Abstract

Landfast ice (LFI) is a prominent climatological feature in the Canadian Arctic. LFI is generally defined as immobile near-shore ice that remains fast along the coast and forms seaward from the land. It affects the coastline dynamics, is important for the near-shore ecosystems, wildlife, and human socio-economic activities. A method is proposed for mapping the LFI using time series of 10-day clear-sky composites derived at the Canada Center for Remote Sensing (CCRS) from the Moderate Resolution Imaging Spectroradiometer (MODIS) 250-m imagery. The delineation of coastal zone ice utilizes simultaneous analysis of the mean and standard deviation of MODIS monthly reflectance maps. The application of this method is demonstrated for a 20-year period (2000–2019) over the coastal zone of Banks Island in the Beaufort Sea. Detailed analyses have been conducted for three LFI parameters: (1) the total area (spatial extent) occupied by LFI; (2) the distance from the coast to the outer seaward LFI edge, and (3) the water depth at the outer seaward LFI edge. Comparison with the Canadian Ice Service (CIS) data demonstrates good agreement. The average correlation coefficients between CIS and CCRS time series in April-June, when the area reaches a maximum, are equal to 0.87–0.88. The mean differences (CIS-CCRS) are 344 km² (5,464 km² vs 5,120 km²) or 6.3% for the spatial extent; 1.3 km (17.6 km vs 16.3 km) or 7.4% for the distance; −2.7 m (−27.4 m vs −24.7 m) or 10% for the water depth. Because the CCRS method uses monthly statistics, it tends to exclude potentially more mobile continuous landfast ice zones than the CIS analysis which is based on data collected on a specific date. The long-term trends of the LFI seasonal cycle in our region of interest since 2000 have shown a tendency for an earlier break-up, later onset, and longer ice-free period; however, these trends are not statistically significant.

摘要

陆冰（LFI）是加拿大北极地区的主要气候特征。LFI通常被定义为不动的近岸冰块，它沿海岸保持快速运动并从陆地向海形成。它影响海岸线动态，对于近岸生态系统，野生动植物和人类社会经济活动非常重要。提出了一种方法，该方法使用加拿大遥感中心（CCRS）从中分辨率成像分光光度计（MODIS）250米图像中得出的10天晴空复合图像的时间序列来绘制LFI。海岸带冰的划定利用MODIS月反射率图的均值和标准差的同步分析。该方法的应用在波弗特海的班克斯岛沿海地区进行了为期20年（2000-2019年）的演示。已经对三个LFI参数进行了详细的分析：（1）LFI占用的总面积（空间范围）；（2）从海岸到外侧LFI边缘的距离，以及（3）在外侧LFI边缘的水深。与加拿大冰服务局（CIS）数据的比较显示出良好的一致性。当该区域达到最大值时，4月至6月CIS和CCRS时间序列之间的平均相关系数等于0.87–0.88。平均差异（CIS-CCRS）为344公里 当该区域达到最大值时，4月至6月CIS和CCRS时间序列之间的平均相关系数等于0.87–0.88。平均差异（CIS-CCRS）为344公里 当该区域达到最大值时，4月至6月CIS和CCRS时间序列之间的平均相关系数等于0.87–0.88。平均差异（CIS-CCRS）为344公里²（5,464 km ²对5,120 km ²），或者在空间范围上为6.3％；1.3 km（17.6 km vs 16.3 km），或者距离的7.4％；-2.7 m（-27.4 m vs -24.7 m）或水深的10％。由于CCRS方法使用月度统计数据，因此与基于特定日期收集的数据的CIS分析相比，它趋向于排除可能更多的移动连续陆上冰区。自2000年以来，我们关注区域的LFI季节周期的长期趋势显示出有更早的破裂，更晚的发作和更长的无冰期的趋势；但是，这些趋势在统计上并不显着。