Browsing by Author "Bajo, Petra"
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- Persistent influence of obliquity on ice age terminations since the Middle Pleistocene transitionPublication . Bajo, Petra; Drysdale, Russell N.; Woodhead, Jon D.; Hellstrom, John C.; Hodell, David; Ferretti, Patrizia; Voelker, Antje; Zanchetta, Giovanni; Rodrigues, Teresa; Wolff, Eric; Tyler, Jonathan; Frisia, Silvia; Spötl, Christoph; Fallick, Anthony E.Radiometric dating of glacial terminations over the past 640,000 years suggests pacing by Earth’s climatic precession, with each glacial-interglacial period spanning four or five cycles of ~20,000 years. However, the lack of firm age estimates for older Pleistocene terminations confounds attempts to test the persistence of precession forcing. We combine an Italian speleothem record anchored by a uranium-lead chronology with North Atlantic ocean data to show that the first two deglaciations of the so-called 100,000-year world are separated by two obliquity cycles, with each termination starting at the same high phase of obliquity, but at opposing phases of precession. An assessment of 11 radiometrically dated terminations spanning the past million years suggests that obliquity exerted a persistent influence on not only their initiation but also their duration.
- The SISAL database: a global resource to document oxygen and carbon isotope records from speleothemsPublication . Atsawawaranunt, Kamolphat; Comas-Bru, Laia; Amirnezhad Mozhdehi, Sahar; Deininger, Michael; Harrison, Sandy P.; Baker, Andy; Boyd, Meighan; Kaushal, Nikita; Ahmad, Syed Masood; Ait Brahim, Yassine; Arienzo, Monica; Bajo, Petra; Braun, Kerstin; Burstyn, Yuval; Chawchai, Sakonvan; Duan, Wuhui; Hatvani, István Gábor; Hu, Jun; Kern, Zoltán; Labuhn, Inga; Lachniet, Matthew; Lechleiter, Franziska A.; Lorrey, Andrew; Pérez-Mejías, Carlos; Pickering, Robyn; Scroxton, Nick; Veiga-Pires, C.Stable isotope records from speleothems provide information on past climate changes, most particularly information that can be used to reconstruct past changes in precipitation and atmospheric circulation. These records are increasingly being used to provide “out-of-sample” evaluations of isotope-enabled climate models. SISAL (Speleothem Isotope Synthesis and Analysis) is an international working group of the Past Global Changes (PAGES) project. The working group aims to provide a comprehensive compilation of speleothem isotope records for climate reconstruction and model evaluation. The SISAL database contains data for individual speleothems, grouped by cave system. Stable isotopes of oxygen and carbon (δ18O, δ13C) measurements are referenced by distance from the top or youngest part of the speleothem. Additional tables provide information on dating, including information on the dates used to construct the original age model and sufficient information to assess the quality of each data set and to erect a standardized chronology across different speleothems. The metadata table provides location information, information about the full range of measurements carried out on each speleothem and information about the cave system that is relevant to the interpretation of the records, as well as citations for both publications and archived data.