Prof. John Marshall
Department of Earth, Atmospheric and Planetary Sciences, MIT

"Modulation of ITCZ migrations by the ocean's overturning cells"

Using observations and a hierarchy of models we discuss the role that the ocean's meridional overturning cells plays in modulating the position of the Inter-tropical Convergence Zone (ITCZ). We argue that the displacement of the ITCZ north of the equator is a consequence of the ocean's deep overturning cell in the Atlantic, the AMOC, which warms the NH troposphere relative to the SH. Since the ITCZ is found in the warm hemisphere, in the annual-mean it resides in the NH. We also discuss the role of the ocean's subtropical cells (STCs) in the Pacific which are strongly coupled to the trade winds. Heat transport by the STCs makes the position of the ITCZ over the ocean 'sticky' strongly damping meridional migrations.