NOAA@NSIDC would like to make you aware of a change to the data used to produce the U.S. National Ice Center Arctic and Antarctic Sea Ice Concentration and Climatologies in Gridded Format, Version 1 data set.
As of October 2021, USNIC revised the way they indicate first-year ice (FYI) on the Arctic weekly ice charts that are the basis for this data set. USNIC has chosen to only use WMO SIGRID code “86, First-Year Ice” for all FYI designations. Thus, all charts on the USNIC website, as well as the SIGRID-3 format version of those charts that serve as input for this product, will have FYI indicated by 86 only. Gradations within the first-year category will no longer be routinely charted. These sub-categories are SIGRID codes 87, 88, 89, 91, and 93 which correspond to thin FYI, thin FYI - stage1, thin FYI - stage2, medium FYI, and thick FYI, respectively.
USNIC has made this change to reduce the time analysts need for charting FYI. The U.S. National Ice Center Arctic and Antarctic Sea Ice Concentration and Climatologies in Gridded Format data set is not affected by this change because this product already groups all FYI categories into one. However, this is a change to the input data for the product, and we have noted the change in the User Guide. USNIC invites operational chart users to contact them if they need special support for operations because of this change at email: nic.cdo@noaa.gov.
To access these data and view the documentation, visit the data set landing page. Data Set DOI: https://doi.org/10.7265/46cc-3952