## 1 Introduction  
An extreme ice feature (EIF) is an ice feature that could cause an extreme design load on an offshore platform from a fixed-structure point of view, ice scouring seafloor facilities or significant ship damage. EIFs include rubble fields, ridges, hummocks, stamukhi, icebergs, ice islands and multiyear (MY) floes. An ice ridge is a line or wall of broken ice forced up by pressure [1]. A rubble field is an area of many ridges with similar characteristics. Multiyear ice floes (pieces of ice 20 m or more across) are old ice floes that have survived at least two summers' melt and are much thicker (up to 4 m and more [2]) than younger ice. Stamukhi are pileups of deformed sea ice that are grounded to the sea floor and are found in shallow water. A hummock is defined [1] as a hill of broken ice that has been forced upward by pressure. The hummock field can produce significant seabed gouging (up to 3.5 m in depth), fragmented during the grounding process [3]. The presence of EIFs in the Canadian Arctic has been a topic area of interest for many years with records available starting from 1946 [4]. EIFs in the Beaufort are most likely to occur along the northwest edge of the Queen Elizabeth Islands and in the pack ice of the Arctic Ocean [5]. More recently, the warming Arctic appears to have affected both the occurrence and characteristics of these ice features. With the increasing impact of climate change, the hazardous ice features remain a threat to stationary and mobile infrastructure in the southern Beaufort Sea [6] because of the increased frequency and relative velocities of certain ice hazards [7]. Ice islands are generated as a result of calving from glaciers and ice shelves that are present along the east coast of Canada and the Beaufort Sea. The size of the ice islandsmay be up to 1000 or more square miles and their thicknesses up to 75 m. In the Beaufort Sea, ice islands are large tabular icebergs that calve from the ice shelves located along the northern coasts of Ellesmere and Axel Heiberg islands and drift into the Arctic Ocean where they circulate in a clockwise direction for many years [5]. Although definitions vary, ice islands can also be described as any tabular icebergs whose waterline lengths range from hundreds of meters to many kilometers, generally have freeboards under 20 m and an overall thickness of up to 55 m [8]. However, Beaufort Sea ice islands generally have maximum dimensions of tens of meters or smaller. Beaufort Sea ice islands predominantly come from Ellesmere Island ice shelves, which are a combination of fresh and salt water ice formed from snowfall and sea-ice accretion. The low freeboards of ice islands make them challenging to detect and their low drafts allow them to pass over continental shelf areas. For decades, upward-looking sonar have been used to study ice in the Beaufort Sea, and for the last 30 years, satellite imagery have been used to report on surface ice conditions. One of the first remote sensing studies to detect EIFs was conducted by [PERSON] et al. [5], who used satellite imagery and concluded that a spatial resolution of at least 15 m on both radar and optical is required for detecting EIFs with 500 m diameters. By comparing RADARSAT-1 and Quickbird images [9], it was concluded that RADARSAT-1 Extended High images were best at detecting ice features. Fine-mode images provided more details, but it was difficult to identify new features in the data. Quickbird images provided exceptional detail, but clouds and darkness were severe limitations. Rubble fields were difficult to detect during freeze-up and in land-fast ice, but they could be characterized using satellite SAR. During break-up, grounded rubble fields would persist after other ice had melted and it was possible to detect them even with RADARSAT-1 ScanSAR imagery. Work by [9] indicated that RADARSAT-1 fine-mode data with 8 m resolution were good at characterizing but not identifying many ice features of interest.