischen und sozio-kulturellen Entwicklung. Dieses integrative Schutzkonzept versteht den Menschen als zentrales Element eines nationalen und weltweiten Netzes an einzigartigen und repräsentativen Natur- und Kulturlandschaften, indem naturschonende Lebens- und Wirtschaftsformen verwirklicht werden. Dazu gehört auch der Tourismus als ein Handlungsfeld der Entwicklungsfunktion der Biosphärenreservate, der direkte und vorgelagerte indirekte regionalökonomische Effekte auslösen und so zum regionalen Wirtschaftskreislauf beitragen kann. Im Rahmen einer 2010 gestarteten Projektreihe wurde der Tourismus in den deutschen Biosphärenreservaten mit seinen regionalökonomischen Effekten untersucht. Mit Unterstützung des Bundesamts für Naturschutz liegen dadurch erstmalig für alle 18 Biosphärenreservate in Deutschland empirisch erhobene Primärdaten zum Besuchsaufkommen und dessen regionalökonomische Effekte vor. Auf dieser Datenbasis ist es möglich, eine evidenzbasierte Gesamtschau des bundesweiten Biosphärenreservatstourismus zu präsentieren. Die im Rahmen aufwändiger empirischer Erhebungen ermittelten Resultate können ein erster Anstoß in Richtung eines fortlaufenden Monitorings dieses sozioökonomischen Indikators sein.

Regardless of political developments, natural gas in Germany and the EU is an important building block on the way to a complete conversion to a renewable energy supply. The most important component of natural gas is methane, the second most important greenhouse gas in the current climate change and, according to current figures, responsible for 30 % of the anthropogenic temperature increase. After agriculture and waste management, the fossil fuels coal, oil and natural gas are the most important anthropogenic sources of methane in the atmosphere. Methane is a much more potent greenhouse gas than carbon dioxide, and minimising methane emissions is also a lever for achieving short-term effects on greenhouse gas emissions due to its short lifetime in the atmosphere of only about 12 years. However, this also requires improved knowledge of the man-made sources of methane. Methane emissions in the so-called supply-chain or German “Vorkette” (including production, transport and storage) are often poorly understood and vary greatly depending on the country and type of production. Under certain circumstances, methane losses in the upstream chain can massively minimise or even counteract the greenhouse benefit compared to coal use (e.g. in the basic electricity supply). One aspect when considering the climate relevance of natural gas (and oil) emissions is methane leaks from old or abandoned wells on- and offshore. There are currently only few data on this potential source for emissions and no comprehensive studies have been carried out in Germany in particular, although here too - with a focus on Lower Saxony - there are about 20,000 old wells drilled by the oil and gas industry. The lecture will present current aspects of projects on these topics at the Federal Institute for Geosciences and Natural Resources (BGR). These include analyses of the climate relevance of natural gases from various supplier countries to Central Europe. Furthermore, results of investigations on old wells in the German North Sea will be presented. Depending on the audience, the lecture will be held in English or German (with slides in English).

The co-evolution of atmosphere, oceans, continents, and life on Earth and other planets is a fundamental topic for humankind and highly relevant to scientists of diverse research fields. Key questions in this context are how ancient environments became habitable and how these systems interacted throughout Earth's history. The geodynamical evolution of the Earth and its impact to create favourable physico-chemical conditions leading to the development of early life are still incompletely understood. Stromatolites, i.e., lithified microbial mats, as well as Banded Iron Formations (BIFs) are invaluable deep-time archives of Precambrian environments to better understand the evolution of marine environments throughout 3.8 billion years of Earth's history.
In this talk, I will present geochemical investigations of Archean and Proterozoic BIFs and stromatolites to reconstruct ancient marine environments in which BIFs and stromatolites formed. In particular, the physico-chemical conditions in paleo-environments, the sources of elements affecting seawater chemistry, and the potential of BIFs to trace the geodynamical evolution of the Earth are the focus of this presentation. The versatile toolbox of trace element systematics combined with radiogenic (e.g., Sm-Nd, Lu-Hf, 182W) and stable (e.g., Cd) isotopes provides high-resolution insights into relative water depths of the depositional milieu, ambient redox conditions, and the impact of terrigenous weathering and high-temperature, hydrothermal fluids on water chemistry at specific times in Earth’s history. Hence, the geochemical reconstruction of stromatolite and BIF environments further highlights the combined use of Nd-Hf and Cd isotopes as novel geochemical proxies to gather unique insights into the geodynamical evolution of the Earth and element cycling processes in the earliest microbial habitats on Earth.

The deep biosphere is one of the largest habitats on Earth. The vast area covering this low-energy environment results in microbial mediated redox transitions that significantly influence global carbon and energy fluxes. In this talk, I will show how authigenic barite that formed in the deep groundwater system in Äspö (SE Sweden) records early stages of BSR and even activity of sulfide oxidizing bacteria (SOB). The sulfate stemming from this anaerobic sulfide oxidation can fuel anaerobic oxidation of methane, making barite to a potential candidate to record paleo methane fluxes from the deep subsurface to the atmosphere.

Sulfate and sulfide minerals are important archives for biogeochemical studies and reach far back into early Earth’s history. Their oxygen and sulfur stable isotopes are well-established tools for studying the global sulfur cycle, the redox state of the atmosphere, or its CO₂ partial pressure. In this talk, I will focus on a newly developed analytical technique for the analysis of coupled ¹⁸O and ³⁴S substitution (so-called isotope clumping) in sulfate. By combining partial fluorination of sulfate to SO₂F₂ with high-resolution gas isotope ratio mass spectrometry, we are able to identify specific sulfate sources based on the abundance of ¹⁸O-³⁴S clumping, which is controlled by the particular sulfate formation temperature. This novel approach, in conjunction with the simultaneous analysis of already established sulfate isotope systems, provides a new tool to improve the tracing of oceanic sulfate sources and the oxygenation of the atmosphere.