A climate data record of sea ice age using Lagrangian advection of a triangular mesh

Abstract. We present LM-SIAge, a new Climate Data Record (CDR) of Arctic sea ice age spanning the period from 1991 through 2024. The dataset is based on a novel Lagrangian advection scheme applied to a triangular mesh, which conserves sea ice age fractions and reduces numerical diffusion compared to the previous Eulerian approach. LM-SIAge is derived from satellite observations of sea ice concentration and drift, and represents fractional age classes per grid cell. The record captures the spatial and temporal evolution of first- to sixth-year ice, including uncertainty estimates that account for both sea ice concentration and drift uncertainties. We compare LM-SIAge with existing products from NSIDC and C3S, finding consistent large-scale trends – such as the decline of older ice – but also identifying systematic differences. Trend analysis confirms a significant reduction in sea ice age and a general increase in the area of first-year ice. Validation with ice drifting buoys indicates good consistency (LM-SIAge does not underestimate max age of the buoys in 98.3 % of cases), with most discrepancies occurring near the ice edge. The NSIDC product does not underestimate the age in 96.4 % of cases. The LM-SIAge dataset improves the observational basis for Arctic monitoring and contributes to the Global Climate Observing System (GCOS) Essential Climate Variables. It is publicly available and suitable for climate studies, model evaluation, and data assimilation (https://doi.org/10.21343/sqvr-rq75, Korosov and Edel, 2026).