We had a rough transit from Tromsø to the Fram Strait. Six-meter waves and strong winds slowed us down to a sailing speed of six knots (normally this type of vessel navigates at 10-11 knots). We left Ramfjord at about 15:00 on Saturday (the 17th) and arrived on-site The Vestnesa Ridge on the west-Svalbard continental margin three days later.
Text and photos: Andreia Plaza Faverola. Researcher CAGE, project manager SEAMSTRESS.
On Vestnesa we will conduct experiments, which we designed to test the following hypothesis: The core of the SEAMSTRESS project is that the opening of the mid-ocean ridges compresses the sediment against Svalbard. This leads to high fluid pressures that eventually result in gas expulsions. Just like in a closed casserole with boiling water in the kitchen. On the Vestnesa Ridge, the gas expulsions have occurred everywhere for the last 20.000 years (since the last big ice age). But the release of gas remains abundant only towards the east of the margin. So what happened towards the west of the margin?
We have selected four stations along the margin to measure the pressure of the water and the gas in the sediment. For this, we will use the Ifremer piezometer I mentioned in the previous post.
We need to carefully select the locations for the instruments because we do not want to reach a fault (we want the background pressure of the fluids). The ship is steered precisely by an amazingly skilled crew, keeping position within two meters. We are having fun! We also survey the ground with the sub-bottom profiler (acoustic waves) to be sure we are not aiming for dangerous structures. In one of the stations, we also placed five ocean bottom seismometers carefully around the piezometer. We want to search for a relationship between microseismicity, pressure pulses in the sediment and pressure changes due to tides.
So far, we have placed two piezometers that have hopefully been recording data over three days. The plan is to recover them between today and tomorrow. If time and weather allow we would like to put them back for the remaining two stations.
In-between, we have been measuring the temperature of the Earth. Temperatures are key for modelling the zone where gas hydrates form. From these temperatures, we can calculate how fast the heat is transferred through the sediment and we can predict the movement of warmer overpressured fluids from deep sediment toward the seafloor.
Since we arrived the sea has been calm and generous. We hope the Viking gods continue to be on our side.
