Thermohaline feedback loops and Natural Capital

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.