North Atlantic response to a quasi-realistic Greenland meltwater forcing in eddy-rich EC-Earth3P-VHR hosing simulations

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Abstract. The vast majority of studies examining the impact of freshwater from ice sheet melting on the Atlantic Meridional Overturning Circulation (AMOC) use climate models that cannot resolve mesoscale ocean processes and do not include an accurate spatio-temporal distribution of the freshwater forcing. These two factors critically affect the nature of the AMOC response. Our study fills that gap with a set of three hosing experiments performed with the global configurations of the eddy-rich climate model EC-Earth3P-VHR. The model is forced for 21 years with a spatial and monthly distribution of Greenland meltwater fluxes derived from observations, equal to 0.04 Sv on an annual average. Within the first year, we observe a response of reduced salinity in the Greenland and Labrador currents. This is accompanied by an acceleration and a cooling along the currents that lead to a rapid weakening of the AMOC at subpolar latitudes. Around year 7, deep mixing in the Labrador Sea begins to weaken due to as freshwater anomalies accumulate through lateral exchanges with the boundary currents. This shallowing of the mixed layer further weakens the AMOC, resulting in a stronger reduction that reaches also the subtropical latitudes. By the end of the simulation, the AMOC has weakened by almost 3 Sv at subppolar latitudes (i.e. a decrease of around 20 %), with an average relative decrease of 10 % for the whole Northern Hemisphere. The reduction in the AMOC is strong enough for some global climate impacts to emerge, such as the “bipolar seesaw” temperature response.

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