Journal Article

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

Lilien, David A., Fudge, T. J., Koutnik, Michelle R., Conway, Howard, Waddington, Edwin D., Stevens, C. Max

2023

Overview

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.

• Publisher: Cambridge University Press,Cambridge University Press/International Glaciological Society
• Subject: Algorithms / Antarctic glaciology / Boreholes / Climate / Coffee / Compaction / Constitutive relationships / Densification / Density / Density profiles / Earth Resources and Remote Sensing / Energy Production and Conversion / Firn / glaciological instruments and methods / Ice accumulation / Ice sheets / Life Sciences (General) / Methods / polar firn / Seasonal variation / snow rheology / snow/ice surface processes / South Pole / Uncertainty