Enhancing international collaborations for the retrieval of sea ice floe size distribution (FSD) from satellite SAR imagery

Rapid decline in Arctic sea ice has been observed, and climate models predict even more dramatic changes in the near future. One of the key components that cause such rapid sea ice reduction is sea-ice floe (pieces) breakup in the margin of the ice area during spring and summer. At the edge of sea-ice area, sea-ice floes are exposed to waves and winds and break into smaller pieces. As they become smaller, they become easier to melt from the side and exposing more open water areas. More exposed open water areas then leads to warmer ocean as more sunlight absorb into the ocean, which in turn make sea ice more fragile and breakable. This process can accelerate sea ice retreat in summer and thus impact the minimum ice extent.

To understand the effects of such process on summer sea ice retreat, reliable information on sea-ice floe size distribution (FSD) is necessary. Such observations can be made from satellite Synthetic Aperture Radar (SAR) that can observe sea ice through cloud and darkness. There is an increasing number of satellite SAR images being acquired in the Arctic, and often at spatial resolutions in the images as good as 1-20 m. More importantly satellite SAR images are being acquired over autonomous buoy systems and in conjunction with field campaigns. This provides the ideal framework to measure the full range of ocean, sea-ice and atmosphere parameters to investigate complex floe breakup process.

However the challenge we have is a lack of proven-quality algorithms that can derive FSD from satellite SAR images fast and accurately. Thresholding algorithms previously applied to the problem are not adequate for quantitative analysis and the performance has not been precisely assessed. Recently NERC TPoC funded us to conduct research to develop cutting-edge algorithm for the retrieval of sea-ice FSD from SAR images.

In this IOP proposal we expand our current project internationally in order to add values to the current NERC TPoC project as well as have impacts on wide research communities and commercial companies.

- Formation of cohesive research and user group. The major impact of this IOP project is to form a focused research group that has common interested in FSD retrieval algorithm (image processing) as well as the use of retrieved data (sea ice observations and modeling, and commercial companies). In this proposal we propose the workshop that involve wide-range of research areas including image processing, sea ice modelling and commercial companies. The workshop provides opportunity to identify and address any sea-ice FSD related issues, and will be the stepping stone to develop a research/user consortium in the future.

- Case study. While the proposed workshop take a holistic approach, the case study will have direct impacts on adding values on current NERC project. We carefully selected four key partners in image processing and remote sensing and one key partner in sea ice FSD modelling. These key partners will be directly involved in the case study that improve image processing algorithm and conduct inter-comparison and validation of the model outputs. This will have significant impacts on improvement of efficiency and accuracy of the sea-ice FSD retrieval algorithm, and also improve sea-ice FSD model parameterisations.