Extended Data Fig. 11: Analysis of potential shipping emissions impacts on the observed mixed layer temperature budget during the 2023 North Atlantic marine heatwave.
From: Drivers of the extreme North Atlantic marine heatwave during 2023
(a) MLT budget as per Fig. 5a of the main paper, included here for comparison, using ERA5 estimates for the surface heat flux terms. Note that the ERA5 reanalysis does not include the effects of interannual variability in shipping emissions. (b) Same as panel (a), but showing the MLT budget terms recalculated imposing an additional 1 W m−2 anomaly in the incoming solar radiation term QSW during 2023, to examine the potential impact of reduced shipping emissions on the observed MLT budget. The additional 1 W m−2 is applied over the whole North Atlantic in 2023. For reference, estimates of the impact of reduced shipping emissions typically vary between 0.1 — 0.3 W m−2, with highest estimates for the basin-averaged North Atlantic corresponding to an increase in QSW of 0.56 W m−2 during 2023 (ref. 31). In this way, panel (b) can be interpreted as an upper bound on the effects of shipping emission reductions in the MLT budget calculation. The methods and bar chart terms shown match the terms shown in Fig. 5a.
