HR: 1340h
AN: PP43B-1282    [Abstracts]
TI: Global and Regional Controls on Alkenone Sea Surface Temperature and Productivity Records for the Pleistocene From the Arabian Sea
AU: * Alpert, A E
EM: alice_alpert@brown.edu
AF: Brown University Department of Geological Sciences, 324 Brook St, Providence, RI 02912, United States
AU: Cleaveland, L C
EM: laura_cleaveland@brown.edu
AF: Brown University Department of Geological Sciences, 324 Brook St, Providence, RI 02912, United States
AU: Herbert, T D
EM: timothy_herbert@brown.edu
AF: Brown University Department of Geological Sciences, 324 Brook St, Providence, RI 02912, United States
AB: The Arabian Sea is home to one of the modern ocean's largest upwelling zones and represents a region that is sensitive to the dynamics of the Asian monsoon system as well as glacial-interglacial climate changes. High sedimentation rates in this region enable highly resolved climate reconstructions, which provide the opportunity to evaluate the impacts of both local and global forcing of oceanographic conditions in the Arabian Sea. We present high-resolution (1.5 kyr) alkenone SST and alkenone abundance data for the last 1.8 Myr from Ocean Drilling Program Site 722 in the northwest Arabian Sea. Over the course of the Pleistocene, SST at this site ranges from 23.3°C to 27.8°C with a long term decrease of 0.7°C/Myr. Like the well-known benthic oxygen isotope record, the SST record contains a long-term increase in amplitude and a switch from 41 kyr cyclicity to 100 kyr cyclicity across the mid-Pleistocene transition. Because of the strong similarity between our Arabian Sea SST record, ice volume, carbon dioxide (where data are available), and an additional SST record from the Eastern Equatorial Pacific upwelling zone, we conclude that SST at Site 722 is strongly linked to global glacial-interglacial climate variability throughout the Pleistocene, with warmest water temperatures occurring during interglacial periods and vice versa. Our data indicate that Site 722 SST was decoupled from the monsoon system on orbital timescales and was likely driven by variations in subsurface mode water temperatures, ultimately linked to high latitude climate. Alkenone abundance, which we relate to productivity, is highly variable over the last 1.8 Myr, ranging over two orders of magnitude. Average productivity and productivity variability both decreased during the early Pleistocene and remained low through the mid-Pleistocene transition. During the late Pleistocene both average productivity and productivity variability increased. Throughout the Pleistocene, inferred productivity at Site 722 appears to be related to monsoon-driven upwelling based on the similarity between our alkenone abundance record and a grain size record from Site 722, which responds to variations in wind speed.
DE: 4934 Insolation forcing
DE: 4954 Sea surface temperature
DE: 4964 Upwelling (4279)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting