Machine Learning Eliminates Reanalysis Warm Bias and Reveals Weaker Winter Surface Cooling Over Arctic Sea Ice
Abstract The surface energy budget governs Arctic sea‐ice growth/melt, yet observations are sparse, and reanalysis data sets suffer from systematic biases. Here, we train a neural network with observational data to bias‐correct hourly ERA5 fluxes over Arctic ice‐covered regions (≥70°N; sea‐ice concentration >80%) for 1994–2024. Training data cover two full seasonal cycles and different sea‐ice regimes. The neural network reduces RMSE for net shortwave radiation by ∼40%, downward longwave radiation by ∼16% and the total surface energy budget by ∼55%, eliminating the wintertime warm bias of ∼4 K in ERA5. Wintertime surface cooling is reduced by ∼50%, yielding thermodynamic ice‐growth estimates of ∼80–120 cm, consistent with SMOS–CryoSat satellite thickness increases and in contrast to the 150–200 cm growth implied by ERA5. Our bias‐corrected data capture the observed clear/cloudy states of the winter boundary layer and can be used to study Arctic climatology, evaluate climate models and drive sea‐ice‐ocean models.
Authors
- Akil Hossain (ORCID: https://orcid.org/0000-0001-8340-3056)
- Felix Pithan (ORCID: https://orcid.org/0000-0003-4382-3077)
- Christopher J. Cox (ORCID: https://orcid.org/0000-0003-2203-7173)
- Paul Keil (ORCID: https://orcid.org/0000-0002-6502-4148)
- Jutta Vüllers (ORCID: https://orcid.org/0000-0002-6483-1159)
- Von P. Walden (ORCID: https://orcid.org/0000-0003-3857-4416)
- Stephen R. Hudson (ORCID: https://orcid.org/0000-0002-6498-9167)
- Michael Tjernström (ORCID: https://orcid.org/0000-0002-6908-7410)
- Mats A. Granskog (ORCID: https://orcid.org/0000-0002-5035-4347)
- Michael Gallagher (ORCID: https://orcid.org/0000-0002-7457-108X)
- Heather Guy (ORCID: https://orcid.org/0000-0003-3525-0766)
- Ian M. Brooks (ORCID: https://orcid.org/0000-0002-5051-1322)
- Matthew D. Shupe (ORCID: https://orcid.org/0000-0002-0973-9982)
- Harsh Grover
- P. Ola G. Persson
Institutions
- Karlsruhe Institute of Technology (DE)
- Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung (DE)
- National Oceanic and Atmospheric Administration (US)
- University of Leeds (GB)
- Cooperative Institute for Research in Environmental Sciences (US)
- University of Bremen (DE)
- University of Colorado Boulder (US)
- German Climate Computing Centre (DE)
- National Centre for Atmospheric Science (GB)
- NOAA Physical Sciences Laboratory (US)
- Helmholtz-Zentrum Hereon (DE)
- Bolin Centre for Climate Research (SE)
- Washington State University (US)
- Norwegian Polar Institute (NO)
Publication Details
- Journal
- Geophysical Research Letters
- Published
- 2026-06-19
- DOI
- https://doi.org/10.1029/2025gl121289
- Primary Topic
- Arctic and Antarctic ice dynamics
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- Polarforskningssekretariatet
- Global Ocean Monitoring and Observing Program