Millennial climate oscillations controlled the structure and evolution of Termination II

Area of Science:

• Paleoclimatology
• Climate Dynamics
• Quaternary Geology

Background:

• Understanding glacial terminations is crucial for predicting future climate change.
• The controls on the timing and structure of past terminations remain poorly understood.
• Previous studies lacked a synchronized timescale for correlating global climate events during terminations.

Purpose of the Study:

• To investigate the two stages of Termination II (T-II) using a precisely dated tufa deposit.
• To correlate major climate events across different Earth systems on a common timescale.
• To elucidate the mechanisms driving glacial terminations and deglaciation.

Main Methods:

• Chronological synchronization of Iberian tufa deposits with North Atlantic ocean sediments.
• Analysis of climate oscillations during T-II using speleothem records.
• Correlation of paleoclimate data to establish a unified timescale for major climate events.

Main Results:

• Termination II comprised two distinct stages.
• The first stage featured millennial climate oscillations linked to ice-sheet decay and Nordic sea interactions.
• The second stage, initiated by a glacial outburst, involved Thermohaline Circulation collapse, a Heinrich event, and the Bipolar Seesaw Mechanism (BSM), leading to irreversible deglaciation.

Conclusions:

• The pace of millennial oscillations in the first stage controlled the onset of the second stage of T-II.
• The Bipolar Seesaw Mechanism (BSM) played a critical role in completing Termination II and accelerating global deglaciation.
• Different climate interactions triggering the BSM suggest diverse modes of glacial terminations.