Archive for July, 2011

Right handed and left handed marine solar systems.

Friday, July 29th, 2011

Hey ¡ Buenos días a todos ¡

Obviously, it looks that challenger 1 mission, a huge international oceanographic mission becomes by moments the MCXXIII chapter of STARTREK and our brave Silbo, more than a glider, becomes the mythic Enterprise …

As Nilsen posted, he has generated an intense traffic of emails and procedures this week. Homework has been focused on battery power consumption forecasts, converting to kmz the data sets available to be included in the website of the mission in real time, Barnacles and finally, object of this post, liquid solar systems. Not so bad: “barnacles and liquid solar systems”.

Some weeks ago, on 24 june, we reported the presence of a liquid meccano of alternatives eddiies belt of different sign at different meso and submesoescales space time. When we made a zoom we observed that this marine eddy galaxy (!??) was engaged forming by different solar systems that seemed to follow the same premise. A belt of eddies was sorrounding another of contrary sign. Thus on 8th july, Silbo was flying the first of this gears. We had a number of cold core eddies surrounding a warm core eddy that were in our path (figure 1).


 

 

 

 

 

FIGURE 1. SSHa 8 jul 11. Left handed solar system formed by a warm eddy (sun) in the centre and cold eddies (planets) gyring and translating anticlockwise around.

Two weeks later, Silbo (“enterprise”) follows finding and sailing/flying some liquid solar systems organized in a very espectacular, effcient and simple way. Look that he is heading a new one. However there are some differences with the previous one. This new target is right handed marine solar system (cold sun and warm planets). We would also expect translation movement (to the right) around the cold eddy of the centre that we expect that will not move (figure 2).

 

 

 

 

 

Figure 2. SSHa 27th jul 11. A right handed marine solar system.

 

When we compared both solar system the simetry and size appear evidents. Both translate around a static sun located in the middle at (to check it) apparently the same speed of 8-12 km/day (figure 3 a,b).

 

 

 

 

 

 

Figure 3a and 3b. SSHa field on 8th and 27th jul 11. Left handed and right handed marine solar systems.

 

We thought the best course of action is to follow these eddies around and try and shoot ourselves as far south as we can by using the alternating currents caused by the cold and warm eddies (cold eddies spin counter clockwise while warm spin clockwise). And we did it. Now, we are applying the symetric protocol to cross this new but right handed liquid system. To cross the initial planetary belt of warm eddies by its right side and, (W path) cross the sun (55 N) by the western side and then the eastern side of the warm eddy located at south (54 N). However there is another solution. To move the Waypoint to the E and attack the warm eddies located SE silbo until arriving to 22 E.  Then turn again to SW to leave the solar system and heading the warmer South (figure 4)…

 

 

 

 

 

 

Figure 4. SSHa 8th and  27th jul 11. Path plannings to cross both marine solar systems.

 

Incredible...Isnt it ?  Force, wind, sea and honor to all

Antonio G Ramos

RCO Division (Robotic and Computational Oceanography, ULPGC)

 

Changing currents from one hour to the next

Thursday, July 28th, 2011

Hey All!

 

Well Challenger has been continuing on it way south while combating the draw of a number of eddies. 

The above picture is where Challenger 1 surfaced Monday, with a sea surface height overlay. After a few days of strenuous battle, Challenger 1 was almost completely clear of the Eastern eddy field's influence (next picture is of yesterday's update with a sea surface temperature overlay).

We have sailed along the Western edge of the eddy for roughly 112km (70miles) and are slowly inching our way out of its pull. And what's to our South? Southernly heading currents for the time being! The HYCOM does not reveal it but it seems as if there is another eddy Southeast of our position. If the past repeats itself, there will be more storms ahead for Challenger 1 and hopefully bring us fast flowing currents past any hurdles.

Currents and everything that affects them are a curious thing. Just as I update Google Earth, a hour after my previous statement yesterday, the currents end up looking like this. They are all facing completely north and there does not seem to be any relief to our West or East, be we shall keep pressing on!

Today, July 27th, the currents aren't looking much better, still all completely North and no relief is in immediate sight.

And just like that, the currents have changed a little since the last hour. Now we have a little room for maneuvering, even though these currents do seem a little powerful.

The image above was provided by Antonio and shows sea surface height of our journey ahead. We have a solar system of eddies ahead of us, but we have a number of defeated eddies under our belt already, so they should be no sweat.  We will just need to keep an eye on our surfacings to make sure we don't get dragged full circle around one of the stronger ones.

To try and make more accurate predictions about what the currents will be doing, I overlayed the currents provided to us by ULPGC on top of the geostrophic currents from HYCOM.  In the figure below, we can see how there are some similarities and differences between what each of the models are showing.

U. Las Palmas Gran Canaria Currents overlayed with HYCOM geostrophic currents and sea surface height model relative to Challenger's latest position

Looking at the weather conditions, we see what may be causing the discrepancies between the models.  It looks like there is a strong wind system blowing directly north courtesy  of  the jet stream.  There also seems to be another storm headed our way which will undoubtedly add more mixing to the direction of the currents between the movements of the eddies.

It looks like there is a long road ahead of us but I have no doubt Challenger will fight valiantly.

Oliver & Nilsen

 

 

 

Estimated end date

Tuesday, July 26th, 2011

Hi all!

I have rewritten the script for the Estimated_End_Date and the up-to-date results are in
http://marine.rutgers.edu/~marrero/figures/Silbo_Estimated_End_Date.png

Click on the image to get the up-to-date image

The blue curve is a linear fit for all the m_coulomb_amphr_total data, that actually predict the end on 31-Jan using 718Ah.
The green one is another approximation that calculates an average with different weights for the last 5 days ah/day in order to be able to follow the last changes in the way we use the energy. On this method the prediction actually is 7-Feb.

 

Let's see how it changes!

 

Alberto & Rubén

 

 

Roads go ever ever on…

Friday, July 22nd, 2011

"Far over the misty mountains cold (North Atlantic waters)
To dungeons deep and caverns old
(1000m depths)
We must away ere break of day
To seek the pale enchanted gold"
(shores of the Canarys)

Hey all!

I liked the quote that Antonio included in the previous blog entry from J.R.R. Tolkien's Lord of the Rings, so I figured I'd include a quote from The Hobbit.

Challenger 1 is currently staring into the face of an eddy. Like an alluring siren, its currents beckon to us, desiring to reel us in and interfere with our quest. Our muscles and batteries are sore, eyes and oil pump fatigued...the call of the eddy is ever so enticing. But Challenger 1 will not give in, in this moment our glider wings, perseverance, and mettle will cut through the lure of the eddy like a blade through evil; Challenger 1's blunt face deflecting the pull of the currents like a shield against the blows of a mythical hydra.

Our plan is to navigate to the west of the eddy, where we can safely sail for the time being. The overlay for both pictures is sea surface temperature, which has been showing a warming trend reflected in the sub surface data collected by Challenger 1.  In the second picture below, we see that the thermocline has been getting deeper this is a good sign since over the past couple days we have been having a couple pretty important discussions, one of which is on battery life.

 

As we have mentioned in earlier posts, keeping an eye on the batteries is crucial as the battery life of the gliders are shortened when in colder waters such as the far North Atlantic or the Antarctic Ocean.  Since deployment, there has been a bit of unease amongst everyone working on this project from TWR, Iceland, The Canaries, and Rutgers over whether or not our hopes of making it all of the way from Iceland to the Canaries were too ambitious.   But after long discussion it seems we may just have enough. Ruben Marrero, an electronics engineer from PLOCAN who has been at Rutgers for a few weeks came up with a plot that was matched by Lauren Cooney's (Teledyne Webb Research) saying that based off of an estimation of having 718 Amp hours total, ~610 Amp hours left which should give us enough juice to fly until the end of January.  With this estimate based off of our current conditions, it looks like we will be cutting it very close.  We may need to continue looking for ways to conserve battery power to ensure we have enough for the final leg of our journey

 

So far Challenger 1 has gone ~600km of the estimated 4000km it will take to get to the Canaries

Another issue that has been a topic of discussion lately has been bio-fouling.  During the 27 mission, biological growth caused an incredulous reduction in speed until it was cleaned near the Azores.  The most recent talks however have been about whether the bio will be as effective in slowing down Challenger as it was with 27.  Throughout her mission, Scarlet was only flying to about 200 meters due to the grade of her pump.  Now Challenger 1 is class of glider called 'Deep Glider' as it's pump allows it to go down to over 1000m!  The pressure and temperature difference that Challenger goes through as he goes from nearly the surface to 1000m depths is so great, it is theorized that we should slow, if not prevent the growth from occurring.  The debate against this comes form our friends down under at the University of Western Australia who have flown long endurance missions off their coast and have also suffered.  They, however first flew shallow for some time before going deep.  It will be interesting to see if Challenger will be be immune to the biological growth.

By Antonio Ramos ULPGC

By Antonio Ramos ULPGC

The two graphs above come our good friend Antonio at University Las Palmas at Gran Canaria where he calculated how long it took 27 to get bogged down by the bio fouling.  In the first image, he shows that it took us 115 days at sea for the biology to slow us down.  This was through the months of April-August when the North Atlantic is warming with the effects of the summer months and in turn being incredibly productive biologically.  The second graph, shows it takes a little longer to be slowed to 10% speed, 143 days.  We think it took longer for the second bout of growth since it occurred during the months of August-November when the waters begin to cool and become less active.

Gooseneck Barnacle- the main culprit of the bio-fouling that slowed 27's progress

 

 

 

 

 

 

 

 

 

 

 

 

Barnacles and other biological growth seen during the recovery of RU27 "Scarlet" off of Spain

The picture above shows some gooseneck barnacles which will likely be the most common bio fouling we will see flying through the North Atlantic.  With the necks of the barnacles growing out from the hull of the glider, plus the feather-like projections, a large amount of drag is produced as the glider flies through the water column thus severely reducing speed (a lot like opening the flaps on the wings of an air plane to reduce speed).  The effects of these and other little critters will definitely be watched with critical eyes as we go further along our journey.  With Scarlet, we didn't see these effects until about 50 days into the mission.  I think with the waters being much colder where we deployed Challenger we may have bought ourselves some more time.

Seen above, Challenger continues to fly a very smooth path through the water column while keeping a pretty steady vertical velocity of ~20 cm/s.  We also continue to push the records of this glider as over the past few days we came very close to breaking speed records for this mission by recording .46m/hr (our standing record is .47m/hr).  Recently however the effects of the eddy we discussed at the beginning of this post have slowed us a bit as it brings a head current to the glider.

Looking at the satellite imagery of what is going on meteorologically above us, it seems we are now also seeing the effects of our 9th storm since deployment exactly 1 month ago.  It has been a long battle so far for Challenger 1 and there is still much to come!

 

Nilsen & Oliver

Flying downhill ….

Thursday, July 21st, 2011

Buen día a todos …

“Ents love to go South, my dear hobbits … It is like walking downhill”…

Treebeard in “the Lord of the rings” ..

Definitely, Silbo agrees with this deep, magic and wisdom thought… In two days, after our 7th and 8th storms (figure 1) current field finally changed and turn to SW.

Figure 1a and 1b.- Inertial oscillation generated by the 7th storm on 17 and 18 july.

To express it simply, “we were hanged to 11,s km", Oscar dixit.  Our brave Silbo flew 39 km in 24 hours... He had 2 stints flying at 0.46 m/s and 0.46 m/s (!), the second record (0.47 m/s) of the hole mission (figure 2).

Figure 2.- Last surfacings. Inertial oscillation generated by the 9th storm today ??

If we observe the SSHa anomaly and the chl a field, our primary target is crossing the eastern side of a warm eddy (W Silbo) and then, the western side of a cold eddy (S SIlbo) (figure 3 and figure 4).

Figure 3.- SSHa field on 20th july 2011.

Figure 4.- Chl a field on 20th july 2011.

Our focal point is located at 57 N 26.5 W. Here we have a toll in the highway with three good options/roads. Eastern, Central or Western road. All of them out of the < 1000 m depth. (figure 5).

Figure 5.- The next...SSHa field on 20th july 2011.

Finally the 9th storm arrived today. It perturbated the current field (as expected) and the last surfacing shows that current turned from SW to W (figure 2). However, one important remark: it keeps the speed up to 0.35 m/s, we would expect a new change again to SW at good speeds like yesterday.

That would means that Silbo would follow "flying downhill without brakes" for a while .… (fasten your seatbelts again).

However “the man proposes, and the sea decides”.

Thanks again to mi great team and have a nice day dear friends and colleagues.

Antonio G. Ramos (RCO Division, ULPGC).

“Fasten Your Seatbelts!” -Antonio

Wednesday, July 20th, 2011

Hey All!

So after being bombarded with a number of storms and unfavorable currents, Challenger 1 has finally caught a break.

Yesterday afternoon, Antonio (ULPGC) and Ben (TWR) proposed options for a new way point if we felt changing would be advantageous.  I looked into what the two proposed options were and we had the choice of moving our way point to the east and try and catch an eddy in that direction, or to continue along our path.

Antonio's SSH and Currents figure for 7/18 with the two arrows showing our options

The team at Rutgers then decided that we wanted to keep the most recent way point and ride the eddy south instead of making strictly easterly movement by moving the way point.  We proposed our thoughts to Antonio and Ben who agreed with us and we continued with the current way point.  By making this decision, Challenger 1 continued on its path and was rocketed south, hitting 1.25 km/hr and covering over 33km in just under 1 day.

This is excellent news, as we have been reminded of how close we will be cutting it battery wise as we move our way to the Canaries.  After nearly a month at sea, Challenger 1 has covered 15% of the distance needed to reach the Canaries (~4000km), however we need to begin saving more battery power to guarantee we have enough juice to reach our destination.  As we continue on our general south-west direction it seems like keeping the Azores as an option for a pit stop may be a good idea as a possible place to rebattery and brush off the biological growth that will undoubtedly slow us down.

But as for now, we continue on our path to the south, but as we continue jumping eddy to eddy, we will discuss where we want to fly and if we will swing west to the Azores.

On another note, we are just being relieved of  the influence of the 7th storm since deployment.  This one had much less of an effect on the currents than we have seen in the past and so did not disrupt our flying too much compared to the gyring force of the eddies.

Nilsen & Oliver

Glider flying and scuba diving!

Sunday, July 17th, 2011

When dealing with the oceans, especially scientifically, there is one rule: always expect the unexpected. The ocean is largely under-sampled and poorly understood, especially considering its size, vastness, complexity, and dynamic nature. After all, oceanography is still a very new science. Oceanography really only became prevalent within the past century or so. There is more information known about the surface of the moon than that of our own ocean. This is particularly surprising considering that we live on the OCEAN PLANET - the ocean covers over 70% of the Earth's surface (it should really be called "Ocean", rather than "Earth"!). Even more so, it's particularly surprising because the ocean is the primary driver of Earth's weather patterns and climate. The ocean and atmosphere interact 24/7, and the ocean is a massive thermal reservoir. This is the reason that hurricanes gain extraordinary strength over warm ocean waters yet die out quickly once over land. Not only does the ocean affect the atmosphere and its weather patterns, but what we humans do on land affects the ocean as well, even from what we can't physically see with the naked eye (ex: carbon budgets, etc.).

Anyway, we digress...getting back to expecting the unexpected with the ocean. This of course applies to gliders, which are extremely subject to oceanic currents. Our initial plan was to fly SG514 and SG520 along predetermined patterns throughout Perth Canyon, which is relatively a very small area, ocean-wise. However, the ocean, of course, had different plans. Generally the Leeuwin Current flows southward and the Leeuwin Undercurrent flows northward a bit stronger than the Leeuwin Current. But of course, there was a large eddy right over Perth Canyon which made the Leeuwin Current flow northward along with the Leeuwin Undercurrent, causing a large net water movement northward. The current was too strong for the gliders to be able to fly against, so we've had to put a hold on our predetermined flight patterns and make some new flight plans to the to use the currents to the gliders' advantage. The result is that we have flown SG520 around the eddy and to the south of Perth Canyon while we flew SG514 to the north of Perth Canyon. Once we get all the data back, it will actually be really cool to analyze because we will be able to see how the eddy over the Perth Canyon affects the flows of the Leeuwin Current and Leeuwin Undercurrent north and south of the Perth Canyon! We will be able to detect this by locating varying temperature, salinity, and dissolved oxygen signatures sampled by the science sensors on the glider in the water column layers.

 

This past week has been a lot of computer work to pilot the gliders, though we've had some work in the glider lab as well! We've been troubleshooting a compass problem on the Slocum gliders. Whenever the compass reports a bad reading, generally when the glider is at an extreme pitch, roll, or is experiencing fluctuations in magnetic fields, the glider takes the compass out of active service, and therefore the glider aborts its dive segment, comes to the surface, and calls in via satellite to report that something is wrong. This happens because gliders fly via heading towards a directed heading or waypoint (GPS point), so if it can't use the compass, it can't fly effectively. We've made some headway on solving the problem, but have also discovered that a large portion of the problem may be on the manufacturer's side (not the manufacturer of Slocum gliders, the manufacturer of the compass that Slocum gliders use). We're also awaiting some new battery packs to arrive so we can refurbish U209 to send her out off of Perth again to study the Leeuwin Current to get more data for our project!

 

Last week, Dennis took us scuba diving! We did a shore dive in Fremantle, a few kilometers south of the University of Western Australia, called Robb's Jetty. As you very well may have guessed, it was formerly a jetty before it was dismantled. Now all of the pilings and other debris form some great underwater structure for marine life, making it an awesome dive! We saw an octopus, cuttlefish, stingrays, nudibranchs, and a variety of fish! It was an awesome dive, but extremely cold!!! The water was 59 degrees F, which is not nearly as cold as we are used to diving in back in New Jersey, but we only had our spring-time wetsuits with us (3/2 mm thickness) and no gloves or hood, so it was very cold being underwater for 45 minutes (the water depth was only about 21 feet max)! Definitely worth it though, the dive was so cool! Here's picture of a cuttlefish we saw, check out the amazing camouflage! They not only ave the ability to change the COLOR of their skin, but the TEXTURE of their skin as well!!! I (Dave) have some HD video footage from our dive as well I took with my GoPro HD Hero camera, and will get a video together at some point as well!

 

 

Dennis also took us to a National Park that had a Koala enclosure! All the Koalas we sleeping, some very high in the trees, but luckily one of them woke up to stretch for a moment so we got a decent picture of him semi-awake!

 

 

 

 

We also took a day-trip to Rottnest Island, "Rotto" for short. Rottnest Island is about 10 miles or so off the coast of Perth. Rotto used to be part of the reef system when sea level used to be higher, but now it is exposed and has become a beautiful island. We woke up early and took the first ferry out at 7:30 AM, and let us tell you all...it was WELL worth getting up early! We went out to one of the beaches called Salmon Bay, a rather large beach expanse, and we were the ONLY people on that beach for 2 full hours! The weather was BEAUTIFUL, barely any wind, and calm seas with some nice clean waves breaking farther out over the shallow reef. Amazing. Picturesque Australia.

 

We went snorkeling for almost an hour in Salmon Bay, and it was incredible! The limestone-reef structure was SO cool, there were so many little caves and crevices which were homes to SOOO many fish and other marine life! We saw TONS and tons of fish, as well as another octopus! The water depth probably only averaged about 8 feet or so, though it fluctuated, but it was even cooler than some [scuba] dives we've done!

 

After we snorkeled Salmon Bay, we explored around the island a bit, had lunch on another beach totally by ourselves, and then headed to a beach area called Green Island for some more snorkeling. Green Island is a fairly large limestone rock exposed above the surface...and it's called "Green Island" because it has green plants that grow on top of it. The snorkeling here was awesome, too! I (Dave) have a LOT of HD video footage from my GoPro from snorkeling at Rotto which I'll make into a video at some point as well!

 

We also saw quokkas, which are native animals to Rottnest Island (actually where Rotto gets its name from)! Quokkas are kind of like miniature kangaroos, they're really cool! And as long as you move very slowly and calmly, they come right up to you! Here's a photo we took of one of the many quokkas (they're actually nocturnal, but can be found during the day sometimes too!):

 

 

We have about two weeks left here in Perth (time has gone by so fast!!!), and then we head to Cairns for a week to scuba dive the Great Barrier Reef! So much to do still before we leave!...although we will be flying the gliders for about 4 more months from NJ and then processing and analyzing the data. Late next week, one of our friends will be coming to Australia to visit us and we'll most likely be going to stay in a bungalow on Rottnest Island for a few days!

 

Here's some pictures from Rottnest Island! Thanks for reading along everyone!

 

-Dave & Shannon 🙂

 

 

 

 

 

 

 

 

And He’s at the 50!

Friday, July 15th, 2011

Hey All!

Well after a week of amazing flying, Challenger 1 has now made it south past the 60° N Latitudinal mark and is now in the 50's!  This past week, the glider has maneuvered it's way through the solar system of eddies Antonio has described previously of the warm core eddy surrounded by a number of cold core ones spinning in the opposite direction.  By using these gyres, we were able to fly south at a pretty awesome speed (reaching 1.35km/hr at some pooints) going nearly 30 km in one day, even though the overall geostrophic flow of the surface currents were to the North.

Total Currents Field from Antonio

In the above image, Antonio plotted up for us the total current field along with sea surface height to best show the position and movement of the eddies in our area.  You can see how to the North West of us there is the warm core eddy that we just used to send us to the south into the cold eddy that we now plan to utilize to swing us around along the path of the arrow.

Even in the presence of all of the storms we have seen, we are still making progress.  It is looking like for the weekend at least we are going to have good weather but as the beginning of next week rolls around we may see a shift in wind and another storm headed our way. In the bottom left side of the pic below you can see the next storm system that will be making its way towards Challenger 1...

Satellite Map of the storms from Antonio

Also Looking at the forecast for the jet stream, it confirms that we have what looks like favorable weather for the next 2 days or so but that starting early next week we may have some violent shifts in the wind patterns above us.  Below is a picture of the current conditions for the jet stream, but if you click on it, it links to a gif that will show the forecasted progression over the next week.

It should be interesting what we see over the next couple days, as this will be the first weekend we fly without current correction on.  Our plan is to follow the path of the cold core eddy we are currently flying near and following it around to the south, allowing Challenger 1 to drift with it.  This will use less energy as we will not be trying to fight the currents as the glider tries to fly directly to it's most recent way point (opposed to flying with current correction on and fighting the currents to fly a direct path).

After now being at sea for 3 weeks Challenger 1 has flown over 500km and collected some really cool looking data.  Below we have nearly continuous cross sections from the deployment through the most recent surfacing of Density, Salinity, Temperature, and Sound Velocity respectfully.

Density

 

Salinity

 

Temperature

 

Speed of sound through water column

Finally, we have an update on what has been going on over the past couple days with the deployment of RU 28 that we helped with on Wednesday.

It's Wednesday, July 13, a beautiful afternoon in Jersey City, New Jersey, today is the day where we deploy our first shallow (30m) glider. As we (Nilsen, Alberto, Ruben, Lindsay, Garz, and myself) are unloading the glider van, taking out RU28, a CTD, and other various instruments; we are greeted by our captain and two EPA members. The view as we left the dock was quite humorous, to our right was a huge landfill with a squadron of cranes, swiveling about moving who-knows-what; to our left was Manhatten with the Chrysler Building and the Statue of Liberty in all their glory. The seas were excellent that day, only the occasional semi-massive wave would knock you slightly off balance. As we sailed to our destination, we passed some bluefish, packs of seagulls, shipping boats, sailboats, and a lonely beachball, forever deprived of the playfulness of a child. When we reached our destination, Sandy Hook was visible on the horizon and deployment mode was switched on, Lindsay and Mike delved into the pre-launching routine while everyone else got RU28 ready to depart from the back of the boat.

Oliver Standing by on the back deck with RU28 as we sailed out to the deployment site

All systems were go, Dave from IMCS gave us the green light and RU28 was cast off. After a preliminary dive and surfacing, RU28's job had begun and we sailed back to base, escorted by seagulls and terns.

Garz and Nilsen deploying RU28 off the NJ Coast by Sandy Hook

So now we have two gliders out in the water, Challenger 1 and RU28, located off the coast of Iceland and Sandy Hook, respectively.

Nilsen & Oliver

From storm to storm

Wednesday, July 13th, 2011

Hey all,

Well Challenger 1 has really had a run for its money since deployed almost 3 weeks ago.  We are now being affected by our 5th storm!

Even after being battered and bruised over the past few weeks, we are still making good progress!  In the midst of the storm, the currents are for the time being moving North East as Challenger 1 cuts to the south west thus avoiding the direct head current.  By doing so we have gone 9 km two surfacings ago and just over 11 on the most recent! (much better progress than we have been seeing recently)

In the above picture, we can also see the liquid meccano that our friend Antonio has been mentioning over the weeks.  There are a number of eddies in our area that have caused curves to appear in the overall northern current.  In the upcoming weeks we will take advantage of these as we continue our progress to the south.

I'd like to take this time to introduce our new student allies from the Canary Islands, Rubén Marrero and Juan Alberto González from La Universidad de Las Palmas de Gran Canaria, who will be staying with us for the next few weeks. Rubén is specializing in electronic engineering and Juan Alberto is specializing in oceanography.

Alberto (left) & Ruben (right)

Finally, I would just like to mention another glider related mission our group is working on.  Later today we will be out on the water deploying RU28 which is a shallow glider (depth range of about 30m) off of Sandy Hook and it will work its way down to Cape May NJ after a 3 week cruise.

Nilsen & Oliver

Sun and planets liquid constellation…

Monday, July 11th, 2011

Hey... Buenos días a todos ¡

Silbo has generated an intense job during these first 2 weeks of mission... However, we are learning a lot. We could say that now,

1.- we know where we are,

2.- where we want to go,

3.- why, and, most important,

4.- how to do it.

1.- Where we are ? Some posts ago, we showed that silbo was crossing an eddy field that seemed to organize as a liquid meccano formed by different cold (warm) eddies (PLANETS), gyring around a warm (cold) eddy (SUN) in the center of each gear of this incredible gear (figure 1).

Fig 1.- SSHa. Liquid constellation of cold and warm eddy planets and suns..

 

2.- Where we want to go ?. Our main objective was to fly the cold eddies to pass the first sector and heading the South...But we suffered two effects. The first, reported on 3-4 july, consisted in a inertial oscillation that seemed to be associated to 3 july storm pass. It changed the current field 360 degrees around silbo during a period of 24-36 hours. However, one day and a half later (5th july), the inertial perturbation disappeared and we returned to the periodic NW-W current field observed at the beginning of the mission (figura 2).

Fig 2.- Inertial Oscillation.

We got dense discussions in the core group and we concluded that, first, we knew now what changed the current field (storm pass) around silbo. Second, we designed new protocoles in order to minimize this effect.
3.- Why ?. However, on 6-8 july, we had another change on current field that did not gyre around silbo but that changed the current from WNW to N-N !!  We were crossing a anticlockwise cold eddy (a planet). We were trying to head the warm eddy in the center (the sun) of this incredible liquid meccano/constellation (figure 3).

Fig 3.- SSHa. Translation movement.

Fig 3.- SSHa (3D). Translation movement of the cold eddies around the warm eddy.

Looking to the ground current field targeted by silbo, we thought in another inertial wave, but the current field did not change 360 degrees around him. That would mean that another effect has to be got into account. The answer came with the analysis of the Sea Surface Height anomaly for these 3 days. The three SSHa model forecasts sent from Australia (Dave/Shannon team), USA (Nilsen team) and Las Palmas (our team) showed the same landscape. Silbo  that we were suffering a change of the position of the eddy that we were crossing…(figure 4).

 

Fig 4.- Translation movement reported by Silbo.

The eddy moves..to the W. Independently of the ROTATION (clockwise the warm eddy, anticlockwise the cold eddy) this system had (has) a complemen- tary TRANSLATION movement. Figure 5 shows the position of the eddy in the yellow line located at 60 N. He has drifted to the N. We calculated the component of the translation drift of the eddy on 8-12 km/day. If we kept to silbo fixed to the 24 W (7-8 july), the eddy would cross us and we would be sailing the eastern side (NNW current fields).

Fig 5. SSHa fields on 6th and 8th july.

4.- how to do it ?. For that, we decided for the last weekend to move the WP a little bit W. In spite of the storm passed yesterday, silbo looked to relax his flight moving to the SW with the same pattern of 5-5.5 km by stint (0.59-0.64 km/h) during 3 days !!.

Our primary target is the green line on figure 5, located in the 24.7 -25 W.

Fig. 6.- Silbo location update on 11th july 11.

We want to fly the warm eddy (SUN) located in the centre of this “liquid planetary”. The reason is really simple and fascinant. He does NOT TRANSLATE !. We want to fly him using the same protocole described by Scott et al with RU17 and RU27: Flying the eastern side looking for currents going to South. At this moment, we would move the WP again, keeping the nose of silbo heading the warmer south...

Finally, the landscape today (figure 6). The last night storm moved the current field direection again to the right side (inertial oscillation again ?). There are 2 possibilities:

1.- We will wait for the next surfacing, but it looks that we will not suffer any inertial perturbation since the current of the last surfacing become to the original NW position before the storm.

2.- Our translation speed (u component of silbo movement) showed 8-10 km/day.. a little bit lower than the meccano does (10-12 km/day). May be that we are being passed by the eddy translating W again.

We would have the answer to this question in the next surfacings. If the current field becomes to flow NW again, that would mean that current changes observed are associated to the storm. If so, we would be retarding our translation movement since our U speed is slower that the u speed of the cold eddy that we are crossing right now...

Cheers all and thanks to my incredible ULPGC team again.
Antonio G.Ramos (Robotic and Computational Oceanography division, Univ of Las Palmas de Gra Canaria).