Climate models project that the Atlantic Meridional Overturning Circulation (AMOC) will weaken in the 21st century, but the magnitude is highly uncertain. Some of this uncertainty is structural, as most climate models neglect increasing meltwater from the Greenland ice sheet and do not explicitly capture mesoscale ocean eddies. Here, we quantify the impact of Greenland meltwater on the AMOC until 2100 under SSP5-8.5 forcing for the first time in a strongly eddying (1/10° horizontal resolution) ocean model. The meltwater-induced additional AMOC weakening is small (0.6 $\pm$ 0.2 Sv) compared to the weakening due to warming alone, and similar at high and low resolution. The same meltwater would cause a stronger AMOC weakening under present-day climate conditions. We link both resolution-independence and state-dependence to large-scale controls of the AMOC. Our results demonstrate that the background ocean state is more important than resolution in determining how Greenland meltwater affects the AMOC.
Human-caused global warming is expected to cause a weakening of the Atlantic Meridional Overturning Circulation (AMOC) and increased melt of the Greenland ice sheet.
However, most current climate models do not represent the interaction between these two systems. The question of how strongly Greenland melt will impact the AMOC in the 21 st century has already been studied in climate models with an ocean resolution of around 100 km. However, this is too coarse to explicitly capture mesoscale eddies, which could influence how meltwater propagates in the North Atlantic and how it affects the AMOC. Here, we quantify the impacts of Greenland meltwater on the AMOC until 2100 in a high-resolution (around 10 km horizontal resolution) eddy-rich ocean model. We find that the AMOC response to Greenland meltwater under global warming is similar at high and low resolution, and -consistently with previous studies -that it is small compared to the AMOC weakening driven by global warming alone. The same amount of meltwater also weakens the AMOC less strongly under global warming than under present-day climate conditions. This shows that the background ocean state is more important than resolution in determining how Greenland melt affects the AMOC.
The Atlantic Meridional Overturning Circulation (AMOC) is expected to play an important role in shaping the climate response to future anthropogenic greenhouse gas emissions (Liu et al., 2020;Bellomo et al., 2021;Bellomo & Mehling, 2024). While there is high confidence in climate model projections that the AMOC will weaken in the 21 st century (Weijer et al., 2020), the magnitude of this weakening is highly uncertain (Fox-Kemper et al., 2021). This is not only due to large inter-model spread in the simulated AMOC decline (Gregory et al., 2005;Reintges et al., 2017;Weijer et al., 2020;Bonan et al., 2025), but also due to the potential of nonlinear AMOC changes such as an abrupt AMOC collapse or tipping, the probability of which remains poorly quantified in climate models (Dijkstra & van Westen, 2026;Loriani et al., 2025).
Based on evidence from current-generation climate models, the IPCC Sixth Assessment Report assessed with “medium confidence” that the AMOC “will not experience an abrupt collapse before 2100” (Fox-Kemper et al., 2021). The main reasons for assigning only “medium confidence” to this finding were structural deficits such as model biases related to AMOC stability (Liu et al., 2017;Mecking et al., 2017;van Westen & Dijkstra, 2024) and neglected meltwater influx from the Greenland Ice Sheet (GrIS).
The impact of realistic Greenland meltwater input on 21 st -century AMOC changes has been extensively studied in IPCC-class climate models with a typical ocean resolution of around 1°(e.g., Lenaerts et al., 2015;Bakker et al., 2016;Ackermann et al., 2020;Mehling et al., 2025). These models show a moderate response of less than or around 1 Sv (1 Sv = 10 6 m 3 s -1 ) meltwater-induced additional AMOC weakening until 2100 but do not explicitly capture mesoscale ocean eddies. It has been shown that, under historical climate conditions, resolving mesoscale eddies can have a potentially important effect on how Greenland meltwater affects the large-scale ocean circulation (Weijer et al., 2012;Böning et al., 2016;Swingedouw et al., 2022;Martin & Biastoch, 2023;Martin-Martinez et al., 2025). While 21 st -century climate projections have recently been carried out at eddy-rich (1/10°or higher) resolution (Chang et al., 2020;Jüling et al., 2021), the effect of Greenland meltwater on the AMOC under 21 st -century climate change has so far not been separately assessed with an explicit representation of mesoscale eddies.
To our knowledge, the only attempt in this direction has been by Li et al. (2023); how-ever, their simulations ended in 2050, focused on the Antarctic Bottom Water response to meltwater, and did not capture any CO 2 -induced AMOC weakening.
In this study, we use a global ocean model at 1/10°resolution to quantify the 21 stcentury AMOC response to Greenland meltwater under a strong global warming scenario.
A high-end but physically plausible estimate of Greenland ice sheet runoff is derived from a fully coupled climate-ice sheet model simulation (Muntjewerf et al., 2020). Comparison with the low-resolution version of the same model and a set of previous, more idealized Greenland meltwater simulations under present-day conditions (Weijer et al., 2012) allow disentangling the impacts of resolution and background climate state on the AMOC response to 21 st -century Greenland melt.
Simulations are performed with version 2α of the Parallel Ocean Program (POP; Dukowicz & Smith, 1994). The high-resolution global configuration of POP (Maltrud et al., 2010;Weijer et al., 2012) (HR-POP hereafter) has a resolution of 1/10°using a tripolar grid in the horizontal and 42 levels in the vertical, with a top-layer thickness of 10 m. This configuration has been extensively used in pr
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