Camille Li: Geophysical Institute, University of Bergen, 5007 Bergen, Norway and Bjerknes Centre for Climate Research, 5007 Bergen, Norway;
David S. Battisti: Department of Atmospheric Sciences, University of Washington, Seattle WA 98195, USA and Bjerknes Centre for Climate Research, 5007 Bergen, Norway;
Catherine Kissel: Laboratoire des Sciences du Climat et de l'Envionnement, CEA/CNRS/UVSQ, 91198 Gif-sur-Yvette Cedex, France.
Measuring isotopes preserved in the shells of ancient single-celled foraminifera, tracking two sets of isotope ratioscarbon-13 to carbon-12, and oxygen-18 to oxygen-16is one of the main tools used by paleoceanographers to reconstruct the temperature of the ancient ocean and global carbon cycling. Foraminifera build their shells from the carbon and oxygen in the seawater, and the relative uptakes of these isotopes change with temperature. Unfortunately, foraminifera shells can undergo a process called "diagenetic recrystallization"the shells can dissolve away and recrystallize long after the creature is dead, resetting the original isotopic ratios. Diagenetic recrystallization is known to be a big problem for those working with foraminifera that live in the surface ocean, but researchers have long assumed that recrystallization is largely irrelevant if the foraminifera lived on the seafloor. Yet, little research has been done to confirm this assumption.
Using foraminifera samples that were drilled from the eastern Pacific ocean, Edgar et al. shore up the utility of deep water foraminiferal temperature reconstructions, finding that though diagenetic recrystallization can occur, it doesn't have a large effect on preserved isotope ratios there. Most recrystallization takes place within the first 10 million years after the shell was buried, they find, suggesting that deep sea foraminifera typically recrystallize under
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American Geophysical Union