TY - JOUR T1 - Fluctuations in export productivity over the last century from sediments of a southern Chilean fjord (44 degrees S) JF - Estuarine Coastal and Shelf Science Y1 - 2005 A1 - Sepulveda, J. A1 - Pantoja, S. A1 - Hughen, K. A1 - Lange, C. A1 - Gonzalez, F. A1 - Munoz, P. A1 - Rebolledo, L. A1 - Castro, R. A1 - Contreras, S. A1 - Avila, A. A1 - Rossel, P. A1 - Lorca, G. A1 - Salamanca, M. A1 - Silva, N. AB - Here we present the first reconstruction of changes in surface primary production during the last century from the Puyuhuapi fjord in southern Chile, using a variety of parameters (diatoms, biogenic silica, total organic carbon, chlorins, and proteins) as productivity proxies. Two sediment cores from the head and the center of the fjord were analyzed and compared to gain insights on past changes in productivity in these two different depositional environments. Higher sedimentation rates found at the head of the fjord result from the combination of a shallower water column and a restricted circulation by the occurrence of a sill. Additionally, sediment mixing depths estimated from (210)Pb data suggest that suboxic conditions may dominate the bottom water and the sediment-water interface in this location.Productivity of the Puyuhuapi fjord during the last century was characterized by a constant increase from the late 19th century to the early 1980s, then decreased until the late 1990s, and then rose again to present-day values. The influence of rainfall on productivity was most noticeable during periods of low rainfall, which coincided with decreased overall productivity within the Puyuhuapi fjord. Simultaneous variations in productivity and rainfall in the study area suggest that marine productivity could respond to atmospheric-oceanic interactions at a local scale. At a regional scale, marine productivity of the area may be related to other large-scale processes such as the El Nino Southern Oscillation. (c) 2005 Elsevier Ltd. All rights reserved. VL - 65 IS - 3 N1 - 975sfTimes Cited:22Cited References Count:53 JO - Fluctuations in export productivity over the last century from sediments of a southern Chilean fjord (44 degrees S) ER - TY - JOUR T1 - 14C activity and global carbon cycle changes over the past 50,000 years JF - Science Y1 - 2004 A1 - Hughen, K. A1 - Lehman, S. A1 - Southon, J. A1 - Overpeck, J. A1 - Marchal, O. A1 - Herring, C. A1 - Turnbull, J. AB - A series of 14C measurements in Ocean Drilling Program cores from the tropical Cariaco Basin, which have been correlated to the annual-layer counted chronology for the Greenland Ice Sheet Project 2 (GISP2) ice core, provides a high-resolution calibration of the radiocarbon time scale back to 50,000 years before the present. Independent radiometric dating of events correlated to GISP2 suggests that the calibration is accurate. Reconstructed 14C activities varied substantially during the last glacial period, including sharp peaks synchronous with the Laschamp and Mono Lake geomagnetic field intensity minimal and cosmogenic nuclide peaks in ice cores and marine sediments. Simulations with a geochemical box model suggest that much of the variability can be explained by geomagnetically modulated changes in 14C production rate together with plausible changes in deep-ocean ventilation and the global carbon cycle during glaciation. VL - 303 IS - 5655 N1 - Hughen, KLehman, SSouthon, JOverpeck, JMarchal, OHerring, CTurnbull, Jeng2004/01/13 05:00Science. 2004 Jan 9;303(5655):202-7. JO - 14C activity and global carbon cycle changes over the past 50,000 years ER - TY - CHAP T1 - Radiocarbon analysis, calibration and applications T2 - Current methods in geochronology: Temporal resolution in geology, palaeontology, archaeoloty, and anthropology Y1 - 2002 A1 - Kromer, B. A1 - Hughen, K. ED - Copeland, P. JF - Current methods in geochronology: Temporal resolution in geology, palaeontology, archaeoloty, and anthropology PB - Kluwer Academic Press N1 - id: 326 ER -