Weekly Ocean News

WEEKLY OCEAN NEWS

DATASTREME OCEAN WEEK FOUR: 24-28 September 2007

Ocean in the News

(Thurs.) DART and ATLAS buoys deployed in Indian Ocean -- NOAA officials and their counterparts in the Indonesian scientific community recently deployed one Deep-ocean Assessment and Reporting of Tsunami (DART™) II buoy and four ATLAS (Autonomous Temperature Line Acquisition System), which are climate monitoring buoys in the waters of the Indian Ocean. The DART buoy is the second tsunami monitoring buoy to have been on station in the Indian Ocean off Indonesia, the site of the disastrous tsunami of 2004, while the ATLAS buoys are part of the Global Earth Observation System of Systems (GEOSS), an international effort to monitor and predict changes in the global environment. [NOAA News]
(Thurs.) Marine bacteria use natural gas -- A team of German and American researchers have discovered a type of anaerobic bacteria in marine sediments that utilize several hydrocarbons including propane and butane found in natural gas for nutrition. [EurekAlert!]
(Thurs.) Deep-sea drilling to study earthquake zone -- The Japanese drilling ship Chikyu embarked on an expedition that will collect samples from below the ocean floor in one of the world's most active earthquake zones off the Japanese coast as part of the Nankai Trough Seismogenic Zone Experiment. [EurekAlert!]
(Tues.) Ice cover record set -- Researchers at the National Snow and Ice Data Center reported that as of one week ago the areal extent of the Arctic sea ice appears to have reached a summer minimum, which marks a record minimum size within the last 28 years of satellite surveillance. [EurekAlert!]
(Tues.) Changes in winter sea ice extent in Arctic depends on location -- Using 26 years of satellite data, researchers at Rutgers University have found that rising surface temperatures across the Barents Sea, located to the northeast of the Scandinavian Peninsula, have contributed to the shrinkage of winter ice across that portion of the Arctic basin, while the extent of the sea ice in the Bering Sea between Siberia and Alaska appears to remain relatively steady. [Rutgers University]
(Tues.) Antarctic snowmelt detected well inland -- Analyzing 20 years of data obtained from sensors on orbiting satellites have led NASA scientists to claim that the Antarctic snow and ice is currently melting farther inland from the coast and at higher altitudes than back when the satellite surveillance began. They also noted increased melting on the Ross Ice Shelf, Antarctica's largest ice shelf. [NASA Goddard]
Eye on the tropics -- During the last week several tropical cyclones (low pressure systems that form over tropical or subtropical oceans) developed and moved across tropical waters:
- In the North Atlantic basin, an area of low pressure that had formed along a frontal boundary off the coast of northeast Florida moved across the Florida Peninsula late last week and once over the northeastern Gulf of Mexico became Tropical Depression 10 on Friday. By Friday evening, it had made landfall along the western coast of the Florida Panhandle, accompanied by locally heavy rain. This system spared New Orleans, LA, which uneasily awaited the approach of this tropical depression. [USA Today]
  Subtropical Storm Jerry formed over the central North Atlantic on Sunday and moved to the north.
- In the eastern North Pacific, the ninth named tropical storm of the season in that basin formed from a tropical depression last week off the Mexican coast and was named Ivo. Near the end of the week this tropical storm had intensified to a Category 1 hurricane on the Saffir-Simpson Scale, but by the weekend, it had weakened to a tropical storm and then a tropical depression as it approached the southern tip of Mexico's Baja California. [USA Today] An image obtained from NOAA's GOES-11 satellite shows the clouds spiraling around Hurricane Ivo late last week. [NOAA OSEI]
- In the western North Pacific, Typhoon Wipha became a supertyphoon at the start of last week as maximum sustained surface winds exceeded 150 mph. This category 4 typhoon on the Saffir-Simpson Scale traveled to the northwest and made landfall along the eastern China coast by midweek. An image from the MODIS instrument on NASA's Aqua satellite shows the broad counterclockwise spiral of clouds around the central eye as Wipha passed to the northeast of Taiwan. After making landfall Typhoon Wipha weakened to a tropical storm as it moved across eastern China, but the winds and the heavy rain that produced landslides were responsible for at least nine deaths and millions of dollars in damage. [USA Today]
  A new tropical storm, with the name Francisco, developed in the South China sea over the weekend and was moving to the west-northwest toward southern China.
Humberto set a record -- Meteorologists at the National Hurricane Center recently reported that the one day that Hurricane Humberto took to develop from a tropical depression off the Texas Gulf coast to a category 1 hurricane (on the Saffir-Simpson Scale) represents a record development in North Atlantic hurricane records maintained at the center in over one century. Images obtained from the radar and microwave imager on NASA's the Precipitation Radar on the Tropical Rainfall Measuring Mission (TRMM) satellite, show the clouds and rainfall rates with the circulation regime when the tropical depression formed and when it made hurricane status just before landfall over one week ago. [NASA Earth Observatory]
Ten years of ocean color measurements by satellite show climate impacts on ocean health -- NASA recently celebrated the 10th anniversary of measurements of ocean color by its SeaWiFS (Sea-viewing Wide Field-of-view Sensor) instrument, noting that the decade-long data set collected shows how changes in ocean color can be used to see how ocean health can be affected by ongoing changes in climate. [NASA]
Emissions could violate ocean-quality standards -- A team of scientists from The United States, Norway, the United Kingdom, Australia, Japan and Monaco warn that future emissions of carbon dioxide by human activity would alter ocean chemistry sufficiently within the next half century and could result in ocean waters violating ocean water quality criteria set by the US Environmental Protection Agency. [EurekAlert!]
Human activity could increase atmospheric water content -- Researchers at several international research centers including Lawrence Livermore National Laboratory claim that satellite observations and climate model results indicate that human activity has not only increased global temperatures, but also the amount of water vapor in the atmosphere due to increased evaporation over the world's oceans. [EurekAlert!]
Earthweek -- Diary of the Planet [earthweek.com] Requires Adobe Acrobat Reader.

Concept of the Week: Variations in Marine Sediment Thickness

Sediments are particles of organic or inorganic origin that accumulate in loose form in depositional environments such as lake or ocean bottoms. Marine sediments, the central focus of this week's investigations, have a variety of sources and exhibit a wide range of composition, size, and shape. Marine sediments settle to the ocean floor as unconsolidated accumulations but ultimately may be converted to solid sedimentary rock via compaction and cementation. The pattern of variations in marine sediment thickness on the ocean floor confirms some basic understandings regarding marine geological processes.

Go to the DataStreme Ocean Website and under "Geological," click on "Sediment Thickness." This map of marine sediment thickness in the ocean basins was compiled by the National Geophysical Data Center (NGDC), Marine Geology and Geophysics Division primarily based on existing maps, ocean drilling, and seismic reflection profiles. Sediment thickness is color-coded in meters from violet (thinnest) to red (thickest). Many factors account for the variation in the thickness of marine sediment deposits including type and location of sediment sources, sediment transport mechanisms, and the age of the underlying crust.

According to the map, sediment thickness generally increases with distance from near the central portion of an ocean basin to the continental margin. This pattern may be explained by the principal sediment source and/or the age of the underlying crust. Rivers and streams that empty into the ocean slow and diverge, releasing the bulk of their suspended sediment load in coastal environments (e.g., bays, estuaries, deltas) and onto the continental shelf. Ocean currents transport sediment along the coast. In some areas of the continental shelf, massive amounts of sediment accumulate, become unstable, and flow down the continental slope to the base of the continental rise and beyond. However, only the finer fraction of river-borne sediment is swept into the deep ocean waters. Thickening of marine sediments in the direction of the continental margin may also reflect the aging of oceanic crust with distance away from divergent (spreading) plate boundaries where new oceanic crust forms. Th e older the crust the longer is the period that sediment rains down on the ocean bottom and the thicker is the blanket of accumulated sediment.

The map indicates that the thickness of marine sediment deposits is greater in the continental margin along the Atlantic coast of North America than along the Pacific coast. The Atlantic coast of North America is a passive margin; that is, the continental margin is not affected significantly by tectonic processes (no plate boundary) and the principal geological processes consist of sedimentation along with erosion by ocean waves and currents. In fact, passive margins and relatively thick marine sediment deposits occur on both sides of the Atlantic. (Passive margins also occur around the Arctic Ocean and surrounding Antarctica.) On the other hand, the Pacific coast of North America is an active margin; that is, the continental margin is associated with plate boundaries and is subject to deformation by tectonic stresses. Active continental margins are relatively narrow so that sediment delivered to the coast by rivers and streams flows directly into deeper water or trenches—preventing thick accumulations of marine sediments from building in the continental margin.

Concept of the Week: Questions

The thickness of marine sediment deposits is greater in the [(continental margins)(deep-ocean basins)].
The thickness of marine sediment deposits generally is greater in [(active)(passive)] continental margins.

Historical Events

24 September 1493...Christopher Columbus set sail with 17 ships on his second expedition to the New World, reaching the Lesser Antilles, the Virgin Islands, Puerto Rico and Hispaniola before returning to Europe in March 1496. (Wikipedia)
25 September 1513...Vasco Núñez de Balboa, a Spanish conquistador-explorer, crossed the isthmus of Panama and reached the Pacific Ocean, which he christened Mar del Sur (South Sea), claiming the ocean and all adjacent lands for Spain. (Wikipedia)
25 September 1939...A West Coast hurricane moved onshore south of Los Angeles bringing unprecedented rains along the southern coast of California. Nearly 5.5 in. of rain drenched Los Angeles during a 24-hr period. The hurricane caused $2 million in damage, mostly to structures along the coast and to crops, and claimed 45 lives at sea. "El Cordonazo" produced 5.66 in. of rain at Los Angeles and 11.6 in. of rain at Mount Wilson, both records for the month of September. (David Ludlum) (The Weather Channel)
25 September 1956...The world's first transatlantic telephone cable system began operating (Clarenville, Newfoundland to Oban, Scotland). Previous cables had been limited to telegraph transmissions. (Today in Science History)
26 September 1580...English seaman Francis Drake returned to Plymouth, England, in the Golden Hind, becoming the first British navigator to circumnavigate the globe. He had commenced his voyage around the world on 13 December 1577 with five ships, but returned with only one ship. During his voyage in the Pacific Ocean, he paused near San Francisco Bay and then traveled as far north as present-day Washington State. He brought back valuable information about the world's ocean to Queen Elizabeth I. (The History Channel)
26-27 September 1959...Typhoon Vera ravaged Honshu, Japan, the nation's largest island, leaving over 5000 dead, more than 40,000 injured, 1.5 million homeless and 40,000 homes destroyed. It was Japan's greatest storm disaster. (The Weather Doctor)
27 September 1854...After colliding with the French ship SS Vesta in dense fog, the American Collins Line steamship Arctic sank with more than 300 people on board near Cape Race, Newfoundland, marking the first great disaster in the Atlantic Ocean. (Wikipedia)
27 September 1922...Report on observations of experiments with short wave radio at the Naval Aircraft Radio Laboratory in Anacostia, DC started US Navy development of radar. (Navy Historical Center)
27 September 1958...A typhoon caused the death of nearly 5000 people on Honshu, the main Japanese island. (Wikipedia)
28 September 1542...Portuguese explorer Juan Rodríguez Cabrillo sailed into present-day San Diego (CA) Bay during the course of his explorations of the northwest shores of Mexico on behalf of Spain. His landing at Point Loma Head apparently was the first known European encounter with California. Before dying on the Channel Islands off the Santa Barbara coast in January 1543, he had explored much of the California coast. (The History Channel)
28 September 1850...An Act of Congress (9 Stat. L., 500, 504) provided for the systematic coloring and numbering of all buoys for, prior to this time, they had been painted red, white, or black, without any special system. The act "prescribed that buoys should be colored and numbered so that in entering from seaward red buoys with even numbers should be on the starboard or right hand side; black buoys with odd numbers on the port or left hand side; buoys with red and black horizontal stripes should indicate shoals with channel on either side; and buoys in channel ways should be colored with black and white perpendicular stripes." (US Coast Guard Historians Office)
29 September 1959...Hurricane Gracie made landfall near Beaufort, SC with sustained winds of 97 mph and a peak gust of 138 mph. Ten people were killed in South Carolina and Georgia. As the weakening storm moved through Virginia on the 30th, the storm spawned an F3 tornado at Ivy, VA, which killed 11 people. On the same day, a storm produced 28 inches of snow in Colorado Springs, CO. (David Ludlum)
30 September 1932...Tropical cyclone rainfall of 4.38 inches at Tehachapi in southern California over 7 hours caused flash floods on Agua Caliente and Tehachapi Creeks resulting in 15 deaths. (The Weather Doctor)
30 September 1954...The USS Nautilus, the world's first nuclear-powered submarine, is commissioned by the U.S. Navy. In addition to breaking numerous submarine travel records to that time, the Nautilus made the first voyage under the Arctic sea ice at the geographic North Pole in August 1958, passing from the Pacific to Atlantic Ocean basins. The Nautilus was decommissioned on 3 March 1980 and is currently on display at the Submarine Force Museum in Groton, CT. (The History Channel)
30 September 1997...Omega Navigation Station Hawaii ceased operation, coinciding with the end of worldwide Omega transmissions. (USCG Historian's Office)