{ "abstract": "On 26 August 2026 a compound bedrock-and-glacier failure on the northern flank of the Langtang Lirung–Tsangbu Ri (Kimshung) massif, Nepal–China border, generated a rock–ice avalanche and a catastrophic downstream flood along the Bhotekoshi–Trishuli river system. A pre-event Sentinel-2 shortwave-infrared (SWIR2–NIR–Red) composite (12 August 2026) shows a sharply bounded, strongly saturated blue-to-cyan patch on the debris-mantled glacier tongue below the slope that failed fourteen days later — a real, reproducible visual feature that a naive reading might treat as a wetness precursor. That reading is tested here against two independent, calibrated baselines built from a 27-year (2000–2026), multi-sensor Landsat/Sentinel-2 reconstruction in Google Earth Engine, using a Shortwave-Infrared Wetness Index, SWI = (NIR − SWIR2)/(NIR + SWIR2). First, a within-glacier climatological baseline, computed directly against Tsangbu Ri’s own official RGI 7.0 outline (RGI2000-v7.0-G-15-05732): the 2026 ablation-season SWI (0.758) against the catchment’s own 2000–2025 record (0.773 ± 0.084) gives z = −0.19 — a small negative departure, not the positive anomaly the visual composite suggests, and modest even in within-glacier terms alone. Second, and more decisively, an across-glacier false-positive calibration that the remote-sensing glacier-hazard literature has generally lacked: the same pipeline applied to 17 matched, non-collapsed control glaciers in the same RGI region (South Asia East), selected programmatically by elevation, area, and aspect similarity to Tsangbu Ri’s own confirmed polygon, with sensor cross-calibration and a fixed observation-density correction applied identically to target and controls. Against this empirical null distribution, Tsangbu Ri’s 2026 departure sits at the 59th percentile (Figure 6; 95% CI 33–82%, Clopper-Pearson) — ten of seventeen independently selected control glaciers show an equal-or-more-negative departure, and eleven of seventeen (65%) independently show a negative 2026 departure of their own, consistent with a regionally shared dry pattern rather than a site-specific signal. Twelve of seventeen controls (71%) show a larger absolute departure, in either direction, than Tsangbu Ri itself. The SWIR mechanism itself — sensitivity to standing/ponded liquid water and to melt-metamorphosed, coarse-grained wet snow or firn via strong SWIR2 absorption — is interpreted here as physically well founded and literature-consistent. For the Tsangbu Ri case specifically, however, neither the within-glacier nor the calibrated across-glacier evidence supports a SWIR-based wetness precursor at the failure site. This is reported as a methodologically load-bearing finding: a visually compelling single-date spectral anomaly, and even an uncalibrated within-glacier z-score, are not sufficient grounds for a precursor claim without a matched-control false-positive rate — and the calibrated pipeline, now run directly against Tsangbu Ri’s own confirmed RGI polygon and validated for reproducibility, is set out here as one that would extend this test to a larger control sample and to other High Mountain Asia compound failures.", "abstract_shown": true, "affiliations": [], "article_type": null, "arxiv": null, "author_total": 1, "authors": [ { "name": "Prakash Pradhan" } ], "bibtex": "https://research.draconitic.com/paper/7cjt226yhg2da.bib", "cited_by": 0, "doi": "10.31223/x56f8s", "fulltext_url": null, "id": "7cjt226yhg2da", "issns": [], "landing_url": "https://eartharxiv.org/repository/view/15093/", "language": null, "licence": "CC-BY-NC-4.0", "licence_label": "CC BY-NC 4.0", "licence_source": "article", "licence_url": "https://creativecommons.org/licenses/by-nc/4.0/legalcode", "metadata_licence": null, "native_subjects": [ [ "bepress", "Applied Statistics" ], [ "bepress", "Geographic Information Sciences" ], [ "bepress", "Geology" ], [ "bepress", "Geomorphology" ], [ "bepress", "Glaciology" ], [ "bepress", "Google Earth Engine" ], [ "bepress", "Hydrology" ], [ "bepress", "Landsat" ], [ "bepress", "Langtang Himal" ], [ "bepress", "Planetary Geology" ], [ "bepress", "Planetary Glaciology" ], [ "bepress", "Remote Sensing" ], [ "bepress", "Sentinel-2" ], [ "bepress", "Spatial Science" ], [ "bepress", "Tectonics and Structure" ], [ "bepress", "early warning" ], [ "bepress", "false-positive calibration" ], [ "bepress", "glacial lake outburst flood" ], [ "bepress", "glacier collapse" ], [ "bepress", "hindcast validation" ], [ "bepress", "rock–ice avalanche" ], [ "bepress", "shortwave infrared" ], [ "bepress", "supraglacial lake" ], [ "bepress", "wet snow" ], [ "openalex", "2308|Landslides and related hazards" ] ], "openalex": "W7213666802", "pdf_url": "https://eartharxiv.org/repository/object/15093/download/26193/", "pmcid": null, "pmid": null, "published": "2026-09-19", "publisher": null, "ris": "https://research.draconitic.com/paper/7cjt226yhg2da.ris", "sources": [ { "first_seen": "2026-10-30T12:17:36Z", "native_id": "15093", "source": "eartharxiv", "url": "https://eartharxiv.org/repository/view/15093/" } ], "subjects": [ { "field": "earth", "origin": "bepress:Geology", "subfield": "geology-geochemistry" }, { "field": "earth", "origin": "bepress:Tectonics and Structure", "subfield": "geophysics" }, { "field": "earth", "origin": "bepress:Hydrology", "subfield": "hydrology-soils" }, { "field": "earth", "origin": "bepress:Glaciology", "subfield": "oceanography" }, { "field": "mathematics", "origin": "bepress:Applied Statistics", "subfield": "statistics" } ], "title": "Was the Pre-Event SWIR Anomaly at Tsangbu Ri a Genuine Glacier-Collapse Precursor? A Calibrated Multi-Glacier Test of the 2026 Case", "title_text": "Was the Pre-Event SWIR Anomaly at Tsangbu Ri a Genuine Glacier-Collapse Precursor? A Calibrated Multi-Glacier Test of the 2026 Case", "type": "preprint", "updated_at": "2026-10-30T12:17:36Z", "url": "https://research.draconitic.com/paper/7cjt226yhg2da", "venue": "EarthArXiv", "versions": [] }