Abstract
Abstract. Deep marine successions of early Campanian age from DSDP (Deep Sea Drilling Project) site 516F drilled at low paleolatitudes in the South Atlantic reveal distinct sub-Milankovitch variability in addition to precession, obliquity and eccentricity-related variations. Elemental abundance ratios point to a similar climatic origin for these variations and exclude a quadripartite structure as an explanation for the inferred semi-precession cyclicity in the magnetic susceptibility (MS) signal as observed in the Mediterranean Neogene for precession-related cycles. However, semi-precession cycles as suggested by previous work are likely an artifact reflecting the first harmonic of the precession signal. The sub-Milankovitch variability, especially in MS, is best approximated by a ~7 kyr cycle as shown by spectral analysis and bandpass filtering. The presence of sub-Milankovitch cycles with a period similar to that of Heinrich events of the last glacial cycle is consistent with linking the latter to low-latitude climate change caused by a non-linear response to precession-induced variations in insolation between the tropics.
Highlights
The origin of sub-Milankovitch climate variability with periods between 5 and 15 kyr (e.g., Hagelberg et al, 1994) remains elusive and is far less understood than cycles directly related to orbital climate forcing
We examined the elemental data as ratio over Al to eliminate this effect and reveal changes relative to terrestrial input, represented by, for example, Al (Figs. 2 and A2 in the Appendix)
Based on results of the generated data and time series analysis, it can be concluded that a dominant 10–11 kyr semi-precession cycle does not solely describe the subMilankovitch variability observed in high-resolution magnetic susceptibility (MS), XRF and color records of DSDP Site 516F cores 113 and 114
Summary
The origin of sub-Milankovitch climate variability with periods between 5 and 15 kyr (e.g., Hagelberg et al, 1994) remains elusive and is far less understood than cycles directly related to orbital climate forcing. Heinrich events denote rapid and massive discharges of icebergs into the North Atlantic during the last glacial cycle, suggesting that ice sheets are either directly responsible for or amplify an initial climate signal They were first described by Heinrich (1988), who linked these to low-latitude climate to explain their recurrence time of ∼ 7–8 kyr. On the contrary, MacAyeal (1993) held internal ice-sheet oscillations responsible for their formation, while other autogenic models favor amplified jökulhlaupt events (Johnson and Lauritzen, 1995) or ice shelf instability (Hulbe, 1997; see Hemming, 2004) They were related to white-noise stochastic forcing with a magnitude similar to random changes in insolation of ≥ 0.5 Wm−2 by Hyde and Crowley (2002)
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