Weekly Ocean News

WEEKLY OCEAN NEWS

DATASTREME OCEAN WEEK SIX: 2-6 March 2009

Ocean in the News

Eye on the tropics -- Tropical cyclone activity continued across the South Indian Ocean early last week. Remnants of Tropical Cyclone Hina that had formed the previous week east of Diego Garcia dissipated as it traveled to the south. Additional information and satellite imagery on Hina can be found on the NASA Hurricane Page.
Warm water helped fuel killer tropical cyclone -- A recent study conducted at the National Taiwan University, Taipei; and NASA's Jet Propulsion Laboratory has found that a pool of warm surface water in the North Indian Ocean appears to have been responsible for the rapid intensification of Tropical Cyclone Nargis in May 2008 to category 4 status (on the Saffir-Simpson Scale) just prior to its landfall in Myanmar (Burma), which led to extensive loss of life. [NASA JPL] [NASA Hurricane Page]
Public comment invited on management of a marine sanctuary -- NOAA has invited public review and comment on the draft of a management plan for the NOAA's Thunder Bay National Marine Sanctuary located in Lake Huron off Michigan's Lower Peninsula. [NOAA News]
Sinkholes under Great Lakes contain exotic ecosystems -- A team of scientists from Grand Valley State University, the University of Wisconsin-Stout, NOAA's Thunder Bay National Marine Sanctuary and the Great Lakes Environmental Research Laboratory has discovered an exotic ecosystem containing varieties of microbes and fish within deep sinkholes that developed in the geologic formations on the bottom of Lake Huron. [EurekAlert!]
Applicants sought for advisory council at a California marine sanctuary -- NOAA’s Monterey Bay National Marine Sanctuary is currently seeking applicants to fill a seat on the advisory council that provides advice to the sanctuary's superintendent, thereby ensuring continued public participation in the management of the sanctuary located in the waters off the coast of central California. [NOAA News]
Maritime shipping is a harmful air pollution source -- A new study by NOAA and the University of Colorado at Boulder indicates that commercial ships emit nearly half the amount of particulate matter into the air as the total amount of pollutants released by the world's other land based vehicles. These results indicate that ships can adversely affect the health of people living along coastlines. [NOAA News]
Polar research indicates major environmental changes -- The World Meteorological Organization and the International Council for Science recently released a report "State of Polar Research" that provides evidence of widespread changes in the environmental conditions in both the Arctic and Antarctic polar cap regions due to increases in global temperatures. This evidence, which includes changes in ice cover, sea level and plant and animal life in polar regions, has been obtained from the research conducted during the International Polar Year (IPY) 2007-2008. [International Council for Science]
Last year was coolest of the 21st century -- Climatologists at the NASA Goddard Institute for Space Studies recently reported that although their data analysis indicates the recently concluded 2008 was the coolest calendar year since 2000, it was also the ninth warmest year since reliable climate records began in 1880. They also noted that the ten warmest years on record have all occurred within the last decade. The scientists found that Eurasia, the Arctic and the Antarctic Peninsula had temperatures in 2008 that were well above the 1951-1980 averages, much of the Pacific Ocean was cooler than average due to the persistence of a La Niña event. The temperature across the US was close to the long-term average in 2008. [NASA GISS] (Editor's note: The GISS global temperature analysis for 2008 differs slightly from that provided by NOAA's National Climatic Data Center because of the averaging techniques employed. [NOAA News] EJH)
Global oceanic temperature fluctuations seen during last Ice Age -- An international team of British, French, German and US researchers who reconstructed oceanic temperatures of the South Atlantic Ocean during the last Ice Age from a sediment core obtained from the floor of the South Atlantic Ocean has concluded that changes in oceanic circulation within the Atlantic basin led to the large and abrupt changes in the temperatures in the North Atlantic and over Greenland at that time. [EurekAlert!]
Conditions that caused formation of Antarctic glacier studied -- Scientists at Purdue University, Yale University, Harvard University, the University of Massachusetts, Amherst and Utrecht University, who reconstructed the temperature variations in the Southern Hemisphere from chemical analysis of ocean cores obtained from the Integrated Ocean Drilling Program report that temperatures dropped rapidly in Antarctica approximately 34 million years ago at the Eocene-Oligocene transition, leading to the development of the Antarctic ice sheet and widespread extinction of animal species. [Purdue University] [EurekAlert!]
An All-Hazards Monitor -- This Web portal provides the user information from NOAA on current environmental events that may pose as hazards such as tropical weather, marine weather, tsunamis, rip currents, Harmful Algal Blooms (HABs) and coral bleaching. [NOAAWatch]
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 and 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 152, in your 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

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 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.
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)