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

据观察，北极海冰正在迅速减少，气候模型预测，在不久的将来，北极海冰会发生更剧烈的变化。造成海冰如此迅速减少的一个关键因素是春季和夏季海冰在冰区边缘的浮冰（碎片）破裂。在海冰区的边缘，海冰浮冰暴露在海浪和风中，破碎成更小的碎片。当它们变小时，它们更容易从侧面融化，暴露出更多的开放水域。更多暴露的开放水域导致海洋变暖，因为更多的阳光被吸收到海洋中，这反过来又使海冰更加脆弱和易碎。这一过程可以加速海冰在夏季的退缩，从而影响最小冰范围。为了了解这种过程对夏季海冰退缩的影响，需要可靠的海冰尺寸分布（FSD）信息。这种观测可以通过卫星合成孔径雷达（SAR）进行，该雷达可以透过云层和黑暗观察海冰。在北极获取的卫星合成孔径雷达图像越来越多，图像的空间分辨率往往高达1-20米。更重要的是，卫星合成孔径雷达图像是通过自主浮标系统并结合实地活动获取的。这为测量海洋、海冰和大气参数以研究复杂的浮冰破碎过程提供了理想的框架。然而，我们面临的挑战是缺乏经过验证的质量算法，可以快速准确地从卫星SAR图像中获得FSD。先前应用于该问题的非线性保持算法不足以进行定量分析，并且性能尚未得到精确评估。最近，NERC资助我们进行研究，以开发尖端的算法，从SAR图像检索海冰FSD。在这个IOP提案中，我们在国际上扩展了我们目前的项目，以便为目前的NERC TIGHTT项目增加价值，并对广泛的研究社区和商业公司产生影响。

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.