Early Pleistocene sea level and millennial-scale climate fluctuations: a view from the tropical Pacific and North Atlantic
Final Report Abstract
The principal objective of this project was to compile paleoclimate proxy records for the latest Pliocene to early Pleistocene interval based on benthic and planktic foraminifera in order to understand the climate evolution across the intensification of Northern Hemisphere glaciation (NHG) and how it relates to millennial-scale variability. Thereby, the main focus was on a highly resolved reconstruction of sea-level change during the latest Pliocene to early Pleistocene. Such a record is essential for assessing the potential role of an ice-volume effect on millennial-scale climate variability under a warmer climate than present. The proposed reconstruction of latest Pliocene to early Pleistocene sea level offered the opportunity to unravel the processes that drive the transition from a world without largeamplitude climate fluctuations to one dominated by high-amplitude fluctuations. To tackle the research questions, planktic and benthic foraminifera from ODP Site 849 (tropical Pacific) and Site 1313 (North Atlantic) have been processed and analyzed for stable isotopes and Mg/Ca for the time interval 2.8-2.4 Ma (i.e., marine isotope stages (MIS) G6-96). While the original project was designed to work on benthic foraminifera only, the planktic foraminifera at Site 849 proved to be exceptionally well preserved despite the large water depth of nearly 4000 m. Therefore, stable-isotopes and Mg/Ca of the surface-dwelling species Globigerinoides ruber and the thermocline-dwelling species Globorotalia crassaformis have been analyzed to produce a high-resolution surface and thermocline temperature record alongside the benthic records. Results of the benthic foraminiferal geochemistry from Site 1313 suggest that the East Antarctic ice sheet was highly unstable and responded dynamically to glacial-interglacial cycles even until the earliest Quaternary (~2.5 Ma). Date from Site 849 support the sea-level estimates derived from the North Atlantic but also show differences that will be the focus of future studies. Utilizing the well-preserved planktic foraminifera from Site 849 led to the generation of geochemical datasets that show (1) substantial changes in Plio-Pleistocene glacial-interglacial productivity related to changed in the tropical Pacific upwelling system, (2) glacial-interglacial changes in the tropical Pacific surface-water structure related to changing positions of the ITCZ, and (3) the development of a stable and deep eastern equatorial Pacific thermocline across the intensification of Northern hemisphere glaciation.
Publications
- (2016): Plio-Pleistocene glacial-interglacial productivity changes in the eastern equatorial Pacific upwelling system. Paleoceanography 31: 453-470
Jakob, K.A., Wilson, P.A., Bahr, A., Bolton, C., Pross, J., Fiebig, J. & Friedrich, O.
(See online at https://doi.org/10.1002/2015PA002899) - (2017). Glacial-interglacial changes in equatorial Pacific surface-water structure during the Plio-Pleistocene intensification of Northern Hemisphere Glaciation. Earth and Planetary Science Letters 463: 69-80
Jakob, K.A., Bolton, C.T., Wilson, P.A., Bahr, A., Pross, J., Fiebig, J., Kähler, K. & Friedrich, O.
(See online at https://doi.org/10.1016/j.epsl.2017.01.028)
