20 Nov 2023
 | 20 Nov 2023
Status: this preprint is open for discussion.

Greenland's firn responds more to warming than to cooling

Megan Thompson-Munson, Jennifer E. Kay, and Bradley R. Markle

Abstract. The porous layer of snow and firn on the Greenland Ice Sheet stores meltwater and limits sea level rise. This buffer is threatened in a warming climate. To better understand the nature and timescales of firn’s response to air temperature change, we use a physics-based model to assess the effects of atmospheric warming and cooling on firn air content. We identify an asymmetric response of Greenland’s firn to air temperature: firn loses more air content due to warming compared to the amount gained from commensurate cooling. In dry firn, this asymmetry is driven by the highly nonlinear relationship between temperature and firn compaction, as well as the dependency of thermal conductivity on the composition of the firn. The influence of liquid water accentuates this asymmetry. In wet firn areas, melt increases nonlinearly with atmospheric warming, thus enhancing firn refreezing and further warming the snowpack through increased latent heat release. Our results highlight the vulnerability of firn to temperature change and demonstrate that firn air content is more efficiently depleted than generated. This asymmetry in the temperature–firn relationship may contribute to the overall asymmetric mass change of the Greenland Ice Sheet in a changing climate across many timescales.

Megan Thompson-Munson et al.

Status: open (until 04 Jan 2024)

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Megan Thompson-Munson et al.

Megan Thompson-Munson et al.


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Short summary
The upper layers of the Greenland Ice Sheet are absorbent and can store meltwater that would otherwise flow into the ocean and raise sea level. The amount of meltwater that the ice sheet can store changes when the air temperature changes. We use a computer model to show that warming and cooling have opposite but unequal effects. Warming has a stronger effect than cooling, which highlights the vulnerability of the Greenland Ice Sheet to modern climate change.