Marine Technology - October 2007 - Page#79

<BODY> <span id="lblContents">Fig. 8 Satellite image from August 28, 2002, showing the movement of Thick First-Year Ice and Old Ice across the northern entrance to Peel Sound into central Barrow Strait across the Northwest Passage. The figure shows a sketch of zone boundaries and Northwest Passage shipping route. tence of this ice in eastern Hudson Strait late into July in a cool summer (Fig. 9). 5.2. Zone 14 (main and alternate routes) Zone 14 covers northern Hudson Bay south of Southampton Island. In average to cooler-than-average summers, high concentrations of Thick First-Year Ice persist in northern Hudson Bay well into July, producing negative numerals for Type B vessels during this period. Evidence of this persistent pack ice in Zone 14 can be seen at the extreme western edge of the satellite image from July 7, 2000 (Fig. 10). Even in a warmer-than-normal summer, such as in 2004, high concentrations of Thick First-Year Ice can persist into July in Zone 14, as evident in the satellite image (Fig. 10). Only in an exceptionally warm summer, as was the case for the summer of 1998, would the ice clear sufficiently to generate positive numerals for a Type B vessel across Zone 14. The implication of this is that it will take many decades of continual warming of the region to get to the situation where the conditions of 1998 would be considered normal for the region. 5.3. Zone 16 (alternate route) Zone 16 covers the western shore of Hudson Bay north of 60 deg N. This zone was created to reflect the fact that the first ice to clear in Hudson Bay is the northwest quadrant due to the prevailing northwest winds in the region. This early clearing is evident in the satellite image in Fig. 10. Vessels attempting access to Churchill early in the shipping season will often take the alternate "northern" route across the south coast of Southampton Island and southward along the west coast of Hudson Bay avoiding the pack ice in the central portion. However, in normal to cooler-than-normal summers, such as occurred in 1992, the clearing of western 250 OCTOBER 2007 Hudson Bay can be delayed well into July resulting in negative numerals for a Type B vessel. Only in warmer-thannormal summers, such as occurred in 1998, would positive numerals for a Type B vessel be expected in Zone 16 in early July. 6. Multi-Year Ice occurrence in zones Kubat and Timco (2003) analyzed events that caused damage to vessels in Arctic waters. They found that Multi-Year Ice was present in the ice regime in 73% of the damage events and that damage was more severe in ice regimes that contain Multi-Year (MY) ice. This indicates that MY Ice must always be treated with caution. The presence of MY Ice in any ice regime will always lead to a higher potential for vessel damage. With this in mind, it is instructive to review the occurrence of MY Ice in various zones in the Northwest Passage. The analysis mentioned previously illustrates the damage potential and hazards presented by MY Ice; therefore, the occurrence of MY Ice in the shipping lanes in the Northwest Passage was analyzed. The ice conditions vary from year to year. In some years, MY Ice is present heavily in the Northwest Passage during the shipping season; in others it is not. The results from analyzing the warmer-than-normal year and colder-than-normal year showed that there is no MY Ice present in the Zone 12 shipping season for Type B vessel and less than 5% in the Zone 13 shipping season. In Zones 6 and 7, the MY Ice is present at the beginning of the shipping season. Thus, cautious travel is still required since MY Ice is difficult to detect and can cause considerable damage to a vessel. It is interesting to note that outside the shipping season there is higher percentage of MY Ice coverage in a warmerthan-normal year compared with a colder-than-normal year in Zones 2, 7, and 13, which is due to the previous year's ice MARINE TECHNOLOGY</span> <br /> <br /> <a href="http://www.digitalwavepublishing.com/" title="Digital Magazine">Digital Wave Publishing</a> </BODY>