A North–South dipole response of the South Atlantic Convergence Zone during the mid-Holocene

Abstract

The South Atlantic Convergence Zone (SACZ) profoundly modulates precipitation from central to southeastern Brazil in the present-day climate. However, the understanding of its long-term behavior responding to various climate forcings remains limited. Here, we use an isotope-enabled atmospheric general circulation model (ECHAM4.6) to examine the precipitation response of the SACZ during the mid-Holocene about six thousand years ago. The model simulates a northward intensification of the SACZ in the mid-Holocene, resulting in a dipole anomaly pattern relative to today's climate. The mid-Holocene precipitation increased along the northern margin of the SACZ due to the strengthening of easterly winds across the tropical Atlantic, while an eastward deflection of the South American low-level jet reduced moisture transport to southern Brazil, resulting in reduced precipitation along the southern margins of the SACZ. The north–south dipole response in precipitation is consistent with the mid-Holocene hydroclimate change observed in proxy records from the region.