Progressive Antarctic ice shelf disintegration revealed by iceberg fluxes

This repository contains the code and supporting spatial files used to establish a basin-based analysis framework for examining the relationships among Antarctic ice-shelf basal melting, surface damage, and iceberg production. The workflow is organized into two main directories. 1. Basin-based analysis framework This directory contains the workflow used to delineate unique marine sectors corresponding to the 26 major Antarctic drainage basins and several individual ice shelves. The Antarctic continental shelf was first discretized into a regular grid with a spatial resolution of 50 km × 50 km. Based on this grid, cells located near the ice-shelf fronts were manually selected as basin seed regions and stored in seed_grid_manual/seed_grid_template.shp. These seed cells represent the initial oceanward membership of each drainage basin or individual ice shelf. Marine-sector boundaries were then delineated using the BYU iceberg trajectory records provided as CSV files in the BYU_iceberg_track directory. When an iceberg trajectory intersected the seed region of a basin, all grid cells visited by that trajectory during the subsequent year were counted as votes for that basin. Votes from all available trajectories were accumulated, and each grid cell was initially assigned to the basin receiving the largest number of votes. The BYU trajectories are used here to represent regional-scale ocean circulation and iceberg transport pathways rather than the drift histories of individual icebergs. A spatial-connectivity constraint was subsequently applied to retain only cells connected to their corresponding seed regions. Cells that remained unassigned were filled iteratively using an eight-neighbour majority rule. Where neighbouring cells provided equal support for multiple basins, the cell was assigned according to its proximity and connectivity to the nearest seed region. The resulting gridded marine-sector partition was manually inspected and smoothed. The final basin-based analysis framework is provided as: step3 manual boundary smoothing/Basin.shp This shapefile defines the unique marine sector associated with each major drainage basin and selected individual ice shelves and is used as the spatial basis for the subsequent iceberg and ice-shelf analyses. 2. Data analysis This directory contains the scripts used to quantify iceberg and ice-shelf characteristics within the basin-based analysis framework. Ice-shelf basal-melt and surface-damage datasets provided by Adusumilli et al. and Izeboud et al., respectively, were spatially aggregated for each basin. The analysis derives representative annual or multi-year mean basal-melt rates and surface-damage metrics for the ice shelves associated with each basin. Annual circum-Antarctic iceberg datasets from 2018 to 2023 were then intersected with the corresponding marine sectors. Icebergs were assigned to individual basins according to the locations of their polygon centroids. Giant icebergs with areas of at least 1,000 km² were excluded because they primarily represent episodic large-calving events associated with long-term stress accumulation, rather than the sustained fragmentation processes examined in this study. For each basin and year, the scripts calculate 2018-2023 means: iceberg number; iceberg mass; the power-law slope of the iceberg size distribution. These basin-scale statistics are compared with ice-shelf basal-melt intensity and structural damage to establish observational links between oceanic iceberg distributions and the state of their source ice shelves.