Interaction of polar and tropical influences in the mid-latitudes of the Southern Hemisphere during the Mi-1 deglaciation

• Published in: Global and Planetary Change
• Main Authors: Fox, B. R. S., D'Andrea, W. J., Wilson, G. S., Lee, D. E., Wartho, J.-A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2017
• Subjects: Antarctic; Antarc*; ice core
• Online Access: https://oceanrep.geomar.de/id/eprint/38804/; https://oceanrep.geomar.de/id/eprint/38804/1/Fox.pdf; https://oceanrep.geomar.de/id/eprint/38804/2/Fox_Suppl.pdf; https://doi.org/10.1016/j.gloplacha.2017.06.008

Highlights • The Southern Hemisphere mid-latitudes are characterised by obliquity and semi-precession cycles during the Mi-1 deglaciation • The obliquity variability is attributed to polar influence and the semi-precessional variability to tropical influence • Semi-precession cycles do not appear until 23.01 Ma, corresponding to the onset of Antarctic deglaciation • The interaction between polar and tropical influence is related to the position and strength of the westerly wind belt Abstract It is well-known from geologic archives that Pleistocene and Holocene climate is characterised by cyclical variation on a wide range of timescales, and that these cycles of variation interact in complex ways. However, it is rarely possible to reconstruct sub-precessional (< 20 kyr) climate variations for periods predating the oldest ice-core records (c. 800 ka). Here we present an investigation of orbital to potentially sub-precessional cyclicity from an annually resolved lake sediment core dated to a 100-kyr period in the earliest Miocene (23.03–22.93 Ma) and spanning a period of major Antarctic deglaciation associated with the second half of the Mi-1 event. Principal component analysis (PCA) of sediment bulk density, magnetic susceptibility (MS), and CIELAB L* and b* with a resolution of ~10 years indicates two major environmental processes governing the physical properties records, which we interpret as changes in wind strength and changes in precipitation. Spectral analysis of the principal components indicates that both processes are strongly influenced by obliquity (41 kyr). We interpret this 41-kyr cycle in wind strength and precipitation as related to the changing position and strength of the Southern Hemisphere westerly winds. Precipitation is also influenced by an 11-kyr cycle. The 11-kyr periodicity is potentially related to orbital cyclicity, representing the equatorial semi-precessional maximum insolation cycle. This semi-precession cycle has been identified in a number of records from the Pleistocene and ...