Plenary Lectures

Sunday Evening Public Lecture
5:30 pm, Scotiabank Convention Centre Theatre

“Niagara Falls – Behind the Scenes of the Natural Wonder”

Aaron Thompson
Canadian Co-Chair, International Niagara Board of Control

Niagara Falls has long been recognized for both its natural beauty and energy potential. This presentation will explore the history of hydropower development at Niagara and the historical and present-day governance that was created by Canada and the United States to balance the protection of the beauty of the falls while allowing for the most beneficial use of the water. The presentation will also describe the role of the International Joint Commission, the International Niagara Committee and the International Niagara Board of Control in monitoring the apportionment of the water of the Niagara River, ice management, falls recession, and other activities.

This public lecture is sponsored by:

Monday Morning Plenary
8:00 am, Room Peller C/D

“Earth’s Variable Rotation and its Influence on Decadal Fluctuations in Global Earthquake Productivity”

Roger Bilham1 and Rebecca Bendick2
1CIRES: Cooperative Institute for Research in Environmental Sciences
2University of Montana

Decadal fluctuations in global seismicity and earth’s rotation rate have approximately the same phase and period (25-35 and 60-70 years). We find, as have earlier investigators, that a probable causal relationship exists between deceleration and seismicity, but that changes in rotation rate result in inferred lithospheric displacements that are characteristically much smaller than those considered plausible to induce seismicity. Synchronization processes, however, can occur in the presence of vanishingly weak coupling and are consistent with the observed phase relationships between angular deceleration and seismicity. Whatever the mechanism, on four instances in the past century the mean annual rate of damaging earthquakes (Mw≥6.6) has increased by 25-30% during periods of slow rotation (+2 ms LOD), compared to intervening periods of fast rotation (-2 ms LOD). Moreover, since maxima in angular deceleration lead maxima in global seismicity by 5-7 years, changes in earth’s rotation can be used to anticipate future increased or decreased global seismic hazards. Based on a peak in angular deceleration in 2014 we envisage that seismicity rates will peak in 2020 followed by a decline, a forecast that can be updated annually.

Tuesday Morning Plenary
8:00 am, Room Peller C/D

“Soils and the Ecology of Tropical Forests”

Benjamin L. Turner
Smithsonian Tropical Research Institute

Tropical forests are among the most species-rich plant communities on earth, which challenges conventional approaches to understanding how soils shape their ecology. In this presentation I will explore the extent to which soils influence the productivity, diversity, and distribution of plant species in tropical forests. I will highlight the range of soils that occur in tropical forests and will argue that pedogenesis is a primary driver of forest diversity over long timescales. I will draw on data from a regional-scale network of forest dynamics plots in Panama to show that tree species distributions are determined by dry season intensity and soil phosphorus availability, and will suggest potential mechanistic explanations for this pattern in relation to phosphorus acquisition. Finally, I will present evidence for pervasive species-specific phosphorus limitation of tree growth on strongly-weathered soils in the lowland tropics, and discuss the implications for the response of tropical forests to future environmental change.

Wednesday Morning Plenary and Woo Distinguished Lecture
8:00 am, Room Peller C/D

“Salinity and Methane in Groundwater of the Marcellus Shale Region: Applied Statistics for an Applied Problem”

Laura K. Lautz
Syracuse University

There has been significant attention given to the risk of groundwater contamination during unconventional shale gas production. But, in areas overlying the Marcellus, assessing such contamination is complicated by the natural occurrence of methane and high salinity in shallow groundwater. High volume hydraulic fracturing (HVHF) is currently used to produce shale gas in all states overlying the Marcellus shale, with the exception of New York (NY), where the method is currently banned. Given the similar geology, climate, and land use across areas underlain by the Marcellus in NY and Pennsylvania, studies of domestic wells in NY are representative of conditions prior to HVHF in an area with ongoing conventional gas production. We measured methane concentrations (n=137) and major/minor ions (n=203) in domestic wells in southern NY covering an area of 10,230 km2. Using these results, we developed a multivariate statistical modeling framework for quantitatively fingerprinting natural and anthropogenic sources of high salinity (> 20 mg/L Cl) in shallow groundwater, including formation brines produced by hydraulic fracturing. We validated the statistical modeling approach using samples with known sources of contamination. We have also developed a decision tree model using machine learning methods to identify well characteristics most closely associated with natural methane occurrence. Our results indicate formation brines are the most probable source of salinity in 28% of domestic wells in the study area that have >20 mg/L chloride. We also found that although only 7.7% of domestic wells had >1 mg/L dissolved methane, 52% of valley wells producing Na-rich water had >1 mg/L dissolved methane. Our methods and data can be used to improve future distinction of natural and anthropogenic sources of salinity and methane in groundwater in regions impacted by shale gas production.