Working in partnership with IOC-UNESCO, JCOMMOPS, and NOAA, drifting buoys are being deployed for the first time from a sailing rally fleet. Drifters provide invaluable data to scientists about weather and climate.
What is a drifting buoy?
A drifter consists of a surface float, connected to a drogue (sea anchor), equipped with meteorological and/or oceanographic sensing instruments.
The float contains alkaline batteries, a satellite transmitter, a thermistor (thermometer) to measure sea surface temperature, a tether strain sensor to verify the presence of the drogue, and sometimes other instruments measuring barometric pressure, wind speed and direction, and salinity.
The thermistor is located at the bottom of the drifter because the drifter is designed to measure water temperature, not the heat generated from direct exposure to the sun.
The drogue enables the drifter to follow ocean currents rather than experience the effects of wind at the surface. The nylon cloth “holey sock” drogue is centered at 15 meters beneath the surface to measure mixed layer currents in the upper ocean. Rigid rings with spokes support the drogue’s cylindrical shape. To make sure the drogue remains extended, 2.5 kg (5 lb) are added to the bottom.
Each drifter weighs 20 kg (44 lbs). Before deployment, the drogue and tether are bound with paper tape, which dissolves in the water, and the tether is sometimes wrapped around a water-soluble cardboard tube to protect it from kinking.
The drifter is deployed by throwing it from the stern of a vessel. After deployment, the paper tape dissolves and the drogue sinks to its target depth.
The drifter operates on the surface of the deep sea for about one year.
What data is collected from these buoys?
Data collected by the instruments are sent via satellite to NOAA’s Atlantic Oceanographic and Meteorological Laboratory (AOML) in Miami.
The data collected is used in weather forecasting and is included in climate-quality data sets of ocean currents, temperatures and salinities.
The Global Drifter Program (GDP)
The Global Drifter Program manages a global array of over 1000 satellite-tracked drifters. National and international partners work together to conduct the over 1000 deployments per year needed to maintain the global drifter array.
Drifters were deployed in small numbers starting in 1979 in the tropical Pacific, to study current changes associated with El Niño events. Large-scale deployments started in 1988 across the tropical Pacific, and were extended to cover the Pacific and North Atlantic Oceans by 1992 and the Southern and Indian Oceans by 1994.
The array expanded to include the tropical and South Atlantic Ocean by 2004, and now spans all the world’s oceans.
Why use yachts for deployment?
In the past, most deployments were conducted from oceanographic research ships and from cargo ships.
Cornell Sailing Events is working in partnership with NOAA and JCOMMOPS (the Joint Technical Commission of the World Meteorological Organization and Intergovernmental Oceanographic Commission of UNESCO) which will offer deployment opportunities in new regions of the ocean, some currently poorly sampled.
Deployment from a yacht also has the advantage of not exposing the drifters to the shock of being deployed up to 10m from the sea surface at speeds of 25 kts, as is typical from cargo vessels and may be a leading cause of early instrument failures.
Successful deployment during the Odysseys
In 2013, 2014 & 2015 successful deployments of drifter buoys were made by yachts in the Atlantic and the Pacific Oceans.
Here is a record of all Odyssey boats which have deployed drifter buoys:
The Drifters Deployment Hall of Fame
Why are data collected by drifters so important?
- Drifting buoys measure sea surface temperature, which is critical to predicting climate patterns. Warm sea surface temperature is an enormous source of energy, which fuels storms such as hurricanes and increases their intensity.
- Drifters also help forecast the path of approaching hurricanes because they allow a closer look at hurricane formation and ocean heat which affect storm intensity and movement.
- Drifters predict the movement of pollutants that spill into the sea.
- Drifters measure salinity, which is important in determining the ocean’s chemical make-up. Since marine species such as coral, kelp and phytoplankton are affected by changes in salinity, identifying fluctuations is important. Salinity also affects water density which, in turn, affects ocean circulation patterns that transport heat.
- Drifters measure ocean current velocity, or both the speed and direction of currents. These currents carry much more than water. The Gulf Stream, for example, carries vast amounts of heat and salt northward in the Atlantic Ocean, and this affects the many marine species whose migration is shaped by seasonal temperature changes and ocean currents.
- Satellite technology makes sea surface temperature measurements possible from space, but to ensure these measurements are accurate, drifters are used to compare actual sea surface temperatures to the temperature measurements from space. Without drifter observations to correct satellite measurements, these measurements can err due to dust and other elements in the atmosphere.
- With global climate change, drifters are an important tool for monitoring ocean temperature and circulation and the movements of marine species.
- An Introduction to the Global Drifter Buoy program
Click on ‘latest maps’ for the most up to date picture.
- News, reports and videos on Odyssey yachts deployment of drifter buoys
Adopt A Drifter
Partnering with students around the world, schoolchildren can “adopt” a buoy and track its path and that of the entire global array: NOAA’s Adopt a Drifter Program