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As oil and gas exploration moves to cold climates in arctic and sub-arctic regions, the demand for ice capable vessels such as tankers, lique- ed natural gas (LNG) carriers, oshore support vessels, and mobile d rilling units is growing rapidly. e Arctic Council recently published a document summa- rizing the multi-faceted challenges and issues in the Arctic Marine Shipping Assessment Report in 2009 . e report stated that the Arctic is undergoing extraordinary changes in both the natural environment and the regu- latory environment. Our purpose here is to examine the recent changes in regulatory changes in the Polar region. e International Maritime Organization (IMO) is the most in uential regulatory body promoting maritime safety. Recognizing the need for recommended provisions applicable to ships operating in the Arctic, IMO published Guidelines for Ships Operating in Arctic Ice-covered Waters , in 2002. Ships operating in the arctic environment are exposed to a number of unique risks. Poor weather condi- tions and the relative lack of good charts, communication systems, and other navigational aids pose challenges for mariners. e remoteness of the area makes rescue or cleanup operations dicult and costly, and cold tem- peratures may reduce the effectiveness of numerous components of the ship, ranging from deck machinery and emergency equipment to sea suctions. When ice is present, it can impose additional loads on the hull, propulsion system, and append- ages. e IMO arctic guidelines address requirements for construction provisions, equipment, operations, and environmental protection and damage control. One of the most important aspects of the IMO guide- lines for ship designers, builders, and operators is that the construction provisions refer to the Requirements Concerning Polar Class , developed by the International Association of Classication Societies (IACS). Polar class notation IACS Requirements Concerning Polar Class consists of three parts. Part I is the denition and application of the polar classes, Part II provides structural requirements, and Part III provides requirements for machinery. In Part I, seven polar classes are dened based on dier- ent operational ice conditions as shown in Table 1. IMO arctic guidelines noted that the lowest two polar classes, PC7 and PC6, were commonly accepted as nominal equivalencies to Finnish/Swedish (Baltic) class 1A and 1A super, respectively. e intent of the highest polar class PC1 is to oer a level of capability analogous to that provided by an unrestricted open-water class notation. It denes a ship which can operate year-round in all polar waters, subject to due caution on the part of the master. is caution implies, for example, limiting speed in certain conditions, avoiding aggressive maneuvers, and avoiding impacts with obvious glacial ice features. Structural Requirements Part II of the Requirements Concerning Polar Class pro- vides denitions and requirements for hull area, design loads, shell plate requirements, framing requirements, corrosion/abrasion addition and steel renewal, mate- rial grades, and longitudinal strength requirements. e design load for polar-class ships takes a physics-based approach that ice loads can be rationally linked to the design scenario, which is a glancing collision with an ice edge, such as the edge of a channel or of a oe. e form Development and Harmonization The intersection of arctic region guidelines and requirements BY HAN YU TABLE . POLAR CLASS DESCRIPTIONS POLAR CLASSGENERAL DESCRIPTION PC1Year-round operation in all polar waters PC2Year-round operation in moderate multi-year ice conditions PC3Year-round operation in second- year ice with old ice inclusions PC4Year-round operation in thick ?rst-year ice which may contain old ice inclusions PC5Year-round operation in medium ?rst-year ice with old ice inclusionsPC6Summer/autumn operation in medium ?rst-year ice with old ice inclusions PC7Summer/autumn operation in thin ?rst-year ice with old ice inclusions January 2011 www.sname.org/sname/mt (mt notes )