Tracking Past Shifts of the Eastern Pacific ITCZ with Oxygen Isotopes and Magnesium Paleothermometry

Columbia University, New York NY

Investigators

Abstract

Abstract: Under this award the PIs will reconstruct the latitudinal migrations of the Intertropical Convergence Zone (ITCZ) in the Pacific Ocean. The location and latitudinal range of the ITCZ in this basin is inseparably tied to ENSO dynamics and to the strength of the equatorial upwelling, which affect global climate through various mechanisms such as ENSO teleconnections. Moreover, anomalous tropical rainfall patterns due to ITCZ shifts can impact the ocean's thermohaline circulation through control of surface salinity, and alter moisture and ecosystem balance over land triggering climate feedbacks via land-vegetation and biogeochemical processes (e.g. methane emissions and carbon storage). The proponents propose a study to investigate variability in this system in the orbital frequency band, encompassing the interval 0-250,000 years BP, which includes glacial stages 2, 6 and 8, and interglacial stages 1, 5 and 7. This is sufficiently long to discern glacial-interglacial (G-I) (100 ky) variability in addition to precession and obliquity forcing (19-23 ky, and 41 ky). The work will focus on four deep sea cores in a N-S transect across the equator (7N-2S) and will involve measurements of planktonic foraminiferal oxygen isotope (d18O) and Mg/Ca ratios as proxies of surface ocean hydrology and temperature respectively.