H33K-01
Water Cycle Dynamics in a Changing Environment: Advancing Hydrologic Science through Synthesis
As one ponders a changing environment -- climate, hydrology, land use, biogeochemical cycles, human dynamics -- there is an increasing need to understand the long term evolution of the linked component systems (e.g., climatic, hydrologic and ecological) through conceptual and quantitative models. The most challenging problem toward this goal is to understand and incorporate the rich dynamics of multiple linked systems with weak and strong coupling, and with many internal variables that exhibit multi-scale interactions. The richness of these interactions leads to fluctuations in one variable that in turn drive the dynamics of other related variables. The key question then becomes: Do these complexities lend an inherently stochastic character to the system, rendering deterministic prediction and modeling of limited value, or do they translate into constrained self- organization through which emerges order, and a limited group of "active" processes (that may change from time to time) that determine the general evolution of the system through a series of structured states with a distinct signature? This is a grand challenge for predictability and therefore requires community effort. The interconnectivity and hence synthesis of knowledge across the fields should be natural for hydrologists since the global water cycle and its regional manifestations directly correspond to the information flows for mass and energy transformations across the media, and across the disciplines. Further, the rich history of numerical, conceptual and stochastic modeling in hydrology provides the training and breadth for addressing the multi- scale, complex system dynamics challenges posed by the evolution question. Theory and observational analyses that necessitate stepping back from the existing knowledge paradigms and looking at the integrated system are needed. In this talk we will present the outlines of a new NSF-funded community effort that attempts to forge inter- disciplinary synthesis through research efforts aimed at "improving predictability of water cycle dynamics in a changing environment." The synthesis activities have brought together inter-disciplinary scientific teams to address specific open problems such as: (i) human-nature interactions and adaptations; (ii) role of the biosphere in water cycle dynamics; (iii) human induced changes to water cycle dynamics; and (iv) structure of landscapes and their evolution through time. All synthesis activities will be underpinned by common unifying themes: (a) hydrology as the science of interacting processes; (b) variability as the driver of interactions and ecosystem functioning; (c) search for emergent behavior and organizing principles; and (d) complexity theory and non- equilibrium thermodynamics.
H33K-02 INVITED
Is the Arctic's Freshwater Cycle Changing?
Water evaporated in low and middle latitudes is transported poleward via the atmospheric circulation. Some condenses and falls to the surface at precipitation. Further evaporation returns some of this water back to the atmosphere, which may fall again as precipitation. However, as annual evaporation rates in high latitudes are in general modest, the end result is that most of the north polar region is characterized by positive net precipitation (precipitation minus evaporation, or P-E) in the annual mean. Ultimately, this freshwater excess must be returned to lower latitudes. In its broadest sense, the observed major features of the Arctic's mean annual freshwater budget reflect this large-scale balance requirement. Climate models tell us that as the climate warms in response in response to greenhouse gas loading, the hydrologic cycle should intensify, seen as a general increase in high latitude P-E and increased freshwater export to lower latitudes. Attendant changes in stocks should include more atmospheric water vapor and a fresher Arctic Ocean, with a shrinking proportion of this storage represented by sea ice. Observational evidence for these changes is incomplete and often conflicting, For example, while discharge from Siberian rivers to the Arctic Ocean has increased, this cannot be cleanly linked to changes in terrestrial precipitation, evaporation, or P-E. Oceanic freshwater transports are very difficult to assess. Although it seems clear that freshwater storage in the form of sea ice is declining, quantitative information is lacking. Change detection will always be hampered by deficiencies in available data sets and strong natural variability which characterizes the Arctic system. Finally, we must always remember that our best models are but simplifications of a climate system that often surprises us.
H33K-03 INVITED
Synthesizing Earth's geochemical data for hydrogeochemical analysis
For over 200 years, geochemical, microbiological, and chemical data have been collected to describe the evolution of the surface earth. Many of these measurements are data showing variations in time or in space. To forward predict hydrologic response to changing tectonic, climatic, or anthropogenic forcings requires synthesis of these data and utilization in hydrogeochemical models. Increasingly, scientists are attempting to synthesize such data in order to make predictions for new regions or for future time periods. However, to make such complex geochemical data accessible requires development of sophisticated cyberinfrastructures that both invite uploading as well as usage of data. Two such cyberinfrastructure (CI) initiatives are currently developing, one to invite and promote the use of environmental kinetics data (laboratory time course data) through ChemxSeer, and the other to invite and promote the use of spatially indexed geochemical data for the Earth's Critical Zone through CZEN.org. The vision of these CI initiatives is to provide cyber-enhanced portals that encourage domain scientists to upload their data before publication (in private cyberspace), and to make these data eventually publicly accessible (after an embargo period). If the CI can be made to provide services to the domain specialist – e.g. to provide data analysis services or data comparison services – we envision that scientists will upload data. In addition, the CI can promote the use and comparison of datasets across disciplines. For example, the CI can facilitate the use of spatially indexed geochemical data by scientists more accustomed to dealing with time-course data for hydrologic flow, and can provide user-friendly interfaces with CI established to facilitate the use of hydrologic data. Examples of the usage of synthesized data to predict soil development over the last 13ky and its effects on active hydrological flow boundaries in surficial systems will be discussed for i) a N-S loess climate transect; and ii) a shale catchment.
H33K-04 INVITED
Motivation of synthesis, with an example on groundwater quality sustainability
Synthesis of ideas and theories from disparate disciplines is necessary for addressing the major problems faced by society. Such integration happens neither via edict nor via lofty declarations of what is needed or what is best. It happens mainly through two mechanisms: limited scope collaborations (e.g., ~2-3 investigators) in which the researchers believe deeply in their need for each other's expertise and much larger scope collaborations driven by the ‘big idea.' Perhaps the strongest motivation for broad, effective synthesis is the 'big idea' that is sufficiently important and inspiring to marshal the appropriate collaborative efforts. Examples include the Manhattan Project, the quest for cancer cures, predicting effects of climate change, and groundwater quality sustainability. The latter is posed as an example of a ‘big idea' that would potentially unify research efforts in both the sciences and social sciences toward a common, pressing objective.
H33K-05
Exploring Water in our World – experimental hillslopes in the Biosphere 2 Facility
Over the next 10 years, The University of Arizona will explore the consequences of climate change and human pressures on water resources using the Biosphere 2 facility. By combing existing programs in ecology, hydrology and earth science, UA will construct an integrated, cross-disciplinary effort to mechanistically understand how water moves through soils, plants, and the atmosphere from the scale of individual molecules to that of whole- watersheds. UA will construct experimental landscapes within the Biosphere 2 facility, where the controlled environmental capabilities allow for the careful monitoring of the fate of water molecules as they move from rainfall, into soils, and either through plants or towards rivers. The ability to carry out experimentation at large spatial scales is unique and allows us to tackle two grand challenges in science – linking the biological and physical sciences, and predicting large-scale behavior from small scale understanding. Our new program tackles these issues head-on, using the unique attributes of Biosphere 2 and careful integration with historically strong research programs. The southwest is a unique "natural laboratory" for every discipline in ecology, hydrology and the earth sciences, which results in broad application of knowledge we generate with this new program.
H33K-06
What can Maximum Entropy Production Tell us About General Trends in Land Surface Hydrology and its Predictability?
The proposed principle of Maximum Entropy Production (MEP) states that complex systems organize into steady states that maximize rates of entropy production. Even though the role of thermodynamics in land surface hydrology is not widely recognized, it plays a key role in driving the hydrologic cycle to a state far from thermodynamic equilibrium, as indicated by unsaturated conditions in the atmosphere. In order to investigate the applicability of MEP to the hydrologic cycle, we provide first order estimates of entropy production associated with precipitation, soil wetting, soil moisture redistribution, evapotranspiration, and runoff. We find that the largest contribution comes from evapotranspiration. We then discuss the role that vegetation plays in this budget. It would seem that vegetation acts to enhance and possibly maximize entropy production associated with land surface water exchange. This would have important implications for the response of hydrological fluxes at the land surface to climate variability that could be tested with empirical observations.
H33K-07
Vegetation in a hydrologic setting: from theory to observation
Vegetation and the hydrological cycle are tightly coupled and it is important to understand the dynamics in order to make predictions of the influence of a changing climate. This is particularly true in an increasingly CO2–rich atmosphere where vegetation is expected to respond directly to changes in atmospheric [CO2], potentially altering hydrological regimes, even in the absence of changes in primary hydrological drivers like rainfall and potential evapotranspiration. How vegetation will respond is likely to differ between energy- and water-limited environments. By incorporating satellite-based measures of vegetation with hydro-meteorological observations across Australia, this talk will examine how vegetation has responded to climatic changes over the past 25 years. We will identify some emergent patterns and comment on the conceivable future eco-hydrological responses to climate change in water-limited environments.
H33K-08
Some challenges in eco-hydrology
The importance of the mutual interactions between biosphere in hydrosphere has become increasingly apparent in both the ecological and hydrological sciences. In hydrology, while the role of plants in controlling soil water balance has been recognized from some time, more subtle controls have also been realized, such as the impact of soil organic matter on soil water dynamics and soil properties, the plant control on infiltration, erosion, and geomorphology. Ecosystem dynamics and land-use changes have also been recognized to impact water availability and quality. On the other hand, biologists and ecologists have increased their attention towards the dynamics of the terrestrial water balance and its impact on plants (photosynthesis, plant growth and reproduction) as well as microbial life (and thus decomposition and the entire cycling of nutrients and carbon fluxes). In this eco-hydrological context, we discuss: (i) the need to distinguish complex from complicated eco- hydrologic behaviors, which are both expected to be present in systems with many degrees of freedom, spatial heterogeneity, nonlinearities and feedbacks (and with biological components). (ii) The use of ideas and tools from complex systems science and non-equilibrium statistical mechanics to explore possible emerging behaviors and patterns. (iii) The importance of intermittency and of the entire spectrum of eco-hydrologic fluctuations conferred by the system nonlinearities, and their connection to a possible theory of biologically- meaningful hydroclimatic extremes. (iv) The need for further research of basic questions yet unanswered (e.g., role of organic matter/roots on soil water balance and soil properties; vegetation control on infiltration; competition for water by plants; role of plant control on uptake (e.g., hydraulic lift)). (v) Ways to merge observations, minimalist models and complex numerical simulations as well as to increase communication of hydrologists with physicists, statisticians, mathematicians and biologists.