Formation of ice layers by infiltration and refreezing of meltwater

Abstract

Melt-layer frequency and magnitude in polar and sub-polar ice cores have been interpreted as measures of past summer temperature, and calibrations have been proposed relating frequency of occurrence of ice layers in ice cores to past summer temperatures. But, observations in the percolation facies in Greenland and an analysis of the combined processes of meltwater infiltration and refreezing of water in snow indicate that, in addition to unusually high rates of meltwater input, formation of ice layers will also be facilitated by unusually cold initial conditions or early onset of melt. Uniform warming of both summer and winter conditions has the opposite effect and suppresses ice-layer formation in favor of uniform wetting and refreezing of the snowpack. Numerical modeling of infiltration and refreezing at a stratigraphic fine-to-coarse transition allows quantification of the effects of significant parameters (initial temperature, grain-size and density contrast across the stratigraphic transition, water-input rate and minimum impermeable-layer thickness). Calculations are made to distinguish threshold values of parameters at which infiltration progresses faster than refreezing, resulting in a break-through of water across the stratigraphic transition, from values leading to the formation of an ice layer when refreezing progresses faster than infiltration.