Recent Changes of Arctic Multiyear Sea Ice Coverage and the Likely Causes

Recent changes of Arctic multiyear sea ice coverage and the likely causes are discussed. Changes of multiyear ice (MYI) coverage are dependent on the observed changes in surface air temperature (SAT). Records of fast-ice thickness provide annual measures of ice growth due almost entirely to atmospheric thermodynamic forcing over the vast and shallow Siberian shelves, there there is negligible deep ocean influence on local ice formation. Double-diffusive heat fluxes provide a means for transferring Atlantic Water (AW) heat upward over more than a 100-m depth range toward the upper halocline. The reduction of MYI is driven by, and perhaps even contributes to the albedo-temperature feedback. Thus, the rapid loss of sea ice in response to the atmospheric and oceanic forcing of the past decade appears to have introduced some degree of irreversibility.