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Diving Deeper Shorts: Episode 12 (July 14, 2011) - Currents

HOST: Today on Diving Deeper Shorts, we revisit our interview on currents from August 2009 with Laura Rear-McLaughlin from the Center for Operational Oceanographic Products and Services.  

Let’s listen in.

HOST: Laura, we touched on this question before in an earlier episode of Diving Deeper called what are tides, but can you remind us about the difference between tides and currents?

LAURA REAR-MCLAUGHLIN: Sure thing Kate. As my colleague, Steve Gill, mentioned in that episode, the word tides is a general term used to define the alternating rise and fall in sea level with respect to the land. This means that tides move up and down during the day. Currents are different from tides in that they move horizontally rather than vertically. So currents describe the horizontal motion of the water and they’re driven by several different factors.

HOST: You mentioned that there are several different factors that drive or even can cause currents. Can you elaborate on these a little bit more?

LAURA REAR-MCLAUGHLIN: Absolutely, there are several different factors that drive currents. Let me highlight a few of these different types of currents for you. There’s something that we call ocean currents, tidal currents, and coastal currents. The factors that cause these do vary.

HOST: It sounds like there are many factors and different levels to each of these factors that affects currents and their intensity. Are we able to monitor currents?

LAURA REAR-MCLAUGHLIN: We are Kate. As a matter of fact, mariners have been studying and measuring currents for hundreds, if not thousands of years. The two main components of currents are speed and direction. The easiest way to describe how measuring is done is to say that the basic tools that you need are an observer, a floating object or a drifter, and a timing device. So an observer would stand on say the bow of a ship that’s anchored, throw something into the water like something that floats – a piece of wood or a cork or a bottle even – and then they would measure the time that it takes that object to move along the side of a ship. And that’s the easiest way to understand currents.

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 we use more accurate and sophisticated instruments.


That’s all for today’s Diving Deeper Shorts, where we highlight a few minutes of your favorite Diving Deeper episodes.

Want to learn more? Go to and select the August 2009 podcast archive to listen to the full interview with Laura on currents.

You can catch the next episode of Diving Deeper Shorts in August.