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Volume 12, issue 7 | Copyright
The Cryosphere, 12, 2267-2285, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 12 Jul 2018

Research article | 12 Jul 2018

Melting and fragmentation laws from the evolution of two large Southern Ocean icebergs estimated from satellite data

Nicolas Bouhier1, Jean Tournadre1, Frédérique Rémy2, and Rozenn Gourves-Cousin1 Nicolas Bouhier et al.
  • 1Laboratoire d'Océanographie Physique et Spatiale, UMR 6523, IFREMER, CNRS, IRD, Université Bretagne-Loire, Plouzané, France
  • 2Laboratoire d'Etudes en Géophysique et Océanographie Spatiales, UMR 5566, CNES – CNRS, Toulouse, France

Abstract. The evolution of the thickness and area of two large Southern Ocean icebergs that have drifted in open water for more than a year is estimated through the combined analysis of altimeter data and visible satellite images. The observed thickness evolution is compared with iceberg melting predictions from two commonly used melting formulations, allowing us to test their validity for large icebergs. The first formulation, based on a fluid dynamics approach, tends to underestimate basal melt rates, while the second formulation, which considers the thermodynamic budget, appears more consistent with observations. Fragmentation is more important than melting for the decay of large icebergs. Despite its importance, fragmentation remains poorly documented. The correlation between the observed volume loss of our two icebergs and environmental parameters highlights factors most likely to promote fragmentation. Using this information, a bulk model of fragmentation is established that depends on ocean temperature and iceberg velocity. The model is effective at reproducing observed volume variations. The size distribution of the calved pieces is estimated using both altimeter data and visible images and is found to be consistent with previous results and typical of brittle fragmentation processes. These results are valuable in accounting for the freshwater flux constrained by large icebergs in models.

Publications Copernicus
Short summary
The evolution of two large Southern Ocean icebergs, in terms of area and thickness, are used to study the melting and fragmentation laws of icebergs. The area and thickness are estimated by the mean of satellite images and radar altimeter data. Two classical formulations of melting are tested and a fragmentation law depending on the sea temperature and iceberg velocity is proposed and tested. The size distribution of the pieces generated by fragmentation is also estimated.
The evolution of two large Southern Ocean icebergs, in terms of area and thickness, are used to...