By Danielle Halle and Wesley Van Wychen In higher elevations, firn, frozen water that is something between snow and ice, covers the top of glaciers. Firn plays a critical role in regulating glacial meltwater and sea level rise. It does this by absorbing meltwater, the water released by melting glaciers. The ability of the firn layer to absorb meltwater — its “sponginess” — can be determined by the amount of pore space available, which is impacted by several variables such as temperature, firn grain size and presence of ice layers within the firn layer. A more spongy firn layer allows for more meltwater to be stored as it trickles down and refreezes when it reaches colder temperatures at depth. Layers of firn can exist between refrozen ice layers. The greater…
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