Patterns of Plio‐Pleistocene Ice Volume Variability Recorded by the Large‐Magnitude Explosive Eruptions From the Kamchatka‐Kurile Volcanic Arc.

Marine fallout ash beds can provide continuous, time‐precise records of highly explosive arc volcanism that can be linked with the climate record. An evaluation of revised Plio‐Pleistocene (0–4 Myr) tephrostratigraphies from Ocean Drilling Program Sites 881, 882, and 884 confirms cyclicity of the Kamchatka‐Kurile arc volcanism and a marked increase just after the intensification of the Northern Hemisphere glaciation at 2.73 Ma. The compositional constancy of the Kamchatka‐Kurile volcano‐magma systems through time points to external modulation of volcanic cyclicity and frequency. The stacked tephra record reveals periodic peaks in arc volcanicity at ∼0.3, ∼1.0, ∼1.6, ∼2.5, and ∼3.8 Myr that coincide with maxima of the global ice volume variability that have been linked with the amplitude modulation of the precession (0.3, 1.0 Myr) and obliquity (1.6, 2.5 and 3.8 Myr) bands. A simple model of a decreasing obliquity variance across the mid‐Pleistocene Transition at constant precession variance produces an excellent correlation of ash bed cycles with the variability of global benthic δ18O (r2 = 0.75), which implies that climate, and not direct orbital forcing, modulates Kamchatka‐Kurile arc volcanism. The rising influence of precession variance in the Kamchatka‐Kurile ash bed record after the mid‐Pleistocene Transition contrasts with the dominant 100 kyr signal in the benthic δ18O global ice volume variability, which may either reflect limitations of the ash bed record or an regional rather than global influence of ice volume variability. Our results indicate that climate influences the Kamchatka‐Kurile arc volcanism, which may influence climate only by feedback. Plain Language Summary: Volcanic ash and dust produced during catastrophic explosive volcanic eruptions, such as those of Mount Pinatubo or El Chichón, can cause short‐term global cooling on the scale of a few years. It has long been speculated whether the Earth's long‐term cooling over the past few million years has been augmented by an increase in explosive volcanism about 2.58 million years ago. In order to investigate causal links between the climate evolution and volcanism during the past 4 million years, we obtained a time‐precise and temporally highly resolved record of the Kamchatka‐Kurile arc volcanism from the centimeter‐thick ash beds that were embedded in marine sediments after large eruptions downwind the volcanic sources. When the ash bed record is compared to climate evolution, it clearly shows that explosive volcanic eruptions—regardless of their short‐term effects—do not contribute directly to the long‐term global cooling. Instead, the variations of the Earth's powerful climate system modulate these explosive volcanic eruptions, as the periodic waxing and waning of the large ice shields affect the magma‐producing systems deep in the Earth's interior. However, climate‐active gases and particles produced during periods with more vigorous arc volcanism may still enhance the ice cycles. Key Points: Marine fallout ash beds record cyclicity and acceleration of the Plio‐Pleistocene (0–4 Myr) explosive Kamchatka‐Kurile arc volcanismAsh bed cyclicity correlates with the obliquity and precession variance of the global ice volumeClimate, and not direct orbital forcing, modulates the Plio‐Pleistocene volcanicity of the Kamchatka‐Kurile arc [ABSTRACT FROM AUTHOR]