Atlantic Water is the main oceanic source of heat, salt, and nutrients of the Arctic Ocean. It enters the Arctic Ocean through the Barents Sea or Fram Strait. In the eastern Fram Strait, Atlantic Water flows northward in the West Spitsbergen Current between the surface and about 800m depth. Some of this water makes a shortcut and recirculates to the western Fram Strait on timescales of several months while the rest enters the Arctic Ocean and follows a cyclonic circulation for years to decades.

The AWI long-term observations in Fram Strait have been measuring the temperature, salinity, and velocity in the West Spitsbergen Current since 1997 (Figure 1). In the first decade of observations, the mean temperature in the WSC increased by 1°C and has stayed at the elevated levels around 4°C since. Two anomalous warm events occurred in fall 2006 and in late winter 2012. In the deep ocean, it was also observed that the two water masses present there (the warmer Eurasian Basin Deep Water and the colder Greenland Sea Deep Water) have both been warming at 0.05°C/decade and 0.1°C/decade respectively (Figure 2), which means that they will reach the same temperature in 2020.

Currently, the Helmholtz Infrastructure Initiative FRAM supports the mooring array in the West Spitsbergen Current as well as process study activities that aim to improve the interpretability of the long-term observations. The AWI long-term observations are complemented by a mooring array maintained by the Norwegian Polar Institute that monitors the East Greenland Current which transports Arctic outflow water southwards.