What’s a seiche?

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This animation reveals a standing wave (black) depicted as a sum of two propagating waves touring in reverse instructions (blue and pink). Related in movement to a seesaw, a seiche is a standing wave by which the most important vertical oscillations are at every finish of a physique of water with very small oscillations on the “node,” or heart level, of the wave. Standing waves can kind in any enclosed or semi-enclosed physique of water, from an enormous lake to a small espresso cup.

Seiches and meteotsunamis. What is the distinction?

Seiches and meteotsunamis are sometimes grouped collectively, however they’re two completely different occasions. Winds and atmospheric stress can contribute to the formation of each seiches and meteotsunamis; nonetheless, winds are sometimes extra essential to a seiche movement, whereas stress typically performs a considerable position in meteotsunami formation. Generally a seiche and a meteotsunami may even happen on the identical time. Seiches are standing waves with longer intervals of water-level oscillations (sometimes exceeding intervals of three or extra hours), whereas meteotsunamis are progressive waves restricted to the tsunami frequency band of wave intervals (two minutes to 2 hours). Seiches are often restricted to partially or totally enclosed basins, akin to Lake Erie. Meteotsunamis can happen in such basins however are additionally prevalent on the open coast. A single meteotsunami can journey lengthy distances and affect a really massive vary of the shoreline.

You probably have noticed water sloshing forwards and backwards in a swimming pool, bathtub, or cup of water, you might have witnessed a small-scale seiche (pronounced saysh). On a a lot grander scale, the identical phenomenon happens in massive our bodies of water akin to bays and lakes. A seiche could happen in any semi- or fully-enclosed physique of water.

Seiches are sometimes brought on when robust winds and speedy modifications in atmospheric stress push water from one finish of a physique of water to the opposite. When the wind stops, the water rebounds to the opposite facet of the enclosed space. The water then continues to oscillate forwards and backwards for hours and even days. In a similar way, earthquakes, tsunamis, or extreme storm fronts can also trigger seiches alongside ocean cabinets and ocean harbors.

Lake Erie is understood for seiches, particularly when robust winds blow from southwest to northeast. In 1844, a 22-foot seiche breached a 14-foot-high sea wall killing 78 folks and damming the ice to the extent that Niagara Falls quickly stopped flowing. As just lately as 2008, robust winds created waves 12 to 16 toes excessive in Lake Erie, resulting in flooding close to Buffalo, New York. Lake Pontchartrain, Louisiana, can also be recognized to routinely kind small seiches after the passage of afternoon squall strains throughout summer time months.

In among the Nice Lakes and different massive our bodies of water, the time interval between the “excessive” and “low” of a seiche might be as a lot as 4 to seven hours.  That is similar to the time interval between a excessive and low tide within the oceans, and is commonly mistaken as a tide.

What’s an Operational Forecast System?

hourly forecast of water levels for Chesapeake Bay

These maps present typical hourly forecasts of various oceanographic circumstances for Chesapeake Bay. Comparable hourly spatial animations for the following 48 hours can be found on-line for different areas and are up to date each six hours.

An Operational Forecast System (OFS) gives a nowcast and forecast (as much as 120 hours) of water ranges, currents, salinity, water temperatures, and winds for a given space. These methods are positioned in coastal waters across the nation and the Nice Lakes in vital ports, harbors, and estuaries.

Nowcasts and forecasts are scientific predictions concerning the current and future states of oceanographic and meteorological parameters inside coastal areas. A nowcast covers the previous 24 hours to the current and gives mannequin output for areas the place observational information will not be obtainable. A forecast gives info from the current time as much as 48 hours out and these are up to date each six hours. Nowcasts and forecasts are generated from NOAA real-time and forecast circumstances.

Actions wherein winds, water ranges, currents, water temperature, or salinity are necessary might profit from the data supplied by an operational forecast system. These versatile methods can be utilized for all the things from search and rescue to leisure boating and fishing to storm impact monitoring.

Operational Forecast Techniques are operated and maintained by NOAA’s Heart for Operational Oceanographic Merchandise and Companies.

Operational Forecast System vs. NOAA Tide Tables

For many years, mariners within the U.S. have trusted NOAA’s Tide Tables for the most effective estimate of anticipated water ranges and tidal currents. These tables present correct predictions of the astronomical tide and tidal currents (i.e., the change in water degree and present as a result of gravitational results of the moon and solar and rotation of the Earth). Nevertheless, they can’t predict localized water degree modifications and variations in currents attributable to wind, atmospheric stress, and river movement, which are sometimes vital. Because of this, OFS had been established to offer water degree, present, temperature, wind and salinity nowcasts and forecast steering primarily based on real-time statement information, meteorological forecasts, and astronomical predictions.

What’s a marsh organ?

An installed marsh organ at the Apalachicola National Estuarine Research Reserve in the Florida Panhandle

An put in marsh organ on the Apalachicola Nationwide Estuarine Analysis Reserve within the Florida Panhandle. A NOS-sponsored venture within the Gulf of Mexico employs the marsh organ to imitate sea stage rise impacts on marsh vegetation and inform forecast fashions. Picture courtesy of Jim Morris, College of South Carolina.


Scientists are at all times searching for methods to measure sea-level rise and its long-term results on coastal processes. To that finish, the College of South Carolina and NOAA’s Nationwide Facilities for Coastal Ocean Science developed a easy system known as a “marsh organ” (as a result of its graduated “pipes” resemble these of an organ) to find out how nicely an estuary could reply to rising sea ranges.

Organising the marsh organ is a very muddy course of. Scientists working to put in the instrument could discover themselves waist-deep within the comfortable marsh sediments! As soon as the organ is in place, they fill the tubes with mud and plant marsh grasses in every one. In a yr or two, they return to the marsh organ to reap the grass and measure how a lot it has grown. 

Every “pipe” of the marsh organ represents a various water-level “elevation.” Because the tides ebb and stream, the marsh and the pipes are topic to rising and falling water ranges. Relying on the quantity of flooding and different components, the marsh vegetation develop accordingly. The info is then used to tell a mannequin that helps scientists forecast the future well being of the marsh.

How does NOAA monitor water ranges across the nation?

A National Water Level Observation Network station in San Francisco, California

An NWLON station in San Francisco, California.


The Nationwide Water Degree Commentary Community (NWLON) is a everlasting observing system that features 210 repeatedly working water degree stations all through the U.S. and its territories. NWLON is the “go-to” supply for presidency and commercial-sector navigation, recreation, and coastal ecosystem administration.

Correct water degree knowledge is crucial for a lot of coastal actions, from navigation and engineering to restoration and preservation. Along with water ranges, the stations measure different oceanographic and meteorological parameters resembling water temperature and wind pace. NOAA makes use of this info to make sure protected navigation via entry to real-time knowledge 24 hours a day, seven days every week. NOAA nowcast and forecast fashions use the information to offer a glance into current and future oceanographic situations, which might improve tsunami and storm surge warnings. NOAA additionally makes use of this knowledge to publish annual tide predictions.

NWLON supplies historic in addition to present-day water degree info. Historic knowledge is used to compute relative native imply sea degree traits and to grasp the patterns of excessive tide occasions. The primary water degree observing stations had been established within the 1850s, and a few have been gathering knowledge ever since!

NWLON is managed by NOAA’s Middle for Operational Oceanographic Merchandise and Companies.

What’s a present survey?

Do you know?

An Operational Forecast System offers a nowcast and forecast (as much as 48 hours) of water ranges, currents, salinity, water temperatures, and winds for a given space. These methods are positioned in coastal waters and the Nice Lakes in important ports, harbors, and estuaries.

NOAA’s Heart for Operational Oceanographic Merchandise and Companies offers tidal present predictions to business and leisure mariners who depend on this data for protected navigation.  With the intention to present probably the most correct predictions attainable, NOAA should periodically resurvey numerous coastal and estuarine areas.  Survey areas are chosen based mostly on mariners’ navigation wants, oceanographic analyses, and the period of time that has handed because the final survey. Given trendy enhancements in measurement and computing know-how, these surveys vastly enhance the accuracy of tidal predictions. In 2017, for instance, NOAA concluded a three-year present survey of Puget Sound, Washington, to replace the area’s tidal present predictions. Previous to the survey, predictions had been based mostly on restricted quantities of information collected within the Nineteen Thirties-Nineteen Sixties.

To gather the info they want, NOAA scientists usually deploy Acoustic Doppler Present Profilers (ADCPs) to measure currents all through the water column at numerous areas for a interval of 1 to 4 months. The observations collected from the ADCPs are used to generate tidal present predictions at these areas.  Along with present measurements, NOAA typically deploys salinity, temperature, oxygen, and stress sensors at choose areas to trace the motion of assorted water lots. Whereas the mixed information is used to create higher tidal prediction fashions, additionally it is used to help the creation of NOAA Operational Forecast System (OFS) hydrodynamic fashions.  These fashions present short-term forecasts of water ranges, currents, water temperature, and salinity in coastal areas. 

Infographic Transcript: Coastal & Estuarine Present Surveys

Instrument Deployments: Annually NOAA measures ocean currents at completely different coastal and estuarine areas by deploying dozens of short-term devices.

Currents: Ocean currents describe the motion of water from one location to a different. Currents are noticed at depths all through the water column and are measured over a interval from one to 4 months.

Acoustic Doppler Present Profiler (ADCP): This instrument measures the currents by emitting beams of sound, which mirror off of particles within the water and again to the ADCP.

Harmonic Evaluation: After the ocean present measurements are collected, oceanographers obtain
the info after which analyze it via a pc program. A statistical course of
known as harmonic evaluation determines the half of the present attributable to the tides.
This “tidal present” can then be predicted at that location for a few years into the
future. Different components that affect the present, resembling wind, can’t be forecast for
various days and aren’t included within the prediction.

Tidal Present Predictions: Within the graph above, NOAA predicts at “Lovely Bay” that the tidal present will flood (stream inland) at 1 pm, slack (low present pace) at 4 pm, and ebb (stream out to sea) at 7 pm. The quickest currents seem at peak flood and ebb.

How are present predictions used? Because of NOAA tidal present predictions, kayakers trying to depart “Lovely Bay” know to keep away from the time of peak flood at 1pm after they could be paddling
towards the present. Tidal present predictions present important data for each
leisure and business marine navigation. Predictions of the tidal present might be
accessed on-line for 1000’s of coastal and estuarine areas.

 

What’s a meteotsunami?

a stormy ocean, iStock image

Stormy climate over the ocean can typically gasoline the event of meteotsunamis, a sequence of waves usually a lot smaller and fewer harmful than these related to seismically generated tsunamis.

Seiches and meteotsunamis. What is the distinction?

Seiches and meteotsunamis are sometimes grouped collectively, however they’re two totally different occasions. Winds and atmospheric stress can contribute to the formation of each seiches and meteotsunamis; nevertheless, winds are usually extra necessary to a seiche movement, whereas stress typically performs a considerable function in meteotsunami formation. Generally a seiche and a meteotsunami may even happen on the similar time. Seiches are standing waves with longer durations of water-level oscillations (usually exceeding durations of three or extra hours), whereas meteotsunamis are progressive waves restricted to the tsunami frequency band of wave durations (two minutes to 2 hours). Seiches are often restricted to partially or absolutely enclosed basins, resembling Lake Erie. Meteotsunamis can happen in such basins however are additionally prevalent on the open coast. A single meteotsunami can journey lengthy distances and affect a really massive vary of the shoreline.


You’ve heard of tsunamis—these large oceanic waves triggered primarily by earthquakes that may roll ashore, inflicting lack of life and catastrophe. However have you ever heard of meteotsunamis?

Meteotsunamis are massive waves that scientists are simply starting to raised perceive. In contrast to tsunamis triggered by seismic exercise, meteotsunamis are pushed by air-pressure disturbances typically related to fast-moving climate occasions, resembling extreme thunderstorms, squalls, and different storm fronts. The storm generates a wave that strikes in direction of the shore, and is amplified by a shallow continental shelf and inlet, bay, or different coastal function.

Meteotsunamis have been noticed to succeed in heights of 6 ft or extra. They happen in lots of locations all over the world, together with the Nice Lakes, Gulf of Mexico, Atlantic Coast, and the Mediterranean and Adriatic Seas.

Figuring out a meteotsunami is a problem as a result of its traits are nearly indistinguishable from a seismic tsunami. It may also be confused with wind-driven storm surge or a seiche. These uncertainties make it tough to foretell a meteotsunami and warn the general public of a possible occasion. Nonetheless, NOAA scientists have recognized atmospheric circumstances which are more likely to generate a meteotsunami and proceed to work on methods to forecast them.