U.S. flag An official website of the United States government.

dot gov icon Official websites use .gov

A .gov website belongs to an official government organization in the United States.

https icon Secure websites use HTTPS

A small lock or https:// means you’ve safely connected to a .gov website. Share sensitive information only on official, secure websites.

Tides and Currents

Diving Deeper: Episode 57

Chesapeake City tide station

Monitoring Water Levels in Chesapeake City

This image shows the Chesapeake City Tide Station, an active water level gauge that is part of NOAA's National Water Level Observation Network, located in Chesapeake City, Md.


HOST: Tides and currents data….we all want it, but what goes into making these products available for safe navigation or just to help us plan that weekend getaway at the beach? Let’s go behind the scenes with the office that brings us real-time tides and currents data for the U.S. This is Diving Deeper and I’m your host, Kate Nielsen.

Here to join us today is Pat Burke, an oceanographer with NOAA’s Center for Operational Oceanographic Products and Services. Hi Pat, welcome to our show.

PAT BURKE: Hi Kate. Thanks for inviting me here today.

HOST: So Pat, to start and just to be sure we’re all on the same page here, can you remind our listeners what is the difference between tides and currents?

PAT BURKE: Sure. Tides are changes in water level due to the gravitational pull of the sun and the moon and the rotation of the Earth. As a real-life example, usually when you go to the beach, in the morning you can go set your chair up near the water’s edge, you might be building a sand castle, then for a couple of hours you go out and swim and enjoy other aspects, and in the afternoon you notice that you might have to move your chair back up the beach and your sand castle’s disappeared and that’s because the tide has come in and you’re at a high tide condition.

With currents, it’s really the movement of water and this is due to a number of reasons. One reason could be due to the tide. As we said the water level goes up and down and when that happens the water does move from one region to another. Great examples of this are when you go to a bay environment like the Chesapeake Bay or Cook Inlet in Alaska, you’ll see these currents coming in and out of the entrance to the channels.

Another example of a current would be due to waves or winds. In this case, the winds and the waves are moving water and it’s also moving the sand that’s underneath and this is relevant to coastal managers who are interested in beach erosion and even for lifeguards looking for rip currents.

A third example of currents would be something associated with large scale motions like the Gulf Stream where water is moving along the East Coast from areas of the tropics up into the northeast and out to Europe and these types of currents are associated with the currents we are experiencing here in the United States.

HOST: Great, thank you. And why do we need to study tides and currents?

PAT BURKE: Well, there’s a multitude of reasons for studying these processes and it really depends on the audience. For NOAA, we have an important mission to support safe and efficient navigation. But others are interested in just knowing where the fish are. People are trying to prepare for oncoming coastal hazards – a tsunami, tidal flooding event, or anything associated with storm surge. Others are looking to support emergency response events such as oil spills or even the onset of a hurricane approaching the coast. City planners sometimes are looking to determine property boundaries and so they’re looking for information relating to datums or mean sea level which is associated with the tide. People are looking to understand the effects of climate change through long-term water level records that we have at CO-OPS and others like me are just curious about the tides and currents, we go out to the beach or we have a boat and we just want to go out and enjoy the outside.

HOST: I’m sure we could do a whole podcast on this, but can you tell us, maybe just briefly explain to our listeners what tools you use to collect tides and currents data?

PAT BURKE: I’d like to say first, that technology’s come a long way in the last 10-15 years. Our ability to study tides and currents has really been reflected in this improvement with computers and processing and technology. With tides, you can place a stick in the water, so that’s what we call a tide staff and just make a manual reading off of that stick or you can use scientific instrumentation. Here at CO-OPS we use a multitude of technologies ranging from acoustic and microwave technology and out to pressure sensors. This equipment is usually land-based, meaning it’s tied to a supporting structure like a pier and we record all our data electronically.

So with currents, the technology’s really driven the sophistication of how we collect our data. A lot of this is below the surface, so it’s not really transparent to the public, but we have a variety of sensors as well. We have what we call acoustic Doppler profilers, which we usually place at the ocean bottom and through sound wave technology we collect information. We also can deploy our current meters on buoys and also on piers as well. And emerging technology such as drifters and gliders and Hf radar are also available to us to collect information about currents.

HOST: So Pat, how are NOAA scientists, NOAA oceanographers on your team involved in collecting and distributing tides and currents data for all of us to use. Can you paint the picture for us for what happens from deploying a current meter or installing a water level gauge to maintaining it, collecting that data and analyzing it, to ultimately getting it up there on your website so we can see it, we can get that data?

PAT BURKE: Sure, here at CO-OPS we operate and maintain a large network of real-time water level gauges and current meters across the country. Some of our larger programs are the National Water Level Observation Network and the Physical Oceanographic Real-Time System. We collect this data continuously and beam this data to satellites which then send our data to our office.

We monitor the observing systems 24 hours a day, seven days a week to make sure that the data are good for all of our users. We analyze these large data sets to develop numerous products such as our tide predictions and our tidal current predictions that are used by the mariners and the recreational boating community every day. We also deploy water level gauges and current meters over shorter durations for special studies and operate several water level stations on the Great Lakes as well.

All of this information can be accessed by a click of a button on our tides and currents website.

HOST: And do you or can you collect data on tides and currents during storms?

PAT BURKE: Of course we can. A lot of our systems have been designed with the intent to withstand large storms such as Hurricane Katrina or Sandy. As storms approach, users flock to our website to get real-time information about rising water levels near their location. We have a product called QuickLook that gives you very easy access to a lot of our stations across the coast in the affected area.

NOAA weather forecasters and storm forecasters also use our real-time data to help them issue coastal hazard watches and warnings. This is what we can do to keep the public safe.

HOST: So Pat, are the stations designed any differently in these hurricane prone areas to be sure you get that critical data?

PAT BURKE: Over the last few years, we have set a priority to go back and attempt to what we call ‘harden’ some of our stations. Basically what we have done is we have fortified our stations in a way to withstand a hurricane. And this effort is ongoing and we’ve done a lot of work in the Gulf of Mexico and now along the East Coast in New Jersey and New York. And we hope to continue this effort in areas that are prone to hurricane-type storm surges and flooding.

HOST: Pat, I know many of us refer to your products, the products from your office, as we plan for an upcoming trip or day at the beach. But who are some of the other main users of your data?

PAT BURKE: So for CO-OPS, our main users are the maritime commerce community. They use our data every day for safe maneuvering and docking operations and to determine if their large ships can fit under bridges. We also work very closely with coastal managers and city planners and recreational boaters and the larger recreational community. We also support emergency responders and search and rescue operations. For example, when a plane may go down in the ocean, people come to us to get the supporting information that they can use to run their trajectory models. Another important user group are coastal engineers and people interested in habitat restoration for planning and design. And the larger scientific community in general – colleges, universities always come to our website looking for information to support their studies.

HOST: So, back now to that general public audience, probably most of us listening here today, what is your most popular resource for us to use to get tides and currents data?

PAT BURKE: As an operational data hub, many people visit our site every day to access our vast library of water levels and currents data. Some of our more popular resources are the real-time water level and currents data we provide through our Physical Oceanographic Real-Time Systems as well as our prediction tools – either our NOAA tides or NOAA currents predictions. People are always interested in knowing when the next high tide is arriving or the next maximum current will be coming.

The tide tables are part of NOAA’s navigation services and many people use our tides and currents data in conjunction with nautical charts.

HOST: Pat, you have tidal data for just thousands of locations. Can you tell us, or do you know, what is the most frequently downloaded dataset?

PAT BURKE: It’s really hard to say what our most popular location is, but I would like to say that we have a continuous water level record in San Francisco Bay dating back to the 1850s. Coastal scientists and engineers and climate scientists will download decades of monthly means and hourly data at any time for their research. Popularity is also event driven. For example, when Sandy struck the East Coast, we had a lot of web traffic accessing our data from Florida to Maine. A few years earlier, during Deepwater Horizon, there was a lot of interest in the Gulf of Mexico as well.

HOST: OK, that makes sense. It’s really been great today to explore this topic with you and just now, to help our listeners get to know you a little bit better, can you tell us what inspired you to get into this field?

PAT BURKE: So growing up in New Jersey, I always had an affinity for the beach and being close to what it provided. As I went to college and into graduate school, I found that the combination of science and math along with the opportunity to be outside and explore was a perfect melding of my interests and so I became an oceanographer.

HOST: Great, thank you. So finally Pat, my last question for you today is just to see if you had any final, closing words to leave our listeners with?

PAT BURKE: I’d just like to say that oceanography is a fun and rewarding field. And it’s always changing. I also encourage people to go visit our website. We have a wide variety of products and services in addition to our tides and currents information. For example, we have information on harmful algal blooms as well as model-based forecast information, and long-term sea level trends.

HOST: Thanks Pat for joining us today on Diving Deeper to talk about tides and currents. To learn more, please visit tidesandcurrents.noaa.gov.

That’s all for today’s show. Diving Deeper will be going on a break through September 2014. For more great information on the National Ocean Service, don’t forget to tune into our Making Waves podcast.