HR: 11:50h
AN: PP52A-07    [Abstracts]
TI: Upwelling Cycles During the Last 40 Ka in the Mexican Tropical Pacific.
AU: * Machain-Castillo, M L
EM: machain@mar.icmyl.unam.mx
AF: Universidad Nacional Autonoma de Mexico, Instituto de Ciencias del Mar y Limnologia, Circuito Exterior, Ciudad Universitaria, D. F., Mexico City, 04510, Mexico
AU: Contreras-Rosales, L A
AF: Universidad Nacional Autonoma de Mexico, Instituto de Ciencias del Mar y Limnologia, Circuito Exterior, Ciudad Universitaria, D. F., Mexico City, 04510, Mexico
AU: Ganeshram, R S
AF: University of Edinburgh, Dept of Geology and Geophysics, University of Edinburgh, Scotland, U.K., Edinburg,
AU: Francavilla, S
AF: University of Edinburgh, Dept of Geology and Geophysics, University of Edinburgh, Scotland, U.K., Edinburg,
AB: Planktonic foraminiferal records of IMAGES core MD02 2520 collected on the MONA campaign in the Gulf of Tehuantepec, Mexico, exhibit variations in the dominant assemblages during the last 40ka. Q-mode factor analysis shows that during warm periods, planktonic foraminiferal populations are dominated by Globigerinita glutinata and Globigerina bulloides indicating upwelling conditions. During cold periods, assemblages are dominated by Globorotalia menardii and Neogloboquadrina dutertrei suggesting warm stratified oceans and absence of upwelling. Previous studies off the Mazatlan Pacific margin and other places in the ENTP indicate decrease in ä15N and accumulation of biogenic sedimentary components related to reduced upwelling. The correlation between the ä15N and planktonic foraminiferal assemblages in core MD02-2520 supports this hypothesis. Since upwelling in the Gulf of Tehuantepec is driven by wind, the succession of planktonic foraminiferal faunas during the last 40ka indicates changes in the ocean-atmosphere system. At present, strong northerly winds impact the gulf during winter-spring resulting in upwelling. It has been suggested that the presence and topography of the Laurentide Ice Sheet modified the wind patterns in the western northern hemisphere during the last glacial maximum, and caused the lack of upwelling in the Mexican Pacific margin. The data presented here, suggest a similar mechanism was present throughout the last 40ka.
DE: 0429 Climate dynamics (1620)
DE: 0469 Nitrogen cycling
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Joint Assembly