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. 2020 Oct 9;11(1):5087.
doi: 10.1038/s41467-020-18899-3.

Impact of tides and sea-level on deep-sea Arctic methane emissions

Nabil Sultan  1 , Andreia Plaza-Faverola  2 , Sunil Vadakkepuliyambatta  2 , Stefan Buenz  2 , Jochen Knies  2   3
Affiliations

Impact of tides and sea-level on deep-sea Arctic methane emissions

Nabil Sultan et al. Nat Commun. .

Abstract

Sub-sea Arctic methane and gas hydrate reservoirs are expected to be severely impacted by ocean temperature increase and sea-level rise. Our understanding of the gas emission phenomenon in the Arctic is however partial, especially in deep environments where the access is difficult and hydro-acoustic surveys are sporadic. Here, we report on the first continuous pore-pressure and temperature measurements over 4 days in shallow sediments along the west-Svalbard margin. Our data from sites where gas emissions have not been previously identified in hydro-acoustic profiles show that tides significantly affect the intensity and periodicity of gas emissions. These observations imply that the quantification of present-day gas emissions in the Arctic may be underestimated. High tides, however, seem to influence gas emissions by reducing their height and volume. Hence, the question remains as to whether sea-level rise may partially counterbalance the potential threat of submarine gas emissions caused by a warmer Arctic Ocean.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Study area and distribution of seafloor seepage.
a Location of investigated sites off the western Svalbard margin. Background bathymetry from IBCAO (gray); higher resolution bathymetry from UiT—The Arctic University of Norway database. The distribution of surveyed gas plumes during yearly expeditions to the area is indicated by green circles. Pockmarks without associated gas plumes on the western Vestnesa Ridge are indicated as gray dots. Shaded areas over the bathymetry correspond to mapped bottom simulating reflectors. b Station PZM1 is located within the gas hydrate stability area and near a sediment depression where gas hydrates have been recovered. c PZM2 was deployed in an area characterized by a seismic facies showing parallel reflections and no major vertical discontinuity.
Fig. 2
Fig. 2. Data from piezometer site PZM1.
a Temperature and b pore pressure versus time. The different colors indicate the depth below the seabed. Sensor depths are between 0.8 mbsf (gray curve) and 7.9 mbsf (brown curve). Pressure axis limited to −100 kPa, for better visualization of the majority of the data.
Fig. 3
Fig. 3. Data from piezometer site PZM2.
a Temperature and b pore pressure versus time. The different colors indicate the depth below the seabed. Sensor depths are between 0.8 mbsf (gray curve) and 9.4 mbsf (brown curve). Tidal heights obtained at the piezometer location from the TPXO 9.0 global tidal model, are shown as dashed light blue line.
Fig. 4
Fig. 4. Gas bubble velocities.
a Pore-pressure measurements on the five lowermost sensors in the sediments measured at site PZM1 (record timing in Fig. 2). b Rising velocity of gas bubbles calculated from pore-pressure fluctuations in (a) projected on pore pressure contours at site PZM1.
Fig. 5
Fig. 5. Gas plume heights.
Equivalent continuous gas plume heights versus time (blue curve) derived from pore pressure measured at 0.8 mbsf. The plume height peaks (indicated by numbers in the figure) coincides with temperature peaks measured at the same level (red curve).
Fig. 6
Fig. 6. Thermal and hydraulic processes at PZM1.
a Predicted temperature field in the calculation domain. b The calculated temperature at 0.8 mbsf (red curve) is compared to the measured one (blue curve). c The upward fluid velocity used in the advection calculation. d The black curve indicates eastward tide velocity, while the red one is the tide height.
Fig. 7
Fig. 7. Conceptual model of gas emissions.
Schematic model showing how gas emissions may be affected by tides through fracture opening. a At high tides the system is under a balanced pressure field. b At low tides (<1 m water column height decrease) a subtle fracture dilation would shift the pressure field to favor gas advection and seepage. Pg stands for free gas pressure.
Fig. 8
Fig. 8. Piezometer.
Scheme of the piezometer equipped with differential pore pressure and temperature sensors and ballasted with lead weights. Measured negative pore pressures correspond to the case where the seawater hydrostatic pressure is higher than the sediment pore-water pressure.
See this image and copyright information in PMC

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References

    1. Rehder, G., Brewer, P. W., Peltzer, E. T. & Friederich, G. Enhanced lifetime of methane bubble streams within the deep ocean. Geophys. Res. Lett.29, 10.1029/2001gl013966 (2002).
    1. Greinert J, et al. Methane seepage along the Hikurangi Margin, New Zealand: Overview of studies in 2006 and 2007 and new evidence from visual, bathymetric and hydroacoustic investigations. Mar. Geol. 2010;272:6–25. doi: 10.1016/j.margeo.2010.01.017. - DOI
    1. Dupre S, et al. Tectonic and sedimentary controls on widespread gas emissions in the Sea of Marmara: results from systematic, shipborne multibeam echo sounder water column imaging. J. Geophys. Res.-Solid Earth. 2015;120:2891–2912. doi: 10.1002/2014JB011617. - DOI
    1. Veloso-Alarcon ME, et al. Variability of acoustically evidenced methane bubble emissions offshore western Svalbard. Geophys. Res. Lett. 2019;46:9072–9081. doi: 10.1029/2019GL082750. - DOI
    1. Smith AJ, Mienert J, Bünz S, Greinert J. Thermogenic methane injection via bubble transport into the upper Arctic Ocean from the hydrate‐charged Vestnesa Ridge, Svalbard. Geochem. Geophysics, Geosystems. 2014;15:1945–1959. doi: 10.1002/2013GC005179. - DOI

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