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FRINATEK-Fri prosj.st. mat.,naturv.,tek

Tectonic Stress Effects on Arctic Methane Seepage - SEAMSTRESS

Alternative title: Tektoniske Stress Effekter på metan gass utslipp i Arktis

Awarded: NOK 8.0 mill.

The goal of the SEAMSTRESS project is to investigate the geological mechanisms that control the release of greenhouse gases from the ocean floor in the Arctic. Large amounts of these gases are released from the sediment on the ocean floor. These emissions influence the global carbon cycle, as well as seabed ecology. They also increase the risk of underwater landslides. This is a widespread phenomenon that has been occurring for hundreds and even millions of years with periods of intensification. The SEAMSTRESS project is providing a deeper understanding of how glacial and mid-ocean ridge processes have influenced the timing and the amounts of gas release from Arctic margins. During the first half of the project, we have had a strong focus on collecting an exceptional amount of interdisciplinary data during expeditions onboard Norwegian research vessels R/V Helmer Hanssen and R/V Kronprins Haakon. In the summer in 2019 the first project experiment successfully collected, in collaboration with Geomar, seismic waves records from 21 seismometers placed around a spot where methane bubbles raise from the seafloor for more than 900 m toward the sea surface. In fall 2019, a large expedition was conducted to collect long sediment cores (> 10 m length) for the study of the petrophysical properties of the sediment (e.g., density, permeability, strength, magnetic susceptibility, in-situ pressure and temperature). These data have revealed, among other things, that tides and small changes in the sea level are sufficient to trigger release of gas from shallow gas accumulation under deep waters along the west-Svalbard continental slope. Despite the unusual difficult times due to Corona, the project has developed continuously. In the summer in 2020 we successfully collected 7 seismometers that were recording seismicity around an active gas seepage area since last year. In autumn 2020 Piezometer data (in-situ sediment pressure and temperature) were collected in collaboration with Ifremer on 4 key sites along the margin to study whether pore fluid pressure increases or decreases from the mid-ocean ridge towards the continental shelf off Svalbard. As part of the collaboration with the Alfred Wegener Institute (AWI), we placed 10 additional seismometers at the northern end of the Knipovich ridge. We pick-up these instruments from the ocean floor in summer 2021 and analyzes show that there is a large amount of registered local seismicity that is not recorded by land seismological stations. We are investigating the effect of this local seismicity on seepage activity and sediment instabilities. Another experiment with seabed seismometers was conducted to study how the local stress affects the transport of horizontal waves through gas structures in the sediment. PhD students and postdocs within the project have participated in many marine expeditions and gained invaluable experience in collecting, processing and interpreting geological and geophysical data. Glacially induced stress models for the Fran Strait and the Barents Sea suggest that the stress regime has been favorable to open up faults and fractures in periods following the major glaciations. This mechanism may explain periodic intensification of the gas release. Advanced analyzes of high-resolution 3D seismic data by a PhD student in the project revealed fine scale fractures and fault segments that have promoted fluid advection and release at a scale not investigated before and correlating with specific post glacial periods. These findings have important implications for developing effective approaches for characterizing the shallow subseabed, critical for offshore developments. Numerical simulations of the physical mechanisms that control gas emissions are helping us to understand why methane emissions have stopped along part of the margin. An interplay between the amount of gas in the sediment and the pressure exerted at cracks controls how much and when the gas release occurs. Different geological processes affect the pressure field that controls the seepage. The concepts and approaches developed by SEAMSTRESS for the west-Svalbard margin are proving to be relevant for other regions, e.g., the Barents Sea, where methane seepage is wide spread and dominated by complex post-glacial tectonism. The experiments have motivated national and international collaboration and the data are being used by researchers and professors in various disciplines to advance objectives related to paleo oceanography, paleo climate, near-surface earth dynamic systems, micro-paleontology, and for educational purposes. The project provides unique field constrained case studies for testing numerical simulations of complex mechanical, chemical and sedimentological fluid transport processes interacting in the shallow subsurface. These models and a large amount of geophysical, petrophysical and geological data are available for anybody interested in further analyses.

Main project outcomes include: - Glacially and tectonically induced stress models for the Fram Strait. - Integrated geophysical, petrophysical, geomechanical and geological data sets from Arctic continental margins: • Ocean Bottom Seismological (OBS) data from the Fram Strait – critical for constraining the location of earthquakes and detecting micro-seismicity along the margins. • OBS (active source) P-Wave and S-Wave data sets critical for anisotropy studies • In-situ pressure and temperature data from piezometer and heat flow lance instrumentation • High resolution 2D and 3D seismics • Calypso cores along a main contourite drift in the Fram Strait -Integrated approaches to understand sub-seabed deformation and fluid transport processes in the shallow subsurface (20 peer review articles and several publications and presentations to the general public). Outcomes derived from project results: - Use of the glacial stress model for geohazard analyses (e.g., in France - Damon et al., 2023 https://doi.org/10.1016/j.tecto.2023.230035 ) - Successful development of an IODP proposal in the Fram Strait (schedule for summer 2024). (relies on expertise and data by the SEAMSTRESS team). https://iodp.tamu.edu/scienceops/expeditions/eastern_fram_strait_paleo_archive.html - Establishment of international cooperation with Ifremer to bring instrumentation for petrophysical characterization for slope stability assessments in the Arctic on R/V KH. - Synergies with industry- Equinor Akademia Avtalen funding program – project proposal accepted for funding (post-doctoral position for 2024 for further developing the shallow fracture mapping approach started within seamstress) - Development of educational material (e.g., a case study for a master and PhD student course at UiT – Integrated Geological and Geophysical interpretation) Impacts: The SEAMSTRESS project marks the basis for a long-term research direction focused towards the development of integrated approaches for sub-seabed characterization in glaciated continental margins. The multidisciplinary data generated through the project is now available for a wide range of advanced geophysical and petrophysical studies (e.g., MSCA fellowship). Similarly, the data is being used to generate unique field constrained GeoModels that can be used to benchmark numerical models and simulations developed by international groups to study processes interacting in the shallow subsurface. The project has reinforced cooperation and established new synergies with groups in AWI, IFREMER, Geomar, Marum, NGI, NGU, GEUS, The University of Texas at Austin, and Uppsala University, to advance our understanding of processes that interact in the shallow subsurface at continental margins. These synergies impact climate research, by advancing knowledge on complex carbon transport processes, and support industry in addressing the challenges of offshore developments for the transition to cleaner and more sustainable energies.

Vast amounts of methane are released from marine sediments at continental margins (seepage). The episodic release of methane from the seafloor is one of the most congruent explanations to pre-industrial atmospheric temperature peaks. Despite this, the mechanisms controlling when and how much methane is released are not fully understood. Seafloor methane release is prevalent across the west-Svalbard passive margin where the mechanical behavior of near-surface sediments due to tectonic forcing has not been investigated. I hypothesize that regional stresses from Arctic mid-ocean ridges and post-glacial adjustments of the lithosphere, has controlled the timing and amount of gas released from the seafloor to the oceans over geological time. SEAMSTRESS is the first project investigating the effect of tectonic stresses on methane release across Arctic margins. The project will establish an approach for quantifying in-situ stress filed variations across west-Svalbard and develop a fully field-validated model of seafloor methane release coupled to regional stresses. Four cross-disciplinary experiments (seismological, geomechanical, 3D seismic and petrophysical) are designed to constrain in-situ stresses, sediment properties and fluid pressure to validate regional stress models. High quality experiments will be ensured through close collaboration with specialized national and international geotechnical and marine exploration institutes. After quantifying how stress field variations force methane dynamics across west-Svalbard, the approach pioneered here will be up-scaled to the entire Arctic and even globally, to reconstruct long-term methane fluxes into the oceans, providing a step forward in our understanding of the links between near-surface earth systems, oceans and climate through the geological history.

Publications from Cristin

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FRINATEK-Fri prosj.st. mat.,naturv.,tek