By Justine Kibbe, Naturalist
September 6, 2014
After a particularly windy day mid August, I bicycled down to monitor Race Point. Fishing boats encircled the Lighthouse, Common terns were darting and diving-working the chop, and mounds of seaweed carpeted my trek. Things looked just like usual till I spotted a white piece of canvas baring a faded neon spray painted phone number and the words “DRIFT STUDY”. I laughed, almost relieved, I had not found yet another WWII uniform!
I rode home and phoned Yan Jia across the Sound at Marine Sciences, Avery Point.
It wasn’t till Yan mentioned “sending back a transmitter” that I realized there was more to be discovered at the Race. So, several days later I returned at low tide and found what I now call the “UCONNtraption” under piles of kelp and eelgrass. As I unburied the wood and bamboo structure I found the small transmitter device on top. I happened to note too, the research was sponsored by CT Sea Grant.
Always hoping to bridge local traditional knowledge with Science here on Fishers Island, I asked UCONN for a bit of history as to what exactly I and perhaps others found washed up on our shores:
“The Connecticut River is the largest freshwater source for the Long Island Sound (LIS). Unlike many other estuaries, the Connecticut River enters near the LIS mouth into an area with strong tidal currents. Our research addresses the question: What pathways do the Connecticut River waters take as they flow through the LIS and out to the continental shelf? Where these freshwaters go influences the salinities and ecosystems in the LIS, Block Island Sound (BIS), and the shelf.
Since July 2013 with the help and guidance of James Manning, an oceanographer from NOAA Northeast Fisheries Science Center, we have been building, deploying and recovering satellite-tracked surface drifters. The drifters float within the top one meter water. Each drifter has a GPS and transmitter sending position signals every half hour to satellite; the positions are then posted on the Internet at www.nefsc.noaa.gov/drifter/drift_uconn_2014_4.html. Its main body is made by 4’ by 4’ wood and bamboo. With these low cost and eco-friendly drifters, we are trying to address the freshwater pathway questions.
Six drifters were released from the Connecticut River mouth on August 21, 2013. Eight more were deployed from either the river mouth or south of Clinton harbor (typically the west boundary of the plume) on August 8, 2014 (Figure). Tracks show the freshwater can reach the LIS mouth within 2-3 tidal cycles. It takes them several more tidal cycles to drift into the Block Island Sound (BIS). After that, most drifters go southward crossing the BIS, sometimes they may be pushed back by the tidal current; sometimes they may go directly into open shelf and move down shelf along Long Island in a buoyant coastal current. Two drifters traveled to New York Bight (Red and green in figure) in about two weeks, one of them still working. Last year one drifter cycled around Block Island clockwise before moving farther into the open shelf. Fishers Island (FI) is an interesting point in the tracking map. One drifter circled around the island (black). The other nearly finished a circle (green). Drifters are easily grounded if they approach the island during slack tide. Three out of eight landed on west part of FI this summer (blue, cyan, and magenta in figure).
Map caption: Figure. Tracks of drifters deployed on Aug 8th 2014 near the Connecticut River mouth and south of Clinton harbor.
Justine, you located one near the airport (blue). That one grounded only after two days in water. Tim Cromarty and his associates located the other two last week. One of the drifters (magenta) already visited Montauk, NY before ending its one-week voyage at FI. The grounded drifters suggest the west part of FI may collect floating debris from both sounds.
The drifter tracks have helped answer the surface freshwater pathway question. However, such results lead to a new question: If the river plume water goes out of the estuary ‘directly’, how could the LIS keep its freshness, especially in the central and western sound? A short answer is surface drifters only sit at the top of the water; they are not mixed downward like freshwater. Which means those drifter tracks only tells half of the story. For the other half, we need the help of computer simulation. That is another story to tell.”
