So as the days pass by, Silbo inches further across our maps as he closes in on his last stop before he makes landfall on the shores of Gran Canaria.   The ESTOC Zone.

This area is important in studying seasonal variation in the canaries current, and Silbo's data will make a historical contribution to a long standing time series that has recorded such changes.

But as for now, it looks like we must dodge 'bullets' as we make our way to the desired location before we head for our scheduled recovery on May 21.

Ship Traffic May 10

The bullets mentioned are the shipping traffic through the area.  This past day has been exceptionally busy as a number of large ships have passed close to the estoc zone and near where Silbo will be surfacing over the next few days.

NLOM Sea Surface Height & NCOM Currents May 5-May 9

Because of the increased ship traffic, it is now more important than ever to keep a close eye on the currents to make sure we are not swept into unfavorable areas.  Above, we see the ncom/nlom models from may 5- may 9 showing the movements of eddies around silbo and the rotation of currents towards the south.

Hycom Density & Currents

Hycom Temperature & Currents

Hycom Salinity & Currents

Hycom Sea Surface Height & Currents

While the Hycom model products shown above of density, temperature, salinity and sea surface height show slight resemblance of the south east flux shown by the ncom/nlom, the currents vary at depth resulting in the eastern reading on silbos currents calculations.

Dave Aragon also provided us with a helpful google earth overlay this morning depicting the bathymetry around the island.

Finally, I will leave everyone with a pretty cool image of the modis satellite products of temperature and chlorophyll.

Force Wind Sea and Honor All!

Nilsen & Antonio

Again I apologize for the gaps in coverage, but as Silbo's mission comes to a close, so does the semester.

Silbo is now just under 300km from the shores of Gran Canaria and so our teams are preparing to get out there to recover.  So far, the plan is to take Silbo from his current position and pass the Savage Islands on the eastern side, reach the ESTOC Zone (designated by the push pin) and station keep for 24-48 hours, before continuing towards the Canaries.  Then from the island of Gran Canaria, a team consisting of members from TWR, PLOCAN, ULPGC and Rutgers will venture out for the recovery.  We aim to do the recovery by May 18.  From there, we plan on replacing the old Alkaline Batteries with new Lithium and redeploy within a few days and send Silbo on his way to Cape Verde.

This will be a distance of about 1,350km and should take us about 2 months.  From here, Silbo will aim to be the first glider to cross the equator as we fly from Cape Verde to South America.

Finally, although we took a break in the middle due to a number of technical difficulties, Silbo has now flown 222 days covering 5200km; 1 more day than the historic flight of RU27 as she crossed the North Atlantic from NJ to Spain covering 7400km.  Now if we throw in the flights of Cook & Drake (attempts at crossing the Southern end of the North Atlantic Gyre) and Ru 17 who was our first Trans-Atlantic attempt, we have a solid foundation to the Challenger Mission of nearly 2 years and 3 month of transoceanic missions that have flown nearly 21,000 km!

Force & Honor to all!

Nilsen Strandskov & Antonio Ramos

Sorry for brief hiatus, but this past week I have been bogged down with academics; but back to the Challenger Mission.

Before we get to Silbo, I would like to officially welcome RU29 to the Challenger Family!

RU 29 is a G2 Slocum Electric Glider with an extended battery bay which when packed with Lithiums, will give us nearly 500 days of battery life at sea!  29's goal: to fly from Cape Town, South Africa to the Ascension Islands in the middle of the Atlantic

The trip will be about 4,500 km and deployment is still being determined but we hope some point this summer.

Speaking of the summer,  with the end of the semester being less than a month away, both myself and Silbo are preparing to make land fall in the Canary Islands.

Silbo is now just about 400km from the shores of Gran Canaria, with a estimated arrival date around May 15 and as long as we can avoid the heavier ship traffic as we near the Island, it looks like we should make it.  The battery estimates agree with us as our calculations show that we should be good through the first week of June.

From his location, Silbo will now fly to the south east to most likely the north eastern shore of the Savage Islands (small island chain about half way between Silbo and the Canaries), continue to the ESTOC zone (29º10'N - 015º20'W) where the data collected will be added to the extensive research done in the area, and finally meet us for the celebrations on the shores of Gran Canaria in mid may.

But now back to the mission at hand: piloting silbo safely to his destination.  Where we left off last week, Carlos and his team were sailing out of Madeira to deploy some drifters and we were trying to conduct a visual inspection to see if there was any significant biological growth on his exterior.  However we arrived at the position well ahead of schedule and so to kill time we tried to head north of the island to try and sample an eddy, however we got trapped in a very strong northward current and resulted in us missing the rendezvous.  As we kept an eye on the ship traffic, the drifters were then launched at about 32.6N, 17.4W and within a few days, Silbo caught up and passed them as he continues on his journey south.

A problem we seem to have been encountering recently has been an increase in dropped calls, or interruptions in communications when Silbo is at the surface calling in to doc server.  As we passed the west coast of Madeira, Silbo came within 13km of dangerously shallow bathymetry as a call was dropped that was providing a new way point.  Not only is the lack of data transport potentially disastrous due to dropped calls, but our time spent on the surface making some times multiple calls trying to reconnect to the satellites increases our chance of being struck by a ship.  A very close eye will be needed on this as we get closer to the ESTOC region and the Canaries in general as the traffic increases exponentially.

As Silbo has continued on his way south, we have entered a new eddy solar system that we can see evolve in the movie below from April 22-April 28 thanks to Antonio and the Myocean Data Set.

The presence of the eddy to our south correlates very closely with how the currents recorded by silbo changed as he moved from the smaller warm eddy to the larger one we are on the cusp of at the moment.  This large one is the source of the south east flow we are now encountering.

Above is an image created by Antonio showing the salinity showing that the eddy is so intense, that the effect on salinity can be seen all of the way down to 900m.  This eddy will fuel our progress over the next week or so as we ride it to the south east on our way past the savage islands.

Below we see the Hycom, NCOM and Nlom data sets for today showing a different perspective as the flows are generally in the south west direction:

Hycom Density

Hycom Salinity

Hycom SSH

Hycom Temp

NCOM/NLOM SSH and Currents

Now that we have made enough progress east, we are now in the domain to use a new website, MarineMet.  This website will provide useful data not only for Silbo's continued progress as long as we remain within it's limits, but it will also be useful for 29's mission in the up coming months.

And finally, The Challenger Mission has a new web page with tons of history, background information and interactive images for everyone to see.  This new web page can be found here: http://challenger.marine.rutgers.edu/

For now, Force Wind Sea & Honor

Nilsen, Antonio and Oliver

HYCOM Sea Surface Height

Unfortunately, we have run into a strong head current as we are trapped on the east side of a large cold eddy, which combined with the presence of the Island is producing an incredibly strong northward flux in the area.  We will be keeping a close eye on silbos position as he surfaces. after each single dive to give us a new position.  We are hoping to cut our way through this strong head current to try and make it to a reasonable distance to still pull off a rendezvous.  We are being optimistic, but on the last segment, Silbo only covered 2km..

NCOM/NLOM Sea Surface Height and Currents

Tomorrow morning as our friends sail out for the recovery, we will try and catch their progress using the marinetraffic overlay which will easily prove its worth as we continue to the finish line where the shipping traffic is much busier than the peaceful west side of Madeira.

Marine Traffic Google Earth Overlay

We will keep everyone updated tomorrow with what excitement lies ahead.

Force Wind Sea & Honor to all

Nilsen Antonio & Oliver

Sorry for the gap in coverage on Silbo's mission.  Our brave little droid is continuing to wait patiently in the area of Madeira as our team prepares to inspect and deploy a buoy at the end of this week.

Last week, Silbo went into his station keep agenda as he bounced back and forth between two way points for a few days as we killed some time.  Our team had spent quite a bit of time making calculating how long it would take for Silbo to arrive near Madeira and so we panned accordingly to get our team out there.  However, Silbo set a number of speed records for his mission as we saw some of the most favorable currents we have encountered since deployment back off of Iceland and we arrived quite a bit early.

For now, we have sent Silbo to fly to the North west of Madeira to sample a cold eddy before we swing back down towards Madeira for the rendezvous.

Nilsen & Antonio

So after brainstorming a number of ideas on what to have silbo do to kill time while our team from PLOCAN makes it out to Madeira for the rendezvous, Silbo has now begun operation station keep. Silbo is now only about 100km from Madeira, 8 days before our team will be able to arrive on scene.

Figure 1. Silbo now less than 100km from Madeira

Currently we are crossing the northern side of the warm eddy planet of the series that we have been surfing for the past two weeks.

Although the hycom layers show a northward flow, myocean sub surface currents all show a general flow right towards the island.

Figure 2. Hycom Density

Figure 3. Hycom SalinityFigure

Figure 4. Hycom Sea Surface Height

Figure 5. Hycom Sea Surface Temperature

Figure 6. Myocean Currents at depth

Figure 7. Ncom Nlom Currents and Sea Surface Height

The geostrophic currents in the above image of the ncom currents overlayed on nlom sea surface height agree with the flow shown at depth from myocean showing the current moving towards Madeira.  This flow again would be ideal if it wasn't for the time frame we decided on before Silbo turned on the jets and set speed records as he made amazing progress over the past week and a half.

So to kill some time as our team makes their final preparation we are instating a station keep game plan.  This consists of setting two way points close together  (in this case 1823.8500W 3245.0050N and 1824.0000W 3245.0000N).  Silbo will then bounce back and forth between these two way points over the next couple days until our friends at PLOCAN are ready for us to move the way point back to the meeting point.

In deciding where we would station keep, we had to keep a few things in mind.  We needed to stay far enough away from the island to avoid shipping lanes, unfavorable bathymetry, and the effects of the tides.

Figure 8. Shipping traffic for this evening

Figure 9. Bathymetry around Madeira

We chose to try and keep Silbo west of 18˚ W to keep our heroic little droid out of the bad scenarios listed above.  Luckily the ships are pretty quiet tonight, however we will keep a keen eye on both the marine traffic overlays and the localizada ship traffic.

Finally, we are keeping an eye on the battery consumption to make sure we are not running low.  Currently it looks that we are still in the clear as our plots indicated we should be fine battery wise through to June.

Figure 10. Estimated Battery Consumption

We will update again soon on Silbo's progress with the station keeping.

Nilsen Strandskov, Antonio Ramos, Oliver Ho.

Figure 1. Myocean/IBI ROM Surface Salinity

Figure 2. Myocean/IBI ROM Salinity 220m

Figure 3. Myocean/IBI ROM Salinity 318m

Figure 4. Myocean/IBI ROM Salinity 643m

Figure 5. Myocean/IBI ROM Salinity 760m

Figure 6. Myocean/IBI ROM Salinity 1060m

Figure 7. Myocean/IBI ROM Surface Eastward Current Components

Figure 8. Myocean/IBI ROM Eastern Currents Coomponents 220m

Figure 9. Myocean/IBI ROM Eastern Currents Coomponents 760m

Figure 10. Myocean/IBI ROM Eastern Currents Coomponents 900m

Figure 11. Myocean/IBI ROM Eastern Currents Components 1060m

Figure 12. Myocean/IBI ROM Sea Surface Height

This data will prove to be very useful over the next month as Silbo makes his way to the Canaries and for future missions.  We all look forward to utilizing the 96 hour forecast as it will easily revolutionize how we pilot gliders from a reaction based system to an attack system where we can see what will happen up to 4 days ahead of time and use that to make piloting decisions.

Nilsen Strandskov & Antonio Ramos

So over this past week, I have been working on plotting up some data from Silbo's mission so far and then also spent a little bit of time comparing his data to a near by Argo drifter.

Figure 1. 3d temperature plot of Silbo's track from Iceland to the Azores

Figure 2. 3d Salinity plot of Silbo's track from Iceland to the Azores

In figures 1 and 2, we can see how much the water conditions have changed from being almost uniform in temperature and salinity from surface to 1000m depth to being strongly stratified near the shores of the Azores.

Next I plotted more recent data, comparing Silbo's temperature and salinity to what was recorded by a near by argo drifter, coriolis 6900511.

Figure 3. Temperature and Salinity profiles from Argo unit Coriolis 6900511

Figure 4. Temperature as recorded by Silbo

Figure 5. Salinity as recorded by Silbo

Although the Argo drifter went down another 1000m past what Silbo is capable of, the data shows a very nice correlation showing nearly the same shapes and depths for the thermocline and picnocline.

Nilsen

So Silbo is still barreling on his way towards Madeira as the currents continue to unfortunately be favorable.  With the way the currents have been moving, it seems we may need to take some sort of evasive maneuver to prevent ourselves from getting too close to the island where we will find unpleasant bathymetry and some pretty heavy ship traffic.  The most likely scenario would be to station keep for a while (fly between two close waypoints) until the team with the drifter can get out there to inspect silbo and deploy the drifter.

Figure 1. Hycom Density

In the image above of density along with the images below from the hycom model, we can see that Silbo continues to ride down hill along the mesoscale as he heads towards his waypoint.  According to the models, it looks like if we were to go north a bit and fly with our nose into the cold eddy, we could slow ourselves down.  This could solve our problem of hitting speeds up to .45m/s

Figure 2. Hycom Salinity

Figure 3. Hycom Sea Surface Height

Figure 4. Hycom Temperature

Figure 5. Myocean Surface Conditions

Now looking at the myocean data to see what is going on throughout the water column, the salinity really portrays the best idea of what Silbo is dealing with subsurface.

Figure 6. Myocean Salinity at depth

Figure 7. Myocean Currents at Depth

Figure 8. Myocean Eastern Zonal Component currents at depth

It seems that deep salted cold fluxes of Mediterranean water have increased flow into the atlantic over the past couple months.

During the winter, the convective cell NW mediterranean is really intense (transmitting heat to the french, spaniard, italian coasts thus preventing its freezing.  This cold salted water sunk and streamed along the eastern coast of spain, flowing south and then left the mediterranean through the straight of gibraltar and sank down to 600 m.  The effects of the out reach of this salted mediterranean layer can be seen in the images showing salinity at 600, 800 and 1000m.

If you look at the salinity for the upper ocean, it is pretty uniform from the surface to 400m. However if you go deeper, Med water appears around silbo at 600 m, and have an affect until his deepest diving depth 1000 m.

Looking ahead, there are some salt driven eddies around him coming from the NE.  This most likely is the explanation of how different the current fields are between the surface-500m and 500m-1000m.

But the Mediterranean will not continue to be a huge driving factor much longer.  There is some cold but fresher water reaching up from the south that keeps the mediterranean waters north of Madeira

Force Wind Sea and Honor

Nilsen Strandskov, Antonio Ramos, & Oliver Ho