High-resolution faunal, isotopic, and sedimentologic data from North Atlantic core V29-191 show that sea-surface temperatures increased from 17.5 to 17.3 ka, prior to the Heinrich event 1 (H1) ice-rafting event ca. 17–16 ka. These new data support previous studies that showed that warming predated the extensive climatic warming ca. 15.9 ka. This relationship indicates that H1 occurred after warming had begun. Loss of latent heat during iceberg melting created near-glacial sea-surface temperatures during H1 and kept much of the subpolar North Atlantic cold despite increasing Northern Hemisphere insolation. The cold-ocean conditions influenced proximal terrestrial climates and may also have affected remote regions.