Category: silbo (Page 8 of 22)

Hey All!

So this weekend, Silbo took another step in the V.I.G. club breaking the barrier and recording his 9,000 km since deployment off of Iceland!

Over three deployments beginning in June of 2011, Silbo has spent 433 days (and counting) at sea pushing the limits of the Slocum glider and collecting valuable flight data that is being applied to the Rutgers Gliders that will be used in the Challenger mission, including RU29: Challenger.

And as we have seen a number of times through our experience with Silbo, sometimes our ocean models fall short and do not have a high enough resolution to show us the whole picture of what he oceans are doing.

For example, right now we are flying between a warm and cold eddy which the models show creating a jet shooting out to the northwest. However Challenger is feeling the effects of a current going to the south east.  This combined with the way point to the North, results in Challenger flying due north but making very little progress.  We will discuss a new waypoint and try and make our way out west.

Enjoy Super Bowl Sunday Everyone!

Force Wind Sea & Honor!!

Hey All!

Well it’s official, Challenger has crossed into international waters!!! On the last surfacing, Challenger pushed forward to fly 450km allowing us to finally cross our boundary.  Now we can focus further on setting ourselves up to jump from eddy to eddy on our way to Fortaleza Brazil without worrying about crossing another countries property

Speaking of chasing the eddies, we will continue to fly Challenger to the North West as we move into position to follow the stream of eddies that pours out of the Indian and follows the South Atlantic Gyre to the North West.

By jumping from eddy to eddy in this fashion, we should be able to work our way up towards St. Helena and Ascension Islands on our way towards Brazil.

Looking at the eddies in our vicinity, it looks like we should be having currents more to the north west, however we continue to record currents flowing nearly due south.  Tomorrow I will try and create an image of the depth average currents to see if there are any subsurface currents that may be harmful to our mission.

Today we also ran a steering test, in which we adjusted the gain values to try and beter utilize the fin.  The gains were also adjusted on low power mode, that way when the computer turns on after sleeping for 30 seconds, it doesn’t immediately jump unless there has been a drastic change in direction.

Silbo is continuing to feel the steady north western flux of the north eastern edge of the cold eddy.  As slow as silbo has been moving due to this situation, it is looking more and more as if the large warm eddy to the south may come to the rescue.  As each day passes, it seems this eddy pushes closer, resulting in the cold eddy becoming over powered.  Hopefully within the next couple days, this eddy will become completely irradiated and Silbo will see currents moving to the south for the first time since the second week in October!

Force Wind Sea & Honor!

Hey All!

As Challenger turns to fly to the north west with our new way point, she is closing in on the boarder defining the South African EEZ and the international waters!

It looks like the stream of eddies is moving out to the west so we are feeling less of an affect from the warm eddy to our south, however this is causing us to now feel the added effect of the cold eddy to our north resulting in a little more of a northward current at the surface.  Hopefully we will be able to ride this further to the north once we cross into international waters.

To the north, Silbo continues to fight his way through the northern flux created by the cold eddy to the west and warm signature to the east.  However there is some good news: the large warm eddy to the south west seems to be migrating in a north west direction. This we hope will expedite Silbo’s progress into more favorable currents.

Force Wind Sea & Honor!

Hey All!

Today during my discussion with Antonio of the layout of the playing field for Silbo and Challenger, Antonio pointed out something very interesting. The conditions that Silbo and Challenger are flying through are nearly symmetric!

As we fly away from South African waters, Challenger has found the trail of eddies that come from the Indian ocean, round the cape and shoot up into the South Atlantic Gyre, paving the road we plan on taking to the North East towards Brazil.  The depth of the thermocline from the warm eddies in the area also follows a trend Silbo is seeing, where the eddies closer to shore have a deeper signature.

In the north, Silbo again is seeing similar instances with the depth of the thermocline within eddies, but is also seeing a similar trail.  However this trail follows the equator and is formed from the interaction of the Northern and Southern Atlantic Gyres.

The salinity maps also have proven to be symmetric in the North and South Atlantic:

In the south, Challenger is flying away from a region of fresher waters from the upwelling event that has been fueling the plankton bloom we spoke about last week along the coast.

While up in the north, Silbo continues to inch forth towards the prominent Amazonian outflow which yesterday we pointed out causes the concentration of salt to decrease from 37 to 34.

Finally on the next surfacing, we are moving Challenger’s way point further to the north east from the current way point to make an attempt at flying more in a northern direction.  With the way point signified by the red dot in the image below, Challenger has been flying due east.  A heading that we are worried will not be enough to keep us from being sucked into the southern current created by the strong warm and cold eddy to our south and south west.

Force Wind Sea & Honor!

Hey All,

So starting late last week, we began to notice an anomaly with the flight patterns of Challenger.  On down casts, we were seeing a number of heading errors, causing us to fly irregularly.  This spurred a number of questioned followed by a brainstorming session to figure out what could have caused this.  After all, before deployment, the compass had been calibrated and was working well.  Ideas that we bounced around ranged from looking into a recent solar flare, positions of lows in ozone concentration, and high levels of ambient iron in the water; all of which could result in abnormalities in electronic compass readings.  Finally, our team began looking into similar instances we have had where a gliders compass had acted in a similar manor.  One of these instances that came to mind was a few years back when RU26 was flying in the Ross Sea off of Antarctica.  After doing some research, it was discovered that both the region off of South Africa and the Ross Sea are both areas with abnormal lows in the horizontal intensity of the Earths Electromagnetic field.

Now, we think that the problem we are encountering is that this low in horizontal intensity combined with the angle we were diving at causes our compass to have errors in the eastern quadrants, impeding our ability to have complete control of our direction on dives.

Since we have hypothesized this as the reason for our abnormal flying, we have done a number of tests diving at different angles and have now chosen to fly at 20˚ on dives and 25˚ on climbs.

While we were running the tests, we lost a bit of position on the eddy we are flying through, so I have now plotted not only the currents, but the U and V components to find the best route North and West safely into international waters.

U Component blue to the west and red to the east

V component Red being north and Blue to the south

Based off of these maps, we have placed the waypoint up to the North West hoping to weave our way between the fluxes while avoiding crossing into Namibian waters.  Other quick changes we made today were that low power mode has been turned back on at intervals of 30 seconds and current correction has been switched off so we can get a feel of how we can fly.

As for our boy Silbo to the north, he is still pushing along through the northern flux from a cold eddy to our south west.

Antonio has created another fascinating tool with the help of GeoEye and SeaStar showing correlations between the eddies and the depth of the thermocline.

From this map, we can see the presence of these eddies causes changes of up to 100m in the depth of the thermocline as we fly from warm eddy to cold eddy.

With the map above of sea surface height and currents with the overlay of the direction of the eddies, we can see that Silbo is continuing to fly due south between the influences of the large warm and cold eddies to the south east and south west respectfully.

Finally, Antonio left us a 3D map of salinity showing that starting from the Amazon and working out across the North Atlantic showing the range of 34 to 37: an incredible change for distance of 2000km

Force Wind Sea & Honor

Hey All!

So today I began looking into the salinity fields for the North Atlantic in search of any signals that may help fly south towards Brazil.  Our team has been thinking of looking into this to see if the Amazon and its fresh water fluxes may have any extending influences on this area. To start off our investigation, I plotted up some of the myocean data.

What it looks like from this perspective, is that the waters close to Brazil and along the shelf become much fresher and spill out a little into the North Atlantic, however subsurface, we see the Antarctic Intermediate Water creeping north.  This will need much more investigation as we get our other products up and working.

As for the currents, we still have some weak flows to the north, but to the south there is a strong jet that may prove to propel us towards the equator and maybe speed us up a bit.  But only time will tell and as for now, Silbo will continue to fight his way south on his journey across the Atlantic basin.

Today, we also did some testing on Challenger’s compass, which caused us to drop a little to the south due to the influence of the small cold eddy I mentioned last night.

This evening however, once the testing was completed, the waypoint back to the north was reassigned and so on the morning surfacing we should have some new northward progress.

Force Wind Sea & Honor

Hey All!

I just wanted to leave everyone with a quick update before bed.

18 days in, Challenger is continuing to make progress towards the way point to the North West.  The image below shows the sea surface temperature and surface currents:

As we can see, the warm eddy we have been chasing has collapsed a bit, resulting in a small cold core clockwise eddy that has produced a minor counter current that is slowing us down a little bit and pulling us a little to the south.  Over the next day, we will see how this current continues to affect us and may follow up with some changes.

In the north, Silbo is continuing to fight a head current.  Similarly we look at the sea surface temperature where we see a a cool jet rising to the north resulting in the head current and leading into the cold eddy to our west.

This current however is not too strong and so we may just try and power through it towards the large warm jet to our south west.  But we will have more on that soon after we talk more with the team

Force Wind Sea & Honor

Hey All!

Well the hover test we ran last night didn’t give us the positive results we were hoping for:

The idea behind this test was that given the deeper we go, the more northern the current shifts, we wanted to take Silbo and only dive for the first couple hundred meters effectively avoiding the bad currents.

So instead of diving to 1000m on two consecutive yo’s, Ben gave our little droid the command to dive to 200m, and then do his best to maintain a depth of 300m, +/- 100m (defined as the deadband).  Although Silbo was able to follow these commands reasonably well, we made no southern progress and instead drifted just a little bit west.

We also thought that this test would not be very energy intensive.  This turned out not to be true.  On that dive, Silbo used over 3 times as much energy as normal.  Thus we will have to go back to the drawing board to see if we can come up with any other creative ideas to get Silbo out of this head current.

As for Challenger down South, last night she had a bit of an oddity in her flight, but overall is still flying very well.  Last night Challenger made a strangely low amount of progress on a 12 hr mission.  We noticed that although the depth average current was pointed almost directly at the way point, we flew off more to the north.  We think this oddity may have been an error with the current correction command so we may play around with that over the next week to see if we can get some better results.

As the crow flies, we are now just 108 km from leaving South African waters, however the path we will take will be a little longer than that:

Over the next week or so, we will follow a path similar to the white line outlined above. For the next couple of surfacings we will continue to fly towards the way point to the north west, until we reach the outer edge of this counter clockwise warm eddy.  Once we each that northern boarder, we will move the way point out to the west towards a way point Antonio outlined late last week that will carry us from South African Waters safely into the open ocean.

Force Wind Sea & Honor

Hey all!

As our title suggests, our team is still looking for solutions to the head current  Silbo is continuing to contest with.

Later today at the next surfacing, we are going to try a hover mission, where theoretically, Silbo will dive to ~200m and maintain that depth for a few hours.  With this strategy, we intend to dive below the euphotic zone while riding a more favorable current rather than diving deep and hitting the northern current that has been slowing us down.

As for Challenger in the south, she is continuing to make good time as rockets towards the new way point to the North West:

Looking at the surface currents and sea surface height from GeoEye/SeaStar, the new way point lines us up to fly the outer edge of this warm core eddy as we make our way out into international waters.

The presence of this eddy is again supported by the aggregation of chlorophyll a levels to the north of us.  This gives us another view of the way the waters are moving, as the organisms that produce these signals move at the will of the currents.

Finally I will leave everyone with the impressive 3D representation of the sea surface height, showing the path ahead for Challenger:

Tomorrow I will update on the progress of the hover test

Force Wind Sea & Honor!

Hey All!

So today our team bounced some ideas around to see if we could find a solution to Silbo’s predicament.  For the past few months, Silbo has been faced with a strong current ranging from North North-West to North North-East that has slowed us to half of the speed we have flown in the past.  One idea that we had stemmed from an event that happened last week, when Silbo had an error that caused him to only dive to 600m.  When he surfaced he reported that the currents were closer to what the model is telling us: flow to the south west!  So the initial idea thrown around was only having Silbo dive 500m, however this would cause the pump to move twice as often, bleeding the battery.  Another option suggested by Ben from TWR, is to have Silbo dive to a depth we feel would have favorable currents, and maintain that depth and have that favorable current push us for a few hours.

Antonio and I suggested that if we try this ‘hover’ strategy, we should try for 200m.  It seems that the currents  towards the surface may be closer to what the models are telling us, so we chose a depth that wouldn’t take us too far into the unfavorable current.  Another aspect to take into account is that we want to stay out of the productive surface waters.  From our experience and the word of others, the rule of thumb seems to be that barnacles stick to waters >15˚C.  As seen in the temperature time series above from Silbo, 200m keeps us in waters that are roughly 12˚C.  We may not get to this test tomorrow, but I will update you guys on our progress over the weekend.

Down south, Challenger continues to shoot through South African waters on her way towards open ocean.

Tomorrow, we may move the way point more to the north to take better advantage of this northward current we are seeing and ride it out for a few years.  It seems the counter clock wise spinning eddy is slowly moving off shore, so we are trying to bring Challenger towards the outer edge to avoid the possibility of being dragged south when we reach the other side of the eddy.

Force Wind Sea & Honor