ENSO variability and teleconnections during glacial climates

Understanding the origin of sub-Milankovitch and millennial-scale abrupt climate change still poses a major challenge. An important role of communicating the orbital-scale forcing into abrupt climate change on millennial and centennial timescales has been hypothesized for the tropics in earlier studies based on the assumption of stationary teleconnections. This paper presents a modelling study for the Last Glacial Maximum and Marine Isotope Stage 3 using the comprehensive climate model CCSM3. Glacial boundary conditions and freshwater hosing at high latitudes of the North Atlantic are imposed to mimic a Heinrich stadial and Dansgaard-Oeschger stadials and interstadials. It is shown that glacial ENSO variability is strongly enhanced by a substantial slowdown of the Atlantic Meridional Overturning Circulation. The simulations also suggest that glacial boundary conditions induce major modifications to ENSO teleconnections and that the “blueprint” of modern ENSO teleconnections should only be applied with caution to glacial climate periods.