DATASTREME OCEAN SPRING BREAK WEEK: 15-19 March 2010

Items of Interest

• Notice the Vernal Equinox --
The vernal equinox, which marks the commencement of astronomical spring, will occur Saturday 20 March 2010 (officially at 1:32 PM EDT, 12:32 PM CDT, and so forth). If you checked the sunrise and sunset times in your local newspaper or from the climate page at your local National Weather Service Office, you would probably find that by midweek, the sun should have been above the horizon for at least 12 hours at most locations. The effects of atmospheric refraction (bending of light rays by the varying density of the atmosphere) along with a relatively large diameter of the sun contribute to several additional minutes that the sun appears above the horizon at sunrise and sunset.
• "Earth-Sun Day"--
Since Saturday 20 March 2010 is the vernal equinox, the day has been declared Earth-Sun Day, which is includes a series of programs and events that occur throughout the year culminating with a celebration on the Spring Equinox. This year's theme is Magnetic Storms, which are disturbances in the Earth's magnetic field associated by solar activity. NASA will have a live Sun-Earth Day Webcast from the exhibit floor of the National Science Teachers Association (NSTA) conference in Philadelphia, PA.

Ocean in the News

• Eye on the tropics --
Tropical cyclone activity was found across the Southern Hemisphere during the past week:
In the South Pacific Tropical Cyclone Tomas formed west of Pago Pago late last week and traveled to the west and then southwest. By late Sunday (local time), Tomas became a major category-3 cyclone on the Saffir-Simpson Scale as it traveled southward. Additional information on Tropical Cyclone Tomas and a satellite image are available on the NASA Hurricane Page.
Tropical Cyclone Ului also formed late last week over the waters of the South Pacific near the Torres Islands in the island nation of Vanuatu to the northeast of Australia. By midday on Sunday (local time), Uliui had become a major category-5 cyclone on the Saffir-Simpson Scale, as maximum sustained surface winds reached 160 mph. At that time, this major tropical cyclone was traveling to the west-northwest. See additional information concerning Tropical Cyclone Ului on the NASA Hurricane Page.
In Southern Indian Ocean, Tropical Storm Hubert formed early last week east of Madagascar. However, this tropical storm was short-lived as it made landfall along Madagascar within two days of formation. Satellite images and additional information on Tropical Storm Hubert are available from the NASA Hurricane Page.
In the South Atlantic basin , a rare tropical cyclone formed off the Brazilian coast. This cyclone, identified as Tropical Storm 90Q, represents only the second documented tropical cyclone to form over the cool waters of this basin. This tropical storm traveled away from the coast and dissipated. NASA Hurricane Page.
• Caribbean hurricane preparedness tour to commence --
Meteorologists and support staff from NOAA and the U.S. Air Force Reserve will begin a ten-day trip on "hurricane hunter" aircraft late this coming week to six coastal communities in Bermuda, Mexico and the Caribbean. This mission, which includes the Director of NOAA's National Hurricane Center, is designed to familiarize the region's residents of the hurricane monitoring and forecast efforts of the US and to urge these residents to prepare for the upcoming hurricane season. [NOAA News]
• Little confidence shown in national hurricane response planning --
A study that involved a telephone survey conducted of residents in southeastern Louisiana last fall by researchers at Louisiana State University shows that while many families had their own well-developed hurricane response plan, less than one third of the respondents felt that the Federal government has an adequate plan. Interestingly they felt that the state and their parish or town had adequate plans. [EurekAlert!]
• Proposal advanced for listing loggerhead sea turtles as endangered species --
NOAA’s Fisheries Service and the U.S. Fish and Wildlife Service have jointly proposed that the loggerhead sea turtle (Caretta caretta) in nine distinct population segment around the globe be identified as "species" for listing as endangered or threatened under the Endangered Species Act. Those population segments in the South Atlantic Ocean and the Southwest Indian Ocean should be identified as threatened, while those population segments that would be listed as endangered reside in the North Pacific Ocean, South Pacific Ocean, Southeast Indo-Pacific Ocean, North Indian Ocean, Northwest Atlantic Ocean, Northeast Atlantic Ocean, and Mediterranean Sea. [NOAA News]
• Hypoxic waters could contribute to climate change --
An oceanographer from the University of Maryland warns that the increasing number and intensity of hypoxic waters, which are oxygen-deprived "dead zones" in the coastal waters, could adversely impact environmental conditions with the large amounts of nitrous oxide, a greenhouse gas, produced in these waters, thereby resulting in elevated global temperatures. The nitrous oxide release could also be detrimental to stratospheric ozone levels. [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, drought, floods, 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, to include 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

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)].

Historical Events

• 15 March 1493...Christopher Columbus returned to Spain after his first voyage to the New World. (Wikipedia)
• 15 March 1778...Nootka Sound, Vancouver Island was discovered by Captain James Cook.
• 15 March 1946...For the first time, U.S. Coast Guard aircraft supplemented the work of the Coast Guard patrol vessels of the International Ice Patrol, scouting for ice and determining the limits of the ice fields from the air. (USCG Historian's Office)
• 15 March 1960...Key Largo Coral Reef Preserve in the Florida Keys was established as the nation's first underwater park. This preserve currently includes John Pennekamp Coral Reef State Park and the adjacent Florida Keys National Marine Sanctuary.
• 16 March 1521...Portuguese navigator Ferdinand Magellan reached the Philippines. He was killed the next month by natives.
• 16 March 1834...The HMS Beagle anchored at Berkeley Sound, Falkland Islands.
• 16 March 1889...A war between the U.S. and Germany was likely averted as a hurricane sank all three U.S. and three German warships in the harbor at Apia, Samoa. Joint U.S., German and Samoan rescue cooperation led to the Treaty of Berlin (1889) that later settled the dispute. (Accord's Weather Calendar)
• 17 March 1891...The British steamer SS Utopia sank off the coast of Gibraltar, killing 574 people. (Wikipedia)
• 17 March 1898...The USS Holland, the first practical submarine, was demonstrated by John Holland as it made its first dive in the waters off Staten Island, New York for one hour and 40 minutes. (Naval Historical Center)
• 17 March 1941...USCGC Cayuga left Boston with the South Greenland Survey Expedition onboard to locate airfields, seaplane bases, radio and meteorological stations, and aids to navigation in Greenland. (USCG Historian's Office)
• 17 March 1959...The submarine USS Skate (SSN-578) surfaced at the North Pole. (Naval Historical Center)
• 20 March 1866...The immigrant ship Monarch of the Seas left Liverpool, England, but was never seen again. The ship with 738 people was officially declared "lost" after 130 days. A message in a bottle was found at Plymouth, supposedly sent by a passenger. In July, wreckage was found around the Dingle coast in Southern Ireland.
• 20 March 2000...A large iceberg measuring approximately 170 mi by 25 mi calved off Antarctica's Ross Ice Shelf near Roosevelt Island. The iceberg was approximately 2.5 times the size of New York's Long Island. (Accord's Weather Guide Calendar)

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Prepared by AMS DS Ocean Central Staff and Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2010, The American Meteorological Society.