WEEKLY OCEAN NEWS

DATASTREME OCEAN SPRING BREAK WEEK: 7-11 March 2005

• Flocking to the coast -- NOAA recently reported that more than half of US citizens live either on or near a coast, including the Atlantic, Pacific, Gulf of Mexico and the Great Lakes. Concern has been voiced that the influx of residents along with tourists could complicate or make impossible evacuation in a advance of a natural disaster such as a tsunami or storm surge from a tropical or extratropical storm system. One possible remedy could involve vertical evacuation. [USA Today]
• Assessing the economics of coast and ocean resources -- The National Ocean Economics Program (NOEP) was been unveiled as a new national initiative aimed at assessing the economic value of the resources associated with the coasts and neighboring waters of the oceans in the local economy. [NOAA Magazine]
• Corals are now listed on the Endangered Species Act -- Officials with NOAA Fisheries recently announce that several species of corals are now listed on the Endangered Species Act, marking the first time that coral have appeared as threatened or endangered species. [NOAA News]
• Grant helps protect coral reefs -- A professor at Florida Tech received a grant for coral reef research in Mexico, Zanzibar and Australia that ultimately would serve to protect these reefs. [EurekAlert!]

• Monitoring changes in marine life from space-- A NASA researcher recently reported that based upon satellite derived data from NASA's Sea-viewing Wide Field-of-view Sensor (SeaWiFS) for the period from 1998 to 2003, phytoplankton have increased globally. This increase is important for the health of the oceanic ecosystems, but could help modulate temperatures from increased atmospheric carbon dioxide levels. [EurekAlert!]
• Unusual life in submarine "Lost City" studied -- Oceanographers recently reported that hydrogen and methane appear to sustain life near hydrothermal vents at the bottom of the ocean in an area called "Lost City." [EurekAlert!]
• Sea floor studied for early life forms -- Researchers at the University of California, Santa Barbara have been studying the microbes and minerals found at hydrothermal sites on the ocean floor off the Pacific coast of Central America in an attempt to understand the evolution of life nearly four billion years ago. [EurekAlert!]
• Life returns to hurricane-ravaged islands -- Following the hurricanes that devastated many areas of Florida last August and September, migratory waterfowl and human "snowbirds" are returning to Sanibel and Captiva Islands along Florida's Gulf Coast near Ft. Myers. [USA Today]
• Famous shipwreck added to historical register -- NOAA officials announced that the wreck of the steam ship SS Portland will be added to the National Register of Historical Places. This vessel, which sank during a storm on 27 November 1898 with the loss of 192 people, was New England's worst maritime disaster. The wreck, located in 2003 by NOAA, rests on the sea bottom in the Stellwagen Bank National Marine Sanctuary off the Massachusetts coast. [NOAA News]

• 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: Abyssal Storms

Until recently, ocean scientists thought of the deep ocean abyss as a dark, cold but serene place where particles rained gently onto the ocean floor. However, instruments lowered to the sea floor to measure ocean motion or currents and resulting mobilization of bottom sediments detected a much more active environment. Scientists found that bottom currents and abyssal storms occasionally scour the ocean bottom, generating moving clouds of suspended sediment. A surface current of 5 knots (250 cm/sec) like the Gulf Stream is considered relatively strong. A bottom current of 1 knot ( 50 cm/sec) is ripping. Although this may be called an abyssal storm, the water motion pales by comparison to wind speeds in an atmospheric storm.

Abyssal currents and storms apparently derive their energy from surface ocean currents. Wind-driven surface ocean currents flow about the margins of the ocean basins as gyres centered near 30 degrees latitude. (Refer to Figure 6.6, page 117, in your DataStreme Oceanography textbook.) Viewed from above, these subtropical gyres rotate clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. For reasons given in Chapter 6 of your textbook, surface currents flow faster, are narrower, and extend to greater depths on the western arm of the gyres. These are known as western boundary currents and include, for example, the Gulf Stream of the North Atlantic basin. Abyssal currents are also most vigorous on the western side of the ocean basins, moving along the base of the continental rise, which is on the order of several kilometers deep.

Abyssal storms may be linked to or may actually be eddies (rings) that occasionally break off from the main current of the Gulf Stream (and other western boundary currents). During an abyssal storm, the eddy or ring may actually reach to the bottom of the ocean where the velocity of a bottom current increases ten-fold to about 1.5 km (1 mi) per hr. While that is an unimpressive wind speed, water is much denser than air so that its erosive and sediment-transporting capacity is significant even at 1.5 km per hr. At this higher speed, the suspended sediment load in the bottom current increases by a factor of ten. Abyssal storms scour the sea floor leaving behind long furrows in the sediment. After a few days to a few weeks, the current weakens or the eddy (ring) is reabsorbed into the main surface circulation and the suspended load settles to the ocean floor. In this way, abyssal storms can transport tons of sediment long distances, disrupting the orderly sequence of layers of deep-sea sediments. Scientists must take this disruption into account when interpreting the environmental significance of deep-sea sediment cores.

Concept of the Week: Questions

1. In the subtropical ocean gyres, boundary currents flow faster on the [(western)(eastern)] side of an ocean basin.
2. Currents in an abyssal storm erode, transport, and redeposit sediments that have accumulated on the [(continental shelf)(deep ocean bottom)].

• 7 March 1778...Captain James Cook first sighted the Oregon coast, at Yaquina Bay near present day Newport.
• 7 March 1932...A severe coastal storm set barometric pressure records from Virginia to New England. Block Island, RI reported a barometric pressure reading of 955.0 millibars (28.20 inches of mercury). (David Ludlum)
• 9 March 1454...Amerigo Vespucci, the Italian navigator, was born in Florence, Italy. The North and South American continents were named in his honor by Matthias Ringmann, a German mapmaker.
• 9 March 1995...The Canadian Navy arrested a Spanish trawler for illegally fishing off Newfoundland.
• 10 March 1496...Christopher Columbus concluded his second visit to the Western Hemisphere when he left Hispaniola for Spain. (Wikipedia)
• 10 March 1849...Abraham Lincoln applied for a patent for a device to lift vessels over shoals by means of inflated cylinders.
• 11 March 2002...The National Ice Center reported that satellite images indicated that an iceberg with an area larger than the state of Delaware had calved from the Thwaites Ice Tongue, a region of snow and glacial ice extending from the Antarctic mainland into the South Amundsen Sea (Accord's Weather Calendar)
• 13-15 March 1952...The world's 5-day rainfall record was set when a tropical cyclone produced 151.73 inches rain at Cilos, Reunion Island in the Indian Ocean. The 73.62 inches that fell in a 24-hour period (15^th-16^th) set the world's 24-hour rainfall record. (Accord's Weather Calendar)

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URL: DSOcean:/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.