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Hey All

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

Force Wind Sea & Honor

Hey All,

Challenger is making quick work of this last stretch before recovery on the shores of Ascension Island.

With less than 260 km remaining between our brave little glider and the end zone, we could potentially make it to shore within 10 days with our average speed being around 26 km/day.   However, we do have some battery left and the potential to do some creative sampling around this little oasis in the middle of the Southern Atlantic.

This will be a topic of discussion in class today, but so far Antonio has proposed two branches of ideas: to circumnavigate the island to study the wake created by the island being in the path of the flow of the gyre, or ahead of us is a region called the Ascension Fracture which is part of the Mid-Atlantic Ridge- the topic of study here would be to look into the oscillations we saw with Silbo crossing the Mid-Atlantic Ridge some months ago in the north.

And the third option which could also be incredibly valuable to our cause would be hiring someone to go out and recover for us sooner rather than later- when Scott and Chip arrive in Ascension there will be a number of tasks to get done on a very limited time frame and if there is less than ideal weather, that could make things much more difficult. However, if we were to recover now that gives us a much larger window to find out what needs to be fixed on the glider, what needs to be in Ascension for the operation to be successful, and more time to get the glider in the water just in case the weather is stormy upon our teams arrival.

We will update later today on what is discussed during class

Force Wind Sea & Honor

It may be a slight exaggeration, but Challenger has picked up her game in the final hour of her mission.

Over the past week, our team has worked very hard meeting deadlines to get all of the necessary equipment for recovery and redeployment slated for arrival in Ascension Island in november. However, Challenger has kicked it into high gear, reaching speeds close to 25 km/day once more.  If this continues, we should be very close to shore within the next two weeks!  Yesterday, as Antonio predicted over 10 days ago, she crossed into the EEZ officially leaving international waters for the last time while on this mission.

Looking at Antonio’s 3-D bathymetry, the Ascension Fracture Zone is all that lies between Challenger and her finish line.  We plan on taking evasive maneuvers around this area even though our maps say it doesn’t rise further than 1600m from the surface just in case the maps are not in a high enough resolution to pick out small points that may be hazardous, and because we have loads of time to kill.

Once we get to the island, we plan to kill time in one way or another.  This will be discussed in class amongst the undergraduate students next week on Tuesday

Force Wind Sea & Honor

Fish & Chips and Roast Beef for all!

Just 350 km from the shores of Ascension, we should be in range for a recovery within the month!

Force Wind Sea & Honor

Hey all

The end is nigh!

Challenger is now just under 500 km from the shores of Ascension, and just 130 km from leaving international waters for the last time on this mission. Over the past week or so, we have noted that she has had what seems to be a head current.

While the currents appear to have changed, Challenger is still making good time, flying over 21 km/ day.  This leads us to believe that there may be a new cohort of barnacles causing drag  once again resulting in the gliders calculation to think there is a head current. This may be problematic over the course of the next few weeks.

As we look at our schedule, our team will be arriving for the recovery of Challenger on the shores of Ascension, however if Challenger continues to keep up the pace (21 km/day) she should be in the area roughly a month ahead of the recovery team.

Because of this we are now weighing our options of way to pass the time until recovery. Two options that have come to mind thus far have been flying a circle around the island, keeping away from the fishing vessels; or revisiting the eddy sampling technique we tried near Madeira in spring of last year where we would fly a wind mill pattern through an eddy- effectively sampling its thermal structure.  As of right now theses are just ideas we are discussing and there is always the option of stationkeeping for the remaining time, however that option is by far less fascinating

Force Wind Sea & Honor

Hey All,

With Silbo now safely on shore and preparations being made  for his safe return to Teledyne Webb Research in Massachusetts, we now can focus solely on Challenger and her mission to cross the South Atlantic.

Now, just under 800 km from the southern shores of Ascension, we set our sights on what is seemingly the last stationary obstacle standing between Challenger and her destination: one last ridge of seamounts.  To prepare for their presence, we set a way point to the north of the island to account for the ~11˚ offset we have grown accustom to flying with over the past months, and with the way point being close to 900 km away we don’t have to worry about hitting it any time soon.

One oddity we have noticed while flying past the previous subsurface mountain range was that there was a noticeable oscillation in the currents

As there was little evidence in the surface current forecast to confidently say what was the cause of this, we delved deeper into the data and found two interesting clues:  the thermocline had deepened and we were flying slightly faster on dives than on climbs.

Antonio pointed out that this was a similar flight scenario as to what a glider sees when crossing a strong warm eddy which sparked an idea in his mind.  To the south west of the island of Gran Canaria, there is an eddy that remains for the most part stationary in its location and is caused by drag as the currents flow through the island chain.

Sea Surface Height

Sea Surface Temperature

Now in our scenario, the sea mounts came within reach of the subsurface flight pattern of Challenger, but did not breach the surface as the islands of Gran Canaria and Tenerife do.  Because of this fact, this warm eddy that we believe we flew Challenger through would not have a signature at the surface and would cause the thermocline to be substantially deeper

Force Wind Sea & Honor

For those of you who have been following us for a while, crossing the 221 days at sea mile stone is a big one.

This 221 Day mark is a historic mile stone set in 2009 when the glider team took the Slocum Glider RU 27 over 7,000 km and crossed the North Atlantic from Tuckerton, NJ to Baiona, Galicia, Spain.

“In spite of neptune & poseidon, the VIG club grows.” When we first started piloting Silbo in June 2011, Antonio and I started the VIG or the Very Important Glider club that we used as a way to acknowledge the gliders we were working with as they pushed the limits of what these gliders could accomplish.  And now after 222 days at sea, we are including Challenger as well.

Since deployment, Challenger has most certainly had her work cut out for her.  Promptly after crossing the shelf break of South Africa, the compass went haywire; she encountered numerous hazardous sea mounts; the deep eastward flux that she fought from February – June; the 10 day siesta in which we had no communications with the glider as she was stuck in an infinite loop underwater; diminishing battery deadlines; and of course, Barnacles!

Moving along, yesterday I gave Challenger a new way point just a little to the north east of Ascension island to try and correct for the roughly 11˚ offset we have been flying at.

However, ahead we have what looks like one last batch of sea mounts that have the potential to be dangerous, so we may need to curve our flight path around them instead of making a b-line for the island.

As it stands now, Challenger is roughly 820 km from the shores of Ascension Island so if we were to maintain >22 km/day, we should be looking at a recovery date by the end of September.

Force Wind Sea & Honor

As our dear friend Antonio exclaimed; GOAL!!!

Over the weekend, Challenger made her way out of St Helena’s EEZ and into open, successfully ducking around the last of the unfavorable bathymetry until the rocky shores of Ascension Island!

In the surface waters over the past couple of days, we have seen the circulation of a large cold core eddy as we transect the center, resulting in the oscillation of the gliders currents from North West to West. The eddy’s signature however is only seen in the first couple hundred meters and at depth we continue to see the deep north east flux shown in the image of pinzon above.

This flux should continue to help us along on the remaining 870 km that stand between Challenger and the shores of Ascension.

Force Wind Sea & Honor