Bipolar seesaw control on last interglacial sea level

Area of Science:

• Paleoclimatology
• Oceanography
• Glaciology

Background:

• Understanding ice-age terminations is crucial for predicting future climate change.
• Current models heavily rely on the last glacial-interglacial transition (Termination I), but its representativeness is uncertain.
• Detailed chronologies for previous terminations, like Termination II, are needed for robust comparisons.

Observation:

• Heinrich Stadial 11 (HS11), a North Atlantic cold episode, occurred between 135,000 and 130,000 years ago.
• HS11 coincided with a major deglacial meltwater pulse during Termination II.
• This meltwater pulse contributed significantly to the glacial-interglacial sea-level rise.

Findings:

• A new chronology reveals HS11 punctuated Termination II and was directly linked to rapid sea-level rise.
• The meltwater pulse primarily entered the North Atlantic, driving approximately 70% of sea-level rise during Termination II.
• Climate and ice-volume dynamics during Termination II differed fundamentally from Termination I, where major sea-level rise post-dates Heinrich Stadial 1.

Implications:

• The distinct behavior during Termination II suggests varying responses to insolation and CO2 forcing.
• HS11-associated Antarctic warming, potentially via bipolar seesaw, promoted Antarctic ice-sheet melting, contributing to the last interglacial sea-level highstand.
• These findings challenge the universality of Termination I as an analog for all ice-age terminations, necessitating revised climate models.