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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.
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When did the Mid-Pleistocene Transition occur in the cited records?
About 1 Myr ago, when the dominant glacial period lengthened from ~40 to ~100 kyr.
Source: The Mid-Pleistocene Transition: a delayed response to an increasing positive feedback? · DOI · quote verified
What is the unforced internal period without strong feedback?
About 14 kyr of decaying oscillations.
Source: The Mid-Pleistocene Transition: a delayed response to an increasing positive feedback? · DOI · quote verified
At what feedback strength does the free period reach 120 kyr?
About 0.12.
Source: The Mid-Pleistocene Transition: a delayed response to an increasing positive feedback? · DOI · quote verified
What orbital period do they impose on the calcifier growth rate?
40 kyr, representing obliquity.
Source: The Mid-Pleistocene Transition: a delayed response to an increasing positive feedback? · DOI · quote verified
How long can the modeled period lag a feedback jump?
Around 10 Myr in one case and ~1 Myr in another.
Source: The Mid-Pleistocene Transition: a delayed response to an increasing positive feedback? · DOI · quote verified
What does a delayed period shift imply for MPT causes?
The Earth-system change may have happened well before the observed period shift.
Source: The Mid-Pleistocene Transition: a delayed response to an increasing positive feedback? · DOI · quote verified
Should MPT explanations be limited to changes at ~1 Myr?
No; earlier changes may still be relevant because of delay.
Source: The Mid-Pleistocene Transition: a delayed response to an increasing positive feedback? · DOI · quote verified
How was the model integrated?
Julia 1.5.3 with a DifferentialEquations KenCarp58 solver.
Source: The Mid-Pleistocene Transition: a delayed response to an increasing positive feedback? · DOI · quote verified
Why use an instantaneous jump in feedback strength?
It is likely unrealistic, but it makes the transient after the change easy to see.
Source: The Mid-Pleistocene Transition: a delayed response to an increasing positive feedback? · DOI · quote verified
What stepwise durations do they target as an MPT feature?
Average cycle length stepping from 40 to 80 to 120 kyr.
Source: The Mid-Pleistocene Transition: a delayed response to an increasing positive feedback? · DOI · quote verified
What kind of cycles does the forced model sustain?
Sawtooth cycles whose periods are multiples of the forcing period.
Source: The Mid-Pleistocene Transition: a delayed response to an increasing positive feedback? · DOI · quote verified