Wobbly ocean conveyor circulation during the Holocene?

Abstract

Compared to the last glacial period, the climate of the Holocene has been quite stable. However, the record does suggest that, at high latitudes in the north, temperatures have cooled at least since the middle Holocene and that this cooling has been modulated by millennial-duration fluctuations that culminated in the Medieval Warm–Little Ice Age oscillation. In this paper, we explore the possibility that these variations were associated with concurrent changes in the strength of the Atlantic's conveyor circulation. Three lines of evidence are considered. One involves records that relate directly to ocean operation; a second involves the tie between sea ice extent in the northern Atlantic and the extent of mountain glaciers in the European Alps and in the cordillera of western North America; and a third involves evidence for a bipolarity in climate changes in the northern and southern polar regions. In addition we look into clues provided by the Atlantic Multidecadal Oscillation (AMO). Although at this point no firm conclusion can be drawn, the case for ocean involvement is sufficiently strong to merit further attention.