AGU Journal Highlights -- March 19, 2008

Title: Solar-terrestrial coupling evidenced by periodic behavior in geomagnetic indexes and the infrared energy budget of the thermosphere

Authors: Martin G. Mlynczak, Christopher J. Mertens, and Ellis E. Remsberg: NASA Langley Research Center, Hampton, Virginia, U.S.A.;

F. Javier Martin-Torres: Analytical Services and Materials, Inc., Hampton, Virginia, U.S.A.;

B. Thomas Marshall, R. Earl Thompson, and Larry L. Gordley: G & A Technical Software, Newport News, Virginia, U.S.A.;

Janet U. Kozyra: University of Michigan, Ann Arbor, Michigan, U.S.A.;

James M. Russell III: Hampton University, Hampton, Virginia, U.S.A.;

Thomas Woods: Laboratory for Atmospheric and Space Physics, Boulder Colorado, U.S.A.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL032620, 2008; http://dx.doi.org/10.1029/2007GL032620

9. North Atlantic Current spins off eddies as it broadens

The warm Gulf Stream flows east offshore of the North American coastline on its way north from Florida to Newfoundland. Southeast of Newfoundland, where it meets the cold Labrador Current, it turns and flows north for roughly 1° of latitude. This branch of the Gulf Stream is called the North Atlantic Current (NAC). At 51°N, the NAC abruptly turns east from Newfoundland, broadens, and slows down. Noting that at this turning point the NAC sheds anticyclonic eddies every few months, Woityra and Rossby analyze 10 years of satellite data to measure the size and exact formation rate of these eddies. Using an energy budget approach, they find that eddy formation is a natural result of the slowing, broadening NAC. The authors hypothesize that as eddies form, severe heat loss due to their exposed position in the southern Labrador Sea causes the water within the eddies to sink. Once they are isolated from the surface, they may survive for years as indicated by their findings south and west in the Sargasso Sea.

Title: Current broadening as a mechanism for anticyclogenesis at the northwest corner of the North Atlantic Current

Authors: Willian Woityra: Graduate School of Oceanography, University of Rhode Island, Kingston, Rhode Island, U.S.A.; now at U.S. Coast Guard, International Ice Patrol, Groton, Connecticut, U.S.A.;

T. Rossby: Graduate School of Oceanography, University of Rhode Island, Kingston, Rhode Island, U.S.A.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL033063, 2008; http://dx.doi.org/10.1029/2007GL033063

10. Plate tectonics in the East African Rift

Although the East African Rift (EAR) is often cited as a modern archetype for rifting and continental breakup, it remains the least understood of all major plate boundaries. In particular, the rate of plate divergence across it, how this divergence is accommodated within the rift, and how the rift connects farther south with the Southwest Indian Ridge (SWIR) remain to be determined. Information needed to solve this problem is sparse, but Stamps et al. find that geological data covering the past 3.2 million years along the SWIR are consistent with current geodetic data in east Africa. They invert the two data sets jointly to obtain the first complete kinematic model for the EAR. They show that the data are consistent with the existence of three subplates embedded within the rift, as previously suggested from earthquakes but left unquantified, illustrating the initial process by which a continent breaks apart.