Code for Dynamic redistribution enables seasonal reversal of Arctic sea-ice anomalies

This repository contains the code and intermediate data used to reproduce the main and supplementary figures. The Code folder includes scripts for calculating intermediate variables from the original inputs and generating the figures. The Data folder contains the final plotting data in NumPy (.npy) format. Detailed instructions are provided in README.txt. Because of their large size, the original input datasets are not included in the Code folder or this deposit. They can be accessed and downloaded through the open-access links provided in the manuscript’s Data Availability statement. Data availability Satellite sea-ice concentration data were obtained from the NASA National Snow and Ice Data Center (NSIDC) Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I–SSMIS Passive Microwave Data, Version 2 (NSIDC-0051; https://doi.org/10.5067/MPYG15WAA4WX). Sea-ice motion data were obtained from the NSIDC Quicklook Arctic Weekly EASE-Grid Sea Ice Motion Vectors, Version 1 (NSIDC-0748; https://doi.org/10.5067/O0XI8PPYEZJ6). ERA5 monthly mean single-level fields are available from the Copernicus Climate Data Store (https://doi.org/10.24381/cds.f17050d7), and ERA5 monthly mean pressure-level fields are available at https://doi.org/10.24381/cds.6860a573. The INTAROS-opt ocean-sea-ice reanalysis used for the process-based sea-ice tendency diagnostics was produced using the adjoint-based MITgcm system described by Lyu et al. (2021, 2025). The model configuration and outputs associated with the Lyu et al. (2025) experiments are publicly available through Zenodo (https://doi.org/10.5281/zenodo.14584780), with the modified MITgcm code available at https://doi.org/10.5281/zenodo.14584929. The extended 2007-2025 INTAROS-opt fields used in this study are available at http://dx.doi.org/10.12157/IOCAS.20260819.001. Lyu, G., Koehl, A., Serra, N., Stammer, D. & Xie, J. Arctic ocean–sea ice reanalysis for the period 2007–2016 using the adjoint method. Quarterly Journal of the Royal Meteorological Society 147, 1908–1929 (2021). Lyu, G. et al. Adjoint-based simultaneous state and parameter estimation in an Arctic Sea Ice-Ocean Model using MITgcm (c63m). Geosci. Model Dev. 18, 9451–9468 (2025).