The past several decades have seen strong warming in the Arctic, as well as a general downward trend in the extent of its floating sea ice cover. As outlined in many studies, these changes can be explained in part as responses to the North Atlantic Oscillation (NAO), which from about 1985 through most of the 1990s was in a generally positive phase during the winter season. However, these relationships have changed. Starting in the late 1990s, the NAO regressed towards a more neutral state. Yet the Arctic has continued to warm and the sea ice retreat has accelerated. The year 2004 continues the trend for Arctic warming, but is most remarkable in representing the third year in a row with extreme minima in September sea ice extent. In some ways, 2004 was itself a departure from the past several years. For example, while the summers of 2002 and 2003 were characterized by a high frequency of cyclone activity over the central Arctic Ocean, the summer of 2004 was relatively storm free. Yet apart from the more “compact” condition of the sea ice in the central Arctic Ocean in 2004, the pattern of sea ice retreat was quite similar to that of the past two years. There is some evidence that these extreme sea ice minima represent a delayed response to the strongly positive NAO period from about 1989-1995. On the other hand, it may be that with continued warming, the sea ice is becoming thin enough so that large areas are now unable to survive the summer melt period.