An observer stands on a ship, throws the drifter into the water, and then measures the time that it takes that object to move along the side of a ship. As technology improved over time, oceanographers began using mechanical current meters. A ship would deploy a meter and usually some sort of rotor would turn and measure the currents. This is still the basic process today; however there are more accurate and sophisticated instruments.

Today in the open ocean, a drifter is similar to a buoy in the water that may be equipped with global positioning system technology or satellite communications that would relay data and information. Drifters can also submerge for long periods of time to measure ocean currents at a particular depth. The drifter would then resurface occasionally to send a signal with its data and position to observers on the land.

In addition to buoys, there are other tools that are used to monitor currents. The Acoustic Doppler Current Profiler is commonly used to measure currents. It is normally deployed on the sea floor or attached to the bottom of a boat. It sends an acoustic signal into the water column and that sound bounces off particles in the water. The instrument can calculate the speed and direction of the current by knowing the frequency of the return signal, the distance it traveled, and the time it took for the signal to travel.

Many oceanographers also use radio antennas and high frequency Radio Detecting and Ranging systems (radar) to measure surface ocean currents. Similar to the Acoustic Doppler Current Profiler, these shore-based instruments use the Doppler effect to determine when currents are moving toward or away from the shore or to measure the velocity of a current.

At NOAA, oceanographers use knots to measure current speed. The term knot is defined as one nautical mile per hour. One nautical mile is equal to 1.85 kilometers (1.15 standard miles). One knot is also 51.44 centimeters per second (3.281 feet per minute).

For more information:
Center for Operational Oceanographic Products and Services
National Current Observation Program
Diving Deeper Podcast, Episode15 (August 12, 2009) - What are currents?
Currents Tutorial, NOS Education

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NOAA's Coastal Georgia Dolphin Health Assessment examines the beloved bottlenose for clues to the wellness of their underwater world....

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On October 19, 2009, NOAA joined Florida, Georgia, South Carolina, North Carolina, and other supporting partners as the states announced an agreement to work together to better manage and protect ocean and coastal resources, ensure regional economic sustainability, and respond to disasters such as hurricanes....

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MEET: Mike Shelby, information technology specialist with the National Ocean Service Communications and Education Division....

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A new ocean observing system on the lower Mississippi River serves up free real-time water and weather conditions for mariners ranging from ship captains to pleasure boaters....

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The Monitor was the first of 14 marine protected areas that make up the National Marine Sanctuary System, which includes more than 388,498 square kilometers (150,000 square miles) of marine and Great Lakes waters. The sanctuary boundaries (2.59 square kilometers or 1 square mile) protect the wreck of the USS Monitor, which lies 25.75 kilometers (16 miles) southeast of Cape Hatteras, NC. Since its sinking in 1862, the Monitor has become a productive artificial reef.

While most of the research conducted in the Monitor sanctuary has focused on the archaeological documentation of the shipwreck, NOAA scientists are now interested in studying the water quality and marine environment of the wreck site. A NOAA data buoy installed in the sanctuary in 2006 is providing scientists and the public the opportunity to monitor weather and sea conditions 24 hours a day.

Management of the sanctuary is focused on preventing further deterioration of the wreck, recovery of important ship components and artifacts, and protecting the wreck from damage by human activities such as vessel anchoring and fishing. Access is generally limited to scientific research conducted under a permit issued by NOAA; however, special-use permits are issued for non-research visits to this historic vessel. For more information:
Office of National Marine Sanctuaries
Monitor National Marine Sanctuary
Diving Deeper Podcast, Episode 8 (May 6, 2009) - What is a national marine sanctuary?
Diving Deeper Podcast, Episode 16 (September 9, 2009) - What is maritime heritage?

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With the release of a new research strategy, NOAA and partners set the stage for future studies about unique coral ecosystems found in deeper tropical waters around the world....

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Losses from catastrophic events such as hurricanes can be extensive. The economic losses from the 2005 hurricane season, which included Hurricanes Katrina and Rita, were $200 billion, the costliest season ever.

For some threats, such as sea level rise, only the projected economic losses are indicated. For example, the vast majority of our nation’s commercial and recreational fisheries are dependent on coastal marshes. Approximately two-thirds of those fisheries spend some stage of their lives in tidal marshes. As sea levels rise, the built-up areas behind these marshes will provide no opportunities for wetlands to migrate. The net result will be billions of dollars in economic impacts affecting the livelihoods and sustainability of many coastal communities.

Coastal threats are different throughout the United States. For example, in the Pacific Islands, there are more potentially catastrophic coastal hazards such as tsunamis, flooding, and even droughts. In the North Atlantic, there are more severe storms, population and development pressures, and regional-scale impacts such as climate change.

It is critical to develop hazard-resilient communities to prepare for these threats and enhance the ability of these communities to absorb impacts and bounce back. This preparation will reduce the lives lost in disasters, secure the economic stability of these communities, and support the health of our coastal ecosystems, including wetlands which are essential for reducing storm impacts on our coastal communities.

For more information:
NOAA Coastal Services Center
Coastal Hazards, NOAA's Office of Ocean and Coastal Resource Management
Local Strategies for Addressing Climate Change (pdf, 1.12 mb)
Diving Deeper Podcast, Episode 10 (June 3, 2009) - What is resilience?
Explore: Natural Hazards Assessment

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According to a new study by NOAA and the U.S. Department of Agriculture (USDA), a powerful fish-killing toxin produced by a type of freshwater algae called Euglena sanguinea could also have cancer-killing properties....

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Over the summer, 20 budding biologists, ranging from ages five to 14, joined NOAA Fisheries scientists for a week-long camp to learn about harmful algal blooms....

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