Abstract: As the complex interplay of forces in the ocean responds to climate change, the dynamics of global ocean circulation are shifting. Is the global ocean circulation driven primarily by the 'push' of dense waters to depth in the polar regions, or the 'pull' of mixing those waters upwards throughout the ocean basins? In the first of a new series of Concepts pieces, Martin Visbeck considers how the complex interplay of forces in the ocean is responding to climate change. 'Push' has been dominant it seems, but 'pull' could become more of a factor.