Age of sea ice derived from weekly averaged ice motion vectors. A value of N indicates ice aged N-1 to N years. A value of 20 represents land; 21 represents ocean cells where ice age was not calculated. Week of maximum extent chosen based on NSDIC's Sea Ice Index 5-day average. === Original Data Source === https://nsidc.org/data/nsidc-0611 The full original data set provides weekly estimates of sea ice age for the Arctic Ocean derived from remotely sensed sea ice motion and sea ice extent. The temporal coverage for this data set is January 1984 through December 2019. For more recent data, see the Quicklook Arctic Weekly EASE-Grid Sea Ice Age data product (https://nsidc.org/data/nsidc-0749). QGreenland displays a subset of data to coincide with information contained in other sea ice layers. Citation: Tschudi, M., W. N. Meier, J. S. Stewart, C. Fowler, and J. Maslanik. 2019. EASE-Grid Sea Ice Age, Version 4. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/UTAV7490FEPB. 2021/01/05. Citation URL: https://doi.org/10.5067/UTAV7490FEPB