Monday, March 31, 2008

Where glider is headed to


The imagery is from the Wisconsin source Sage mentioned today. It's 30 km to get to the to get north of the upper most section of the gulf stream.

A successful weekend

Ru15 is rounding the southern side of the warm core ring. The new waypoint and the swirl velocity will start swinging it around the western side today.
Velocities are staying low, around 50-60 cm/sec.

Temperatures remain around 15C. We are staying on the outer side of the radius of maximum velocity in the ring. We should be able to pull ourselves out this time around.
Still no satellite imagery, so we will fly by the temperature and swirl velocity record. Keep the temperatures decreasing, the swirl velocity decreasing as we head to the north. Our present set of waypoints is based on the position of the ring on March 28, about 3 days ago. Rings propagate to the west, a few kilometers a day. Assuming a relatively fast speed of 5 km/day, we may be adjusting our waypoints 15-20 km to the west over the next day or so as we move up the western side of the ring.


Sunday, March 30, 2008

Closing the Loop

We have just closed our first loop around a warm core ring.

Temperatures are cooler on this lap. Yellows are 14 C, oranges are 16C.
Curretnt velocities are slowly decaying, but still high.
This morning we will change the waypoints and start drawing the glider out into the colder and slower parts of the eddy. This will require several waypoint changes today. If we pull too hard, we leave the eddy, and don't make our destination. If we don't pull hard enough, its another lap or we miss the target ring on the northeast.


Saturday, March 29, 2008

Another Lap

Most recent sst imager indciates the warm core ring with RU15 in it is underneath the cloud cover (white), but the small eddy to the north that is our target is still there. Its centered near 41 N, 64 W and you see the laternating warm and cold bands wrapping around in a clockwise direction.
RU15 couldn't make it out of the ring yesterday on the northwest side yesterday, so Hugh sent it on another lap around. We'll try to stay closer to the edge and exist a bit sooner this time around.




Current speeds are diminishing. So we are making our way to the outer edge of the warm core ring.


Unfortunately we are under the clouds (white in the image) so we don't have a map from today to fly by.





But we do have a map from two days ago. Present glider location is 40 05N, 63 22 W, so we are moving out of the red core of the ring and into the yellows which are about the 14-16 C range.





We seeing cooling in the right hand side of the glider section to the same 14-16C temperature range.


Right now our target waypoint is 39 20 N, 63 30 W. Fine for the overnight shift while we are at the north side of the ring. We just want to start sweeping around to the south, and the swirl will do most of that for us.
As the day goes on, we will want to shift that point farther out in the ring. Right now it is inside the warm center and inside the first lap we took around.
In this case, instead of flying towards a point, we want to fly away from a point. In this case the point we want to fly away from is the center of the eddy. This is a new and interesting behavior for a glider. We care most about using all the glider velocity to go away from the center and we care less about where the swirl velocity takes us. We can time our exit to sweep us around to about where we want to be.
RIght now we can only fly towards a waypoint, so to accomplish this most effectively right now, we would have to set a new waypoint outside the eddy every time the glider surfaces, which is a bit impractical on a long duration mission. So lets try this by setting four waypoints between here and where we want the glider to be on the other side sometime sunday or monday.
1) 39 30 N, 63 00 W, outside the ring in the cold 6C filament wrapping itself around. When we get close, say within 20 km, we switch to:
2) 39 00 N, 63 30 W, just on the southern side of the ring, and on the outer edge. Again, when we get to close (say 20 km), we switch to
3)39 30 N, 64 45 W, at the easter side of the ring, possibly pulling it out. If the temperatures are staying warm and velcoties high, we will have to adjust this point west a bit, say another 15 minutes to 65 00 W. We can make that call as we round the southern side. Then we go for the base of the new eddy and fly up its wester side buy going to
4) 41 00 N, 65 00 W.
Lets give something like this a try over the weekend.



Friday, March 28, 2008

Fighting our way out

Most recent image of the Warm Core Ring centered near 39 30 N, 63 30 W.

RU15 is in the northwest quadrant of this ring, near 40 N, 64 W. Strong currents to northeast. We are using the glider velocity to fly perpendicular to the strong eddy currents that are swirling us clockwise around the center.

Temperatures in the center (right hand side) are very warm.
We want to see these temperatures decrease as well as the currents
to indicate we are leaving the eddy on the north side.


Thursday, March 27, 2008

In the Warm Ring

Clear morning shot of the target warm ring, and another clockwise eddy to the north showing up in the wrapping up of the warm filament.

Tempertures are up on the right had side. We are in a warm ring.


This overlay shows the clockwise currents of the warm core ring.
Our goal is to exit the warm core ring on the north west side, and jump into the new eddy to the north, spinning clockwise around it to the northeast side. Then continue Northeast in the slope water.

Wednesday, March 26, 2008

Free Coffee & Wireless in San Juan

Warm core ring is visible near 63 30 W. 39 30 N . Cold water being wrapped around the eastern and almost to southern side.
Recent temperatues (on right) show the colder surface water about 12 C.

Speeds are up to 50 cm/sec, and direction is the east-south-east.
Consistent with entering the ring on the southeast side.


Map shows present location on the southeast side of the ring in the SST image. We should shoot around the bottom then start heading to the waypoint. Once we make that point, our objective is the warm filament on the northwest side. Something like 40 00N, 64 00 W (due north)
followed by 40 45 N 64 45 W, (towards northwest.)



Tuesday, March 25, 2008

Into the Warm Ring

Temperature on the right hand side is warming. Up to 15C.
Currents have decreased to very slow, like 10 cm/sec.

Shows we are just entering the southeast side of the warm core ring. Looks like we made it. Object now is to continue swiming into the ring, catch the stronger currents and be swept to the west around the southern side of the warm core ring center.


Monday, March 24, 2008

From Old San Juan

Most recent glider CTD data is on the right side of the above image. Temperatures look to be about 12 C or less. We are getting too cold. We are looking for the 15C water in the ring. We are approaching from the southeast, and the band of cold shelf water has wrapped around the eastern side of the ring. It is very clear in the next satellite shot.

Last good SST image of the targetted Warm Core Ring for RU15. Perfectly round, centered at 39 30 N, 63 39 W. A safe spot in the middle of the slope sea. Southern edge of ring is about 39 N. RU15 is getting close. We'll need to change a waypoint soon. Also look on the northwest side of the ring. That warm filament is heading northeast, towards Halifax. That warm filament is our next target. Need to think a few shoots ahead here. Just like that game Dave Martin showed us at the Pioneer Bar in Anchorage.




Here are the current speeds. Slowed down to about 20 cm/sec. Now we can fly where we want.



Here is the present location, and the small current velocity vectors. We are currently at 39 o4 N, 62 37 W. We'll need to change the waypoint sometime soon, like anytime between tonight and tuesday morning. Exact timing doesn't matter so much because of the slow current speeds. Someone can do this when they are rested. A good place to head will be along the southern side of the ring, towards 39 30 N, 64 00 W. The stronger currents are inside the ring, in the orange in the SST map which is about 18C.
If we head to this point, the strong currents will sweep us around to the west along the southern side of the ring. Could be fun.


Sunday, March 23, 2008

A new route home

Above Satellite image of Sea Surfact Temperature shows the Warm Core ring we are targeting to be centered near 39 30N, 63 30 W. We'll have to adjust our target waypoint to be a bit farther west once we get into the ring. But right now we want to fly to the north, so we are ok for the night. Once we are in the ring, the currents will spin us clockwise around it, and it will be a natural adjustment to fly toward 63 45 W. it looks like the southern side of the targeted warm core ring is at about 39 N, and RU15 is just south of that location. We should begin to see the temperatures warm and the currents spin around to flow to the west. Once that current switches direction, we switch the waypoint.

Once RU15 is in the ring, we see the new exit point now on the northwest side. The idea is to leave the ring where you see the warm (yellow) water heading towards the shelf break. This region will have favorable currents. The cold (blue) water is shelf water, and unfavorable currents for our northward journey.

Above is the temperature section. Most recent data on the right. You can see the warming as we head north out of the Stream into the ring.

Above are the current vectors for the last 2 days. You can see the sharp decrease as we leave the Stream, and now the currents are starting to turn. The present waypoint if perfect for now, perpendicular to the currents, pulling us northward into the ring. As soon as the currents switch direction and flow to the west, likely sometime tomorrow during the day, we will switch to a waypoint on the west side of the ring. The current waypoint is on the east side. The new waypoint will be somethin like 39 30 N, 63 45 W. The idea is to put this point on directly west of the ring center, and more than 2/3 of a ring radius out. Because the ring is moving west, subsequent imagery may make that new waypoint as far as 39 30 N, 64 00 W.


Here are the current speeds and directions. Still above 0.5 m/sec, about twice the speed of the glider. So there is no way to fly against this current. We have to use the currents to our advantage to advect us in the directions we want to go, and use the glider speed to move us from one favorable current to another. It is a different way of flying.



Saturday, March 22, 2008

Hit 15 C - Leaving the Stream

The 15C temperatures (yellow, on the right in the above section) mark the north wall of the Gulf Stream. You hit 15 C, and you crossed the line. You are now in the Slope Sea.



Sea surface temperature image form March 19 still the best. Right around 63W -62W, the Stream is heading nearly due east, and the is a perfect Warm Core Ring to the north. Thats were we'll head.


Here we use the slow glider speed to fly perpendicular to the current and swim us out of the Gulf Stream as the Stream pulls us to the east. The velocities drop rapidly as soon as we cross out of the Gulf Stream and into the 15C Slope water. We'll continue heading north, likely with currents running slowly to the east till we hit about 39N. At that point we'll start seeing the switch in direction. As we enter the clockwise rotation of the warm core ring, the currents will pick up heading towards the west, and will sweep us around to the north. Our target here is the warm water heading towards the shelf break. If we can keep the glider temperatures near 15C, we'll be getting good currents. If the temperature drops down to the 6C-9C range, we are in shelf water thats flowing against us.
A nice day of work at sea. We are currently at 63 16.87W longitude. Our target was to leave the Stream somewhere between 63 30 W, and 63 00W. I'd call this one a bullseye. Hats off to the glider pilots on this one.

Time to Exit




Clouds still cover most of the gulf stream we are interested in, Cold air blows over the land from the northwest, heads out to sea over the cold water and stays clear, then hits the warm stream and clouds appear. Typical wintertime scenario. Donglai knows the winds are from this direction, Louis talks of the cloud formation. RU15 is in a strong current to southeast. As it makes this turn, around the bottom of the trough, we want it to start heading to the northeast, then north to get out of the stream. A good way to do this will be to use all the glider velocity to head to the north, and let the Stream do the east component. This means we just head the glider towards the point where we want to pick up the warm ring. That point is number 3 on my waypoint list in the powerpoint I sent last night. The present location, point 2 and point 3 line up almost on a straight line at this time. It flies nearly corner to corner on a 1 degree square. Present location near 38 N, 64W, intended location is 39 N, 63 W. Corner to corner on a 1 degree square should be about 140 km at this latitude. The location of point 3 is 39 00 N, 63 00 W. It will fly us perpendicular to the current. I think the waypoint has to be less than 200 km away for it to be accepted as valid. If it is too far, the second point in my waypoint list still splits the difference. it goes to 38 30 N, 63 30 W. The more distant waypoint (#3) has the advantage of giving us a longer time before we have to change waypoints again. If we need to use the second waypoint, one way to do this is to put the second waypoint in with a big watch circle or about 25 km. As soon as we get close, we go to the third waypoint. If it looks like we are going to miss the second point, then we take over manually and switch to the third. If we miss the waypoint on this surfacing, that is ok. Dave has it going to a point along this same track. RU15 is getting close to the point Dave set early this morning, so we will have to change it soon anyway.






Thursday, March 20, 2008

Around the bend


Around the trough and into the crest.
As we reach the meander crest, we try to stay a little more south of the Gulf Stream north wall to stay well away from that warm eddy.

Wednesday, March 19, 2008

Exit Strategies

The previous post showed the warm ring near 63W as our first potential exit point to get us back to the shelf break. This image gives us two more options. A warm ring located near 59 W, and a meander crest near 54W.
The white clouds in the imagery always seem to be worse the further east you go. Its a lot easier to fly these things when you have that bidrs-eye view from space.

Down in the trough

So here is where we are. Shooting along the bottom of this meander trough traveling at speeds we have hardly ever seen before.
The next satellite shot shows the Gulf Stream in this vicinity quite well.


We'll make our next waypoint during the next surfacing later tonight, then turn left and head north into the next meander crest.
There is a warm ring up there at the top of the crest near 66W that we can use to slingshot us back to the shelfbreak if we need to. But most likely we'll skip this ring, unless we need to go back to Nantuckett. We'll at least shoot for the warm ring near 63W. Its our first possible exit point if we want to make Halifax.




An assist from our Dalhousie family!

Marlon Lewis gets us connected to the ice forecasts. It would be good to get the undergraduates tracking this on a weekly basis. Marlon's inspiration and web link are below
"Hi Oscar; You should be OK until Grand Banks or so (same message they sent to Titanic). Here is the most recent - the main site to check is: http://ice-glaces.ec.gc.ca/App/WsvPageDsp.cfm?ID=1&Lang=eng "
Best, Marlon

AND IF THERE IS A STORM THERE IS........


The storm has increased the sea state dramatically. See the attached figure of the changing wave height and another reason to praise this new era of oceanography.

STORMS STORMS STORMS



Having sailed in the Gulf Stream, and never feeling great in those seas I was pretty excited to be in the Gulf Stream last night, while sipping a beer at home. The storm the glider is going through is large, and the seas are rough. This observatory science is is cool!

Tuesday, March 18, 2008

RU15 on ICOOL Mission #001

At 6:30 am on a Tuesday morning exactly 1 year ago, the RV Lucky Lady left the New Bedford docks with RU16 on board. RU16 is one of our underwater robots, a Slocum Glider, built by Webb Research in Falmouth. It was our 100th Glider mission, and to celebrate, we decided we would attempt the first underwater flight from Massachusetts to New Jersey. With UMass Dartmouth, we deployed RU16 just offshore New Bedford on March 13, 2007, and recovered it in Tuckerton, NJ on April 6, 2007.

Since then we've repeated the MA to NJ flight 5 times. We also sent two gliders south from Tuckerton on interstate trips to Rudy Inlet by Virginia Beach that were picked up by UNC, ODU and UMaryland.

With a year of confidence building behind us, Hugh Roarty decided we were ready for a greater challenge. This time our goal was to fly underwater from New Jersey to Canada. This time our robot would be RU15, the first Slocum Glider equipped with the new "Digi-fin" tail fin, a more rugged assembly designed for longer duration flights.

But beyond the distance, the challenge with this flight is that a straight shot along the coast to Canada is against the current (5 cm/sec to the south as our friend Bill Boicourt recently reminded us at that Italian restaurant in Baltimore). So we chose a different route. To get to Canada from NJ, we will first fly across the continental shelf, cross the dangerous shelf break, then fly across the slope sea and into the Gulf Stream. The Stream will whip us to the east, where eventually we will jump out and ride a warm core ring back to the shelf break off Canada. We'll use our remaining battery life to re-cross the continental shelf up north.

We'll conduct this mission as part of I-COOL, the International Coallition of Ocean Observing Laboratories. We formed I-COOL in Paris in 2005 at a sidewalk cafe with John Cullen from Dalhousie. Our hope is to get this glider at least up to John's office in Halifax, snap a picture, and then repeat as needed.

We kept track of Glider Mission 100 on this blog site. We'll do the same with this I-COOL mission. But we have a little catching up to do. We launched on March 7, 2008, crossed the shelf break danger zone for the first time, survived a storm with 25 foot seas, and caught an extreme Gulf Stream meander crest that is still growing. Right now we are running with the Stream heading southeast into a meander trough that we hope starts to whip us back around to the northeast overnight and into tomorrow. So the next several entries will likely alternate between what we are doing now as we continue on this underwater flight to Canada, and what we did to get us here.

But before signing off for the night on this first entry, we need to add the traditional dedication. For Glider Flight 100, we honored our past. That flight we dedicated to Fred Grassle, our Institute's first Director and the person who brought us all together. For I-COOL Mission #001, we honor our future. We dedicate this flight to our students, 15 years of them to be exact. Through the years they have sustained us, and many times have taught us just as much as we were supposed to be teaching them. We hope they will find this flight as inspirational as we do, and that the thrill of discovery, combined with the personal rewards of teaching others, will sustain them in the challenges they face in a changing world.