AGU journal highlights -- April 22, 2008

Title: Successful prediction of the consecutive IOD in 2006 and 2007

Authors: Jing-Jia Luo, Swadhin Behera, and Hirofumi Sakuma: Frontier Research Center for Global Change, Japan Marine Science and Technology Center, Yokohama, Japan;

Yukio Masumoto and Toshio Yamagata: Frontier Research Center for Global Change, Japan Marine Science and Technology Center, Yokohama, Japan, also at Department of Earth and Planetary Science, University of Tokyo, Tokyo, Japan.

Source: Geophysical Research Letters (GRL) paper 10.1029/2007GL032793, 2008; http://dx.doi.org/10.1029/2007GL032793

5. Corals reveal oceans’ carbon reservoir age

Radiocarbon dating of corals requires correction for the carbon reservoir age of the ocean, a measure of the carbon-14 deficit in ocean surface waters relative to the atmosphere when the corals formed. From 1600 to 1900, the reservoir age is calculated to be about 400 years. In a study of fossil corals from Florida’s Biscayne National Park, Druffel et al. determine the reservoir age for two periods during the Holocene (about 4930 and 3040 years ago) and find it to be significantly lower, about 292 years. They measured thorium concentrations in the corals to obtain their calendar age, and then measured their carbon-14 content. The difference between the carbon-14 content of the atmosphere at the time (from calibration curves based on tree ring data) and that of the coral reveals the oceans’ carbon reservoir age. The authors suggest several mechanisms that could account for the lower reservoir age, including increased ocean stratification during the Holocene periods. The lower reservoir age has implications for radiocarbon dating other corals and shells in the North Atlantic.

Title: Low reservoir ages for the surface ocean from mid-Holocene Florida corals

Authors: Ellen R. M. Druffel, Sheila Griffin, and John R. Southon: Earth System Science Department, University of California-Irvine, Irvine, California, U.S.A.;

Laura F. Robinson: Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, U.S.A.;

Robert B. Halley: U.S. Geological Survey, St. Petersburg, Florida, U.S.A.;

Jess F. Adkins: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, U.S.A.

Source: Paleoceanography (PA) paper 10.1029/2007PA001527, 2008; http://www.agu.org/journals/pip/pa/2007PA001527-pip.pdf . This paper is “in press”.

6. Unusual tremor jiggles Mexican zone