Evolution of Atlantic Meridional Overturning Circulation since the last glaciation: model simulations and relevance to present and future

Abstract

The Atlantic Meridional Overturning Circulation (AMOC) and the associated water masses have changed dramatically during the glacial–interglacial cycle. Here, I review some recent progress in the modelling of the AMOC and water masses since the Last Glacial Maximum and discuss the relevance of these past AMOC studies to the present and future AMOC study. Recent studies suggested that Atlantic water masses were constrained by carbon isotopes (δ 13 C) and neodymium isotopes (ε Nd ), while the strength of the AMOC better was constrained by protactinium/thorium ratio ( 231 Pa/ 230 Th) and the spatial gradient of calcite oxygen isotopes (δ 18 O c ). In spite of the shallower AMOC at the glacial period, its intensity did not differ substantially from the present because of the cancellation of opposite responses to the rising CO 2 and the retreating ice sheet. This article is part of a discussion meeting issue ‘Atlantic overturning: new observations and challenges’.