The late Quaternary earth is characterized by quasi-periodic glacial-interglacial cycles. In the higher latitudes of the North Atlantic these have been registered by large-scale surface water mass movements. During major climatic changes the North Atlantic polar front moved as a line hinged in the western Atlantic south-southeast of Newfoundland, sweeping out an arc larger than 45¿ and increasing in angle slightly to the northeast toward the European mainland. Its position is a critical monitor of whether warm saline North Atlantic Drift water flowed into the northeast Atlantic and southeast Norwegian Sea or turned southeastward and was contained within the subtropical gyre. Only during peak interglacial portions of the last 800,000 years (as at present) did North Atlantic water penetrate into the Labrador Sea and west of Iceland. During most of the 'interglacial' isotopic stages, this flow was cut off by a SSW-NNE polar front alignment that intersected Iceland. During main glacial portions of these cycles the average position of the polar front trended WSW-ENE across the subpolar Atlantic, roughly intersecting the Faeroes. This configuration virtually eliminated North Atlantic Drift flow into the Norwegian Sea and west central North Atlantic.