Human interference now represents an inextricable component of all major ec
osystems. Whether this is through top-down overharvesting of ecosystem prod
uction or bottom-up alteration (deliberate or inadvertent) of the abiotic c
onditions, the planet's ecosphere is in a vicious degradation cycle. For ou
r economy to shift from exploiting to sustaining the natural systems, the s
olution, if there is to be one, will involve incorporation of the value of
natural capital into the economic and political feedback loop. For the scie
nce sector, this will involve developing methodologies to evaluate the nonl
inear and behavioral dynamics of entire systems in ways that can be coupled
with economic models. One essential characteristic of systems science invo
lves the interactions between internal components and external systems. The
rmohaline circulations and their feedback loops illustrate a class of such
interactive pathways. Examples from the Arctic, Mediterranean, and the US E
ast Coast along with some of their associated ecological impacts are review
ed. Understanding how thermohaline interactions provide stability to the ma
rine biotic environment and under what conditions this stability could be d
estabilized is a fundamental step toward evaluating the non-linear response
of marine systems to anthropogenic stress.