GEOPHYSICAL MONOGRAPH SERIES, VOL. 173, PP. 53-74, 2007
The past and future ocean circulation from a contemporary perspective
Meridional overturning of the ocean, particularly the North Atlantic, is commonly invoked as the “trigger” and major cause
of global climate change in a series of stories based upon a very simplified view of the circulation (a “conveyor belt”).
Observational and computational progress in physical oceanography, however, over the last 30 years has rendered obsolete the
old idea that the fluid ocean is a slowly changing, passive, almost geological system. Instead, it is a dynamically active,
essentially turbulent fluid, in which large-scale tracer patterns arise from active turbulence and do not necessarily imply
domination of the physics and climate system by large-scale flow fields. To the contrary, oceanic kinetic energy is dominated
by the time- and space-varying components. The complexity of the resulting fluid pathways is an essential part of any zero-order
description of the system. Thus general circulation models are the essential tool for understanding past, present and future
climate states. Quantification of the likely major errors in using oversimplified models with inadequate turbulence closures
and undersampled data becomes the main issue. Determining the past and future circulations is not easy, but hiding the difficulties
is not a viable option.
Citation: Wunsch, C. (2007), The past and future ocean circulation from a contemporary perspective, in Ocean Circulation: Mechanisms and Impacts—Past and Future Changes of Meridional Overturning, Geophys. Monogr. Ser., vol. 173, edited by