Christoph BöttnerAssistant professor of Marine Seismic Sedimentology

Fluid flow system research for a safe operation of CCS

Fluids are an important agent in almost all geologic processes that shape marine geology. Spatial and temporal variations in fluid flow activity modify total fluxes between geosphere, cryosphere, hydrosphere, and atmosphere. These fluxes have broad implications for geological processes including the formation of natural resources such as water or gas and oil. My research employs new integrated and interdisciplinary approaches to assess the role of fluids for active geologic processes in sedimentary basins around the world and has helped improve the safe operation of offshore carbon capture and storage (CCS). The injection of large volumes of CO₂ during industrial-scale CCS operations is necessary to effectively mitigate anthropogenic greenhouse gas emissions into the atmosphere.

Marine Geohazards & Quantitative Geomorphology

I investigate a multitude of different geohazards including subaqueous landslides, volcanic flank collapses, active faulting, or shallow gas and fluid expulsion. Among these geohazards, the most impressive studies from Northwest Africa showed that submarine gravity flows can ignite and grow hundred times their original size. These gravity flows can reach devastating velocities up to 19 m/s and the volume of single gravity flow can reach more than 150 km³, thereby dwarfing the total annual discharge of rivers worldwide combined. These gravity flows thereby carry substantial amounts of carbon, nutrients, or fresh water but also pollutants such as (micro-) plastic from the continental shelves into the deep sea. Their deposits may be used for reconstructing the geologic record of the Earth which can be untapped via ocean drilling (ICDP and IODP, Land-to-sea drilling campaigns). Naturally, these gravity flows represent a major geohazard for marine infrastructure on which our economies depend such as oil & gas platforms, pipelines, or telecommunication cables, which host 95% of all global data traffic. 

A focus of my research on geohazards are pockmarks and other fluid flow expressions on the seafloor. It is essential to understand the underlying geological processes to assess their importance for the local environment but also their geohazard potential for the surrounding offshore wind farms and submarine cables. I employ geostatistical methods to analyze the spatial distribution and morphometric parameters of these pockmarks (e.g. >50.000 pockmarks in the German Bight). In the light of the green energy transition, my aim is to constrain the impacts of these geohazards because this will be essential to help develop future mitigation and adaptation strategies. Understanding the initiation and dynamics of subaqueous gravity flows are crucial for that task and I will continue my research on the importance of weak layers for landslide initiation, giant gravity flow initiation and evolution on passive continental margins (e.g. NW Africa) as well as volcanic flank collapses.

Greenhouse gas emissions from (Arctic) marine geologic sources

Greenhouse gas emissions from marine sediments can influence global warming, which will be one of the grand challenges for the next decades to centuries. The most abundant greenhouse gas in marine sediments is methane, which appears in the form of free gas, gas hydrates or dissolved in porewater. Methane has a twenty-eight times higher global warming potential than CO₂ and is currently responsible for about a third of the warming. Sources of methane are natural but also of anthropogenic nature. However, especially in the marine environment, a qualitative and quantitative understanding of methane fluxes in the subsurface and the release of methane into the hydro- and atmosphere is challenged by the inaccessibility of offshore regions and associated difficulties in monitoring over sufficient spatial and temporal scales. This results in large uncertainties in quantifying and attributing emissions from marine sources. Realistic estimates of oceanic methane emissions require a profound understanding of the involved fluid flow systems, including spatial and temporal variations, internal architecture, and preferential migration pathways through the overburden. My research investigates natural and anthropogenic fluid migration pathways in the oceanic realm to assess the methane fluxes and estimate their contribution to local greenhouse gas budgets.

Particularly in the Arctic, key players that are likely to have a strong impact on global climate are permafrost soils and marine gas hydrates, because both host substantial amounts of carbon. Permafrost in marine sediments has likely developed in aerially exposed areas during the extreme cold and low sea level of the Late Pleistocene. These conditions (high pressure/low temperature) were also favorable for gas hydrate formation. Thus, “relic” permafrost and gas hydrate may exist in the Arctic to present water depths of 120 m. Current global warming may cause an increase in melting of permafrost and gas hydrates and thus release more greenhouse gases into the ocean or even the atmosphere (climatic feedback). However, the sensitivity of permafrost and gas hydrates to rising temperatures is poorly constrained. My research aims to provide the scientific basis on the underlying geologic processes of greenhouse gas emissions from marine sediments. My focus lies on the interaction of past – and current– climate and fluid flow system activity in Arctic environments.

The interface between the hydrosphere and geosphere

My research on the seafloor interface bridges the gap between existing geophysical and oceanographic methods that allows an integrated Earth System Science to investigate geological processes that act across the sediment-water interface. These sedimentary systems (e.g. meltwater plumes, contourites, sediment waves) not only host an extensive sedimentary record of current and past oceanic processes that may help to understand climatic changes through time but also represent potential resources (i.e. sand, hydrocarbons, water). For example, sediment waves are the most abundant bedform on the ocean floor, and given the ocean cover two thirds of our planet, they are one of the most abundant bedforms on our planet. Yet, the mechanisms responsible for generating sediment waves remain unresolved. Progress on our understanding of the sediment wave generation will have to be made by interdisciplinary teams because they form on the sediment-water-interface.