Rethinking glacial cirque evolution: an exploratory case study of interglacial sediment contributions in Quaternary cirques widening (Vestfirðir, Iceland)

The classical paradigm of glacial cirque evolution, centered on glacial erosion, often underestimates the contribution of interglacial periods. This study quantitatively assesses the role of paraglacial (rock-slope failures, RSF) and periglacial (scree) processes in the morphogenesis of eight Quaternary cirques in Vestfirðir, Iceland. The methodology relies on building a Holocene reference model by quantifying the current volumes of cirques and their internal RSF (61.5%) and scree deposits (38.5%). This model is then extrapolated over 22 Quaternary interglacial cycles. The Quaternary extrapolation reveals a continuum of morphogenic controls: in smaller cirques, interglacial processes can account for the majority of the excavated volume, whereas larger cirques are dominated by glacial erosion. This highlights a scale effect. These findings challenge the traditional glacial-centric view and support a positive-feedback model where glacial and interglacial processes act in a synergistic relationship, driving cirque widening over successive climatic cycles. The study thus re-evaluates the role of interglacial slope dynamics as a crucial, and sometimes primary, agent in cirque development.