Average surface mass balance (SMB) components at 1 km for the Canadian Arctic Archipelago (1958-1995 and 1996-2015), links to RACMO2.3 model results in NetCDF format

The Canadian Arctic Archipelago (CAA) comprises multiple small glaciers and ice caps mostly concentrated on Ellesmere and Baffin Islands in the northern (NCAA) and southern parts (SCAA) of the archipelago, respectively. Because these glaciers are small and show complex geometries, current regional climate models, using 5 to 20 km horizontal resolution, do not properly resolve surface mass balance (SMB) patterns. Here, we present a 58-year (1958-2015) reconstruction of daily SMB of the CAA, statistically downscaled to 1 km from the output of the regional climate model RACMO2.3 at 11 km. By correcting for biases in elevation and ice albedo, the downscaling method significantly improves runoff estimates over narrow outlet glaciers and isolated ice fields. Since the last two decades, NCAA and SCAA glaciers have experienced warmer conditions (+1.1°C) resulting in continued mass loss of 28.2 ± 11.5 Gt yr-1 and 22.0 ± 4.5 Gt yr-1 respectively, more than doubling (11.9 Gt yr-1) and doubling (11.9 Gt yr-1) the pre-1996 average. While the interior of NCAA ice caps can still buffer most of the additional melt, the lack of a perennial firn area over low-lying SCAA glaciers caused uninterrupted mass loss since the 1980s. In the absence of significant refreezing capacity, this indicates inevitable disappearance of these highly sensitive glaciers.

加拿大北极群岛（Canadian Arctic Archipelago，CAA）由众多小型冰川与冰盖组成，其主体分别集中于群岛北部的埃尔斯米尔岛与南部的巴芬岛，对应区域分别为北加拿大北极群岛（NCAA）与南加拿大北极群岛（SCAA）。由于这些冰川体量较小且几何形态复杂，当前采用5~20 km水平分辨率的区域气候模式（regional climate model）无法准确解析其表面物质平衡（surface mass balance，SMB）格局。本研究基于水平分辨率为11 km的区域气候模式RACMO2.3的输出结果，通过统计降尺度（statistically downscaled）方法，构建了CAA地区1958—2015年共58年的日尺度表面物质平衡数据集。该方法通过校正高程与冰反照率的偏差，显著提升了狭窄出山冰川与孤立冰盖区的径流估算精度。近二十年来，NCAA与SCAA冰川均经历了升温过程（升温幅度达+1.1℃），分别以28.2±11.5 Gt yr⁻¹与22.0±4.5 Gt yr⁻¹的速率持续发生物质亏损，较1996年前的平均速率（11.9 Gt yr⁻¹）分别提升至两倍以上与两倍。尽管NCAA冰盖内部仍可缓冲大部分额外消融，但地势较低的SCAA冰川缺乏永久粒雪层区（perennial firn area），自20世纪80年代以来便持续发生物质亏损。由于缺乏显著的融水重冻结能力（refreezing capacity），这意味着这些高度敏感的冰川将不可避免地走向消亡。