Layers

Four layers of sound, each driven by one variable and each with its own mark of light. A bass drone breathes with the average snow and tints the whole image, cyan rings carry the melody from west to east, violet bands are the chords, and white crosses and red swells are the percussion.

20,150 glaciers with at least 20 observed years. The bass follows the average snow and its fragmentation, the melody the usual snow-line position in eight bands of longitude, the chords the gap between the surface still detected and the reference glacier surface, and the percussion the fragmentation of glaciers drawn among the 2,000 largest.

Sound and image come from the same list of 699 notes, so every light on the map is a note you hear.

Eight melody notes a year. The chords go from an open fifth to tight clashing notes as the region drifts from its reference, and crystals and low hits play the percussion. The scale darkens from bright to dark modes.