https://w3id.org/sciencelive/np/RALzO6a4kKOJYXVS-9pEY48i-PDe25x4eBlzTBjGh7n9Y/Head https://w3id.org/sciencelive/np/RALzO6a4kKOJYXVS-9pEY48i-PDe25x4eBlzTBjGh7n9Y http://www.nanopub.org/nschema#hasAssertion https://w3id.org/sciencelive/np/RALzO6a4kKOJYXVS-9pEY48i-PDe25x4eBlzTBjGh7n9Y/assertion https://w3id.org/sciencelive/np/RALzO6a4kKOJYXVS-9pEY48i-PDe25x4eBlzTBjGh7n9Y http://www.nanopub.org/nschema#hasProvenance https://w3id.org/sciencelive/np/RALzO6a4kKOJYXVS-9pEY48i-PDe25x4eBlzTBjGh7n9Y/provenance https://w3id.org/sciencelive/np/RALzO6a4kKOJYXVS-9pEY48i-PDe25x4eBlzTBjGh7n9Y http://www.nanopub.org/nschema#hasPublicationInfo https://w3id.org/sciencelive/np/RALzO6a4kKOJYXVS-9pEY48i-PDe25x4eBlzTBjGh7n9Y/pubinfo https://w3id.org/sciencelive/np/RALzO6a4kKOJYXVS-9pEY48i-PDe25x4eBlzTBjGh7n9Y http://www.w3.org/1999/02/22-rdf-syntax-ns#type http://www.nanopub.org/nschema#Nanopublication https://w3id.org/sciencelive/np/RALzO6a4kKOJYXVS-9pEY48i-PDe25x4eBlzTBjGh7n9Y/assertion https://w3id.org/sciencelive/np/RALzO6a4kKOJYXVS-9pEY48i-PDe25x4eBlzTBjGh7n9Y/langhovde-basal-lead-time-2022-outcome http://schema.org/endDate 2026-10-09 https://w3id.org/sciencelive/np/RALzO6a4kKOJYXVS-9pEY48i-PDe25x4eBlzTBjGh7n9Y/langhovde-basal-lead-time-2022-outcome http://www.w3.org/1999/02/22-rdf-syntax-ns#type https://w3id.org/sciencelive/o/terms/FORRT-Replication-Outcome https://w3id.org/sciencelive/np/RALzO6a4kKOJYXVS-9pEY48i-PDe25x4eBlzTBjGh7n9Y/langhovde-basal-lead-time-2022-outcome http://www.w3.org/2000/01/rdf-schema#label Basal pressure vs acceleration onsets at Langhovde Glacier, January 2022: inconclusive (one event) https://w3id.org/sciencelive/np/RALzO6a4kKOJYXVS-9pEY48i-PDe25x4eBlzTBjGh7n9Y/langhovde-basal-lead-time-2022-outcome https://w3id.org/sciencelive/o/terms/hasConclusionDescription This record cannot tell whether basal water pressure rises before grounded-ice acceleration. The claim is therefore neither supported nor contradicted. What is clear: - In the one instrumented event (2–6 January 2022), rain and melt came first: rain began at 01:50 UTC on 2 January, and the basal pressure rise followed about 19 h later in every processing. What is not clear: - The order of pressure and acceleration depends on the processing. - Centred smoothing of the published 15 min GNSS puts the speed rise about 8 h before the pressure rise. - The same smoothing of the reprocessed 1 s GNSS puts pressure about 6 h before speed. - Every past-only (causal) estimate is indeterminate, with spreads of more than ±10 h. Why sharper data did not resolve it: - The grounded and floating trunk stations share a ~12 h variability in speed that is larger than the event's speed-up. It is mostly not GNSS multipath and not a simple tidal response. - The borehole tilt sensor was still settling. The proposed held-out comparison of three nested models needs several events. In a single-event hold-out, adding basal pressure and uplift did not improve on weather and speed history. https://w3id.org/sciencelive/np/RALzO6a4kKOJYXVS-9pEY48i-PDe25x4eBlzTBjGh7n9Y/langhovde-basal-lead-time-2022-outcome https://w3id.org/sciencelive/o/terms/hasConfidenceLevel https://w3id.org/sciencelive/o/terms/LowConfidence https://w3id.org/sciencelive/np/RALzO6a4kKOJYXVS-9pEY48i-PDe25x4eBlzTBjGh7n9Y/langhovde-basal-lead-time-2022-outcome https://w3id.org/sciencelive/o/terms/hasEvidenceDescription Basal pressure and forcing: - BH2201 basal water level peaked at 51.0 m a.s.l. (97% of flotation) at 23:07 UTC on 3 January 2022; 50.95 m after the measured air-pressure correction. - Rain led the pressure rise by a median of 18.6–18.9 h (causal) and 20.8–23.4 h (centred), in 30–32 of 32 rule × bandwidth × reference combinations. Pressure to GNSS1 (grounded) speed, onset leads (positive = pressure first): - 15 min deposit: - centred median −8.0 h ("level lags", 20 of 30 combinations); - robust causal median +0.6 h, 13 earlier and 13 later ("indeterminate"). - 1 s kinematic GNSS (100% fixed; 5.7 mm and 3.7 mm horizontal SD against the published 15 min positions): - centred median +5.75 h ("level leads", 16 of 32 combinations defined); - robust causal, corrected for detection delay, median +3.6 h, range −7.6 to +36.1 h, 13 of 32 defined ("indeterminate"); - after sidereal filtering and tidal correction, still "indeterminate" (median +4.9 to +6.8 h). - Detection delay of the causal speed estimators on synthetic onsets: 3.0–8.9 h (15 min data); 3.4 h (1 s data, h = 3 h). Sub-daily variability at GNSS1: - 12–13 h period, SD 0.047 m/d at h = 1 h, against an event speed-up of about 0.03 m/d (12.5%). - Sidereal filtering removed 14% (GNSS1) and 32% (GNSS2) of the 10–15 h variance. - A tidal model fitted before the event explained R² = 0.001 and 0.07 afterwards. - GNSS1 and GNSS2 band-passed (6–18 h) residuals correlate at r = 0.97 (east), 0.72 (north) and 0.84 (up). GNSS1 and receiver LG1 correlate at 0.17, 0.23 and 0.00. Bed tilt and nested models: - Bed tilt in BH2201 drifted about 0.9 mrad/h, with 13 steps above 5 mrad (largest 77 mrad). - Nested models, one-event hold-out at GNSS1 (h = 3 h): skill of the pressure-and-uplift model relative to weather-and-speed was −0.24, −0.05 and −0.01 at 1, 3 and 6 h horizons. - Rolling-origin forecasts began only after the event onset. https://w3id.org/sciencelive/np/RALzO6a4kKOJYXVS-9pEY48i-PDe25x4eBlzTBjGh7n9Y/langhovde-basal-lead-time-2022-outcome https://w3id.org/sciencelive/o/terms/hasLimitationsDescription - One event, at one site, in one season. No conclusion about lead time in general, or at other glaciers, can be drawn. - The proposed predictive test was not run. The lead labels describe this event only. - Basal pressure comes from one borehole, about 190 m from the grounded GNSS station. - Onset times depend on the smoothing and the onset rule. All combinations are reported, not a chosen one. - The origin of the ~12 h speed variability is not established: real trunk motion is likely, but differential troposphere cannot be excluded. What the two extra GNSS receivers stand on is not documented in the archive. - The bed-tilt sensor was settling (drift and steps), so its onsets were withdrawn. 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