Perigean spring tide

A proxigean spring tide (also known as a perigean spring tide) is a tide that occurs three or four times per year when a perigee (the point nearest Earth that the Moon reaches during its 27.3-day elliptic orbit) coincides with a spring tide (when the Sun, the Moon, and Earth are nearly aligned every two weeks).[1] This tide usually adds only a couple of inches to normal spring tides.[1]

Astronomical causes

The Moon's orbit around Earth is elliptical, which causes the Moon to be closer to Earth and farther away at different times. The Moon and the Sun are aligned every two weeks, which results in spring tides, which are 20% higher than normal. During the period of the new moon, the Moon and Sun are on the same side of Earth, so the high tides or bulges produced independently by each reinforce each other (and has nothing to do with the spring season). Tides of maximum height and depression produced during this period are known as spring tide. Spring tides that coincide with the moon's closest approach to Earth ("perigee") have been called perigean spring tides and generally increase the normal tidal range by a couple of inches.[2]

The Ash Wednesday Storm of 1962 which inundated the entire Atlantic coastline of the United States from the Carolinas to Cape Cod, resulting in a loss of 40 lives and over 500 million dollars of property damage, coincided with a perigean spring tide.[3]

See also


  1. ^ a b "A perigean spring tide occurs when the moon is either new or full and closest to Earth". National Ocean Service. National Oceanic and Atmospheric Administration. July 18, 2013. Retrieved February 2, 2014.
  2. ^ "Tide Predictions & Data Tidal Current Predictions and Data Data Access Problems FAQ - Tide Predictions and Data". National Oceanic and Atmospheric Administration. Retrieved 15 August 2018.
  3. ^ "The strategic role of perigean spring tides in nautical history and North American coastal flooding, 1635-1976". Retrieved 2012-03-11.


  • Easterbrook, D.J. (1999). Surface Process and Landforms. 2nd ed. Upper Saddle River, NJ: Prentice Hall.
  • Duxbury, A.B., Duxbury, A.C., Sverdrup, K.A. (2002). Fundamentals of Oceanography. 4th ed. New York, NY: McGraw Hill.
  • Wood, Fergus J. (2001). Tidal Dynamics Volume I: Theory and Analysis of Tidal Forces; Volume II Extreme Tidal Peaks and Coastal Flooding. 3rd ed. West Palm Beach, Fl: The Coastal Education and Research Foundation [CERF] ISBN 0-938415-10-7

External links

1869 Saxby Gale

The Saxby Gale was a tropical cyclone which struck eastern Canada's Bay of Fundy region on the night of October 4–5, 1869. The storm was named for Lieutenant Stephen Martin Saxby, a naval instructor who, based on his astronomical studies, had predicted extremely high tides in the North Atlantic Ocean on October 1, 1869, which would produce storm surges in the event of a storm.

Ash Wednesday Storm of 1962

The Ash Wednesday Storm of 1962 occurred on March 5–9, 1962 along the mid-Atlantic coast of the United States. Also known as the Great March Storm of 1962, it was considered by the U.S. Geological Survey to be one of the most destructive storms ever to affect the mid-Atlantic states. Classified as a level 5 or Extreme Nor'easter by the Dolan-Davis scale for classification of Atlantic Nor'easters it was one of the ten worst storms in the United States in the 20th century. It lingered through five high tides over a three-day period, killing 40 people, injuring over 1,000, and causing hundreds of millions in property damage in six states. The storm also deposited significant snowfall over the Southeast, with a regional snowfall index of 12.663.

Bahama Banks

The Bahama Banks are the submerged carbonate platforms that make up much of the Bahama Archipelago. The term is usually applied in referring to either the Great Bahama Bank around Andros Island, or the Little Bahama Bank of Grand Bahama Island and Great Abaco, which are the largest of the platforms, and the Cay Sal Bank north of Cuba. The islands of these banks are politically part of the Bahamas. Other banks are the three banks of the Turks and Caicos Islands, namely the Caicos Bank of the Caicos Islands, the bank of the Turks Islands, and wholly submerged Mouchoir Bank. Further southeast are the equally wholly submerged Silver Bank and Navidad Bank north of the Dominican Republic.

Bay of Fundy

The Bay of Fundy (French: Baie de Fundy) is a bay between the Canadian provinces of New Brunswick and Nova Scotia, with a small portion touching the US state of Maine. It has an extremely high tidal range. The name is likely a corruption of the French word Fendu, meaning "split".

Carbonate platform

A carbonate platform is a sedimentary body which possesses topographic relief, and is composed of autochthonic calcareous deposits. Platform growth is mediated by sessile organisms whose skeletons build up the reef or by organisms (usually microbes) which induce carbonate precipitation through their metabolism. Therefore, carbonate platforms can not grow up everywhere: they are not present in places where limiting factors to the life of reef-building organisms exist. Such limiting factors are, among others: light, water temperature, transparency and pH-Value. For example, carbonate sedimentation along the Atlantic South American coasts takes place everywhere but at the mouth of the Amazon River, because of the intense turbidity of the water there. Spectacular examples of present-day carbonate platforms are the Bahama Banks under which the platform is roughly 8 km thick, the Yucatan Peninsula which is up to 2 km thick, the Florida platform, the platform on which the Great Barrier Reef is growing, and the Maldive atolls. All these carbonate platforms and their associated reefs are confined to tropical latitudes. Today's reefs are built mainly by scleractinian corals, but in the distant past other organisms, like archaeocyatha (during the Cambrian) or extinct cnidaria (tabulata and rugosa) were important reef builders.

Climate change in Tuvalu

Global warming (recent climate change) is dangerous in Tuvalu since the average height of the islands is less than 2 metres (6.6 ft) above sea level, with the highest point of Niulakita being about 4.6 metres (15 ft) above sea level. Tuvalu islands have increased in size between 1971 and 2014, during a period of global warming. Over 4 decades, there had been a net increase in land area in Tuvalu of 73.5 ha (2.9%), although the changes are not uniform, with 74% increasing and 27% decreasing in size. The sea level at the Funafuti tide gauge has risen at 3.9 mm per year, which is approximately twice the global average.Tuvalu could be one of the first nations to experience the effects of sea level rise. Not only could parts of the island be flooded but the rising saltwater table could also destroy deep rooted food crops such as coconut, pulaka, and taro. Research from the University of Auckland suggests that Tuvalu may remain habitable over the next century, but as of March 2018 Enele Sopoaga, the prime minister of Tuvalu, stated that Tuvalu is not expanding and has gained no additional habitable land.Enele Sopoaga, has also said that evacuating the islands is the last resort.

Index of physics articles (P)

The index of physics articles is split into multiple pages due to its size.

To navigate by individual letter use the table of contents below.

King tide

King tide is a colloquial term for an especially high spring tide, such as a perigean spring tide. King tide is not a scientific term, nor is it used in a scientific context. The use of the term king tide originated in Australia, New Zealand and other Pacific nations to refer to an especially high tide that occurs only a few times per year. The term has now come to be used in North America as well, particularly in low-lying South Florida, where they cause sunny day tidal flooding.


Kiribati (), officially the Republic of Kiribati (Gilbertese: Ribaberiki Kiribati), is a sovereign state in Micronesia in the central Pacific Ocean. The permanent population is just over 110,000 (2015), more than half of whom live on Tarawa Atoll. The state comprises 32 atolls and reef islands and one raised coral island, Banaba. They have a total land area of 800 square kilometres (310 sq mi) and are dispersed over 3.5 million square kilometres (1.3 million square miles).

Their spread straddles both the equator and the 180th meridian, although the International Date Line goes round Kiribati and swings far to the east, almost reaching the 150°W meridian. This brings the Line Islands into the same day as the Kiribati Islands. Kiribati's easternmost islands, the southern Line Islands, south of Hawaii, have the most advanced time on Earth: UTC+14 hours.

Kiribati became independent from the United Kingdom in 1979. The capital, South Tarawa, which is now the most populated area, consists of a number of islets, connected by a series of causeways. These comprise about half the area of Tarawa Atoll.

Kiribati is a member of the Pacific Community (SPC), Commonwealth of Nations, the IMF, and the World Bank, and became a full member of the United Nations in 1999.

List of submarine volcanoes

A list of active and extinct submarine volcanoes and seamounts located under the world's oceans. There are estimated to be 40,000 to 55,000 seamounts in the global oceans. Almost all are not well-mapped and many may not have been identified at all. Most are unnamed and unexplored. This list is therefore confined to seamounts that are notable enough to have been named and/or explored.

Oceanic plateau

An oceanic or submarine plateau is a large, relatively flat elevation that is higher than the surrounding relief with one or more relatively steep sides.There are 184 oceanic plateaus covering an area of 18,486,600 km2 (7,137,700 sq mi), or about 5.11% of the oceans. The South Pacific region around Australia and New Zealand contains the greatest number of oceanic plateaus (see map).

Oceanic plateaus produced by large igneous provinces are often associated with hotspots, mantle plumes, and volcanic islands — such as Iceland, Hawaii, Cape Verde, and Kerguelen. The three largest plateaus, the Caribbean, Ontong Java, and Mid-Pacific Mountains, are located on thermal swells. Other oceanic plateaus, however, are made of rifted continental crust, for example Falkland Plateau, Lord Howe Rise, and parts of Kerguelen, Seychelles, and Arctic ridges.

Plateaus formed by large igneous provinces were formed by the equivalent of continental flood basalts such as the Deccan Traps in India and the Snake River Plain in the United States.

In contrast to continental flood basalts, most igneous oceanic plateaus erupt through young and thin (6–7 km (3.7–4.3 mi)) mafic or ultra-mafic crust and are therefore uncontaminated by felsic crust and representative for their mantle sources.

These plateaus often rise 2–3 km (1.2–1.9 mi) above the surrounding ocean floor and are more buoyant than oceanic crust. They therefore tend to withstand subduction, more-so when thick and when reaching subduction zones shortly after their formations. As a consequence, they tend to "dock" to continental margins and be preserved as accreted terranes. Such terranes are often better preserved than the exposed parts of continental flood basalts and are therefore a better record of large-scale volcanic eruptions throughout Earth's history. This "docking" also means that oceanic plateaus are important contributors to the growth of continental crust. Their formations often had a dramatic impact on global climate, such as the most recent plateaus formed, the three, large, Cretaceous oceanic plateaus in the Pacific and Indian Ocean: Ontong Java, Kerguelen, and Caribbean.

Perigee (disambiguation)

Perigee is a type of apsis: an extreme point in an object's orbit.

Perigee may also refer to:

Perigee: Publication for the Arts, a quarterly literary journal

Perigee Books, a former imprint of Penguin Group, now part of TarcherPerigee

Perigee moon, or supermoon

Holcomb Perigee, a prototype sportsplane

Physical oceanography

Physical oceanography is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters.

Physical oceanography is one of several sub-domains into which oceanography is divided. Others include biological, chemical and geological oceanography.

Physical oceanography may be subdivided into descriptive and dynamical physical oceanography.Descriptive physical oceanography seeks to research the ocean through observations and complex numerical models, which describe the fluid motions as precisely as possible.

Dynamical physical oceanography focuses primarily upon the processes that govern the motion of fluids with emphasis upon theoretical research and numerical models. These are part of the large field of Geophysical Fluid Dynamics (GFD) that is shared together with meteorology. GFD is a sub field of Fluid dynamics describing flows occurring on spatial and temporal scales that are greatly influenced by the Coriolis force.

Rance Tidal Power Station

The Rance Tidal Power Station is a tidal power station located on the estuary of the Rance River in Brittany, France.

Opened in 1966 as the world's first tidal power station, it is currently operated by Électricité de France and was for 45 years the largest tidal power station in the world by installed capacity until the South Korean Sihwa Lake Tidal Power Station surpassed it in 2011.Its 24 turbines reach peak output at 240 megawatts (MW) and average 57 MW, a capacity factor of approximately 24%. At an annual output of approximately 500 GWh (491 GWh in 2009, 523 GWh in 2010), it supplies 0.12% of the power demand of France. The power density is of the order of 2.6 W/m2. The cost of electricity production is estimated at €0.12/kWh.

The barrage is 750 m (2,461 ft) long, from Brebis point in the west to Briantais point in the east. The power plant portion of the dam is 332.5 m (1,091 ft) long and the tidal basin measures 22.5 km2 (9 sq mi).


Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun, and the rotation of the Earth.

Tide tables can be used for any given locale to find the predicted times and amplitude (or "tidal range"). The predictions are influenced by many factors including the alignment of the Sun and Moon, the phase and amplitude of the tide (pattern of tides in the deep ocean), the amphidromic systems of the oceans, and the shape of the coastline and near-shore bathymetry (see Timing). They are however only predictions, the actual time and height of the tide is affected by wind and atmospheric pressure. Many shorelines experience semi-diurnal tides—two nearly equal high and low tides each day. Other locations have a diurnal tide—one high and low tide each day. A "mixed tide"—two uneven magnitude tides a day—is a third regular category.Tides vary on timescales ranging from hours to years due to a number of factors, which determine the lunitidal interval. To make accurate records, tide gauges at fixed stations measure water level over time. Gauges ignore variations caused by waves with periods shorter than minutes. These data are compared to the reference (or datum) level usually called mean sea level.While tides are usually the largest source of short-term sea-level fluctuations, sea levels are also subject to forces such as wind and barometric pressure changes, resulting in storm surges, especially in shallow seas and near coasts.

Tidal phenomena are not limited to the oceans, but can occur in other systems whenever a gravitational field that varies in time and space is present. For example, the shape of the solid part of the Earth is affected slightly by Earth tide, though this is not as easily seen as the water tidal movements.


Tuvalu ( TOO-və-loo), formerly known as the Ellice Islands, is a Polynesian island country located in the Pacific Ocean, situated in Oceania, about midway between Hawaii and Australia. It lies east-northeast of the Santa Cruz Islands (which belong to the Solomon Islands), southeast of Nauru, south of Kiribati, west of Tokelau, northwest of Samoa and Wallis and Futuna, and north of Fiji. It is composed of three reef islands and six true atolls spread out between the latitude of 5° to 10° south and longitude of 176° to 180°, west of the International Date Line. Tuvalu has a population of 10,640 (2012 census). The total land area of the islands of Tuvalu is 26 square kilometres (10 sq mi).

The first inhabitants of Tuvalu were Polynesians. The origins of the people of Tuvalu are addressed in the theories regarding migration into the Pacific that began about three thousand years ago. During pre-European-contact times there was frequent canoe voyaging between the islands as Polynesian navigation skills are recognised to have allowed deliberate journeys on double-hull sailing canoes or outrigger canoes. The pattern of settlement that is believed to have occurred is that the Polynesians spread out from Samoa and Tonga into the Tuvaluan atolls, with Tuvalu providing a stepping stone to further migration into the Polynesian outliers in Melanesia and Micronesia.In 1568, Spanish navigator Álvaro de Mendaña was the first European to sail through the archipelago, sighting the island of Nui during his expedition in search of Terra Australis. The island of Funafuti was named Ellice's Island in 1819; the name Ellice was applied to all of the nine islands after the work of English hydrographer Alexander George Findlay. The Ellice Islands came into Great Britain's sphere of influence in the late 19th century, as the result of a treaty between Great Britain and Germany relating to the demarcation of the spheres of influence in the Pacific Ocean. Each of the Ellice Islands was declared a British Protectorate by Captain Gibson of HMS Curacoa between 9 and 16 October 1892. The Ellice Islands were administered as a British protectorate by a Resident Commissioner from 1892 to 1916, as part of the British Western Pacific Territories (BWPT), and then as part of the Gilbert and Ellice Islands colony from 1916 to 1976.

A referendum was held in December 1974 to determine whether the Gilbert Islands and Ellice Islands should each have their own administration. As a consequence of the referendum, the Gilbert and Ellice Islands colony ceased to exist on 1 January 1976, and the separate British colonies of Kiribati and Tuvalu came into existence. Tuvalu became fully independent within the Commonwealth on 1 October 1978. On 5 September 2000, Tuvalu became the 189th member of the United Nations.

Tuvalu Meteorological Service

The Tuvalu Meteorological Service (TMS) is the principal meteorological observatory of Tuvalu and is responsible for providing weather services to the islands of Tuvalu. A meteorological office was established on Funafuti at the time the islands of Tuvalu were administered as parts of the Gilbert and Ellice Islands colony of the United Kingdom. The meteorological office is now an agency of the government of Tuvalu.The main observational office is on Funafuti. TMS operates outstations on Nanumea, Nui and Niulakita. TMS operates or monitors: 4 synoptic stations; 5 rainfall stations; 1 upper air research program; 1 tide gauge with Tsunami warning system; 1 Continuous Global Positioning System (CGPS) station; 1 seismic station.The TMS publishes weather forecasts, warnings as to tropical cyclones, weather charts and weather satellite images on its website, with weather forecasts and storm warnings also broadcast by the Tuvalu Media Corporation, which operates Radio Tuvalu.

Undersea mountain range

Undersea mountain ranges are mountain ranges that are mostly or entirely underwater, and specifically under the surface of an ocean. If originated from current tectonic forces, they are often referred to as a mid-ocean ridge. In contrast, if formed by past above-water volcanism, they are known as a seamount chain. The largest and best known undersea mountain range is a mid-ocean ridge, the Mid-Atlantic Ridge. It has been observed that, "similar to those on land, the undersea mountain ranges are the loci of frequent volcanic and earthquake activity".

Wave base

The wave base, in physical oceanography, is the maximum depth at which a water wave's passage causes significant water motion. For water depths deeper than the wave base, bottom sediments and the seafloor are no longer stirred by the wave motion above.

Ocean zones
Sea level


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