• Jim Manning

GOMI contributing to our local ocean observing system: Drifters

[endif]--What happens to a particle of water suspended in a river such as the Merrimack as it enters the sea? Where does it end up? How long does it take for this particle to exit the continental shelf and make its way across the Atlantic? These are the questions being answered by the GOMI drifter project. Beginning in 2012, several satellite-tracked drifters were built and deployed each year by local schools in the North Shore of Boston and monitored for months at sea as they reported their positions every few hours.

The drifter tracks are displayed, served, and archived on a NOAA computer where oceanographers as well as the general public can access the data. The primary purpose of the deployments is to provide data in validating local ocean circulation models. We can think of these drifters as the “weather balloons” of the sea. They are following the currents in the same way that balloons follow the winds and the information is used to test numerical simulations of the ocean current. Most of the drifters built by GOMI projects are designed to mark the upper meter of the ocean but some are tethered to subsurface drogues (or sea anchors) to follow the currents deeper in the water column.

[endif]--As seen in the photo of Beverly High School students, the standard surface drifter is constructed in the classroom with commonly available materials (aluminum square pipe mast, aluminum rod spars, canvas cloth sails, lobster buoy flotation, and a set of hose clamps) that are cut, drilled, glued, secured, and decorated by the students. The cell-phone-sized satellite transmitter which gets lashed on top is supplied by the Gulf of Maine Lobster Foundation in Kennebunk, ME working closely with NOAA’s Northeast Fisheries Science Center in Woods Hole, MA. Well over 100 schools around the region have been involved since the project started in 2003 resulting in over 1000 multi-month tracks with bi-hourly fixes.

[endif]--While we strive to maintain oceanographic standards in terms of the shape and size of drifters, we experiment with the materials used to build the various drifter designs. With help from Brad Balkus at the Nock Middle School, for example, a biodegradable plastic housing was developed using their 3-d printer. In a recent development this past year, GOMI has also been involved with designing and testing a eco-friendly drogued drifter including a surface float made of natural mushroom material. Emily Flaherty’s group at the Salem Sound Coast Watch facility conducted the experiment with a series of deployments. As with any tethered drogue in shallow waters, there were some issues with premature groundings and damage to the float (see photo) but they were nevertheless the first to demonstrate the possibility of using this eco-friendly material. The students were also involved with constructing the drogue.