Indian Ocean planktic foraminiferal distribution and sea surface temperature estimates of the warm mid-Piacenzian with implications for the instability of monsoon-related upwelling and the Indian Ocean dipole

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Author(s): Robinson, M. M.; Dowsett, H. J.; Stoll, D. K.
Author Affiliation(s): Primary:
U. S. Geological Survey, Eastern Geology and Paleoclimate Science Center, Reston, VA, United States
Volume Title: AGU 2012 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2012; American Geophysical Union 2012 fall meeting, San Francisco, CA, Dec. 3-7, 2012. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The Indian Ocean is characterized by a uniquely complicated set of ocean-atmosphere interactions including the Indian Ocean Dipole (IOD), the El Niño/Southern Oscillation (ENSO) and the Asian monsoon. The combination of these interactions has historically led to climate extremes throughout the tropical Indian Ocean region, but the manner in which they have related to one another has changed over time. Understanding these relationships, as well as the evolution of the individual interactions, is key to determining the climate response in both past and future climates. The most recent climate interval similar to what is projected for the near future occurred ∼3.3 to 3.0 Ma, during the Piacenzian Age of the Pliocene Epoch. This warm Pliocene climate was characterized by global temperatures ∼2 to 3°C warmer than modern, but with most of the warmth concentrated toward the poles, and a possible mean El Niño-like state in the equatorial Pacific Ocean. Despite the wealth of sea surface temperature (SST) data available for the warm mid-Piacenzian, the Indian Ocean has remained a region of sparse geographic coverage. Here we present a detailed analysis of the microfossil assemblages found in mid-Piacenzian samples at Indian Ocean ODP Sites 709, 716, 722, 754, 757, 758 and 763, as well as SST estimates based on modern analogs. Key differences exist between the warm mid-Piacenzian and modern biogeographic distributions: the transitional (between subtropical and subpolar) biogeographic province assumed a more northerly position than it does today, while the subtropical province occupied the Bay of Bengal, which is a tropical province in the modern ocean. In addition, the percent of Globigerina bulloides in the Arabian Sea in an area of modern monsoonal upwelling is very low (∼4%), indicating a possible decrease in upwelling intensity during the mid-Piacenzian. Compared to modern, mid-Piacenzian SSTs were similar in boreal winter, but in boreal summer, mid-Piacenzian SSTs were cooler in the tropics with tropical temperatures extending further south. The IOD mode can be identified in the modern ocean by the difference in SST in boreal summer between the tropical western Indian Ocean (warmer) and the tropical southeastern Indian Ocean (cooler). In the modern ocean, the difference is 4.1°C, but during the mid-Piacenzian, the difference is 0.1°C, suggesting relatively fewer and/or weaker IOD events. This new Indian Ocean reconstruction describes the mean climate state resulting from the ocean-atmosphere interactions during the warm mid-Piacenzian with implications for the interaction among IOD, ENSO and the Asian monsoon.
Year of Publication: 2012
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Arabian Sea; Cenozoic; Exmouth Plateau; Indian Ocean; Leg 115; Leg 117; Leg 121; Leg 122; Neogene; Ninetyeast Ridge; ODP Site 709; ODP Site 716; ODP Site 722; ODP Site 757; ODP Site 758; ODP Site 763; Ocean Drilling Program; Piacenzian; Pliocene; Sea-surface temperature; Tertiary; Upper Pliocene
Coordinates: S203512 S203511 E1121232 E1121231
N163718 N163719 E0594746 E0594745
S035454 S035454 E0603306 E0603306
Record ID: 2015005657
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