Drift-dependent changes in iceberg size-frequency distributions

Although the size-frequency distributions of icebergs can provide insight into how they disintegrate, our understanding of this process is incomplete. Fundamentally, there is a discrepancy between iceberg power-law size-frequency distributions observed at glacial calving fronts and lognormal size-frequency distributions observed globally within open waters that remains unexplained. Here we use passive seismic monitoring to examine mechanisms of iceberg disintegration as a function of drift. Our results indicate that the shift in the size-frequency distribution of iceberg sizes observed is a product of fracture-driven iceberg disintegration and dimensional reductions through melting. We suggest that changes in the characteristic size-frequency scaling of icebergs can be explained by the emergence of a dominant set of driving processes of iceberg degradation towards the open ocean. Consequently, the size-frequency distribution required to model iceberg distributions accurately must vary according to distance from the calving front.The study was supported by Polish National Science Centre grant no. 2011/01/B/ST10/01553. Seismic equipment was provided by the Natural Environment Research Council Geophysical Equipment Facility, SEIS-UK (loan number 984). The modelled tide data for Ilulissat was kindly provided by Palle Bo Nielsen at the Danish Meteorological Institute. Logistical support was provided by Arctic Station, Qeqertarsuaq. Thanks go to Antony Long and Nick Cox for inspiring the ideas that underpin this work. M.C.S. is supported by NCN FUGA Fellowship (2013/08/S/ST10/00585)