On the representation of capsizing in iceberg models

TitleOn the representation of capsizing in iceberg models
Publication TypeJournal Article
Year of Publication2017
AuthorsWagner T.JW, Stern A.A, Dell R.W, Eisenman I
JournalOcean Modelling
Date Published2017/09
Type of ArticleArticle
ISBN Number1463-5003
Accession NumberWOS:000410800500007
Keywordsantarctic icebergs; Capsizing; coupled climate models; ecosystems; event; greenland ice-sheet; icebergs; interactive; meltwater; Modelling; sea-ice; southern-ocean; stability

Although iceberg models have been used for decades, they have received far more widespread attention in recent years, due in part to efforts to explicitly represent icebergs in climate models. This calls for increased scrutiny of all aspects of typical iceberg models. An important component of iceberg models is the representation of iceberg capsizing, or rolling. Rolling occurs spontaneously when the ratio of iceberg width to height falls below a critical threshold. Here we examine previously proposed representations of this threshold, and we find that there have been crucial flaws in the representation of rolling in many modeling studies to date. We correct these errors and identify an accurate model representation of iceberg rolling. Next, we assess how iceberg rolling influences simulation results in a hierarchy of models. Rolling is found to substantially prolong the lifespan of individual icebergs and allow them to drift farther offshore. However, rolling occurs only after large icebergs have lost most of their initial volume, and it thus has a relatively small impact on the large-scale freshwater distribution in comprehensive model simulations. The results suggest that accurate representations of iceberg rolling may be of particular importance for operational forecast models of iceberg drift, as well as for regional changes in high-resolution climate model simulations. (C) 2017 Elsevier Ltd. All rights reserved.

Short TitleOcean Model.

We have found that rolling can substantially impact the drift and decay of individual icebergs, especially those that are relatively small (length ≲ 500 m). For example, we find that for fixed surface velocities and SSTs, rolling icebergs typically live substantially longer and drift farther than non-rolling icebergs. This suggests that in regions where more small icebergs calve off glaciers or ice shelves, capsizing may have a large impact on meltwater fluxes. Hence the results presented here may be relevant to both operational iceberg forecast models and regional climate model simulations. Nonetheless, we have shown that iceberg rolling has a relatively small impact on the large-scale iceberg meltwater flux in the global climate system.

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