A new model of dry firn-densification constrained by continuous strain measurements near South Pole

• Published in: Journal of Glaciology
• Main Authors: C. Max Stevens, David A. Lilien, Howard Conway, T. J. Fudge, Michelle R. Koutnik, Edwin D. Waddington
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press 2023
• Subjects: Antarctic glaciology; glaciological instruments and methods; polar firn; snow/ice surface processes; snow rheology; Environmental sciences; GE1-350; Meteorology. Climatology; QC851-999; Antarctic; South Pole; The Antarctic; Antarc*; Ice Sheet; Journal of Glaciology; South pole
• Online Access: https://doi.org/10.1017/jog.2023.87; https://doaj.org/article/d725d94676d44dd99dde3e01e5f8dbf4

Converting measurements of ice-sheet surface elevation change to mass change requires measurements of accumulation and knowledge of the evolution of the density profile in the firn. Most firn-densification models are tuned using measured depth–density profiles, a method which is based on an assumption that the density profile in the firn is invariant through time. Here we present continuous measurements of firn-compaction rates in 12 boreholes near the South Pole over a 2 year period. To our knowledge, these are the first continuous measurements of firn compaction on the Antarctic plateau. We use the data to derive a new firn-densification algorithm framed as a constitutive relationship. We also compare our measurements to compaction rates predicted by several existing firn-densification models. Results indicate that an activation energy of 60 kJ mol−1, a value within the range used by current models, best predicts the seasonal cycle in compaction rates on the Antarctic plateau. Our results suggest models can predict firn-compaction rates with at best 7% uncertainty and cumulative firn compaction on a 2 year timescale with at best 8% uncertainty.