Postglacial North Atlantic

Abstract

In the North Atlantic Ocean, sea-surface temperature (SST) and thermohaline circulation changes during the Postglacial period were small compared to those that occurred during the last glaciation. This was because the large terrestrial ice sheets that adjoined the North Atlantic basin and greatly influenced the climate of the region had mostly disappeared by the beginning of the Holocene. In the high-latitude North Atlantic (north of 35° N), SSTs peaked (+0.5–2 °C relative to today) during the Holocene thermal maximum between 8.5 and 5.5 ka, and cooled gradually afterward. In the low-latitude North Atlantic (south of 30° N) and adjacent oceans, SSTs increased gradually over the past 10 kyr. This seemingly contradictory trend in surface ocean temperatures can be explained as a linear response to the mean annual insolation which has decreased through time in the high-latitude regions but increased in the low latitudes. Although relatively small Holocene ocean circulation changes are difficult to detect, changes in salinity, temperature, and ice-rafting proxies suggest that deepwater formation has not been stable during the Holocene and that comparable thermohaline circulation changes in the northeastern and western North Atlantic appear to be out of phase.