The Ocean-Atmosphere-Cryosphere s- tem of the Arctic is of unique importance to the World, its climate and its peoples and is changing rapidly; it is no accident that the Arctic Climate Impact Assessment (ACIA) was the first comprehensive regional assessment of climate-impact to be conducted. Reporting in 2005, ACIA concluded that changes in climate and in ozone and UV radiation levels were likely to affect every aspect of life in the Arctic. In effect, the ACIA process was essentially one of prediction: projecting that large climatic changes are likely to occur over the 21st century and documenting what might be their projected impacts. Although the ACIA Report was based on the most modern synthesis of obser- tions, modelling and analysis by hundreds of Arctic scientists, it notes with clarity that its conclusions are only a first step in what must be a continuing process. nd Reporting in November 2007, the 2 International Conference on Arctic Research Planning (ICARP II) has recently made much the same point. To make its proj- tions with higher confidence, --- to take the crucial second step in other words, -- both reports plainly state the need for a more complete and detailed understanding of the complex processes, interactions, and feedbacks that drive and underlie 'change' at high northern latitudes, including particularly the long-term processes of circulation and exchange in our northern seas where much of the decadal 'm- ory' for Arctic change must reside.

The two-way oceanic exchanges that connect the Arctic and Atlantic oceans through subarctic seas are of fundamental importance to climate. Change may certainly be imposed on the Arctic Ocean from subarctic seas, including a changing poleward ocean heat flux that is central to determining the present state and future fate of the perennial sea-ice. And the signal of Arctic change is expected to have its major climatic impact by reaching south through subarctic seas, either side of Greenland, to modulate the Atlantic thermohaline 'conveyor'. Developing the predictive skills of climate models is seen to be the most direct way of extending the ability of society to mitigate for or adapt to 'global change' and is the main justification for continuing an intense observational effort in these waters. As records have lengthened, they have shown that important aspects of oceanic exchange through subarctic seas are currently at a long-term extreme state, providing further motivation for their study. As one important example, the longest records of all show that the temperature of the main oceanic inflow to the Norwegian Sea along the Scottish shelf and slope, and the temperature of the poleward extension of that flow through the Kola Section of the Barents Sea have never been greater in >100 years. However, we are only now beginning to understand the climatic impact of the remarkable events that are currently in train in subarctic waters, and models remain undecided on some of the most basic issues that link change in our northern seas to climate. Reviewing the achievements of an intense recent observing and modelling effort, this volume intends to assemble the body of evidence that climate models will need if they are one day to make that assessment, quantifying the ocean exchanges through subarctic seas, describing their importance to climate as we currently understand it, explaining their variability, setting out our current ideas on the forcing of these fluxesand our improved capability in modelling the fluxes themselves and the processes at work. Much of that evidence is assembled here for the first time.

Audience:
This book will be of interest to researchers and scientists in oceanographic and climate research institutions, fisheries laboratories, arctic/polar institutions, climate change policy advisors.