EMPIRICAL AND THEORETICAL CONTRIBUTIONS OF JIM KNOX TO OUR UNDERSTANDING OF THE QUATERNARY GEOMORPHOLOGY OF THE UPPER MISSISSIPPI RIVER

With a career spanning four decades, Jim Knox has not only witnessed the successful intellectual evolution of Quaternary geomorphology, he has very much been at the forefront of these achievements. This talk presents Jim Knox’s contributions to Quaternary geomorphology: rather than merely chronicling these accomplishments, the goal of the presentation is also to provide the broader context for these key contributions and to demonstrate their sustained impact on the field.

When Jim began his career in the late 1960s, climate change research focused primarily on Quaternary chronologies of ice advances/retreats. Because of his academic position at Wisconsin, Jim interacted with climatologists and paleo-climatologists, ultimately incorporating synoptic climatology into Quaternary climate change science. Jim’s early field-based studies in the Northwest Territories and the Driftless Area helped him conceptualize two of his most important theoretical contributions: the “Concept of the Graded Stream” and the “Biogeomorphic Response Model”. In perhaps his most seminal early article, Jim advanced upon the classic paper by J. Hoover Mackin on channel equilibrium to show how climate change is a first order control on channel dis-equilibrium; that climate change operates at timescales shorter than previously thought; and that globally synchronous climate changes occurred during the Holocene. This work further showed the temporal differences in response between climate change, vegetation, erosion, and thus sediment yield leading Jim to couple them conceptually as the Biogeomorphic Response Model.

Because of his extensive field work throughout the Upper Midwest, Jim has evaluated the sensitivity of river systems to environmental change on timescales from the contemporary, to the historical, and to the pre-Quaternary. This research trajectory included topics ranging from human impacts on post-settlement floodplain alluviation to the late Neogene-to-present evolution of the Upper Mississippi River basin. These extensive field endeavors not only represent major scientific contributions, but they also serve as critical management protocols and important methodological approaches. Future scholars and students will be indebted to the tremendous knowledge production that Jim’s efforts have provided.