New approaches to field-model data comparison: Numerical modelling of the last glacial cycle in the Welland catchment, England

Abstract

The extent to which deposition within river systems is driven by climate over glacial-interglacial timescales, and the nature of such linkages, is much debated. Answering such questions from the geological record is often limited by a lack of geochronological precision. Numerical modelling allows us to scale up what we know of climate response on short timescales to these longer timescales. To generate a robust reconstruction, relevant parameters need to be included in the model setup, and model output needs to be evaluated against the geological record. Here we introduce the model Cleopatra (CybErosion-based Landscape Evolution On Periglacially Altered TeRrAin), the first reduced complexity model to include periglacial processes explicitly within a river catchment. We also use a pattern-oriented sampling approach to model evaluation and introduce innovative methods, particularly the quantification of the comparison of synthetic borehole data with geological sequences using Spearman rank correlation. Sediment starvation is observed within the model compared with the geological data, suggesting either the importance of sediment reworking within the catchment or that we have yet to specify the full complexity of periglacial processes in the model. In this sediment-starved situation, gelifluxion drives sediment supply but climate is less important in dictating the timing of aggradation and incision than intrinsic controls and elapsed time.