Coherent deglacial changes in western Atlantic Ocean circulation

Area of Science:

• Paleoclimatology
• Oceanography
• Climate Science

Background:

• Abrupt climate changes are linked to Atlantic Meridional Overturning Circulation (AMOC) variations.
• Past AMOC shifts' timing and magnitude are not fully understood, limiting knowledge of climate variability mechanisms.

Purpose of the Study:

• To reconstruct western Atlantic circulation changes during the last deglaciation.
• To investigate the role of melting ice in driving AMOC slowdowns and associated climate transitions.

Main Methods:

• Utilized the 231Pa/230Th proxy to reveal circulation changes.
• Analyzed data covering the last deglaciation and millennial-scale climate transitions.

Main Results:

• Observed an early slowdown of western Atlantic circulation from 19 to 16.5 ka, coinciding with Eurasian ice melt.
• Identified a persistent weakened AMOC state from 16.5 to 15 ka, with significant Laurentide ice sheet rafting.
• Demonstrated a two-step AMOC slowdown driven by melting ice.

Conclusions:

• Melting ice played a key role in initiating a two-step AMOC slowdown during the last deglaciation.
• This process sustained iceberg calving and climate change during Heinrich Stadial 1.
• Provides a clearer picture of past circulation dynamics and climate variability.