Miocene Climate Dynamics and Ice Sheet Evolution

The Miocene epoch (∼23 to 5 million years ago) witnessed a complex interplay between prolonged warmth, transient warming events and the gradual expansion of polar ice. Initial warmth peaked during the Miocene Climatic Optimum, driven by elevated carbon dioxide concentrations from volcanic and tectonic sources, with temperatures several degrees above pre-industrial values. Following this interval, a sustained cooling trend culminated in the Middle Miocene Climate Transition, marked by the rapid initiation and growth of the Antarctic ice sheet. Changes in ocean circulation patterns, notably the reorganisation of deep water formation and meridional overturning, modulated heat transport and ice-sheet sensitivity. Proxy records reveal episodes of Antarctic retreat under relatively modest warming and high-latitude amplification, highlighting threshold behaviour of continental ice. Simultaneously, variations in carbonate chemistry and ocean stratification influenced global carbon storage and feedbacks. Attempts to simulate Miocene warmth have exposed persistent model–data mismatches, particularly in equator-to-pole temperature gradients and ice-sheet dynamics. Understanding the combined roles of sustained CO₂ forcing, palaeogeography, orbital modulation and ocean–cryosphere coupling during the Miocene provides critical analogues for future climate trajectories under ongoing greenhouse gas rise.

Research from Nature Portfolio

Recent multiproxy analyses from the western equatorial Pacific and complementary basins demonstrate that deep water overturning shifted to greater depths during the Climatic Optimum in response to reduced density stratification and weakened latitudinal thermal gradients. This reorganisation appears closely tied to Antarctic ice cover variations and Southern Ocean wind stress, setting up a near-modern circulation by the onset of global cooling. Concurrent geochemical work has identified a marked osmium isotope excursion between 17 and 15.8 Ma, attributable to enhanced magmatic input that plausibly raised atmospheric CO₂ by tens of parts per million and triggered the optimal warming phase. Foundational work on Antarctic margins further documents episodes of ice-sheet retreat and readvance in Wilkes Land during mid-Miocene warmth, emphasising the coupling of ocean-driven melting and continental ice dynamics under elevated temperatures.

Miocene Climate Dynamics and Ice Sheet Evolution publication trend

The graph below shows the total number of articles in miocene climate dynamics and ice sheet evolution across all publications each year (not limited to Nature Index journals).

Technical terms

Miocene Climatic Optimum (MCO): Interval of peak warmth in the middle Miocene characterised by high CO₂ and reduced polar ice.

Middle Miocene Climate Transition (MMCT): Rapid global cooling and Antarctic ice-sheet expansion following the MCO.

Deep water overturning: Global circulation whereby dense surface waters sink and drive large-scale ocean currents.

Carbonate saturation state: Measure of seawater’s capacity to precipitate or dissolve calcium carbonate minerals, influencing marine carbon storage.

Boron isotope pH proxy: Geochemical method using δ11B in foraminifera to reconstruct past seawater pH and infer CO₂ levels.

References

1. Re-organization of Pacific overturning circulation across the Miocene Climate Optimum. Nature Communications (2024).
2. Enhanced magmatism played a dominant role in triggering the Miocene Climatic Optimum. Communications Earth & Environment (2023).
3. Constraining the evolution of Neogene ocean carbonate chemistry using the boron isotope pH proxy. Earth and Planetary Science Letters (2018).
4. The challenge of simulating the warmth of the mid-Miocene climatic optimum in CESM1. Climate of the Past (2014).
5. Southern Ocean warming and Wilkes Land ice sheet retreat during the mid-Miocene. Nature Communications (2018).
6. Simulating Miocene Warmth: Insights From an Opportunistic Multi‐Model Ensemble (MioMIP1). Paleoceanography and Paleoclimatology (2021).
7. Warm Middle Miocene Indian Ocean Bottom Water Temperatures: Comparison of Clumped Isotope and Mg/Ca‐Based Estimates. Paleoceanography and Paleoclimatology (2020).