Climate forcing is affecting the physical oceanography of the ecoregion. The Norwegian Sea is influenced by the amounts and properties of Atlantic water flowing in from the south through the Gulf Stream. It is also influenced by the advection of Arctic Water from the Greenland and Iceland Seas. Understanding of the governing mechanisms relating to exchanges between the Atlantic and Arctic regions of the Norwegian Sea remains limited.
The long-term climate variability of the Norwegian Sea follows the Atlantic Multidecadal Oscillation (AMO), which is measured as the mean surface temperature of the Atlantic Ocean between equator and 60oN. Long-term AMO data indicate that warm phases have grown warmer and cold phases less cold, consistent with anticipated and observed warming conditions in the ecoregion. The local evidence suggests an increase in the integrated relative heat content of the 0–1000 m depth layer since the early 2000s and a recent freshening (Figure 7), which is linked to the general freshening of Atlantic water, and increased inflow of the Arctic water to the ecoregion. (Figure 7). The recent freshening was associated with only a slight cooling, probably due to reduced heat loss to the atmosphere as a result of enhanced generally relatively warm westerly winds.
Warming of the Norwegian Sea is expected to affect ecosystem structure and processes, but these remain to be investigated in the ecoregion.
Figure 7 (click to enlarge): A subset of climate indicators for the Norwegian Sea: a) Relative Heat Content and b) Relative Freshwater Content.A subset of climate indicators for the Norwegian Sea: a) Relative Heat Content and b) Relative Freshwater Content.