The proposed project is aimed at investigating the possible impact on the lacustrine environment (e.g. the biological and hydrophysical characteristics) of methane seeps related to destabilizing gas hydrates in Lake Baikal. Results of this study will further our fundamental scientific understanding of the processes of methane venting in association with gas hydrates, and will be useful in the assessment of the possible environmental consequences for the pristine state of Lake Baikal of this natural process of methane release at its lake floor.
Major questions that are planned to be addressed are:
- What is the extent of the phenomenon (in space)?
- Is there only one seep area, or are there more?
- Do the seep areas have one or several individual seeps?
- Are all methane seeps associated with destabilizing gas hydrates?
- How continuous is the phenomenon (in time)?
- On geological time-scales: Is it just a single short-lasting seeping event, or is it a longer-lasting, sustained process?
- On time-scales of months/years: Do the seeps represent a continuous process of gas release or is it intermittent, with pulses of activity and periods of quiescence?
- What are the effects of the methane seeps on the physical and chemical characteristics of the water column, on the heat flux from the lake floor to the lake water, and on the lake sediments?
- What is the methane content in the water column in the seep areas?
- Is there an increased methane flux at the lake surface in the seep areas and how does the methane concentration in the air vary spatially?
- What are the temperature effects of the seepage on the bottom water properties?
- What is the fate of the seep fluids and how do they interact with the bottom sediments and the lake water?
For accomplishing the objectives, it is attempted to use a multi-disciplinary approach, involving both classic, traditional methods as well as innovative technologies:
- Acoustic remote sensing techniques (echosounding, high-resolution seismic profiling, side-scan sonar profiling) will be used to define the regional context and nature of the seeps - both in the water column and in the subsurface - by providing information about geological setting, relationship with destabilizing hydrates, dimensions and geometry of the seeps, plume height and shape;
- Passive hydro-acoustic techniques will be applied to characterize the plume's acoustic signature and to develop a novel method of detection of seeps by hydro-acoustic directional antenna's, and advanced mathematical modelling techniques will be used to translate this signature into quantitative data about bubble shape, volume, rising speed;
- Different monitoring approaches over different time scales (days, weeks and months) will be used in order to get a better understanding of the temporal variability of the seeping process: chrono-sequential echosounding profiles for monitoring plume activity through time, chrono-sequential measurements of heat-flow and bottom-water-temperature with a specially designed autonomous thermograph for monitoring mass and heat exchange in the seep, chrono-sequential hydrophysical measurements of water temperature, salinity, density, oxygen and methane concentration for monitoring plume behavior and the impact on the water column;
- Methane concentrations will be measured by different methods (by gas chromatography, by atmosphere laser methane measurements, by water methane sensor measurements) and at different levels (lake floor, water column, plume, water surface, atmosphere) in order to get a thorough understanding of the fate of the released methane and to quantify the methane fluxes through different interfaces.