HR: 0800h
AN: PP41A-0631    [Abstracts]
TI: Southern Hemisphere Signature in Glacial-Deglacial Sequence of SST and Denitrification Along the Peru Margin
AU: * Herbert, T D
EM: Timothy_Herbert@brown.edu
AF: Dept. of Geological Sciences Brown University, Box 1846, Providence, RI 02912 United States
AU: Liu, Z
EM: Zhonghui_liu@brown.edu
AF: Dept. of Geological Sciences Brown University, Box 1846, Providence, RI 02912 United States
AU: Altabet, M A
EM: maltabet@umassd.edu
AF: School for Marine Science and Technology University of Massachusetts Dartmouth, 706 Rodney French Blvd, New Bedford, MA 02744-1221 United States
AU: Higginson, M
EM: matthew.higginson@forensicalliance.com
AF: School for Marine Science and Technology University of Massachusetts Dartmouth, 706 Rodney French Blvd, New Bedford, MA 02744-1221 United States
AU: Higgins, S
EM: sean@ldeo.columbia.edu
AF: Dept. Earth, Atmospheric and Planetary Sciences M.I.T., 77 Massachusetts Ave., Cambridge, MA 02139 United States
AB: We present results of a multi-proxy investigation of the sea surface temperature (SST), paleoproductivity, and dentrification history of the Peru margin over the last 55 ka. A high resolution(sedimentation rates 10-25 cm/kyr)composite record from the latest Holocene to about 19 ka was obtained by combining AMS ¹⁴C alkenone ages and δ ¹⁵N stratigraphy. An off-margin core offers lower deposition rates, but contains carbonate microfossils for oxygen isotope stratigraphy, and extends the records to early MIS 3. We find that denitrication largely dissapeared at the Last Glacial Maximum, and remained weak through the remainder of the Glacial sequence. SSTs were tightly coupled to δ ¹⁵N, even on a millenial scale, with colder temperatures corresponding to less enriched nitrogen isotope values and less intense denitrification. Both δ ¹⁵N and alkenone-derived SSTs led sea level changes by about 5 kyr at the last deglaciation, in a pattern reminiscent of high latitude southern hemisphere temperature changes. The high productivity of the present Peru margin lagged both these changes, indicating that the SST and denitrification "switches" were remotely forced, in all probability by changes in the temperature and nutrient properties of Antarctic mode waters. Within the Holocene, the coupling of SST and denitrification persisted, but less tightly than observed for the glacial-interglacial time scale
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0469 Nitrogen cycling
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005