Climate and Environment

Exploring Earth’s Interconnected Climate and Environmental Systems

Enlarge

The Earth’s climate and environment are controlled by a complex interplay of geological, biological, and chemical processes. Our research within the Climate and Environment focus area seeks to decipher these fundamental mechanisms, from the microscopic life that governs global element cycles to the vast geological forces that shape our planet’s surface and atmosphere. A major theme is the Carbon cycle, which is inextricably linked to climate stability. For instance, the chemical weathering of silicate rocks sequesters approximately 0.1 gigatons of carbon per year from the atmosphere, compensating for CO₂ emissions from the solid Earth and stabilizing Earth’s climate. A significant portion of this global weathering may occur in sediments stored on floodplains. Through geochemical analyses of water and sediments, we quantify the carbon sequestered by weathering on these floodplains, aiming to mechanistically understand these processes and predict their crucial role in Earth’s long-term carbon cycle. Furthermore, we are interested in how life survives under persistent energy limitation deep below the seafloor over geological timescales, investigating microbial communities subsisting in various energy-limited settings from deep sea red clay to continental margin sediments. We focus on how abiotic and biological hydrogen production supports these ecosystems at thermodynamic conditions close to the energetic limit to life.

Enlarge

A deeper understanding of our planet’s past is provided by the study of the Paleo-Environment. This involves exploring fossiliferous archives and analyzing preserved life forms, coupled with sedimentological data, to reconstruct past environments and climates. For example, the detailed analysis of exceptionally well-preserved fish fossils from Miocene paleolakes in the Central Kenya Rift, together with co-occurring fossils and samples for pollen and clay mineralogy, allows for crucial paleoenvironmental and paleoclimate reconstructions. These studies on evolutionary history and past environments are crucial because they provide direct information for understanding how organisms respond to environmental change, particularly given the poor known fossil record for African freshwater fish fauna. The investigation of these ancient deposits links directly to the current state of our oceans, where dramatic changes are taking place due to anthropogenic activity. Global oceanic oxygen reserves have been reduced, leading to an expansion of oxygen minimum zones (OMZs).

Enlarge

This brings us to the core of Biogeochemistry, the interdisciplinary field that connects life and the environment through element cycling. We investigate the effects of ocean deoxygenation on the sequestration of dissolved organic matter (DOM), which stores as much carbon as atmospheric CO₂, and its interaction with microbial communities and the marine carbon and sulfur cycles. Using advanced analytical methods like Fourier transform ion-cyclotron resonance mass spectrometry (FT-ICR-MS) and metatranscriptomics, we are able to characterize DOM at the molecular level and predict the specific functions of microbial communities in OMZs. This work is also extended to the Antarctic region, where climate change is most visible, aiming to understand the environmental drivers behind microorganisms and DOM pool functioning in response to warming. Furthermore, we decipher the identity of key microbial groups responsible for important C and N cycling processes, utilizing quantitative DNA stable isotope probing to investigate which microbes are more important than others for the assimilation of specific carbon and nitrogen chemicals.

Enlarge

Geological processes, such ash volcanic eruptions, also exert a significant, often dramatic, influence on climate. Specifically, we study volcanic ash-gas interaction, which results in gas scrubbing, impacting our global quantificaiton of volcanic emission. We also study volcanic lightning and the electrification of volcanic plumes, which impact ash transport, reaction, deposition and remobilization. Much like in thunderclouds, volcanic lightning can be detected remotely, providing real-time mapping of ash plumes. We are exploring the link between electrification and eruptive parameters (mass eruption rate and grain-size distribution). Beyond volcanology, this research provides a fundamental understanding of electrification processes in dusty environments, relevant to industrial processes, Earth and planetary electricity, and as catalyst for the origin of life. Collectively, these research streams highlight the essential, interwoven roles of geological processes, chemical transformations, and biological activity in maintaining and altering the complex global systems that dictate our climate and environment.