Observation and modeling of hydrothermal response to the 2015 eruption at Axial Seamount, Northeast Pacific: An OOI Cabled Observatory case study
Abstract
The 2015 eruption at Axial Seamount, an active volcano at a depth of 1500 m in the Northeast Pacific, marked the first time a seafloor eruption was detected and monitored by a cabled observatory - the Cabled Array operated by Ocean Observatories Initiative (OOI). Following the eruption, eight cabled and non-cabled instruments recorded a temperature increase across the southern half of the caldera and neighboring areas. These temperature signals were very different from those observed after the 2011 and 1998 Axial eruptions. The 2015 temperature increase occurred later (3.5 days after deflation started versus 6-18 hours) and had a larger amplitude ( 0.7°C versus 0.2-0.5°C), a much slower increase and decay and smaller short-term fluctuations. Most remarkably, the 2015 temperature signals were synchronous and uniform across the 3 x 4.5 km2 area covered by the eight instruments. We hypothesize that the eruption triggered the release of a hydrothermal brine stored in the crust. In this interpretation, the observed temperature increases were due to a dense, bottom-hugging layer of warm salty water that was created when hot brine in the crust was flushed out after the dike intersected the zone where the brine was stored. In the absence of near-bottom salinity observations, we test this hypothesis by using a numerical model of ocean flow and transport to simulate the thermal response within the vicinity of the caldera following a brine injection. We set up the model with realistic background flows, hydrography, and seafloor topography. We simulate brine release as seafloor heat and salt inputs at locations inferred from seismic and geologic observations. Comparison of model bottom temperature with measurements shows a reasonable match. If our interpretation is correct, this is the first time that the release of a hydrothermal brine has been observed due to a submarine eruption. Prior to the next eruption, the Cabled Array observatory should be enhanced to improve the monitoring of the water column in the caldera.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.T33G..02X
- Keywords:
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- 0450 Hydrothermal systems;
- BIOGEOSCIENCES;
- 3035 Midocean ridge processes;
- MARINE GEOLOGY AND GEOPHYSICS;
- 4568 Turbulence;
- diffusion;
- and mixing processes;
- OCEANOGRAPHY: PHYSICAL;
- 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICS