title: Regime shifts under forcing of non-stationary attractors: Conceptual model and case studies in hydrologic systems.
abstract: We present here a conceptual model and analysis of complex systems using hypothetical cases of regime shifts resulting from temporal non-stationarity in attractor strengths, and then present selected published cases to illustrate such regime shifts in hydrologic systems (shallow aquatic ecosystems; water table shifts; soil salinization). Complex systems are dynamic and can exist in two or more stable states (or regimes). Temporal variations in state variables occur in response to fluctuations in external forcing, which are modulated by interactions among internal processes. Combined effects of external forcing and non-stationary strengths of alternative attractors can lead to shifts from original to alternate regimes. In systems with bi-stable states, when the strengths of two competing attractors are constant in time, or are non-stationary but change in a linear fashion, regime shifts are found to be temporally stationary and only controlled by the characteristics of the external forcing. However, when attractor strengths change in time non-linearly or vary stochastically, regime shifts in complex systems are characterized by non-stationary probability density functions (pdfs). We briefly discuss implications and challenges to prediction and management of hydrologic complex systems.
authors.affiliation: School of Urban and Civil Engineering, Hongik University, Seoul, 121-784, South Korea; School of Civil Engineering, Purdue University, West Lafayette, IN 47907, USA. Electronic address: jeryang@hongik.ac.kr.
authors.forename: Jeryang
authors.initials: J
authors.lastname: Park
authors.affiliation: School of Civil Engineering, Purdue University, West Lafayette, IN 47907, USA; Agronomy Department, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: P Suresh C
authors.initials: PSC
authors.lastname: Rao
mesh_terms: D002980:Climate; D060587:Groundwater / Q000737:chemistry*; D062070:Hydrology; D008962:Models, Theoretical; D054712:Salinity; D012987:Soil; D014874:Water Pollutants, Chemical
chemical_list: D012987:Soil; D014874:Water Pollutants, Chemical
keywords: Complex systems; Multi-stability; Non-stationarity; Resilience; Tipping points