Last Monday (7/13/09) we deployed SG130 around NH15 (Newport Hydrographic Line). Conditions were great – almost no wind and very small swells. Captain Mike took us out on the R/V Elakha, OSU’s trusty day-trip vessel. Here you see Justin and I easing the glider off of the fantail, with Mike’s help.
If you want to follow SG130 during it’s mission, follow this link to the Glider Research Group web page. It will be traveling on a path that looks like a capital “E”, where the top of the “E” is the NH line, the middle line is a visit to Heceta Bank, and the bottom is an east-west line near the mouth of the Umpqua River. The last time that SG130 was deployed, we saw some very interesting patterns of sediment resuspension – I am hoping that we see the same patterns again.
We continued to have communication problems with SG157, so we decided to call on our Chilean colleagues to help with a rescue on July 10th. The Seaglider was close to the coast at the time, so the pilot worked to keep it as close as possible to the port of Iquique despite a current pushing it to the south.
The plan was to have a student, Nadin, fly from Concepcion to Iquique to help with the recovery, since he helped us with the deployments and recoveries back in March. We communicated with our Chilean colleagues mostly via Email, so sometimes things were happening there faster than we could follow. It turns out that before Nadin could get from Concepcion to Iquique, the Chilean Navy was already on sight and recovering our glider! Jack’s words were, “Chilean Navy to the rescue!” We were all surprised that they had gotten involved, but I guess it’s not every day that a misbehaving Seaglider needs to be rescued off of the Chilean coast. We were (are!) very grateful for their assistance, and they did a great job on the recovery. By the time they got the glider back to shore, Nadin was able to get there and shut the glider off with the magnet. All’s well that ends well in the world of Seagliders!
We received this clipping from a Chilean newspaper yesterday (click for bigger)…
sg157 stopped communicating with the basestation sometime late last Friday (06/26/09). sg157 disappeared for 4 days, and then finally called in Tuesday evening. Anatoli and Justin handled it like pros, and figured out that the glider had happily continued to dive and receive GPS fixes, during it’s seclusion. This means there’s nothing wrong with the antenna and that the antenna is getting far enough out of the water. It also means that there’s nothing mechanically wrong with the glider.
The problem appears to be isolated to the Iridium satellite phone communications.
sg157 has been calling in more consistently since then, but misses a scheduled call in every now and then …
Out plan is to continue to fly sg157 onshore. If we get another big disappearance, then we’ll have to figure out an emergency recovery. If things continue to go OK, then we’ll send Laura out at the beginning of August to put sg158 in before the MOOMZ cruise, and we’ll send Justin out at the end of August to recover sg157.
Anatoli turned on the CT and set the science file to:
250 52 1000 180
600 104 1000 300
1000 104 1000 360
There was little difference in the energy consumption!
We’ve been experimenting with some power saving strategies on sg157 this week. In the plot of energy consumption, you can see that the blue 10V battery is draining a lot faster than the red 24V battery. The 10V battery powers the onboard computer and the scientific sensors. The 24V battery mainly powers the buoyancy pump. So, our energy consumption for science is rapidly outpacing our energy consumption for flying.
How to fix that? Shut off the science sensors! So we tried that starting MondayJun 08 by uploading a one-line science file:
// Science for OSU sg157 and/or sg158 with PAR sensor
/depth time sample gcint
1000 600 0000 600
This file determines that from the surface to 1000 m the sampling interval is 600 seconds (10 minutes), none of the sensors are turned on (0000), and the guidance and control interval (time between steering) is also 600 seconds. This had an immediate affect:
Notice the major drop near dive 540. This is great, it extended our mission duration from end of August to end of October! Nevermind the fact we are no longer collecting data … and this had an added complication of suddenly erratic flying by the glider. With the glider checking in only every 10 minutes to steer and make flying decisions, sg157 would fly past 1000 m, go to deep and rocket up to the surface in what I’m assuming is an emergency manuever.
Anatoli did some experimentning, and now we are flying with shorter gcints and the CT sensor on, consuming only slightly more power than everything off, and having no more erratic dives.
Here is my short report about what happened to bob.
Before I disassembled glider I turned it on and took some variable values:
m_vacuum = 3.98 inHg
m_battery = 14.1V
Then I opened the aft section first. I prepared small bucket under the glider expecting some water from it. It was nice surprise that not a one drop came out between end cap and hull section. Evidence that leak was not big. No water traces I found on the inside surface of the end cap. Means that leak is not coming from the aft section. Next I deattached science bay from aft hull section and found some water drops at the bottom of aft battery:
Next I deattached science bay from front section and removed small bag of desiccant, which was placed by Webb during previous repairs. Evidently water traces can be seen at the bottom and water absorption bag looks like a great deal to keep glider drier when leak is not big:
Looks like water was coming from front section.
Next I inspected front section. Water traces at the bottom of pressure case. Leak detect sensor is wet. Water drops on the inside part of the front cap. Salt water traces on the buoyancy pump cylinder, which tells me that buoyancy pump assembly is the cause of the leak:
I decided to open the front plastic cap to inspect buoyancy membrane and here is what I’ve found:
I hope this is not a new species called buoyancy pump killer fish.
Glider Bob decided to spring a leak late Friday (05/22) night. Is there any better timing than that? To make matters worse, Glider Bob was about as far offshore as possible with the prevailing currents pushing him offshore and to the south (cyan track).
Fortunately, Justin was out on the Wecoma and they were able to recover bob early, early Sunday morning without much apparent hassle. We’ll have to talk to Justin to find out for sure. I monitored the recover via glider terminal and the Wecoma’s webcam, while I fed Dashel a bottle around 2am.
Laura left bright and early Tuesday morning on the Elakha to retreive bob from the Wecoma, her report: The transfer went well. Glider and cart were tied to a line and dropped in the water from the Wecoma, and we winched it on board the Elakha. We lucked out with the weather, and as far as I could tell Bob did not hit either of the two ships.
Now we’re waiting to hear from Anatoli just how much water is inside …
I spent some time today looking at patterns of CDOM along our glider sections. As an introduction, CDOM is colored dissolved organic matter, also known as “yellow substance,” “gilvin,” and “gelbstoff.” CDOM is a subset of the pool of dissolved organic material in the ocean (and lakes, streams, estuaries, etc.) that is optically active (i.e. has color). CDOM appears yellow or brown to the eye depending on it’s concentration, it absorbs light very strongly in the blue region of the spectrum, and fluoresces in the blue as well. CDOMs optical characteristics enable us to monitor it’s concentration and distribution with a fluorometer on the Seaglider (WET Labs ECO-Puck; CDOM fluorescence excitation/emission at 370/460 nm). CDOM is an important parameter to keep track of for many reasons (see excellent review by P. Coble, Chem. Rev., 2007, 107, 402-418), but for our purposes we are primarily interested in monitoring the variability of sources and sinks of carbon in the OMZ.
Here is a plot of all of the CDOM-depth profiles from our most recent complete section, Line 11, with oxygen concentration in color. The red line is a running average at each depth bin.
A couple of things pop out right away. CDOM is degraded by sunlight very quickly, which is evident here in the surface data. That’s just a good double-check that the fluorometer is working. Second, there appears to be (maybe?) two discrete pools of CDOM – one associted with phytoplankton production and degredation in the chlorophyll maximum (photic zone, high O2), and one associated with the microbial community in the OMZ (low light/aphotic & hypoxic). However, it is impossible to tell from these data alone if the source of the CDOM in the OMZ is local or if it was derived from far away sources and has been transported with the water mass. Collecting water samples for CDOM spectral absorption measurements will tell us a great deal about the nature and origin of CDOM in this area. It’s also important to remeber that not all CDOM is fluorescent, so we are actually looking at a sub-pool (the fluorescent bits) of a sub-pool (the colored bits) of the pool of dissolved carbon. However, the CDOM data that we are able to collect autonomously could be very instructive when considered in conjuncion with other variables like chlorophyll, backscattering, and physical indecies of mixing and mass transport.
This is just a first-look at the data, and I’m still trying to get my head around it. Feedback in the comments is encouraged!
Hey all – just realized that Seaglider 157 made it’s 400th dive off of Iquique on Saturday (9 May, 2009). Very exciting! The glider is now on it’s usual onshore-offshore route, about 2/3 the way through the seventh ~135 km, cross-shore transect. The eastern south Pacific oxygen minimum zone has never been sampled over these time and space scales, so I hope you all can share some of my enthusiasm for these unprecedented data. Now, if we could just find a research vessel so that we could get out there and do some discrete sampling…
Anyhow – thanks to everyone involved for your continued efforts.