| The rapid loss of Arctic sea ice,caused by global warming,has made it possible for the Arctic Passage to be fully opened as the extent and thickness of sea ice continue to shrink.The opening of the Arctic Passage will shorten the distance of traditional shipping routes,reduce the transport pressure of traditional shipping,provide more opportunities to explore the Arctic's rich resources,further affecting the global shipping situation and trade pattern.As a country near the Arctic,successful opening of the Arctic Passage will bring China great commercial and economic benefits,as well as great significance to the construction of Ice Silk Road and maritime power.However,there are still some problems in the research on sea ice monitoring and navigability of the Arctic Passage,including that low resolution sea ice data is difficult insufficient to monitor ice details,single sea ice data cannot fully reflect ice conditions,and the risk quantification model is not perfect enough to quantify the ice condition.Therefore,it is worthwhile to monitor the sea ice conditions of the Arctic Passage comprehensively and accurately,and to plan suitable and feasible routes for sailing ships.In order to achieve accurate monitoring of ice conditions in the Arcitc Ppassage and provide safe and reliable navigation guidance for polar ships,we use ICESat-2ATL10 sea ice freeboard products and Sentinel-2 optical images to extract high spatial resolution sea ice parameters in four regions of the Northwest Passage and analyze the navigability of the PC6 class icebreaker.Meanwhile,the shipping route results obtained under different route planning methods were compared and analyzed.First,the Sentinel-2 ice water binary results of threshold classification are used to extract sea ice concentration with high spatial resolution at 100 m.At the same time,the regression model between Sentinel-2 albedo and ATL10 data is established to obtain sea ice freeboard consistent with the Sentinel-2 image range.Then,100 m high spatial resolution sea ice thickness is obtained from sea ice freeboard through the static equilibrium model,which made up for the deficiency that ICESat-2 data cannot extract dense information under a complete area due to the large spacing of vertical track.Then the navigation ability of PC6 icebreaker is analyzed using the concentration data and thickness data of sea ice.Experimental results show that high spatial resolution sea ice parameters can not only reflect the distribution of large sea ice and open water,but also can completely and clearly identify the details of sea ice conditions such as leads.,thereby realizing the accurate expression of real ice conditions and accurate division of navigable region.Secondly,we introduce the landscape pattern index of landscape ecology into the sea ice field,and calculate landscape pattern index on the simulated images with the same sea ice concentration but different distribution of sea ice.Then,the corresponding relationship between landscape pattern index and sea ice fragmentation degree in the broken ice region is confirmed,and we define the index result of principal component analysis as a new sea ice parameter named sea ice fragmentation,which realizes the quantification of sea ice fragmentation degree.Sea ice concentration,sea ice thickness and sea ice fragmentation with 3.125 km low spatial resolution are also extracted,and the ice-distance quantization model is established by different spatial resolution sea ice parameter results and distance factors.A variety of models with different spatial resolution and parameter types are used to plan routes for the PC6 icebreaker.Researches show that routes planned by high spatial resolution ice-distance quantization model can along the most appropriate navigable area,while routes planned by low spatial resolution parameters sometimes cross the large sea ice because of poor identification about ice conditions,making it possible to use fuel to break ice.Planned routes with sea ice fragmentation tend to pass through areas with less sea ice concentration and thickness and more fragmented sea ice,which may result from the sea ice fragmentation improving the comprehensiveness of the original sea ice parameters to describe ice conditions,so that navigable areas with lighter ice conditions can be found.Finally,this paper compares and analyzes the difference of planning routes between the high spatial resolution four-parameter ice-distance quantification model and the risk quantification model.Research shows that,although the risk quantification model commonly used in ice navigation research can use corresponding comprehensive to quantify all kinds of ice conditions,the classification is too broad to reflect the details of real ice conditions,which leads to the identification of navigable areas is not accurate enough.As a result,routes planned by the risk quantification model often pass through areas with heavy ice conditions in order to shorten the distance,which increases the risk of navigation.The ice-distance quantization model based on the results of high spatial resolution sea ice parameters can express the real ice conditions more comprehensively and accurately,which ensures the correct selection of navigable areas.Although the distance of routes planned by ice-distance quantization model is relatively long,routes can be distributed in areas with light ice conditions as far as possible,and the safety of navigation is high. |
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