Air temperatures have increased almost twice as fast in the Arctic than the global average over the last 50 years. Models predict that air temperatures will continue to increase considerably, and summer sea ice in the Arctic will disappear before the middle of this century and winter sea ice by the end of the current century. Because of the complex dynamics of the Barents Sea ecosystem, and because the effects of climate change will interact with other major factors, such as acidification and the impact of fisheries, it is difficult to predict what the total effect on the ecosystem will be.
However, it can be predicted with fair certainty that ice-associated fauna and flora will be lost, or significantly reduced. Also, a number of species, e.g. cod and capelin, will likely have a more northern and/or eastern distribution and boreal species such as blue whiting and mackerel may become common in the Barents Sea. These changes will likely result in potentially large changes in community composition and it is possible that the structure of the ecosystem may shift irreversibly. The probability of this happening may increase if the pressures from other types of impacts, such as fisheries and acidification, are high.
In addition to the problems of understanding how the ecosystem will respond to varying degree of warming, there are large uncertainties associated with what the patterns of warming may actually be. For example, at the 2008 ICES workshop on cod and future climate change it was pointed out that many of the IPCC 2007 regional climate models downscaled from Global Circulation Models (GCMs) demonstrate large differences with observations on a regional basis. Also the Global Circulation Models (GCMs) are not able to reproduce well the two major modes of variability over the last century, the Atlantic Multidecadal Oscillation (AMO) and the North Atlantic Oscillation (NAO). Thus, the conclusion of the workshop was that the available global and regional climate models are not currently adequate for impact studies on the marine ecosystem. Without the development of regional climate model systems and the development of adequate downscaling strategies it is not possible to go on to implement coupled biological models of lower trophic level dynamics and its consequences for species at higth trophic level for the next 20–50 years. A considerable scientific effort will be required to design, initialize, run and test regional models which produce output that is relevant to impact studies. Until this is done the impact assessments will have to be based on “what if” scenarios.
Below, projections for future climate change are discussed first. Then, effects on biological components in the ecosystem are considered