Assessment of Oceanic Anomalies of Predictive Potential (D2.5)

• Main Authors: Eldevik, Tor, Årthun, Marius
• Format: Report
• Language: English
• Published: Zenodo 2019
• Subjects: Arctic; Arctic Ocean; Norway; North Atlantic; North Atlantic oscillation; Sea ice
• Online Access: https://doi.org/10.5281/zenodo.3361567

Climate prediction is the challenge to forecast climatic conditions months to decades into the future with a skill and regional detail that is of practical use. Will, for example, Arctic sea ice cover increase the next winter? Will Scandinavian hydroclimate be particularly beneficial for hydropower production? Will Southern European summers be excessively warm through the 2020s? To what extent such conditions are predictable in nature and to what extent predictability can be realised in operational climate forecast systems and translated to useful stakeholder information, i.e., the climate equivalent to weather forecasting, remain unknown. It is commonly understood that predictability resides with the more inert components of the climate system and particularly—as is the focus of Blue-Action—with ocean circulation. Blue-Action has substantiated this premise by exploring observations, climate models, and reanalyses (model simulations tightly constrained by available observations). Successful avenues of research and progress made in Blue-Action include mapping out the dominant timescales of European interannual-to-decadal climate variability, the identification of consistent and predictable variability in Atlantic-to-Arctic ocean circulation, the link of ocean variability to fluctuating climate over land and sea ice extent, and making actual climate forecasts toward 2020. We find that winter surface air temperatures for much of continental Europe, and generally for Eastern Europe, are characterized by a 5–10 year timescale. This reflects the variable strength of the large-scale westerly winds, commonly summarized in the so-called North Atlantic Oscillation (NAO) index. The longest timescale that our observation-based record resolves is a 25–40 year fluctuation characteristic for Western Europe (Iberia and England). This we associate with more hemisphere-scale coherent temperature fluctuations, the so-called Atlantic Multidecadal Oscillation (AMO). The winter temperature over Northwest Europe (Norway, Sweden and ...