Abstract
The compensation between the meridional heat transports in the atmosphere and ocean is studied through a coupled model's water-hosing experiments. It is found that the atmospheric heat transport (AHT) change compensates the oceanic heat transport (OHT) change very well in the extratropics, while the former over-compensates the latter in the tropics. Similar to previous studies, the fresh water input in the high latitude Atlantic weakens the Atlantic meridional overturning circulation and thus the northward Atlantic OHT significantly, leading to a warming (cooling) in sea surface temperature in the Southern (Northern) Hemisphere and in turn a southward shift of atmospheric convection. This results in an enhanced Hadley Cell (HC) and stronger northward AHT, compensating the reduced Atlantic OHT. Meanwhile, the wind-driven Subtropical Cell in the Indo-Pacific oceans is enhanced in response to the HC change, increasing the northward OHT in the Indo-Pacific, which partly offsets the reduced OHT in the Atlantic. The response in the Indo-Pacific is responsible for the overcompensation of the AHT to the global OHT. The Held's mechanism works very well in the tropical Indo-Pacific in our experiments. This is substantially different from previous studies.
Highlights
Assessing the meridional heat transport (MHT) and its oceanic and atmospheric partition is a classical question of climate research (Carissimo et al, 1985; Vallis and Farneti, 2009)
The decrease of the global oceanic heat transport (OHT) can be compensated by the increase of the atmospheric heat transport (AHT)
In response to the fresh water forcing in the high-latitude Atlantic, the Atlantic meridional overturning circulation (AMOC) and the OHT are weakened significantly
Summary
Assessing the meridional heat transport (MHT) and its oceanic and atmospheric partition is a classical question of climate research (Carissimo et al, 1985; Vallis and Farneti, 2009). There is a slight undercompensation in the tropics and strong undercompensation in the high latitudes (408N poleward) Those modelling studies have recognised its existence in the climate change, Bjerknes compensation is still not well-established because of the fundamental controversies on its applicability. Even if the data were available, the direct calculation of ocean and atmosphere heat transport from velocity and temperature fields would contain a big error, which might be even bigger than the absolute values of AHT and OHT (Wunsch, 2005) and may result in being unfeasible to validate the Bjerknes compensation in the real world. The ocean wind-driven circulation changes again in response to atmosphere change This causes the compensation and overcompensation in different latitudes. The mechanism of the AMOC impact on the wind-driven circulation is discussed
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