DATASTREME OCEAN SPRING BREAK WEEK: 7-11 March 2011

• Eye on the tropics -- As meteorological summer concluded in the Southern Hemisphere, no tropical cyclone activity was found across the tropical waters of the Southern Hemisphere during the past week.
• Upcoming Latin American hurricane preparedness tour announced -- Meteorologists and support staff from NOAA and the US Air Force Reserve will begin a six-day trip on "hurricane hunter" aircraft in two weeks to six coastal communities in 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]
• Marine animal migration data incorporated into national ocean observing system -- Officials with the US Integrated Ocean Observing System (IOOS®) recently announced that data collected from electronic tags attached to marine animals will be incorporated into (IOOS), a federal, regional and private-sector partnership working to enhance our ability to collect, deliver and use ocean information. Inclusion of the marine animal date should provide scientists with an opportunity to understand how these animals move with the flow of tides and currents and ultimately, how those patterns may be affected by climate change. [NOAA News]
• Measures to increase groundfish and scallop fishing proposed -- Officials with NOAA's Fisheries Service recently invited public comment on proposed new measures designated for the 2011 groundfishing season that would provide anglers greater opportunity to fish in Northeast waters, assist small vessel owners, and continue important stock rebuilding. Those fishing for scallops would also benefit for the new rule that is based on recommendations by the New England Fishery Management Council. [NOAA News]
• Tsunami warning lead time shortened by new system -- Seismologists at the Georgia Institute of Technology have developed a new system known as RTerg that could be used to warn populations of an impending tsunami only minutes after the initial earthquake, helping to provide residents in affected coastal areas increased time to relocate to safer ground. [Georgia Tech Research Institute]
• Great hammerhead shark migration is tracked -- Scientists from the Rosenstiel School of Marine & Atmospheric Science at the University of Miami and their colleagues recently reported on the migratory patterns and habitat use a great hammerhead shark based on results collected from their successful tracking of a shark using satellite tag technology. [University of Miami Rosenstiel School of Marine & Atmospheric Science]
• Rare sightings of seals along North Carolina coast -- During the last several weeks, at least three sightings of harp seals were made along the Atlantic beaches of North Carolina, which is unusual as the southern range of harp seals generally is along the coast of southeastern Canada. [jdnews] [Editor's note: Special thanks go to Terri Kirby Hathaway, AMS Oceans LIT Leader and Marine Education Specialist with North Carolina Sea Grant, for forwarding this article. EJH]
• Bath toys make landfall after 15-year journey --Some plastic bath toys have recently washed ashore along the British Isles after taking a 15-year circuitous 17,000 mile route around the global oceans after falling off a container ship in the North Pacific back in January 1992. [Daily Mail Online] [Editor's note: Special thanks are extended to Dr. Toni Lynne DeVore, AMS LIT Leader and faculty member of Ohio Valley University, Vienna, WV. EJH]
• Wintertime air chemistry studied -- Scientists from NOAA's Earth System Research Laboratory, the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado at Boulder and the University of Washington have been gathering a variety of atmospheric data along Colorado's Front Range as part of a month-long study of the chemistry of the wintertime atmosphere. They are studying the formation of nitryl chloride, a compound often association with marine atmospheres, that also forms during the wintertime nights in continental locales. The presence of nitryl chloride has important implications in air quality and climate change considerations. [NOAA News]
• 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)].

• 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 Guide Calendar)
• 13-15 March 1952...The world's 5-day rainfall record was set when a tropical cyclone produced 151.73 inches rain at Cilos, Reunion Island in the Indian Ocean. The 73.62 inches that fell in a 24-hour period (15^th-16^th) set the world's 24-hour rainfall record. (Accord's Weather Calendar)

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Prepared by AMS DS Ocean Central Staff and Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2011, The American Meteorological Society.