Abrupt pre-Bølling-Allerød warming and circulation changes in the deep ocean

Area of Science:

• Paleoceanography
• Climate Science
• Marine Geology

Background:

• The last deglaciation featured rapid climate shifts, including Northern Hemisphere warming and changes in ocean circulation, but their causes remain debated.
• The Bølling-Allerød warming and Atlantic meridional overturning circulation (AMOC) restart are key events, yet their triggers are not fully understood.

Observation:

• Fossil deep-sea corals from the western North Atlantic reveal a unique ocean thermal structure during Heinrich stadial 1.
• A reversed thermal stratification was observed, with deep waters being significantly warmer than surface waters, alongside increased salinity at depth.

Findings:

• The study identifies a warm, salty, and radiocarbon-depleted deep water mass originating from the Southern Ocean during Heinrich stadial 1.
• This deep ocean heat reservoir is proposed as the trigger for the subsequent Bølling-Allerød warming and AMOC re-initiation.

Implications:

• The findings highlight the critical role of deep ocean heat storage and release in driving abrupt climate changes during deglaciation.
• This research provides new insights into ocean-climate feedbacks and the complex mechanisms governing past climate transitions.