Consistent and continuous data on glacier surface velocity are important inputs to time series analyses, numerical ice dynamic modeling and glacier mass flux computations. Since 2014, repeat-pass synthetic aperture radar (SAR) data have been acquired by the Sentinel-1 satellite constellation as part of the Copernicus program of the EU (European Union) and ESA (European Space Agency). It enables global, near-real-time-like and fully automatic processing of glacier surface velocity fields at up to 6 d temporal resolution, independent of weather conditions, season and daylight. We present a new global data set of glacier surface velocities that comprises continuously updated scene-pair velocity fields, as well as monthly and annually averaged velocity mosaics at 200 m spatial resolution. The velocity information is derived from archived and new Sentinel-1 SAR acquisitions by applying a well-established intensity offset tracking technique. The data set covers 12 major glacierized regions outside the polar ice sheets and is generated in an HPC (high-performance computing) environment at the University of Erlangen-Nuremberg. The velocity products are freely accessible via an interactive web portal that provides capabilities for download and simple online analyses: http://retreat.geographie.uni-erlangen.de (last access: 6 October 2021). In this paper, we give information on the data processing and how to access the data. For the example region of Svalbard, we demonstrate the potential of our products for velocity time series analyses at very high temporal resolution and assess the quality of our velocity products by comparing them to those generated from very high-resolution TerraSAR-X SAR and Landsat-8 optical (ITS_LIVE, GoLIVE) data. The subset of Sentinel-1 velocities for Svalbard analyzed in this paper is accessible via the GFZ Potsdam Data Services under the DOI https://doi.org/10.5880/fidgeo.2021.016 (Friedl et al., 2021). We find that Landsat-8 and Sentinel-1 annual velocity mosaics are in an overall good agreement, but speckle tracking on Sentinel-1 6 d repeat acquisitions derives more reliable velocity measurements over featureless and slow-moving areas than the optical data. Additionally, uncertainties of 12 d repeat Sentinel-1 mid-glacier scene-pair velocities have less than half (< 0.08 m d⁻¹) of the uncertainties derived for 16 d repeat Landsat-8 data (0.17–0.18 m d⁻¹).

中文翻译：

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来自 Sentinel-1 数据的冰川表面速度的全球时间序列和时间镶嵌

冰川表面速度的一致和连续数据是时间序列分析、数值冰动态建模和冰川质量通量计算的重要输入。自 2014 年以来，作为欧盟（欧盟）和欧空局（欧洲航天局）哥白尼计划的一部分，Sentinel-1 卫星星座已获取重复通过合成孔径雷达 (SAR) 数据。它能够以高达 6 d 的时间分辨率对冰川表面速度场进行全局、近实时和全自动处理，不受天气条件、季节和日光的影响。我们提出了一个新的全球冰川表面速度数据集，其中包括不断更新的场景对速度场，以及 200 m 空间分辨率下的月度和年度平均速度镶嵌图。通过应用成熟的强度偏移跟踪技术，速度信息来自存档的和新的 Sentinel-1 SAR 采集。该数据集涵盖极地冰盖外的 12 个主要冰川区域，是在埃尔兰根-纽伦堡大学的 HPC（高性能计算）环境中生成的。速度产品可通过交互式门户网站免费访问，该门户提供下载和简单的在线分析功能：http://retreat.geographie.uni-erlangen.de（最后访问时间：2021 年 10 月 6 日）。在本文中，我们提供了有关数据处理和如何访问数据的信息。对于斯瓦尔巴群岛的示例区域，我们展示了我们的产品在非常高的时间分辨率下进行速度时间序列分析的潜力，并通过将它们与从非常高分辨率的 TerraSAR-X SAR 和陆地卫星生成的产品进行比较来评估我们的速度产品的质量。 8 光（ITS_LIVE、GoLIVE）数据。本文中分析的斯瓦尔巴群岛 Sentinel-1 速度子集可通过 DOI https://doi.org/10.5880/fidgeo.2021.016（Friedl 等人，2021 年）下的 GFZ 波茨坦数据服务访问。我们发现 Landsat-8 和 Sentinel-1 年速度镶嵌图总体上非常一致，但是，与光学数据相比，Sentinel-1 6 d 重复采集上的斑点跟踪在无特征和缓慢移动的区域上获得了更可靠的速度测量值。此外，12 天重复 Sentinel-1 中冰川场景对速度的不确定性不到一半（<  0.08 m d ^-1 ) 的 16 天重复 Landsat-8 数据 (0.17–0.18 m d ^-1 )的不确定性。