HR: 08:00h
AN: PP41F-01    [Abstracts]
TI: Milankovitch Forcing of Antarctic Climate in the Ross Sea Sector during the Quaternary
AU: * Verosub, K L
EM: verosub@geology.ucdavis.edu
AF: University of California-Davis, UCD Geology Dept. One Shields Ave., Davis, CA 95616, United States
AU: Jovane, L
EM: jovane@geology.ucdavis.edu
AF: University of California-Davis, UCD Geology Dept. One Shields Ave., Davis, CA 95616, United States
AU: Acton, G
EM: acton@geology.ucdavis.edu
AF: University of California-Davis, UCD Geology Dept. One Shields Ave., Davis, CA 95616, United States
AU: Florindo, F
EM: florindo@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, Roma, 00143, Italy
AB: Antarctica is a primary driver of global climate, but to date, there has been no clear evidence that the climate of the Ross Sea exhibits Milankovitich cyclicity. We have been studying the paleomagnetic and environmental magnetic properties of Eltanin 27-21, an 16-meter long piston core collected in the Ross Sea near Cape Adare in 1968 by the USNS Eltanin as part of Operation Deep Freeze. The magnetic polarity of 682 discrete samples from the core was used to develop an age model extending from the top of the Brunhes Chron to the Reunion Subchron. When converted to the time scale, the downcore variations of several environmental magnetic parameters exhibit features consistent with 40-ky cyclicity prior to the mid-Pleistocene transition and 100-ky cyclicity afterward. In order to better understand the nature of these features, we determined whether the environmental magnetic parameters had high or low values at each magnetic polarity boundary and compared that result with the marine oxygen isotope stage associated with the boundary. In general, high magnetic concentrations and finer magnetic grain-sizes occurred in interglacials while low concentrations and coarser grain-sizes occurred in glacials. These conclusions are consistent with findings from environmental magnetic studies of older (pre-Quaternary) sediments from other cores from the Ross Sea, such as CIROS-1 and the Cape Roberts Project. In those cores, increases in magnetic concentration and decreases in magnetic grain-size were associated with warmer, more humid conditions. Our results demonstrate for the first time that during the Quaternary, the climate of the Ross Sea sector was subject to Milankovitch forcing. They also provide a distal record of environmental magnetic paleoclimate proxies in the Ross Sea that can be compared with the proximal records being obtained from the ANDRILL project.
DE: 1512 Environmental magnetism
DE: 1520 Magnetostratigraphy
DE: 4207 Arctic and Antarctic oceanography (9310, 9315)
DE: 4910 Astronomical forcing
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting