Indo-Pacific evidence for cooling subsurface water, stable Indo-Pacific warm pool temperatures, and cooling upwelling regions through the Plio-Pleistocene transition

Author(s): Dekens, P. S.; Ravelo, A. C.; Wara, M. W.
Author Affiliation(s): Primary:
University of California, Santa Cruz, Santa Cruz, CA, United States
Volume Title: AGU 2006 fall meeting
Source: Eos, Transactions, American Geophysical Union, 87( Fall Meeting Suppl.); American Geophysical Union 2006 fall meeting, San Francisco, CA, Dec. 11-15, 2006. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0096-3941 CODEN: EOSTAJ
Note: In English
Summary: Sea surface temperature (SST) reconstructions in the tropical Pacific indicate that the east to west SST difference was greatly reduced in the early Pliocene compared to today, resembling an El Nino-like pattern. How this pattern influenced, or was influenced by, conditions in the Indian Ocean is not well understood due to the scarcity of records in the Indian Ocean. In addition, little is known about the vertical structure of the water column; specifically, changes in the depth and/or temperature of the thermocline in the Pacific and Indian oceans during the Pliocene-Pleistocene climate transition. We generated Mg/Ca temperature records at ODP site 758 in the eastern Indian Ocean (within the Indo-Pacific warm pool) (5°23'N, 90°22'E, 2935m water depth) and ODP site 847 (0°12'N, 95°19'W, 3346m water depth) in the eastern equatorial Pacific cold tongue. At the Indian Ocean site, Mg/Ca of G. sacculifer (a surface dwelling species of foraminifera) indicates that SST remained relatively constant throughout the past 5 Ma; together with a published SST record at western equatorial Pacific ODP Site 806, our data suggest that the SST of Indo-Pacific warm pool did not change significantly even as global climate cooled through the Pliocene and Pleistocene. In contrast, SSTs did cool significantly in all Pacific upwelling regions as global climate cooled. Our new records of Mg/Ca of G. tumida (a foraminifer which lives at ≈100m water depth) shows that subsurface temperatures also cooled gradually by ≈2-4°C from the early Pliocene to the Pleistocene in both the Indian (ODP Site 758) and the Pacific (ODP Site 847) Oceans. This implies that cooling of upwelling regions may have been related to a globally shoaling thermocline. These observations will be considered in the context of processes that could have influenced tropical SST patterns and thermocline structure. These processes include tectonic changes that restricted flow through the central American and Indonesian seaways, and extratropical climate changes that influence the character of the ventilated thermocline.
Year of Publication: 2006
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Alkaline earth metals; Calcium; Cenozoic; Cooling; Depth; Eastern Indian Ocean; El Nino; Equatorial Pacific; Foraminifera; Globigerina; Globigerina sacculifer; Globigerina tumida; Globigerinacea; Globigerinidae; Indian Ocean; Indo-Pacific Warm Pool; Invertebrata; Leg 121; Leg 138; Magnesium; Metals; Microfossils; Neogene; ODP Site 758; ODP Site 847; Ocean Drilling Program; Pacific Ocean; Pleistocene; Pliocene; Protista; Quaternary; Rotaliina; Sea-surface temperature; Tertiary; Thermocline; Upwelling; Ventilation
Coordinates: N052300 N052300 E0902200 E0902200
N001200 N001200 W0951900 W0951900
Record ID: 2009095963
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