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This study investigates the relationship between North Atlantic sea surface temperatures (SST) and persistent drought in North America using modern observations, proxy paleo-data, and simulations from multiple climate models. The observational results show that persistent droughts in the Great Plains and the southwest North America are closely related to multidecadal variations of North Atlantic SST (Atlantic Multidecadal Oscillations, AMO). During the AMO warm (cold) phases, most of North America is dry (wet). This relationship is persistent since at least 1567 AD, as based on proxy SST for the North Atlantic and the reconstructed drought index for North America. On centennial timescales, proxy SST records from the North Atlantic and proxy drought records for North America suggest that major periods of AMO-like warm (cold) SST anomalies during the last 7.0 ka correspond to dry (wet) conditions in the Great Plains. The influence of North Atlantic SST on North American droughts is examined using simulations made by five global climate models. When forced by warm North Atlantic SST anomalies, all models captured significant drying over North America, despite some regional differences. Specifically, dry summers in the Great Plains and the southwest North America are simulated by all models. The precipitation response to a cold North Atlantic is much weaker and contains greater disagreement among the models. Overall, the ensemble of the five models could well reproduce the statistical relationship between the dry/wet fluctuations in the North America and North Atlantic SST anomalies. Our results suggest that North Atlantic SSTs are likely a major driver of decadal and centennial timescale circulation, including droughts, in North America. Possible mechanisms that connect North Atlantic SST with North American drought, as well as interactions between North Atlantic and tropical Pacific SST and their relative roles on drought are also discussed.

A new and significant correlation is found between the amplitude of mean-winter atmospheric anomalies over the North Atlantic Ocean and those over the North Pacific Ocean and western North America three winters later. It is as strong as the previously known and much discussed correlation between the ocean temperature in the eastern tropical Pacific (El Nino region) and the North Pacific winter atmospheric anomalies. No physical explanation is given at this time for this correlation. A statistical prediction model for mean-winter conditions is constructed based on the above new and previously known correlations. The prediction model is tested on 36 winters of the past. The model predictions are shown to be of remarkable quality over the North Pacific and western North America.

The North Atlantic is one of the world’s most utilised ocean bodies, most strategic militarily and commercially, and one of the most marine-resource rich. The North Pacifiic is probably its closest rival in these respects. The North Atlantic has a rich history of political and economic development both among its littoral states and in comparison with other ocean regions around the world. With the break-up of the Soviet Union and the growing economic integration of eastern and central Europe, the geopolitical structure of the North Atlantic is changing somewhat; however, its status as an economic force is still great.

Evidence for a cooling event synchronous with the Younger Dryas (12,000 calendar years before present) has been found in the North Pacific Ocean north of 30° N in records of surface1–5 and subsurface water properties6,7. These changes may be related to a temporary shut-down of North Atlantic Deep Water formation and associated surface cooling over the North Atlantic. It has remained unclear, however, whether this North Atlantic cooling was communicated to the North Pacific Ocean through the atmosphere or the ocean. Here we report results of a sensitivity experiment with a coupled ocean–atmosphere general circulation model that support a primarily atmospheric forcing of North Pacific climate variations. Changes in wind strongly affect coastal upwelling at the North American west coast, and surface cooling by the atmosphere causes better ventilation of the thermocline waters of the northeast Pacific. This effect is amplified by oceanic progagation to the Pacific of the signal arising from collapse of North Atlantic Deep Water formation. These teleconnections may also explain earlier North Pacific and western North American millenial-scale cooling events of a similar nature8–12.

A distinct core of tritium (from nuclear weapons testing in the atmosphere) marks the southward flowing jet of the deep western boundary current of the North Atlantic circulation at 30 °N latitude. The concentrations, of the order of 0.5–1.0 TU (1 tritium unit = 1 3H atom per 10 8H atoms), indicate a roughly 10-fold dilution of source waters in the far north. This thin jet, 50 km in width, carries water into subtropical regions which, until recently, were free of anthropogenic tritium. It underlies the more extensive distributions of tritium found in more rapidly renewed waters above the permanent thermocline.

The wind pattern in the North Atlantic (Fig. 1) is more or less clockwise, and therefore the easiest way to cross the Atlantic from east to west is by the southern route, and from west to east along the northern route. In between, in the middle of this rotary system, are the horse latitudes where winds tend to be light and variable. Superimposed on this wind system, of course, is a series of depressions which commonly move from west to east across the North Atlantic, each depression having its own system of winds rotating anti-clockwise: on the south side of the depression winds tend to be westerly whilst on the north side they tend to be easterly.

Two 10,000-year periods of Northern Hemisphere continental ice-sheet growth stand out prominently within the last full interglacial-to-glacial cycle. During the first half of each rapid ice-growth phase, the subpolar North Atlantic from 40 degrees N to 60 degrees N maintained warm sea-surface temperatures comparable to those of today's ocean. The juxtaposition at latitudes 50 degrees N to 60 degrees N of an "interglacial" ocean along-side a "glacial" land mass, particularly along eastern North America, is regarded as an optimal configuration for delivering moisture to the growing ice sheets.

WHILE the interest attaching to Sir William Dawson's Presidential address at Birmingham is still fresh, I wish to be allowed to offer a few observations on that part of it which deals with the geological age of the North Atlantic Ocean. The President in referring to those writers who, like Mr. Crosby in America, Mr. Mellard Reade and myself in Britain, maintain that the North Atlantic and the American continent have in the main changed places in Palaeozoic times, makes the following statement. Admitting the correctness of the facts as to the swelling out of the Palaeozoic sediments in the direction of the Atlantic seaboard, he endeavours to account for these very striking phenomena thus: “I prefer, with Hall, to consider these belts of sediment as in the main the deposits of northern currents, and derived from Arctic land, and that, like the great banks of the American coast at the present day, which are being built up by the present Arctic current, they had little to do with any direct drainage from the adjacent shore.” Now, in reading this passage it occurs to me that Sir W. Dawson must have felt he had a very questionable case when he attempted to support it by such an hypothesis. To liken the great sheets of sediment which spread themselves sometimes over half the North American continent south of the Great Lakes to the banks heaped up along the Atlantic coast is a point of analogy in which, probably, he will find few to concur. The Palaeozoic sediments are certainly not banks, but sheets originally spread over the sea-bed, and distributed according to certain recognised laws of increase and decrease of thickness.

No meteorologist could be less disposed than myself to underrate the importance of Greenland as a factor in determining the characteristic circulation over the North Atlantic Ocean, but I challenge the extravagant contention that cyclonic circulation, which is an integral part of the general circulation, depends entirely upon the “katabatic” operations of a relatively small and accidental feature in the configuration of the northern hemisphere like Greenland. To contend that the analogous Pacific centre of cyclonic activity, scarcely less intense than the Atlantic, is nourished by the same katabatic action of Greenland's ice-dome is surely out of the question.