Oscillations, Oscillations EVERYWHERE
So since Antonio's video call last week with the Ocean Observatories class, we have made the decision to sample the Ascension Rift over the upcoming weeks as our team prepares for recovery in the first weeks of November.
Back in April as Silbo crossed the Mid-Atlantic Ridge, Antonio discovered that there was a noticeable counter clockwise oscillation in the depth average currents. These seem to be localized features caused by the flow of the gyre across the subsurface mountain range.
The plan we arrived upon for Challenger's last ditch science mission will follow the path outlined below
The path runs us about 550 km from our latest location, which should take up roughly 23 days before we arrive near the western shore of Ascension island. In preparation for this test, we have bumped up the sampling on the glider, now collecting data on all dives and climbs instead of on the first dive of each segment as we have done previously as a power saving technique. But now as we have plenty of battery for what we have left to do before recovery, we will take advantage of the opportunity we have been given. Within the next 6 surfacings, we should be just about ready to change the way point towards the west to make our first crossing of the fracture zone.
As we approach the ridge, Challenger has also come across a sub surface eddy that we have have traversed over the past couple days.
As seen in the depth average current calculated by the glider, we can see a clear rotation of the current following the pattern that could be associated with a warm counter clockwise rotating eddy.
A third oscillation we have noticed, is the depth of the thermocline.
Since the siesta back in May, the thermocline has been moving up and down in roughly two week periods overlaid with 3 day oscillations. We are bouncing some ideas around with what could be causing this, but with the increased sampling rate, we may even be able to detect smaller scale shifts.
We will keep everyone updated on our project as it develops and we come to any conclusions
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