Rodinia was a Mesoproterozoic to Neoproterozoic supercontinent that assembled around 1.3–0.9 billion years ago (Ga) and broke up between roughly 750–633 million years ago (Ma). It is the best-known Precambrian supercontinent and played a major role in the extreme climate and evolutionary events of the Late Proterozoic.

Rodinia formed through worldwide orogenic (mountain-building) events, notably the Grenville Orogeny (~1.3–1.0 Ga), by accreting fragments of the older supercontinent Columbia (Nuna). Most reconstructions place Laurentia (ancestral North America + Greenland) at its center, with other cratons arranged around it.

Rodinia was largely positioned in low to tropical latitudes (equatorial belt), unlike later supercontinents. It was surrounded by the superocean Mirovia. Reconstructions rely on paleomagnetism (for latitude), matching orogenic belts, and geological correlations, as longitude is harder to constrain.

The breakup increased continental margins, seafloor spreading, and exposure of fresh rock, boosting chemical weathering.

Role in Snowball Earth

Rodinia’s tropical position was critical for the Cryogenian “Snowball Earth” glaciations (~720–635 Ma):

• Enhanced silicate weathering: Warm, wet tropics accelerated CO₂-consuming reactions on silicate rocks, drawing down atmospheric greenhouse gases.
• Bare rock albedo: No land vegetation existed, so continents had high reflectivity (~0.35 for granite), reflecting strong tropical sunlight and amplifying cooling.
• Breakup further increased weathering rates by creating more exposed surface area and a more active hydrological cycle.

These factors, combined with a fainter Sun (~94–95% modern luminosity) and ice-albedo feedback, helped push Earth into extreme glaciations. Models show that a Rodinia-like configuration with bare continents makes Snowball states achievable at much higher CO₂ levels than today.

Rodinia exemplifies how supercontinent cycles drive long-term climate, carbon cycle, and biological evolution. Its story ties directly into the ice-albedo feedback, temperature-dependent radiative processes, and isotope records we’ve discussed.

The Neoproterozoic carbon cycle (roughly 1,000–541 Ma) was highly dynamic and anomalous compared to the Phanerozoic. It featured extreme carbon isotope excursions, prolonged low-latitude glaciations (Snowball Earth events), and major shifts in oxygenation, all linked to Rodinia’s assembly/breakup, enhanced weathering, and evolving biological and tectonic influences.

During glaciations, weathering nearly shut down under ice, flipping the cycle toward CO₂ accumulation.

The carbon cycle was tightly coupled to oxygen. Increased organic burial helped rise atmospheric O₂, stressing anaerobic life but enabling complex multicellular organisms (Ediacaran biota). Anoxic or ferruginous oceans during glaciations led to banded iron formations. Post-glacial oxygenation pulses followed.

Overall, the Neoproterozoic carbon cycle acted as a volatile “thermostat” pushed to extremes by unique tectonic (Rodinia) and solar conditions. It created environmental stresses that likely accelerated the evolution of complex life leading into the Cambrian.

Snowball Earth refers to extreme global glaciations (primarily in the Cryogenian period, ~720–635 million years ago) where ice sheets reached the equator, covering much or nearly all of the planet’s surface. Evidence includes glacial deposits in tropical paleolatitudes, “cap carbonates,” and other geological markers. These events ended with massive CO₂ buildup from volcanoes, creating a greenhouse effect strong enough to melt the ice.

A recent study highlights how a bare supercontinent like Rodinia, positioned mostly in the tropics around 700–600 million years ago, could have helped trigger or amplify “Snowball Earth” glaciations during the Neoproterozoic era.

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Temperature-dependent feedbacks drive the pattern of Antarctic temperature change

A recent study (Markle & Steig, PNAS, May 2026) identifies a fundamental, persistent pattern in Antarctic temperature changes driven by temperature-dependent feedbacks, primarily a nonlinearity in the greenhouse effect at very cold temperatures.

This paper identifies a robust, predictable spatial pattern in Antarctic temperature variability across timescales (millennial to orbital, ~400,000 years) using refined ice-core water-isotope reconstructions: warmer baseline sites (typically coastal/lower-elevation, e.g., ~−20°C to −30°C) exhibit larger temperature changes (ΔT) than colder interior/high-elevation sites (e.g., −50°C to −60°C) for the same large-scale forcing.

This holds for both warming (e.g., deglaciation) and cooling phases and across different drivers (orbital, CO₂, ocean heat transport, etc.). It explains most inter-site differences in records like WAIS Divide (stronger response) vs. Dome C or Vostok (weaker).

Simple Planck Response

The Planck response (blackbody radiative cooling) predicts the opposite: colder surfaces should show larger ΔT for a given energy imbalance because outgoing longwave radiation (OLR) follows σT⁴. Differentiating gives dT/dF ≈ 1/(4σT³), so sensitivity rises sharply at low T.

In Antarctica’s temperature range, this alone would imply coldest sites amplify changes most. Observations show the reverse for large-scale events, ruling out uniform response or pure Planck as the dominant pattern.

The Dominant Mechanism: Nonlinear Greenhouse Effect as a Temperature-Dependent Feedback

The key is the greenhouse effect (GHE = surface upward LW − TOA OLR) becoming strongly nonlinear at Antarctic temperatures (below ~−20°C).

Water vapor dominance: Its saturation vapor pressure follows the Clausius-Clapeyron relation (~exponential with T). At very cold temps, the atmosphere holds extremely little water vapor → GHE approaches zero, and TOA OLR nears blackbody surface emission.

As T rises modestly, water vapor increases more effectively (especially from warmer baseline sites), strengthening the GHE (more downward LW to surface). This amplifies warming.

The slope d(GHE)/dT steepens with higher initial T in the Antarctic range → greater positive feedback (amplification) at warmer sites.

This integrates what are often separated as water vapor + lapse-rate feedbacks (plus some shortwave/cloud effects). It is diagnosed from reanalysis/satellite (e.g., AIRS, NCEP) and matches radiative-convective models and GCM output (e.g., CESM).

Feedback equation (simplified, following Roe 2009):
ΔT = [λ₀ ΔF] / [1 − c(T) λ₀]
where λ₀ is Planck sensitivity (~larger at cold T), and c(T) = d(GHE)/dT (increases with T in Antarctic range). The net effect reverses the Planck pattern.

This feedback is “fast” (atmospheric) and responds to any mean energetic forcing, explaining its persistence across timescales and mechanisms.

Evidence and Robustness

• Ice cores: Consistent pattern in 8+ deep cores after improved isotope-to-temperature conversion (accounting for source effects and distillation nonlinearities). pnas.org
• Modern observations/reanalysis: Matches spatial patterns.
• Models: Radiative and full GCMs reproduce the nonlinearity.
• Deviations: Residual differences from the expected pattern allow isolation of local effects, e.g., ice-sheet elevation changes. The paper revises WAIS Divide elevation history during deglaciation, aligning with geology and modeling.

Evidence and Robustness

• Ice cores: Consistent pattern in 8+ deep cores after improved isotope-to-temperature conversion (accounting for source effects and distillation nonlinearities).
• Modern observations/reanalysis: Matches spatial patterns.
• Models: Radiative and full GCMs reproduce the nonlinearity.
• Deviations: Residual differences from the expected pattern allow isolation of local effects, e.g., ice-sheet elevation changes. The paper revises WAIS Divide elevation history during deglaciation, aligning with geology and modeling.

This is a elegant process-based insight from paleodata that refines how we interpret Antarctic records and model polar climate. It highlights basic physics (water vapor thermodynamics + radiative transfer) creating predictable emergent patterns. The study is very recent (May 2026), so further model intercomparisons and proxy tests are likely.

Published: PNAS

DOI: DOI: 10.1017/s1473550426100329

Authors: Bradley R. Markle  and Eric J. Steig 

Abstract

Antarctica is an important component of the Earth’s climate system.

Here we investigate temperature change in Antarctica across a range of timescales, from millennial to orbital, over the last  y, using a compilation of ice-core water-isotope records.

We identify a persistent pattern of change in which the temperature variability of an Antarctic site increases with its mean surface temperature.

When the entire continent warms, the warmest parts of Antarctica warm more; when the entire continent cools, the warmest parts cool more.

This pattern is inconsistent with the Planck response, the simplest possible null hypothesis for Antarctic temperature change.

However, a temperature-dependent feedback explains the fundamental pattern of temperature change.

The feedback arises from a nonlinearity of the greenhouse effect, evident only at the cold surface temperatures of the Antarctic.

This feedback may be initiated by any mean energetic forcing and thus manifests across all timescales.

Local deviations from the expected pattern of temperature change indicate regional forcing such as changes in ice-sheet elevation.

We reconstruct the surface elevation of the main ice divide in West Antarctica over the last deglaciation, finding a history that is supported by geological and glaciological evidence and consistent with ice-sheet modeling.