Glacial cycles are not random; they follow a predictable rhythm determined by the Earth's orbit. A study analyzing climate records from the past 800,000 years has found that specific arrangements of the Earth's wobble, tilt and orbital shape determined when ice ages began and ended. The forward dip primarily initiated glacial periods, while the backward dip locked in warm interglacial periods. Without human-driven climate change, the next ice age could begin in 11,000 years.
Ice ages on Earth didn't happen randomly -- they followed a clear, predictable pattern that was determined by the way our planet moves through space, according to a new study. The researchers identified the key roles of eccentricity, tilt and eccentricity, which influence the tilt, wobble of the Earth's axis and the shape of its orbit around the Sun. These factors, collectively known as "orbital forcing," determine the advance and retreat of glaciers, providing a framework for predicting past and future glacial cycles.
Scientists have known for years that changes in the Earth's orbit drive ice age cycles, but pinpointing the impact of each orbital factor has been difficult. One of the main problems is that the forward tilt period (about 21,000 years) and the obtuse second harmonic period (about 20,500 years) are strikingly similar, making it difficult to distinguish their respective effects. Another long-standing mystery - often referred to as the "100,000-year problem" - is why ice ages tend to end at intervals that match key eccentricity periods (the shape of the Earth's orbit).
To address these issues, Stephen Barker and colleagues took a novel approach. Rather than relying solely on age estimates from climate records, they analyzed the shape and sequence of glacial transitions over the past 800,000 years, a period characterized by glacial cycles of about 100,000 years. By studying three independent benthic oxygen isotope records, they determined that glacial transitions coincided with the relative timing of forward and backward movements. Their results suggest that precession plays the largest role in triggering glacier regression, while declination is more important in sustaining warm interglacial periods and triggering the next glacial period.
Research shows that glaciations typically end when proclination reaches a minimum and recedion increases - especially after eccentricity decreases. Based on these models, the researchers estimate that without human-caused greenhouse gas emissions, Earth would usher in another ice age in about 11,000 years as the planet's axial tilt continues to decline.
Compiled from /ScitechDaily