MPC released its drifter on Nov 14 in Monterey Bay. In the 2.5 months since release, it drifted south, nearly to the latitude of Pt Conception. Then, with the onset of winter storms and the presumable winter-time emergence of the Davidson Current (the slow, northward flowing current that replaces the California Current in the winter months), it has reversed direction and flowed northwards. It now lies farther north than we released it.
Archive | Tracking the Drifter
Now *That* got my Students' Attention
To begin my lecture on gyres and surface currents this morning, I showed them this image.
This data, collected by our colleagues at Cape Fear Community College, definitely got their attention. This is especially noteworthy because we’re getting towards the end of the semester where students are dealing with all kinds of assignments and are just trying to survive. A lecture about gyres and the differences between strong and swift western boundary currents and weak and meandering eastern boundary currents that is usually met with bored indifference was suddenly incredibly relevant.
That track was made in two months folks! Heck, I had no idea the Gulf Stream was *that* fast.
Here’s the same data with current SST data behind it.
Does anybody know where I can get a kml file showing higher resolution SST data for the North Atlantic that would show all of the eddies in more detail?
I did find this kml file, but it is from 2005 and the location of the eddies is quite different.
Thanks!
Ever Feel Like You’re Just Drifting in Circles
The MPC Drifters are back in the water this week as our MBARI collaboration continues for a second week. The data on the image above represents about 27 hours of data, from the afternoon of October 5 to about 6 pm local time of October 6. It illustrates quite nicely the 24-hour periodicity that is evident in much of our data. We have semi-diurnal tides here on the coast of California, so that pattern is not tidal. The drifters tend to have a stronger SE component of motion in the afternoons and a stronger NW component of motion in the early morning hours.
I’m trying to get some images of students deploying and retrieving the drifters. I’ll post them as soon as I get them.
-Fred
MPC Drifters Retrieved!
A couple of MPC Oceanography students accompanied the MBARI team to recover the drifters yesterday. They quickly found both of them and brought them back on board. They were out for almost exactly 48 hours. After drifting south for the first 12 hours or so, perhaps due to strong NW winds that day, they turned and drifted north and west, along the expected counterclockwise rotation of surface water in Monterey Bay.
Here is a quick and dirty cut and paste job of their complete paths. I don’t have the software set up yet to make my own maps of their paths. These are from the AeroStar tracking website. They generally drifted from southeast to northwest.
We’re very happy with this first deployment of the drifters and thank the MBARI team of John Ryan and Erick Rienecker. The MPC students seemed to enjoy it as well. Four of the five we sent came back very enthused about the whole experience. They took some pictures, but I haven’t been able to get their pics downloaded onto my computer. Maybe we’ll see some next week.
So I’m thinking about how to integrate this stuff into my lesson plans for next week. I’m thinking of creating a short activity where we ask the question, “Did the tsunami affect the movement of the drifters?” This will involve the following aspects of data manipulation:
- Determining the time the Tsunami hit Monterey
- Making a hypothesis about whether or not the tsunami affected the drift
- Identifying exactly what we would see, and on what timescale, if the tsunami affected motion.
- Manipulating the Aerostar tracking site to find times and positions of data points
- Looking at the data to determine if the identified changes in motion did or did not take place.
The anticipated outcome is that the tsunami did not, in fact, influence the movement of the drifters. Hopefully, this will be a useful realization that wave motion and current motion can be totally different because they are totally different processes. We know, for example, in the northeastern part of Monterey Bay that the longshore drift of the sand on the beaches is in exactly the opposite direction (west and southwest towards Moss Landing) than the surface currents (north and west, as our drifters demonstrated). So it would follow that tsunami motion would not necessarily be detected, especially at the temporal resolution available to the drifters (one measurement every half hour).
I’ll share this if I get it going.
Over and out.
Drifters survive a tsunami on their maiden voyage
This is what the path of one of the drifters looks like today, approximately 24 hours after deployment. Remember yesterday, the drifter was taking a southerly route. Today, the drifters have turned northwards. Today is not as windy as yesterday.
This is what the other drifter path looks like today. It has also turned north after drifting south the first day. This one may have drifted further south the first day because it was deployed closer to the Salinas Valley, where the onshore winds are strongest. Well, maybe.
Here’s what the winds look like today. You can definitely see that the wind speeds are lower today, especially in the northeast portion of the bay where the drifters were deployed.
We had a bit of a distraction today with the Samoan earthquake and tsunami. The tsunami made it all the way to Monterey by yesterday evening, although its amplitude was only a few centimeters by the time it made it here.
In the image above (click on it for a larger image), you can see that the tsunami entered Monterey Bay at just past 0400 on Day 273, which is Sept 30, 2009. I guess we can say that the drifters survived a tsunami on their maiden voyage.
I just got word from the MBARI guys that the drifters will be recovered tomorrow. We’ll be sending a few more students on the cruise with them.
The drifters are adrift here in Monterey Bay
Well, the drifters are adrift here in Monterey Bay. They were deployed mid day today, local time by a team from the Monterey Bay Aquarium Research Institute (MBARI) and three Oceanography students from Monterey Peninsula College. The study is part of an intensive effort to look at the physical oceanography associated with harmful algal blooms (HABs) After four messages to the satellite (configured at 48/day), the image looks like this:
You can see two drifters are out there; the single position is from when the ship was on the way to deployment. Both of the drifters are drifting south or southeast. This is somewhat unexpected as we thought the circulation in Monterey Bay was counterclockwise as I explained in my previous blog.
Wonder why the drifters are drifting southsouthwest? They are moving directly towards the Salinas Valley, probably as a result of seabreezes that pick up every afternoon here. At least that’s my current (ha ha) hypothesis. The winds today are shown on the image above, blowing straight towards the Salinas Valley, which is between Moss Landing and Del Monte Beach on the image above. The drifters were deployed northeast of Moss Landing, somewhat north of the MO buoy as shown on the image above.
Follow along at the usual spots. I’ll share the response of the students in a later installment.
Over and out for now,
-Fred