Evolving AMOC multidecadal variability under different CO2 forcings

The Influence of Increased CO2 Concentrations on AMOC Interdecadal Variability Under the LGM Background

“…In the case of the modern climate, global warming generates weakened AMOC interdecadal variability, manifested by the weaker amplitude of AMOC variability in RCP4.5 (red line in Figure 2a) compared with pre‐industrial conditions (blue line in Figure 2a), accompanied by a significant reduction in the primary period (Figure 2a). This response aligns with previous findings (Cheng et al., 2016; Ma et al., 2021). Conversely, under the LGM background climate, the amplitude of AMOC variability intensifies in response to the increased CO 2 concentration, manifested by the stronger amplitude of AMOC variability in LGM‐highCO 2 (red line in Figure 2b) compared with that in LGM‐lowCO 2 (blue line in Figure 2b), with a primary period only slight reduced (Figure 2b).…”

“…Where g, is the gravitational acceleration, 𝜌 0 is the reference ocean density, and 𝐴𝐴 𝑑𝑑𝑑𝑑 𝑑𝑑𝓏𝓏 denotes the differential of the potential density concerning the vertical coordinate 𝐴𝐴 𝓏𝓏 . The Brunt-Väisälä frequency can explain the features of ocean oscillation: A stronger ocean stratification and buoyancy frequency are associated with faster westward-propagating baroclinic Rossby waves across the Atlantic basin, reduced convective activity over the subpolar North Atlantic, and ultimately weakened AMOC interdecadal variability (Cheng et al, 2016;Ma et al, 2021;Sgubin et al, 2017).…”

“…Moreover, given that the AMOC interdecadal variability involves a variety of processes, these mechanisms include, but are not limited to, the exchange of freshwater between the North Atlantic and the Arctic Ocean (Delworth et al., 1997; Hawkins & Sutton, 2007; W. Liu & Fedorov, 2022; W. Liu et al., 2019), the westward propagation of large‐scale baroclinic Rossby waves (Buckley et al., 2012; Frankcombe et al., 2008), the westerly winds over the Southern Ocean (Delworth & Zeng, 2008), and the North Atlantic Oscillation (NAO) (Kim et al., 2023; Megann et al., 2021; Ruprich‐Robert & Cassou, 2015; Timmermann et al., 1998). The aforementioned future warming studies all emphasize the oceanic process in modulating the AMOC variability (Cheng et al., 2016; Ma et al., 2021). Whether it is applicable in different climate backgrounds still unknown.…”

“…Liu et al, 2019), the westward propagation of large-scale baroclinic Rossby waves (Buckley et al, 2012;Frankcombe et al, 2008), the westerly winds over the Southern Ocean (Delworth & Zeng, 2008), and the North Atlantic Oscillation (NAO) (Kim et al, 2023;Megann et al, 2021;Ruprich-Robert & Cassou, 2015;Timmermann et al, 1998). The aforementioned future warming studies all emphasize the oceanic process in modulating the AMOC variability (Cheng et al, 2016;Ma et al, 2021). Whether it is applicable in different climate backgrounds still unknown.…”

Presentation and Evaluation of the IPSL‐CM6A‐LR Ensemble of Extended Historical Simulations

“…We show that this variability is damped in the model along the historical periods, probably due to the effect of external forcing on this mode (e.g. Ma et al (2021)). If it had remained unchanged, this variability would have modulated the temperature changes over the historical period by about 0.4 K per century.…”