Weekly Ocean News

DATASTREME OCEAN SPRING BREAK WEEK: 6-10 March 2006

This is Break Week for the Spring 2006 offering of the DataStreme Ocean course. This Weekly Ocean News contains new information items and historical data, but the Concept of the Week is repeated from Week 6.

Ocean in the News

(Fri.) Coral offers a great climate proxy record -- An international team of scientists associated with the IODP (Integrated Ocean Drilling Program) Tahiti Sea Level Expedition are analyzing coral fossil samples that were retrieved last fall from Pacific waters off Tahiti. The nearly 2100 feet of cored fossil material would appear to offer an excellent record of the temperature and salinity changes in the south Pacific over the last 20,000 years. [EurekAlert!]
(Fri.) Space-age image of a novel bridge-tunnel -- NASA recently released a high resolution satellite image taken by an imaging instrument called ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) onboard the orbiting Terra satellite that shows a portion of the 10-mile long Oresund Link, a combination tunnel, artificial island and cable-supported bridge linking Malmo, Sweden (right), and Copenhagen, Denmark. [NASA Earth Observatory]
(Fri.) Monitoring height of Pacific sea level from space -- Data collected from radar altimeters onboard the European Space Agency's Envisat satellite indicate that the differences in height of the waters between the eastern and western equatorial Pacific would support the claim that a La Niña event is underway. A La Niña event, marked by abnormally cold water in the eastern Pacific and warm waters farther to the west, is linked to a variety of anomalous weather events over many areas of the planet. [ESA]
(Tues.) Awards given for an environmentally-friendly anchor -- The NOAA Monterey Bay National Marine Sanctuary and the Monterey Bay Aquarium Research Institute recently announced the winners of a competition for the design of reusable and disposable anchors that are considered environmentally friendly. [NOAA News]
(Tues.) Massive freshwater flood could have resulted in climatic change -- Using a sophisticated atmosphere-ocean coupled computer model, scientists at NASA's Goddard Institute for Space Studies and Columbia University have been able to replicate a reported abrupt climatic change that occurred approximately 8200 years ago by simulating the rapid flow of freshwater from the North American continent into the North Atlantic Ocean, thereby giving greater credence to the theory that oceanic circulation changes induced by the pulse of freshwater could result in widespread climatic change. [NASA Earth Observatory]
(Tues.) Importance of mangroves cited -- A team of researchers from Florida State University and Germany reports that mangrove plants, which cover less than 0.1 percent of the global land surface, are even more important to the maritime biosphere than previously thought, providing more than ten percent of the dissolved organic carbon to the world's ocean from the continents. [EurekAlert!]
(Tues.) A new ocean model unveiled -- Scientists with the University of Miami's Rosenstiel School and the Naval Research Laboratory have developed a three-dimensional ocean model called HYCOM (HYbrid Coordinate Ocean Model) that will be used operationally using data collected by the Naval Research Laboratory and NOAA's National Centers for Environmental Prediction. [University of Miami Rosenstiel School of Marine Atmospheric Science]
Right whales spotted off the Florida Gulf Coast -- Officials from the NOAA Fisheries Service and the Florida Fish and Wildlife Conservation Commission report that an endangered right whale mother and calf were seen traveling southward in the eastern Gulf of Mexico off the coast of southwest Florida, a somewhat rare sight. [NOAA News]
Goliath grouper removed from concern list -- The NOAA Fisheries Service announced that the goliath grouper (one of the grouper species in the western Atlantic that is also known as the jewfish) has been removed from the species of concern list due to an increase in abundance, but its numbers remain at levels that would make it off-limits to commercial and sport fishing according to the Magnuson-Stevens Fishery Conservation and Management Act. [NOAA News]
Loss of Antarctic ice noted -- Using data collected from the joint NASA and German GRACE (Gravity Recovery and Climate Experiment) mission, scientists at the University of Colorado, Boulder have found that the mass of the Antarctic ice sheet decreased significantly between 2002 and 2005. The amount of ice lost would be equivalent to a rise in global sea level by about 0.05 inches. [NASA Earth Observatory]
Timely forecast of dangerous ocean eddy involves satellites -- A new forecast service called Ocean FOCUS began issuing forecasts in mid February just in time to warn oil and gas producers operating offshore wells in the Gulf of Mexico of an impending new warm eddy that could cause significant damage to their underwater equipment. The service, which was developed by a consortium from the European Space Agency and groups from France, the United Kingdom and Norway, produces forecasts using a combination of ocean models and satellite measurements. [ESA]
Cruise ships enlisted to collect ocean data -- Scientists have been encouraging operators of cruise and cargo ships to measure ocean temperatures and currents during their regular routes, so the collected oceanic and meteorological data could be used by the scientific community. [ENN]
Listening to underwater sounds -- A physical oceanographer from the University of Washington has been using Passive Aquatic Listeners submerged well below the ocean's surface to listen for and distinguish between the various sounds and noise that are often heard in the ocean. [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.

This Concept of the Week is repeated from Week 6.

Concept of the Week: Abyssal Storms

Until recently, ocean scientists thought of the deep ocean abyss as a dark, cold but serene place where small 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) 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 atmospheric storms.

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 131, in your DataStreme Ocean 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 and this week's Supplemental Information, 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-transport 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

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

Historical Events

6 March 1521...The Portuguese explorer Ferdinand Magellan reached Guam in his around the world voyage. (Wikipedia)
6 March 1987...The British ferry Herald of Free Enterprise capsized in the English Channel off the coast of Belgium with the loss of 189 people.
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)