The weather at middle latitudes is largely unpredictable more than a week or so in advance, whereas fluctuations in the ocean may be predictable over much longer timescales. If decadal fluctuations in North Atlantic sea surface temperature(1-6) could be predicted, it might be possible to exploit their influence on the atmosphere(7-10) to forecast decadal fluctuations in climate(11). Here we report analyses of shipboard observations that indicate significant decadal predictability of North Atlantic sea surface temperature, arising from the advective propagation of sea-surface-temperature anomalies(4) and the existence of a regular period of 12-14 years in the propagating signals. The same timescale can be identified in a dipole-like pattern of North Atlantic sea-level pressure variability(1,7,12). We propose a mechanism which may connect these oceanic and atmospheric fluctuations, possibly as part of a coupled ocean-atmosphere mode of variability(7). Our results are encouraging for the prospects of forecasting natural fluctuations in the climate of the North Atlantic region several years in advance.