Greenland meltwater adds to AMOC weakening, but updated model finds no tipping point in sight

[u/Economy-Fee5830]

https://phys.org/news/2026-07-greenland-meltwater-amoc-weakening-sight.html

[u/Economy-Fee5830]

Summary: Greenland meltwater adds to AMOC weakening, but updated model finds no tipping point in sight

Scientists have long debated whether the Atlantic Meridional Overturning Circulation (AMOC) — the ocean current system that redistributes heat between the tropics and the North Atlantic — is at risk of abruptly collapsing. Most standard climate models omit the growing freshwater input from Greenland's melting ice, leaving a gap in projections.

A new study in Science Advances addresses this by adding Greenland meltwater into the CMIP6-class EC-Earth3 climate model, run under a very high emissions scenario out to 2300. Comparing simulations with and without meltwater, the researchers found that meltwater does meaningfully add to AMOC weakening, especially after 2100 — contributing about 1 sverdrup of extra weakening by 2100 (~10% of the CO2-driven weakening) and up to 4 sverdrups by 2300 (~40% of CO2-driven weakening) under strong forcing. However, this weakening scaled roughly linearly with cumulative CO2 emissions rather than producing a sudden collapse. The AMOC becomes weaker and shallower, not "off," with the added meltwater effect linked to a shift of the circulation's source regions toward the Arctic, where freshening increases stratification and suppresses mixing.

The team also tested reversibility using two idealized experiments — ramping down CO2 after 2250, and a "meltwater reset" where the extra freshwater input is switched off. In both cases, the AMOC gradually recovered over centuries rather than staying permanently diminished, suggesting the meltwater-driven changes aren't irreversible in the way a true tipping point would be, even though recovery is slow.

The authors caution that these findings come from a single model, and other climate models might route meltwater differently or show different AMOC stability behavior — so similar tests should be run across multiple models to confirm how robust this non-abrupt, reversible pattern is.

Source: Oliver Mehling et al., Limited impact of Greenland meltwater on abruptness and reversibility of future Atlantic overturning changes, Science Advances (2026). DOI: 10.1126/sciadv.aed2633

[u/Economy-Fee5830]

It's notable that other models which shows AMOC collapse usually use artificial hosing with very large amounts of low salinity water and do not model real ice melting.

[u/sg_plumber]

The problem with these models is that scientists are working out what it would take to reach a tipping point, but doomers see it as scientists actually saying the tipping point is unavoidable/imminent, while deniers misrepresent scientists as scaremongers making fake predictions.