Subdecadally resolved paleoceanography of the Peru margin during the last two millennia

TitleSubdecadally resolved paleoceanography of the Peru margin during the last two millennia
Publication TypeJournal Article
Year of Publication2008
AuthorsAgnihotri, R, Altabet, MA, Herbert, TD, Tierney, JE
JournalGeochemistry Geophysics Geosystems

Using multiproxy sediment core data from the El Nino-Southern Oscillation (ENSO)-sensitive Peru margin, subdecadally resolved (down to similar to 0.6 year) surface productivity and subsurface denitrification are reconstructed for the last similar to 2300 years. Scanning XRF generated major elemental data (Ti, Fe, Si) correlate well with discrete inductively coupled plasma-atomic emission spectometry (ICP-AES) analyses and together with X-radiography (core density) are used as productivity indices. As surface productivity in this marine region is strongly impacted by ENSO, higher (lower) periods of surface productivity are inferred to represent a persistent normal/La Nina (El Nino)-like state. Surface productivity and subsurface denitrification appear to have remained intimately coupled during this period due to direct stimulation of requisite subsurface suboxia and/or hydrographic restructuring. The late Holocene Peru margin is characterized by persistent moderate productivity and subsurface denitrification punctuated at centennial scale by shorter-duration periods of high production and intense denitrification. These centennial-scale events are likely analogous to modern observations of decadal-scale "regime shifts'' but of higher amplitude and provide a background history for future natural changes to this system. Solar (irradiance) variability is suggested to have influenced Peru productivity as evidenced in numerous high-resolution paleorecords from the northern hemisphere.