Variations in the Arctic's multiyear sea ice cover: A neural network analysis of SMMR‐SSM/I data, 1979–2004

A 26‐year (1979–2004) observational record of January multiyear sea ice distributions, derived from neural network analysis of SMMR‐SSM/I passive microwave satellite data, reveals dense and persistent cover in the central Arctic basin surrounded by expansive regions of highly fluctuating interannual cover. Following a decade of quasi equilibrium, precipitous declines in multiyear ice area commenced in 1989 when the Arctic Oscillation shifted to a pronounced positive phase. Although extensive survival of first‐year ice during autumn 1996 fully replenished the area of multiyear ice, a subsequent and accelerated decline returned the depletion to record lows. The most dramatic multiyear sea ice declines occurred in the East Siberian, Chukchi, and Beaufort Seas.