Ocean circulation
AMOC collapse adds only a few ppm of CO2
Open access · cc by · source: Europe PMC
Forcing CESM2’s AMOC off with North Atlantic freshwater raises 2100 atmospheric CO2 by only 2.6–4.2 ppm under low and high emissions.
Study at a glance
- Design
- Computational / modelling — CESM2 SSP runs with and without North Atlantic freshwater hosing to collapse AMOC
- N
- Paired control/hosing simulations under SSP1-2.6 and SSP5-8.5 (2015–2100)
- Population
- CESM2 global carbon cycle under AMOC collapse scenarios
- Outcome
- Small atmospheric CO2 increase (2.6–4.2 ppm by 2100) after strong AMOC weakening
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
Hosing weakens the AMOC from 17 Sv to 6 Sv by 2045. Extra atmospheric CO2 in 2100 is 2.6 ppm (SSP1-2.6) and 4.2 ppm (SSP5-8.5). Feedbacks are 0.44 and 1.3 ppm Sv−1. Low-emission extra CO2 comes from land and ocean; high-emission extra CO2 is ocean-only. Compensating regional carbon changes keep the global signal small.
Methodology
Authors ran CESM2 from 2015–2100 under SSP1-2.6 and SSP5-8.5, with control and hosing cases that added 0.5 Sv of freshwater at 50–70°N to collapse the AMOC, then diagnosed ocean and land carbon responses.
Limitations
Hosing is an imposed freshwater flux, not a freely tipping AMOC. There is no dynamic vegetation, and the small multi-decadal CO2 response may differ on millennial timescales or in other ESMs.
How this study connects
Role on claims
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Evidence for the claim as stated.
Forcing CESM2’s AMOC off with North Atlantic freshwater raises 2100 atmospheric CO2 by only 2.6–4.2 ppm under low and high emissions.
Evidence for the claim as stated.
A CESM freshwater hosing or an Arctic gyre study is not a measured AMOC collapse.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
A CESM freshwater hosing or an Arctic gyre study is not a measured AMOC collapse.
Related papers in this topic
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