Office: Chemistry Physics C4043
Telephone: 709.864.2675
Fax: 709.864.8739
E-Mail: lev At mun D0t ca

Local links

Other Stuff

Welcome

I'm a generalist figuring out how to survive in an academic specialist world. Along the way I've traveled from a Ph.D. in Quantum Gravity to a Canada Research Chair in glacial systems modelling, with a stop as an organic farmer. I've also long had an on-going interest in radical social change (with a focus on theatrical media), wilderness sports, and systems design. In these pages you will find an overview of my current research, list of collaborations, some thoughts on pedagogy and strategy for social change, and some advice for computer modellers.

Research orientation

I'm generally interested in the modelling of complex systems, with an expertise in glacial systems (combining ice, climate, and earth). Modelling is well suited to those of us who like to build/create things. It offers the opportunity to explore virtual worlds, probe myriads of "what ifs", and create piles of data. The challenge is to come up with meaningful results with limited computational resources. Limited resources and limited understanding implies that models of complex physical systems will invariably require simplifications and parameterizations. Along with uncertainties in initial and boundary conditions, the analysis and interpretation of model results becomes a major challenge.

A key point in this regard (for which ice-sheet and climate modelers have been generally deficient) is the need to create meaningful error bars, or better yet probability distributions, for the results of models when used in the context of prediction or retrodiction. The determination of meaningful probability distributions by means of Bayesian calibration of models against observational constraints has therefore become a central focus of my work.

I am also very interested in improving our ability to constrain the changing variability of systems and associated potential thresholds. In the context of climate change, this is arguably both the greatest scientific challenge and the aspect that carries the highest potential impacts. My current approach to this challenge involves three key steps. First, identify the bounds on dynamical processes potentially controlling variability and thresholds. Second, constrain the spatial and temporal scale sensitivities of the representation of these key dynamical processes and their interactions. Finally, develop probability distributions of potential response through a combination of large ensemble data-calibrated modelling with stochastic probing of the bounding critical dynamics.

Glacial systems model

Probably the favourite aspect of my work (aside from learning) is model building. The MUN/UofT Glacial Systems model has been my baby and continues to undergo development. The core elements are a thermo-mechanically coupled 3D ice-sheet model and a global visco-elastic bedrock deformation model. Other important components include a bed thermal/permafrost module, physically-based surface mass-balance module, ice calving module, sub-glacial till-deformation representation, and a fast surface drainage solver. Optional modules can compute high-resolution Semi-Lagrangian tracer tracking and gravitationally-self-consistent relative sea-level. The newest additions created within my group are a subglacial sediment production/transport module and subglacial hydrology. The critical surface boundary condition is provided by coupling of the glacial systems model to a hierarchy of climate models and forcings.

A number of additional components are or will be under development. These include: a higher order ice-dynamics model that accounts for longitudinal and horizontal shear stresses to improve the representation of ice-streams and ice-shelves, sub-grid mass-balance, and a hierarchy of ice-calving modules. A key focus is improving diagnostic components to enable expanded comparisons of model results against observational data. There are thus a range of opportunities for students to get their hands dirty with model building.

Research questions

My general focus is on constraining and understanding the interactions between the cryosphere and the rest of the climate system. This includes both past, present, and future contexts. The past offers a major opportunity to develop and test our understanding of climate dynamics. The present and future stability of the cryosphere and associated interactions with the rest of the climate system are major environmental concerns. Questions that are currently absorbing my attention include the following:

What is the probability distribution for the future evolution of the Greenland and Antarctic ice sheets?

How can we improve constraints on potential instabilities?

What are the past and potential future impacts of meltwater and iceberg discharge on the climate system? What are the key uncertainties and controls on polar climate stability?

What controlled the climate system response to meltwater pulse 1-a and to the discharge associated with Heinrich events and the Younger Dryas? How will the variability of polar and sub-polar climate change in our future?

What drove the glacial cycle?

What are the critical feedbacks in the cryosphere and climate system that drive the 100kyr glacial cycles? What was the source of the mid-Pleistocene transition? What is the probability distribution for the ice, meltwater, and climate chronology of the last glacial cycle?

What is the phase space of the glacial climate system?

What is the order of the dynamical system? What other limit cycles and attractors are accessible (ie. how robust is the glacial cycle)? What controls the dynamical structure?

How can the calibration of computationally expensive models against observational constraints be improved?

How do different methodologies compare for this type of data inversion problem? How can they be advantageously combined? How can the error associated with the limited phase space of the model be quantified? More generally, how can we generate meaningful uncertainty estimates (and full probability distributions) for climate and glacial system changes (past, present, and future)?

Research group

I am blessed with a keen research group:

Past students (completion date)