08 Sep 2021
08 Sep 2021
Status: a revised version of this preprint was accepted for the journal TC.

Sea ice floe size: its impact on pan-Arctic and local ice mass, and required model complexity

Adam William Bateson1, Daniel L. Feltham1, David Schröder1,2, Yanan Wang3, Byongjun Hwang3, Jeff K. Ridley4, and Yevgeny Aksenov5 Adam William Bateson et al.
  • 1Centre for Polar Observation and Modelling, Department of Meteorology, University of Reading, Reading, RG2 7PS, United Kingdom
  • 2British Antarctic Survey, Cambridge, CB3 0ET, United Kingdom
  • 3School of Applied Sciences, University of Huddersfield, Huddersfield, United Kingdom
  • 4Hadley Centre for Climate Prediction and Research, Met Office, Exeter, EX1 3PB, United Kingdom
  • 5National Oceanography Centre Southampton, Southampton, SO14 3ZH, United Kingdom

Abstract. Sea ice is composed of discrete units called floes. The size of these floes can determine the nature and magnitude of interactions between the sea ice, ocean, and atmosphere including lateral melt rate, momentum and heat exchange, and surface moisture flux. Large-scale geophysical sea ice models employ a continuum approach and traditionally either assume floes adopt a constant size or do not include an explicit treatment of floe size. Observations show that floes can adopt a range of sizes spanning orders of magnitude, from metres to tens of kilometres. In this study we apply novel observations to analyse two alternative approaches to modelling a floe size distribution (FSD) within the state-of-the-art CICE sea ice model. The first model considered, the WIPoFSD (Waves-in-Ice module and Power law Floe Size Distribution) model, assumes floe size follows a power law with a constant exponent. The second is a prognostic floe size-thickness distribution where the shape of the distribution is an emergent feature of the model and is not assumed a priori. We demonstrate that a parameterisation of in-plane brittle fracture processes should be included in the prognostic model. While neither FSD model results in a significant improvement in the ability of CICE to simulate pan-Arctic metrics in a stand-alone sea ice configuration, larger impacts can be seen over regional scales in sea ice concentration and thickness. We find that the prognostic model particularly enhances sea ice melt in the early melt season, whereas for the WIPoFSD model this melt increase occurs primarily during the late melt season. We then show that these differences between the two FSD models can be explained by considering the effective floe size, a metric used to characterise a given FSD. Finally, we discuss the advantages and disadvantages to these different approaches to modelling the FSD. We note that the WIPoFSD model is less computationally expensive than the prognostic model and produces a better fit to novel FSD observations derived from 2-m resolution MEDEA imagery but is unable to represent potentially important features of annual FSD evolution seen with the prognostic model.

Adam William Bateson et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2021-217', Anonymous Referee #1, 27 Sep 2021
    • AC1: 'Reply on RC1', Adam Bateson, 04 Feb 2022
  • RC2: 'Comment on tc-2021-217', Anonymous Referee #2, 03 Nov 2021
    • AC2: 'Reply on RC2', Adam Bateson, 04 Feb 2022

Adam William Bateson et al.

Data sets

Simulations of the Arctic sea ice comparing different approaches to modelling the floe size distribution and their respective impacts on the sea ice cover Adam Bateson

Adam William Bateson et al.


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Short summary
Numerical models are used to understand the mechanisms that drive the evolution of the Arctic sea ice cover. The sea ice cover is formed of pieces of ice called floes. Several recent studies have proposed variable floe size models to replace the standard model assumption of a fixed floe size. In this study we show the need to include floe fragmentation processes in these variable floe size models and demonstrate that model design can determine the impact of floe size on size ice evolution.