DATASTREME OCEAN WEEK SEVEN: 14-18 March 2005

• A tropical system reaches Australia-- Tropical Cyclone Ingrid accompanied by maximum sustained winds of 143 mph moved across the Cape York Peninsula in northern Australia late last week and heading for the coast of northwest Australia. This tropical cyclone, which is Australia's counterpart of a hurricane, was the most powerful to hit the Queensland coast in more than 30 years, attaining a Category 4 status on the Saffir-Simpson Scale. [USA Today] [Editor's Note: For an Australian perspective, see The Australian News. EJH] This storm also caused damage to Australia's cultured pearl industry. [The Australian News]
• An Oregon community becomes TsunamiReady -- Officials from the National Weather Service recently announced that Lincoln City, along the Oregon coast, has become the first TsunamiReady community in the nation since the disastrous Indian Ocean tsunami of last December. [NOAA News]
• Guiding sailboats from space -- Sailors racing three yachts in the one million-dollar Oryx Quest 2005 race across the Southern Ocean encircling Antarctica are relying on ice-sensitive radar sensors onboard European Space Agency satellites to avoid collision with icebergs. [ESA]
• Stranded dolphins succumb despite aid -- Over one hundred dolphins became stranded in the shallow waters and beaches of the middle Florida Keys approximately two weeks ago. Despite efforts by volunteers, at least eight of the stranded dolphins died. [New Scientist]
• Oceans are vulnerable to agricultural runoff-- Stanford scientists report that based upon their analysis of SeaWiFS images obtained from orbiting satellites during a five-year span, large marine algal blooms in the offshore waters, such as Mexico's Gulf of California, have been the result of runoff from large scale agricultural operations. These blooms can disrupt the marine ecosystem and are even capable of producing "dead zones." [EurekAlert!]
• Gulf of California targeted -- The Natural Resources Defense Council recently announced that it has targeted the overfishing and decline in the ecosystem in Mexico's Gulf of California by declaring the Gulf as one of its BioGems, an environmentally sensitive area threatened by development. [Monterey Herald]
• Ocean waters became colder and less salty in a decade -- Scientists with the Antarctic Climate and Ecosystems Cooperative Research Centre report that deep waters of the Southern Ocean between Antarctica and Australia have gotten colder and less saline during the last decade. [Edie Net]
• Modified salmon could be introduced -- While Alaskan fishers are concerned, a Massachusetts company is hoping that the US Food and Drug Administration will permit sale of genetically enhanced salmon for consumption across the US. [ENN]
• An aquatic aggressor invades the Great Lakes-- Scientists from McMaster University report that the round goby has invaded the waters of the Great Lakes during the last 15 years and appears to have aggressively become a dominant species at the expense of native species. [EurekAlert!]
• Global and US Hazards/Climate Extremes -- A review and analysis of the global impacts of various weather-related events, including drought, floods, and storms during the current month. [NCDC]
• Earthweek -- Diary of the Planet [earthweek.com] Requires Adobe Acrobat Reader.

Concept of the Week: Seiche Model

A seiche (pronounced "say-sh") is a rhythmic oscillation of water in an enclosed basin (e.g., bathtub, lake, or reservoir) or a partially enclosed coastal inlet (e.g., bay, harbor, or estuary). With this oscillation, the water level rises at one end of a basin while simultaneously dropping at the other end. A seiche episode may last from a few minutes to a few days. (Refer to pages 156-157 in your DataStreme Ocean textbook for more on seiches.)

With a typical seiche in an enclosed basin, the water level near the center does not change at all although that is where the water exhibits its greatest horizontal movement; this is the location of a node. At either end of an enclosed basin, vertical motion of the water surface is greatest (with minimal horizontal movement of water); these are locations of antinodes. The motion of the water surface during a seiche is somewhat like that of a seesaw: The balance point of the seesaw does not move up or down (analogous to a node) while people seated at either end of the seesaw move up and down (analogous to an antinode).

Go to the University of Delaware's Seiche Calculator at http://www.coastal.udel.edu/faculty/rad/seiche.html. Set the "Modal Number" to 1 and then press "Calculate" for a graphical simulation of a seiche in an enclosed basin.

Partially enclosed basins usually have a node located at the mouth (rather than near the center) and an antinode at the landward end. Go to the Seiche Calculator, set the "Modal Number" to 0.5 and then press "Calculate" for a simulation of a seiche in a basin open to the right. Furthermore, some basins are complex and have multiple nodes and antinodes; these can be simulated on the Seiche Calculator by selecting different values of "Modal Number" greater than one.

The natural period of a seiche depends on the length and depth of the basin and generally ranges from minutes to hours. The period is directly proportional to basin length. For example, the natural period of a seiche in a small pond is considerably less than its period in a large coastal inlet. Also, for the same basin, the natural period is inversely proportional to water depth; that is, the period shortens as water deepens. Using the Seiche Calculator, you may wish to experiment with different basin lengths and depths. Conversely, one can determine the average depth of a lake by determining the period of the seiche and the length of the lake.

Concept of the Week: Questions

1. In an enclosed basin the node of a seiche is located [(at either end) (near the center)] of the basin.
2. The natural period of a seiche [(depends on) (is independent of)] the size of an enclosed basin.

• 14 March 1891...The submarine Monarch laid telephone cable along the bottom of the English Channel to prepare for the first telephone links across the Channel.
• 14 March 1903...President Theodore Roosevelt issued an executive order making Pelican Island near Sebastian Florida a "preserve and breeding ground for native birds", including pelicans and herons, marking the birth of the National Wildlife Refuge System. (Wikipedia)
• 14 March 1918...The first US concrete seagoing ship was launched at Redwood City, CA. (Today in Science)
• 15 March 1493...Christopher Columbus returned to Spain after his first voyage to the New World. (Wikipedia)
• 15 March 1778...Nootka Sound, Vancouver Island was discovered by Captain James Cook.
• 15 March 1946...For the first time, U.S. Coast Guard aircraft supplemented the work of the Coast Guard patrol vessels of the International Ice Patrol, scouting for ice and determining the limits of the ice fields from the air. (USCG Historian's Office)
• 15 March 1960...Key Largo Coral Reef Preserve in the Florida Keys was established as the nation's first underwater park. This preserve currently includes John Pennekamp Coral Reef State Park and the adjacent Florida Keys National Marine Sanctuary.
• 16 March 1521...Portuguese navigator Ferdinand Magellan reached the Philippines. He was killed the next month by natives.
• 16 March 1834...The HMS Beagle anchored at Berkeley Sound, Falkland Islands.
• 16 March 1889...A war between the U.S. and Germany was likely averted as a hurricane sank all three U.S. and three German warships in the harbor at Apia, Samoa. Joint U.S., German and Samoan rescue cooperation led to the Treaty of Berlin (1889) that later settled the dispute. (Accord's Weather Calendar)
• 17 March 1891...The British steamer SS Utopia sank off the coast of Gibraltar, killing 574 people. (Wikipedia)
• 17 March 1898...The USS Holland, the first practical submarine, was demonstrated by John Holland as it made its first dive in the waters off Staten Island, New York for one hour and 40 minutes. (Naval Historical Center)
• 17 March 1941...USCGC Cayuga left Boston with the South Greenland Survey Expedition onboard to locate airfields, seaplane bases, radio and meteorological stations, and aids to navigation in Greenland. (USCG Historian's Office)
• 17 March 1959...The submarine USS Skate (SSN-578) surfaced at the North Pole. (Naval Historical Center)
• 19 March 1866...The immigrant ship Monarch of the Seas sank in Liverpool killing 738 people.
• 20 March 2000...A large iceberg measuring approximately 170 mi by 25 mi calved off Antarctica's Ross Ice Shelf near Roosevelt Island. The iceberg was approximately 2.5 times the size of New York's Long Island. (Accord's Weather Guide Calendar)

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URL: DS Ocean:/news.html
Prepared by AMS DSOcean Central Staff and Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2005, The American Meteorological Society.