WEEKLY OCEAN NEWS

DATASTREME OCEAN WEEK SIX: 28 February-4 March 2005

• Another tropical cyclone threatens the South Pacific islands -- With maximum sustained surface winds of up to 130 mph, Tropical Cyclone Percy was moving across the South Pacific along a track that took it by American Samoa and possibly to within 300 miles of the Cook Islands. This tropical cyclone, the South Pacific's equivalent of a hurricane, follows by a week Tropical Cyclone Otto, which caused damage on the Cook Islands. [USA Today]
• Better El Niño forecasts could aid fisheries management -- An oceanographer at Duke University recently noted that the breakthroughs in computer and satellite technology could lead to better forecasts of El Niño events that could then aid in fisheries management, controlling diseases in marine communities and marine species protection. El Niño events are anomalous changes in oceanic and atmospheric circulation regimes that not only affect the eastern equatorial Pacific, but the weather in many other areas due to complex interactions. [EurekAlert!]
• Agreement reached on definitions -- Representatives of NOAA's National Weather Service and their counterparts in the Meteorological Service of Canada and the National Meteorological Service of Mexico have recently reached a consensus on the definitions and an index that identify El Niño and La Niña episodes, anomalous circulation regimes in the ocean and atmosphere. [NOAA News]
• Wet weather across the Southwest linked to a weak El Niño event-- Scientists at the NOAA Climate Prediction Center point to weak El Niño conditions in the tropical Pacific as being partially responsible for the recent storms that brought record-setting rain to California and other Southwestern States during the last month. [NOAA News]
• Gulf environment altered by island building -- Environmentalists have criticized the extensive building of artificial islands over the coral and oyster beds along the Persian Gulf near Dubai, United Arab Emirates that has caused damage to the marine environment. [ENN]
• Reasons given for a frozen North Pole -- Researchers in Spain and Germany recently announced their theory as to the development of ice sheets across the Arctic during the last 2.7 million years. They suggest that an increased stratification of ocean water by increases in freshwater could have helped increase the differences between summer and winter temperatures that ultimately caused increased snowfall across the region along with the freeze over of the Arctic Ocean. [EurekAlert!]
• Movement of ocean floor microplates studied -- Geologists from Duke University and Woods Hole Oceanographic Institution have discovered that crustal "microplates" appear to be slowly rotating together in a coordinated grinding action in a region of the eastern equatorial Pacific Ocean where new seafloor is being produced. [EurekAlert!]
• Why iron is a major factor in growth of marine life -- An oceanographer at the University of Maine who collaborated with Canadian and Japanese scientists on a field experiment in the western Pacific suggests that certain organisms can scavenge iron sequestered in minerals, making the iron available for use by phytoplankton. [EurekAlert!]
• Reasons given for a frozen North Pole -- Researchers in Spain and Germany recently announced their theory as to the development of ice sheets across the Arctic during the last 2.7 million years. They suggest that an increased stratification of ocean water by increases in freshwater could have helped increase the differences between summer and winter temperatures that ultimately caused increased snowfall across the region along with the freeze over of the Arctic Ocean. [EurekAlert!]
• Previous ice sheet retreat discovered -- Scientists with the British Antarctic Survey and universities in the British Isles report that the an extensive retreat in the George VI Ice Shelf on the Antarctic Peninsula occurred approximately 9500 years ago that coincided with a shift in ocean currents. [EurekAlert!]
• Swirling phytoplankton plumes linked to floods -- NASA scientists have identified the swirling plumes of phytoplankton in the Arabian Sea that were detected by sensors onboard the polar orbiting NASA Aqua satellite as being caused by the nutrient rich water entering the sea from recent floods in Pakistan. [New Scientist]
• High tech sails a possibility -- German engineers have been testing a large inflatable kite on the Baltic Sea for possible use as a means for helping pull ships across the ocean. [New Scientist]
• Indicators of a frozen Martian sea -- Scientists from England and Germany studying images from the High Resolution Stereo Camera onboard Europe's Mars Express spacecraft indicate that the plate-like formations near the Martian equator could suggest a frozen body of water below the Martian surface, far beyond the planet's frozen ice caps. [University College London] [New Scientist] Other scientists using the Planetary Fourier Spectrometer that measures atmospheric composition have claimed that elevated concentrations of methane appear in the atmosphere above the region that could contain a frozen sea, suggesting the possibility of primitive microorganisms. [New Scientist]
• Tsunami couple's last pictures -- A vacationing Canadian couple in Thailand took photos of the approaching tsunami that was to kill them. [BBC News]
• Coastal engineering lessons from the tsunami -- An international team of engineers and scientists touring Thailand and other South Asian countries devastated by the December 2004 earthquake and tsunami have made some recommendations that could improve coastal engineering that might reduce casualties in future tsunamis. [EurekAlert!]
• 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) 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 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 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

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)].

• 28 February 1849...Regular steamboat service to California from the East Coast via Cape Horn arrived in San Francisco for the first time. The SS California had left New York Harbor on 6 October 1848 on a trip that took 4 months and 21 days. (Wikipedia)

• 28 February 1964...A world 12-hour rainfall record was set at Belouve, La Reunion Island in the western Indian Ocean when 52.76 inches of rain fell. World records for 9 hours and 18.5 hours were also set with 42.79 and 66.49 inches, respectively. (Accord's Weather Calendar) (The Weather Doctor)
• 29 February 1504...Christopher Columbus used his knowledge of a lunar eclipse that night to convince Native Americans to provide him with supplies. (Wikipedia)

• 1 March 1498...The Portuguese explorer, Vasco de Gama, landed at what is now Mozambique on his way to India.
• 1 March 1854...The SS City of Glasgow left Liverpool harbor for Philadelphia and was never seen again with 480 people on board.
• 1 March 1902...The first regular light stations in Alaska were established at Southeast Five Finger Island and at Sentinel Island. Both on the main inside passage between Wrangell Strait and Skagway. (USCG Historian's Office)
• 1 March 1905...The first regular light stations in Alaska were established. (USCG Historian's Office)
• 1 March 1927...A system of broadcasting weather reports by radio on four lightships on the Pacific Coast was put into effect. (USCG Historian's Office)
• 1 March 1970...US commercial whale hunting was ended.
• 1 March 1977...The United States extended its territorial waters to 200 miles.
• 1 March 1983...A ferocious storm battered the Pacific coast. The storm produced heavy rain and gale force winds resulting in flooding and beach erosion and in the mountains produced up to seven feet of snow in five days. An F2 tornado hit Los Angeles. Thirty people were injured and 100 homes were damaged. (The Weather Channel) (Intellicast)
• 3 March 1873...US Army Signal Corps established storm signal service for benefit of seafaring men, at several life-saving stations and constructed telegraph lines as original means of communication. (USCG Historian's Office)
• 3 March 1960...The submarine USS Sargo returned to Hawaii from an arctic cruise of 11,000 miles, of which 6,003 miles were under the polar ice, reaching the North Pole on 9 February. This cruise marked the first time that a submarine explored the Arctic in winter. (Naval Historical Center)
• 4-5 March 1899...Tropical cyclone Mahina (the Bathurst Bay Hurricane) crossed the Great Barrier Reef and generated a 48-ft storm surge across Barrow Point, Queensland, Australia. The Australian pearling fleet was destroyed, over 100 shipwrecks reported and 307 people killed. Barometric pressure fell to an unofficial reading of 915 millibars (27 inches of mercury). (Accord's Weather Calendar) (The Weather Doctor)
• 5 March 1914...The Spanish ship the Principe de Asturias that was enroute from Barcelona to Buenos Aires sank with the loss of 445 of the 588 passengers and crew members when it struck the jagged reefs along the Brazilian coast at Ponta Boi in dense fog.
• 5-6 March 1962...The Great Atlantic Coast Storm of 1962 caused more than $200 million in property damage from Florida to New England. Winds along the Middle Atlantic Coast reached 70 mph raising 40-ft waves, and 42 inches of snow fell at Big Meadows, in the mountains of Virginia--a state record. The storm caused greater alteration of the coastline from Cape Hatteras, NC to Long Island than any previous storm, including hurricanes. A new inlet was cut through Hatteras Island and more than 10 miles of Outer Banks barrier dunes were obliterated. The Virginia shoreline was rearranged by historic tidal flooding caused by the combination of the long stretch of strong onshore winds and the "Spring Tides." A 3-mile long boardwalk in Ocean City, MD was wiped out. (David Ludlum) (Intellicast)
• 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.

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