Contents:

General Mission/Goals

History of our drifter production

In 2004, we were funded by NOAA's Northeast Consortium to develop student-built, satellite-tracked, lobstermen-deployed drifters. This was the fourth phase of the Environmental Monitors on Lobster Traps project (see Manning and Pelletier, 2009 and emolt.org). Funded parties including the Gulf of Maine Lobster Foundation, the Southern Maine Community College (SMCC), and NOAA's Northeast Fisheries Science Center were interested in tracking the potential transport of early-staged larvae along the coast of Maine. In subsequent years, we were primarily funded by McGillicuddy et al in another NOAA funded project (GOMTOX) to track the advection of HABs (Manning et al, 2009). Another big boost to the project occurred in the summer of August 2009 when we hosted a NSF-funded workshop to teach a few dozen educators from around the country (from the Marine Advanced Technology Education (MATE) consortium). Applications funded to date include:

One of the primary motivations for drifter deployments is to help validate the many numerical circulation models as well as the growing network of CODAR systems. Given multiple years with multiple fundings, the dataset to conduct such statistics is rapidly growing.
Compilation of all the drifter tracks in the database

eMOLT Drifters vs Davis "CODE" Drifter

Most surface drifters in use today are the "Davis CODE" design first described decades ago by Davis (1985) for the Coastal Ocean Dynamics Experiment. There are specifications and pictures of this type of drifter in each of the manufacturer's web sites below (Table 1). However, since they are often fitted with costly (~$2K) GPS electronics, we found, in our case of very limited budget, it was unwise to use them along the coast of New England due to the high risk of running aground and being picked up by curious lobstermen and pleasure boaters.

Table 1.  Some existing surface drifters that have performed well over the last decade or two

Type Manufacturer Web site Location
Davis-X-shaped CODE Brightwaters http://www.brightwaters.com Stonybrook Univ, Long Island

MetOcean http://www.metocean.com England

ClearWater  http://www.clearwater-inst.com/docs/b_CS1.htm Waltham, Mass.

Technocean http://www.technocean.com/DOCS/argodrifter.htm Fort Myers, Florida
Tri-Star scaled down PacificGyre http://www.pacificgyre.com Santa Barabara, Calif.
Seimac C-AST Barrel Seimac http://www.seimac.com Halifax, Nova Scotia

rachel drifterholey sock drogue

Having eliminated the costly electronics within the housing unit, we simply mount a relatively inexpensive GPS transmitter (similar to those used by the trucking industry on the highway) on a simple wooden 2" by 4" (ballasted appropriately). While in the past we used a 2" diameter foam-filled PVC pipe and vinyl sails, in 2012 we switched to more environmentally-friendly wood or bamboo mast and cloth sails. Since most were built by students at the Southern Maine Community College and originally funded by the Environmental Monitors on Lobster Trap project, these drifters have been called by various names such as the "SMCC/eMOLT" drifters. The various models are named after the students who spent the most time on design and construction. Our latest models, for example, are called the "Dan Drifter" which used an upside-down ski pole with its tipped sawed off for its transmitter mount and mast extension and now the "Irina Drifter" which uses an all-aluminum frame. From our experience in using hundreds of these drifters since 2004, we can reduce the cost GPS drifters 3 times. While these homemade rigs typically survive several months, they do not survive nearly as long as the commercial products noted above. Nevertheless, they have so far logged hundreds of thousands of kilometers of ocean. While they are designed to be expendable for the most part, with some effort and ship time, of course, they are reusable. Batteries are good for several months with near-hourly samples. See more on "survival statistics" below.


How the system works and who is involved

There are six institutions/companies currently involved:

Interested scientist and educators communicate with:

It is best to copy all parties in your email communications. The complete process is documented here.

Assembly

See the latest construction manual here.

GPS Transmitter Setup

Putting units to sleep


Documenting deployments and recoveries

In an attempt to automate the operation, users are asked to enter their deployment and recovery information on a web based forms.
While the complete system is not operational at the time of this writing (Sep 2009), the plan is to serve data and googlemap plots without further human intervention.

Tracking Units on the Web

Evolution of Drifter Configurations


"Kara" drifter w/drogue


These units, prototyped during the winter of 2004 and 2005, are designed to track a subsurface layer. There are three components to the unit:
  1. The drogue is constructed stiff fiberglass hoop rings that supports sheets of heavy-duty vinyl cloth material. The length of the drogue will be adjustable to 1.5 meter lengths. The cloth is glued securely to hoops w/additional strips of cloth in a manner such that the stress is tangential (not normal) to the seam. The bottom-most hoop is weighted slightly and additional buyancy is added to the upper-most hoop to provide a more vertical profile in the water. The cloth has two 30cm-diameter holes cut out in each 1.5m section placed 180 degrees.
  2. The tether is typically a narrow (1/8t") statinless wire connected to a 3-point bridle on the topmost hoop with a stainless ring (either circular or pear shaped) and a swivelling shackle (1/2" of more). Heavy duty stainless wire used for the bridle will be well protected from chaffing particularly at the ring connection. The upper end of the tether is connected to the underside of the surface configuration. Tether lengths will be adjustable depending on the project and terminated with thimbles and sleeves.
  3. The surface configuration of these units has been either:
    • 2-3'-length of 4" PVC pipe that simply acts as a platform for the satellite transmitter riding above a 2-3' length of 2" PVC pipe OR
    • a Norwegian float that absorbs the drogue pull with a separate unit tether behind that houses the transmitter. It is usually configured similar to the "rachel" design described above (without the sails). The length of this surface tether is adjustable.
  4. mvc-142f

    old style holey-sock drogue

    The design follows the specifications of the World Ocean Circulation Experiment to insure that the units have acceptable drag ratios of more than 40:1 and that slippage is minimized. These units were tested in the spring of 2005. A set of them were deployed in the Bay of Fundy in May 2005 and June 2006 and mid-coast Maine in July 2005 (Aretxabaleta et al, 2009).

    "Rebecca" drifter w/telemetered temperature sensors



    We have added additional features to the basic design.
    1. A temperature sensor similar to those used by refrigerator trucks on the highway have been be incorporated by interfacing it with the AXTracker. We tested this feature with at least one unit in April 2005.
    2. Tension sensors are often included on drogued drifters to indicate the presence or absence of the drogue. Alternatively, we may consider including a temperature sensors immediately above and below the water line such that, given the drogue tension loss, should record detectable variations in air temperature.
    3. Internally recording temperature probes can be easily installed at multiple depths to monitor the thermal stratification.
    4. To aid in visibility, orange surface flotation can be easily tethered to the surface configuration and strobe lights can be secure to the PVC housing.

    "Paul" drifter w/reinforced construction for inshore work


    paul drifter with reinforced construction Paul Hodder with the drifter he designed
    SMCC student, Paul Hodder designed this more-rugged design for inshore/estaurine work during  the 2005-2006 school year.  Dozens of deployments have been made since.


    "Kathleen" bucket drifter for very-near surface work

    This model was originally designed for UMASS's Dan McDonald to look at the top 30cm of the Merrimack River Plume in the Fall of 2009.It is simply an inverted plastic bucket that is properly ballast to float just below the surface. The transmitter is mounted a few inches above the seasurface.
    kathleen bucket drifter for very-near surface work UMASSD-CEFM 1st cluster drifter tracks on 08-Nov-2009
    "Super buckets" were also deployed with strobe lights (>4 mile visibility) and internally recording:
    1. temperature (multiple depths)
    2. salinity (StarOddi DST-CT)
    3. more frequent positions (Garmin units)

    "Shawn" Drifter

    This drifter was designed to eliminate flotation at the ends of the sail spars. It uses instead the natural buoyancy of a pressure-treated 4 by 4 fence post. After initial failure in June 2010, we added a few toggle floats and deployed 4 in the Gulf of Mexico successfully.

    Shawn Drifter

    "Miles" Drifter

    This drifter was designed to provide an easy-to-ship unit all contained within a Vinyl 4 by 4 fence post (as sold at Home Depot). After initial failure in June 2010, we adjusted the flotation to successfully deploy 4 in the Gulf of Mexico.

    Miles Drifter

    "Vitalii" Drifter
    This especially low cost drifter was designed by Vitalii Sheremet to deploy inside harbors or estuaries. They were successfully deployed by students in kayaks with Cohasset Harbor, Massachusetts in July 2010.


"Eddie" Drifter

This drifter, first deployed in mid-June 2010, replaced the "rachel" as the standard model for a few years. Some of these survive more than 10 months at sea. It was the least expensive, easiest to make, and most environmentally friendly of the Davis-style surface drifters until it was replaced by the "Dan Drifter" in the fall of 2012.

Eddie drifter-->

"Dan" Drifter

This drifter, first deployed in the summer of 2012, replaced the Eddie as the standard model. The 2by4 mast was originally extended by lashing a broom handle with a screwed-on scrub brush acting as the transmitter mount but those proved to be weak. So, in the fall of 2012, we are planning on an upside-down ski pole with its tip sawed off as our new transmitter mount. Most have used wooden dowels for spars but we are not sure how long they will hold up compared to the fiberglass spars. While we are not sure how long they survive yet, it is the least expensive, easiest to make, and most environmentally friendly of the Davis-style surface drifters. Aside from the transmitter and perhaps the net-buoy flotation, all other parts can be found at most hardware/lumber yards.

Dan drifter-->

Satellite costs

There are three components to satellite fees (not including the transmitter itself) that the service provider charges: So, if you have a transmitter on your office and you do not expect to use it from more than a year, it is a good idea to "decommission" the unit so the satllite company can't charge the $2.45/mth fee. If sometime in the future you want to use the unit, you can "reprovision" it for $30.

Note that if you set the transmitter to report every hour, your cost will be about $100/mth or (0.15*24*30). If you set it at every 6 hours, your cost will be about $20/mth. When asked what rate you should set your transmitter, we usually recommend hourly or at least bi-hourly so the tidal oscillations are depicted but, if you are more interested in tracking the unit for several months, you can choose to report less frequently. One set for every hour should last about 3 months and that is often less than the residence time of drifters on the continental shelf. Id you want your data to be useful to numerical modelers, hourly transmissions are best. We try to keep track of your satellite usage. On a near monthly basis, we update the website .

ID Convention

There are two numbers associated with a deployment. The first is the "electronic serial number" of the transmitter (typically 6 digits) that is assigned by the manufacturer.  The second is a distinct deployment "ID".  This ID is the key field in the database. While it was originally a 5-digit number, in the fall of 2009 it was modified to be a 9-digit number in order to accommodate nation-wide deployments. This ID is automatically generated based on user's entries in the web-served deployment documentation. In other words, users will see what the unique deployment number is after they have entered the deployment information. It is defined as follows:


EXAMPLE: 098430702 is the 2nd drifter dropped in August 2009 at approximately 43N and 070W

References

Aretxabaleta, A. L., D. J. McGillicuddy, Jr., K. W. Smith, J. P.Manning, and D. R. Lynch (2009), Model simulations of the Bay of Fundy Gyre: 2. Hindcasts for 2005–2007 reveal interannual variability in retentiveness, J. Geophys. Res., 114, C09005, doi:10.1029/2008JC004948.

Davis, R. 1985. Drifter Observations of Coastal Surface Currents During CODE: The Method and Descriptive View. J.Geophys.Res.,90,4756-72. 

Lynch, D.R., D. Mcgillicuddy, J.P. Manning, D. Greenberg, A. Bigili, A. Aretxabelata, 2014. Particles in the Coastal Ocean: Theory and Applications. Cambridge University Press. (In press).

Manning, J.P, 2012. Student-built, fishermen-deployed, satellite-tracked drifters. IOOS summit white paper

Manning, J.P. and E. Pelletier, 2009. Environmental Monitors on Lobster Traps (eMOLT): long-term observations of New Englands's bottom-water temperatures, Journal of Operational Oceanography. Vol 2-1, p.25-33.

Manning, J.P. and J.H. Churchill, 2006, Estimates of dispersion from clustered-drifter deployments on the southern flank of Georges Bank. DeepSea Res. II. doi:10.1016/j.dsr2.2006.08.004

Manning, J.P., D. McGillicuddy,  N. Pettigrew, J. Churchill, L. Incze, 2009, Drifter Observations of Gulf of Maine Coastal Current, Continental Shelf
Research. doi:10.1016/j.csr.2008.12.008.