The complex thermal regime of glaciers: cold ice versus warm ice

Glaciers are generally divided into three types of thermal regime depending on whether the ice is at or below pressure-melting point, or a combination of the two states. Thermal regime influences glacier surface mass balance and dynamics, and therefore affects processes of sediment delivery to the ice margin, as well as landform development. Increasingly, glacier thermal regimes are more complex than previously assumed and the actual thermal conditions of any individual glacier can be highly spatially variable. Cold-ice (ice that does not contain any liquid water below pressure melting point) may in fact also be present in isolated pockets within glaciers that are typically classified as temperate. Thus, cold-based processes, including basal freeze-on, may have a significant role for the dynamics of temperate glaciers that are thinning and retreating to higher altitudes (even during, e.g. the exceptional climatic warming observed since 2000). Implications from this hypothesis suggest that cold-based processes may be more widespread than previously thought, and could influence future glacier behaviour in terms of retreat rate and ice flow velocity. Many modelling studies currently do not account for changes to the thermal regime in their predictions, nor the potential knock-on effects on ice dynamics.