Greenland Icesheet CCI Experimental Ice Uplift/Subsidence from InSAR Line-of-sight velocity

The Experimental Ice Uplift/Subsidence from InSAR Line-of-sight velocity product is a prototype product containing time series of single-pair Sentinel-1 InSAR displacement measurements. The aim of this product is to provide a product with high temporal resolution tailored to study rapidly varying and transient ice uplift/subsidence phenomena, such as those associated with subglacial water transport. Observing such phenomena on the ice cap is challenging, as the InSAR method is sensitive only to displacements in the radar line-of-sight direction, and these contain contributions from both horizontal ice flow and subsidence/uplift of the ice surface, with the horizontal flow contribution typically being much larger, and the subsidence/uplift typically appearing only sporadically and on a much smaller spatial scale. With careful interpretation, however, the product can be used for tracing subglacial water propagation pathways (by assuming the subsidence/uplift is caused by subglacial water displacing the ice surface), and, in some cases, quantify the amount of water propagating. Despite its name, the LoS-IV product actually provides a time series of vertical displacement estimates (uplift/subsidence), derived from the InSAR LoS displacement under the assumption of stable horizontal ice flow. The product contains all information necessary to easily convert the provided uplift estimate back to LoS velocity, which could be relevant, for example, if multiple products acquired from different tracks were combined to derive both horizontal flow and vertical displacement. To support such calculations, also the line-of-sight vector elevation and azimuth angles are provided in the product.
The data presented here is a prototype data product from the Greenland Icesheet Climate Change Initiative (CCI+) Phase 2. It is described in Andersen, et.al.:"Episodic Subglacial Drainage Cascades Below the Northeast Greenland Ice Stream", DOI https://doi.org/10.1029/2023gl103240. Previously, isolated data from manually identified uplift events have been published (https://doi.org/10.11583/DTU.22060061.v1) along with the paper, whereas the present dataset contains the full-grid timeseries, in order to allow potential users to familiarize themselves with this new type of product.

基于合成孔径雷达干涉测量（InSAR）视线向速度的冰体抬升/沉降实验产品是一款原型产品，包含成对Sentinel-1 InSAR位移测量时间序列。该产品旨在提供高时间分辨率的数据集，以适配快速变化及瞬时性冰体抬升/沉降现象的研究，例如与冰下输水相关的此类现象。在冰盖之上观测此类现象极具挑战，因为InSAR仅对雷达视线方向的位移敏感，而此类位移同时包含冰体水平流动与冰面沉降/抬升的贡献，其中水平流动的贡献通常占比更大，且沉降/抬升现象往往仅零星出现，空间尺度也要小得多。然而，通过细致的解译，该产品可用于追踪冰下输水通道（假设沉降或抬升由冰下水体推挤冰面所致），在部分场景中还可量化输水的水体体积。尽管名为LoS-IV产品，但该产品实际提供的是垂直位移（抬升/沉降）估算时间序列，该序列基于稳定冰体水平流动的假设，由InSAR视线向位移推导而来。该产品包含将所提供的抬升估算值轻松转换回视线向速度所需的全部信息，例如在结合不同轨道获取的多份产品以同时推导水平流动与垂直位移时，该转换功能便具有实际意义。为支持此类计算，产品中同时提供了视线向矢量的仰角与方位角。
本次展示的数据为格陵兰冰盖气候变化倡议（CCI+）第二阶段的原型数据产品。该产品相关研究见于Andersen等人发表的《Episodic Subglacial Drainage Cascades Below the Northeast Greenland Ice Stream》，DOI链接为https://doi.org/10.1029/2023gl103240。此前，该团队曾随论文发布过人工识别抬升事件的孤立数据（https://doi.org/10.11583/DTU.22060061.v1），而本次数据集则包含全网格时间序列，以便潜在用户熟悉这类新型产品。