The Mid-Pleistocene Transition: a delayed response to an increasing positive feedback?

Area of Science:

• Paleoclimatology
• Climate Dynamics
• Earth System Science

Background:

• Glacial-interglacial cycles exhibit natural variations in Earth's climate.
• The Mid-Pleistocene Transition (MPT) signifies a major shift in dominant cycle periodicity from approximately 40,000 years to 100,000 years.

Purpose of the Study:

• To investigate the hypothesis that the MPT resulted from an increasing internal period of the climate system.
• To explore the role of positive feedbacks in mediating climate cycle periodicity.

Main Methods:

• Utilized a carbon cycle model incorporating feedbacks between calcifier populations and ocean alkalinity.
• Simulated atmospheric CO2 levels and their influence on climate system periodicity.

Main Results:

• Demonstrated that the internal period of the climate system is sensitive to the strength of positive feedbacks.
• Successfully simulated stepwise periodicity changes analogous to the MPT using the carbon cycle model.
• Observed that periodicity shifts can manifest millions of years after changes in feedback strength.

Conclusions:

• The MPT may have been triggered by changes in climate system feedbacks occurring long before the observed periodicity shift.
• Internal dynamics of the climate system, particularly feedback mechanisms, play a crucial role in long-term climate variability.