Grounding Line Products of the Antarctic Ice Sheet Climate Change Initiative Project

Abstract

The grounding line location (GLL) is a geophysical product of the Antarctic Ice Sheet Climate Change Initiative (AIS_cci) ESA project. It has been derived for major ice streams and glaciers around the continent through the InSAR technique, covering the period 1994 – 2023 from ERS-1/2 era to Sentinel-1 A/B. The AIS_cci GLL product’s metadata annotations include information about model-based ocean tide levels and air pressure at satellite acquisition times for meaningful and interpretable comparison of GLLs. The position of the grounding line shifts in two distinct ways: (a) over short timescales, it experiences temporary migration caused by vertical uplift of ice shelves due to ocean tides, and (b) over longer timescales, it undergoes more consistent migration, typically retreating landward as a result of ice thinning. Recent grounding line products have acknowledged the short-term variation of the grounding line position, annotating a grounding zone instead of single grounding lines (Rignot et al., 2023). In line with the need to quantify the grounding line movements, we propose an additional parameter for the AIS_cci GLL, the Grounding Line Migration (GLM). The AIS_cci GLM product aims to provide short-term temporal variations within the grounding zone and separate this short-term position change from a long-term climatic-induced relocation of the grounding zone. We use the time-annotated AIS_cci GLLs to derive an average grounding line for a certain period (e.g. one year). Our custom procedure fills the gaps with grounding lines from manual and machine-learning delineations (Ramanath Tarekere et al., 2024) of temporally close Sentinel-1 DInSAR interferograms and external datasets. The next step for GLM generation is to investigate various metrics to quantify the distance between two or more GLLs acquired in different periods. In the present work, we plan to show preliminary results over a test site prone to grounding line retreat with a dense time series of GLLs and outline the specifications and contents of the new GLM product.