On June 2nd 2021, WMC-Beijing launches Arctic sea ice and boreal summer intra-seasonal oscillation (BSISO) monitoring products developed by Beijing Climate Center.

The Arctic sea ice cover has rapidly declined in the past three decades, which could exert substantial impact on the remote large-scale atmospheric circulation and surface weather and climate in the extratropical Northern Hemisphere. To measure the Arctic sea ice variability, a sea ice index is defined as the regional-averaged sea ice concentrations over 60°–90°N. The Arctic sea ice index is now updated monthly via the WMC-Beijing website.