MPT may lag a stronger ice-age feedback
A carbon-cycle oscillator locks ice-age periods to 40, 80, then 120 kyr as feedback grows, and the period jump can lag the parameter change by up to ~10 Myr.
Source
The Mid-Pleistocene Transition: a delayed response to an increasing positive feedback?
Study at a glance
- Design
- Computational / modelling — Calcifier-alkalinity carbon-cycle oscillator with growing weathering feedback under obliquity
- N
- Idealized dynamical-system experiments; not an observational sample N
- Population
- Modeled glacial–interglacial carbon-cycle oscillator under 40-kyr forcing
- Outcome
- Period locking to 40/80/120 kyr with delayed response after feedback strengthening
Structured fields used in claim comparison tables when every cited study has a complete layer.
What they did
Authors added a bounded positive weathering feedback to the calcifier-alkalinity model, forced it with 40-kyr obliquity, and jumped the feedback strength to watch how locked cycle length responded.
What they found
Unforced oscillations last 14 kyr until a Hopf bifurcation; stronger feedback stretches the free period toward 120 kyr near γ≈0.12. With forcing, duration locks at 40, 80, and 120 kyr, but after an abrupt feedback jump the period can take ~1–10 Myr to move to the next multiple.
The limits
What it doesn't show
The 2-equation alkalinity toy model is not a GCM; the instantaneous γ jump is admitted to be unrealistic; this paper does not fit new paleo time series, so the delay is a mechanism, not a dated MPT cause.
Key terms
- Mid-Pleistocene Transition (MPT)
- Shift ~1 Myr ago from ~40-kyr to ~100-kyr glacial cycles.
- Ramping with frequency locking (RFL)
- Internal period grows until cycles lock onto multiples of orbital forcing.
- Calcifier-alkalinity model
- Two-variable oscillator of ocean alkalinity and calcifiers that sets CO2.
- Positive weathering feedback (γ)
- Alkalinity input rises at high alkalinity (e.g. exposed shelves).
- Hopf bifurcation
- Birth of a stable limit cycle as feedback strength increases.
Flashcards
Research intelligence for this paper
See its role on concept claims, tensions it is part of, placement history, and related discoveries.
Quiz yourself
The MPT is described as a shift about 1 Myr ago from roughly:
Common questions
When did the MPT occur in the records they cite?
About 1 Myr ago, with dominant period lengthening from ~40 to ~100 kyr.
What forcing period do they use?
40 kyr, for obliquity, unless otherwise specified.
How long can the period delay last?
Around 10 Myr in one experiment and ~1 Myr in another.
Why look before the MPT for causes?
The period may lag the underlying Earth-system change.
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