Ice displacement anomalies documented in "Episodic Subglacial Drainage Outbursts Below the Northeast Greenland Ice Stream"

This repository contains data documenting ice displacements resulting from a cascade of subglacial drainage outbursts below the Northeast Greenland Ice Stream (NEGIS). The data is presented and analyzed in the manuscript: "Andersen et al. (2023) Episodic Subglacial Drainage Outbursts Below the Northeast Greenland Ice Stream" (submitted to Geophysical Research Letters).

The repository contains the following:

- UpliftEvents_vlosDiff_T112D.zip a collection of GeoTIFF files, each containing measurements of ice displacement anomalies for a local inferred uplift event. The displacements are measured with the DInSAR (Differential Synthetic Aperture Radar Interferometry) method using Sentinel-1 satellite data. The displacement anomalies are projected to the slanted satellite line-of-sight vector, and are given as a velocity anomaly (in units of meters/year), as this is the output of the applied DInSAR algorithm. Converting the observed line-of-sight anomaly, vLoS, to a vertical displacement, dvert, is then done through:

               dvert = vLoS / cos(a) * T      (1)

where a is the local incidence angle of the satellite line-of-sight and T is the temporal baseline (6 days for all measurements). All measurements are from the descending Sentinel-1 track 112. Filenames follow the format "vlosDiff__YYYYMMDD_YYYYMMDD_X.tif", where the two dates reflect the first and second acquisition dates used to make the measurement and X refers to the event number/index (some retrievals contain multiple individual uplift events). Measurements are provided on a 50x50 m grid (EPSG:3413).

- T112D_incidence_angle.tif GeoTIFF file containing the incidence angle for Sentinel-1 track 112 over the entire study area (can be used to convert line-of-sight anomaly measurements to vertical displacements, as per eq. (1) above). Provided in 50x50 m grid (EPSG:3413) in units of degrees.

- InferredDrainagePathways.zip Subglacial drainage propagation pathways inferred from all DInSAR measurements carried out in the study (cf. Figure 1 of the manuscript). 

Corresponding author: Jonas Kvist Andersen ([e-mail])

本存储库收录了记录东北格陵兰冰流（NEGIS）下冰川融水排水爆发引起的冰面位移的数据集。这些数据在以下手稿中进行了呈现与分析：Andersen 等人（2023年）撰写的《东北格陵兰冰流下周期性冰川融水排水爆发》（已投稿至《地球物理研究快报》）。存储库包含以下内容：

- UpliftEvents_vlosDiff_T112D.zip：包含一系列 GeoTIFF 文件，每个文件均记录了局部推断的抬升事件引起的冰位移异常。位移是通过使用 Sentinel-1 卫星数据，采用差分合成孔径雷达干涉测量法（DInSAR）进行测量的。位移异常被投影到斜向卫星视线矢量上，并以速度异常（单位为米/年）的形式给出，这是应用 DInSAR 算法得到的输出。通过以下公式将观测到的视线异常，vLoS，转换为垂直位移，dvert：

               dvert = vLoS / cos(a) * T

其中，a 是卫星视线在局部的入射角，T 是时间基线（所有测量均为 6 天）。所有测量均来自下降的 Sentinel-1 轨道 112。文件名遵循“vlosDiff__YYYYMMDD_YYYYMMDD_X.tif”的格式，其中两个日期分别反映了用于测量的首次和第二次获取日期，而 X 则代表事件编号/索引（一些检索包含多个单个抬升事件）。测量以 50x50 米的网格（EPSG:3413）提供。

- T112D_incidence_angle.tif：包含整个研究区域 Sentinel-1 轨道 112 的入射角的 GeoTIFF 文件（可用于将视线异常测量转换为垂直位移，如上述公式（1）所示）。以 50x50 米的网格（EPSG:3413）提供，单位为度。

- InferredDrainagePathways.zip：从研究中进行的所有 DInSAR 测量推断出的冰川融水传播路径（参照手稿中的图 1）。

对应作者：Jonas Kvist Andersen（[e-mail]）