Weekly Ocean News

DATASTREME OCEAN WEEK SEVEN: 16-20 October 2006

Ocean in the News:

(Thurs.) Antarctic ice loss tied to greenhouse gases -- British and Belgian scientists found that higher greenhouse gas levels have caused stronger circumpolar winds. These warmer winds have crossed the Antarctic peninsula to weaken the ice leading to collapse of the Larsen B shelf. [CNN]
(Thurs.) A new coral reef management guide has been published -- A new guide entitled "A Reef Manager’s Guide to Coral Bleaching" was released last week by NOAA, the Australian Great Barrier Reef Marine Park Authority and The World Conservation Union that is designed to provide coral reef managers around the world with the latest scientific information concerning the causes of coral bleaching and to offer them innovative strategies for conserving coral reefs. [NOAA News]
(Thurs.) Stirring of the ocean by phytoplankton could affect climate -- Oceanographers at Florida State University have determined that the annual amount of chemical energy stored by phytoplankton is approximately five times the annual power consumption by humans and that approximately one percent of this energy is converted to mechanical energy, which is used by plankton feeds to stir the water, resulting in deep ocean mixing of the water that could indicate that stirring could equate to climate control. [EurekAlert!]
(Thurs.) Tropical sea surface temperature website is designed to aid in hurricane and climate research -- NASA has unveiled a webpage that provides the public and researchers with relatively current sea surface temperature information obtained from NASA satellites, especially across tropical and subtropical oceans, which is important for understanding hurricane formation, ocean currents, climate and climatic change. [NASA Earth Observatory]
(Thurs.) Ocean temperatures and pollution are affecting oysters -- Researchers from the Alfred Wegener Institute for Polar Marine Research, and the University of North Carolina at Charlotte report that pollution from cadmium has reduced the tolerance of oysters to rising ocean temperatures, resulting in a reduction of the oyster population in coastal waters of the eastern United States. [EurekAlert!]
(Tues.) NOAA's ocean education efforts are highlighted -- An article in the "NOAA Magazine" has recently highlighted its efforts intended to improve ocean literacy and science education through a variety of national regional and local efforts at developing ocean education curricula and teacher professional development programs. [NOAA Magazine]
(Tues.) Viewing a mangrove forest from space -- An image made from sensors onboard NASA's Landsat 7 satellite show the world's largest remaining mangrove forest in the Sundarbans of southwestern Bangladesh and southeastern India along the Bay of Bengal. [NASA Earth Observatory]
(Tues.) Detection of microalgae in coastal waters sought -- A marine scientist at the Dauphin Island Sea Lab in Alabama has been awarded a grant to explore a method for detecting microalgae in coastal waters using a laser. [EurekAlert!]
(Tues.) Effects of the Amazon felt out in the Atlantic -- Images produced from data collected by the MODIS (Moderate Resolution Imaging Spectroradiometer) sensor on NASA’s Aqua satellite show the impact that a plume of high nutrient river water from the Amazon River has upon the concentrations of chlorophyll in the surface waters of the tropical Atlantic Ocean. [NASA Earth Observatory]
(Tues.) Views of human migration could be altered by rapid rise in Arctic Ocean -- After studying ocean cores from the Chukchi Sea, scientists from Woods Hole Oceanographic Institution, Scripps Institution of Oceanography and the University of Massachusetts, Amherst have concluded that a rapid rise in the level of the Arctic Ocean could have occurred approximately 11,000 years ago, resulting in the closure of the possible land bridge across the Bering Strait to human migration about1000 years earlier than previously believed. [Woods Hole Oceanographic Institution]
Eye on the tropics --
- In the eastern North Pacific, remnants of former Tropical Storm Norman reorganized and were identified as Tropical Depression Norman early Sunday morning off the coast of Mexico near Manzanillo. Earlier last week, a visible image obtained from NOAA's GOES-11 satellite shows then Tropical Storm Norman well off the southwest Mexican coast soon after it formed. [NOAA OSEI]
- In the Central North Pacific, remnants of former Tropical Depression 4-C were moving eastward approximately 700 miles to the south-southwest of the Hawaiian Islands on Sunday morning.
- In the western North Pacific, Tropical Storm Soulik was moving to the northeast, passing to the southeast of the Japanese archipelago on Monday (local time). At the end of last week, this tropical cyclone had been a Category-2 typhoon on the Saffir-Simpson Intensity Scale. A visible satellite image from Japan's MTSAT satellite shows then Typhoon Soulik at the end of last week as it passed near Iwo Jima. Note the cloud-free eye in the center of this typhoon. [NOAA OSEI]
Dust can influence Atlantic hurricane activity -- Researchers at NOAA Atlantic Oceanographic and Meteorological Laboratory's Hurricane Research Division and the University of Wisconsin studying 25 years of satellite data found that during times when strong duststorms over northern Africa's Saharan Desert spread dust westward across the Atlantic, fewer hurricanes were reported across the North Atlantic and Caribbean, while years with little dust clouds were those with more intense hurricane activity. [NOAA News] [University of Wisconsin News]
Hawaiian earthquake does not produce tsunami -- An earthquake with a magnitude of 6.3 was detected off the west coast of Hawaii's Big Island near Kailua Kona on Sunday morning. Although the earthquake, which was felt across the Aloha State, had caused a landslide blocking a major highway on the Big Island, no risk of a Pacific-wide tsunami was reported by the Pacific Tsunami Center. [CNN]
High-resolution coastal relief models are developed for improved tsunami forecasting -- NOAA scientists from the National Geophysical Data Center and the Cooperative Institute for Research in Environmental Sciences have developed high-resolution digital elevation models for the near-shore seafloor along with the coastal land mass along the Carolina coast of the Atlantic basin, a section of the northern California coast and the Alaska Peninsula and Aleutians in the Pacific basin in order to improve forecasting for early tsunami warning systems. [NOAA News]
Storm surge blamed in part on "trapped wave" -- Scientists at Florida State University and NOAA's Tropical Prediction Center have found that the 10-foot storm surge in northern Florida's Apalachee Bay associated with the passage of Hurricane Dennis may have been amplified by a "trapped wave" that had proceeded northward along the west coast of Florida from near Naples in southwest Florida. [EurekAlert!]
Congress to act on ocean clean up -- The US House recently passed a bill that would help clear ocean debris that has been accumulating in the newly established Northwestern Hawaiian Islands Marine National Monument, as this monument resides near a region of the Pacific where slowly rotating ocean currents appear to be concentrating floating trash from elsewhere. [Christian Science Monitor]
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 textbook for more on seiches.)

With a typical seiche in an enclosed basin, the water level near the center does not change at all but 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

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

Historical Events:

16 October 1877...Bjørn Helland-Hansen, the Norwegian pioneer of modern oceanography, was born on this date. His studies of the physical structure and dynamics of the ocean were instrumental in transforming oceanography from a descriptive science to one based on the principles of physics and chemistry. (Today in Science History)
17-20 October 2004…Humid air from a former typhoon east of Japan helped deepen low pressure to 941 mb over the Gulf of Anadry west of Nome, AK (18th). Winds between 50 and 80 mph, with an unofficial gust to 114 mph at Red Dog Mine on the 19th, raked western Alaska. Storm surges reached approximately 11 feet. As much as $19.9 million in damage resulted from this storm. (Accord Weather Guide Calendar)
18 October 1910...Northeasterly winds as high as 70 mph (from a hurricane moving northward up the Florida peninsula) carried water out of Tampa Bay and the Hillsboro River. The water level lowered to nine feet below mean low water. Forty ships were grounded. (The Weather Channel)
19 October 1843...Captain Robert Stockton of the Princeton, the first screw propelled naval steamer, challenged the British merchant ship Great Western to a race off New York, which Princeton won easily. (Naval Historical Center)
20 October 1892...After ten years of difficult and costly construction, the St. George Reef Lighthouse, built on a rock lying six miles off the northern coast of California, midway between Capes Mendocino and Bianco, was first lighted. (USCG Historian's Office)
20 October 1956...A German physician, Dr. Hannes Lindemann, began a voyage on which he would become the first person to cross the Atlantic in the smallest craft. Using a double-seat folding kayak that was 17 feet in length and outfitted with an outrigger and sail, he made the trip from Las Palmas in the Canary Islands to St. Thomas in the US Virgin Islands in 72 days. He had made a prior crossing in a 23-foot African dugout canoe. He later wrote a book, Alone at Sea, describing his experiences. (Today in Science History)
20 October 1984...The Monterey Bay Aquarium opened on Cannery Row in Monterey, CA as the largest artificial environment for marine life, housing 500 marine animals from at least 525 species. The aquarium also supports active research and conservation programs. (Today in Science History)
21 October 1797...The USS Constitution was launched at the Charlestown Navy Yard in Boston, MA. The ship, nicknamed "Old Ironsides," is now the oldest commissioned ship in the U.S. Navy. (Naval Historical Center)
21 October 1580...Portuguese navigator Ferdinand Magellan on his famous circumnavigation voyage of the globe reached Cape Virgenes and the strait at the tip of South America that now bears his name. Only three ships entered the 373-mile long passage separating Tierra del Fuego (land of fire) and the continental mainland. Navigating the treacherous strait in 38 days, the expedition entered the South Pacific Ocean, which Magellan named "Mar Pacifico" for the relatively tranquil seas that he found. However, one ship had been wrecked and another deserted. (The History Channel)
21-26 October 1998...Hurricane Mitch, a category 5 hurricane (on the Saffir-Simpson Scale), developed as a tropical depression over the southwestern Caribbean Sea about 360 mi south of Kingston, Jamaica on the 21^st. It would intensify over the next few days to become the second deadliest Atlantic hurricane on record, on the 24^th. By the 26^th, Mitch finally dissipated after remaining a category 5 hurricane for 33 hours. Estimated rainfall totals of up to 75 in. caused devastating flooding and mudslides in Honduras and Nicaragua for days. Estimated death toll from this hurricane was more than 11,000, the worst since 1780. (The Weather Doctor) (Accord Weather Calendar)
22 October 1988...A "nor'easter" swept across the coast of New England. Winds gusted to 75 mph, and large waves and high tides caused extensive shoreline flooding. (The National Weather Summary) (Storm Data)