Reconstructing hydroclimate over the Common Era is essential for understanding the dominant mechanisms of precipitation change and improving climate model projections, which currently suggest Northeast Mexico will become drier in the future. Tree-ring reconstructions have suggested regional rainfall is primarily controlled by Pacific sea surface temperatures (SST). However, tree ring records tend to reflect winter-spring rainfall, and thus may not accurately record total annual precipitation. Using the first multiproxy speleothem record spanning the last millennium, combined with results from an atmospheric general circulation model, we demonstrate mean annual rainfall in Northeast Mexico is highly sensitive to Atlantic SST variability. Our findings suggest precipitation in Northeast Mexico may increase in the future in response to the relative warming of Tropical North Atlantic SSTs.

The teleconnection between the Quasi-Biennial Oscillation (QBO) and the Arctic polar vortex is investigated using Coupled Model Intercomparison Project phase 6 (CMIP6) models. We use 14 CMIP6 models, reanalysis, three experiments with prescribed QBOs, one of which has no free polar stratospheric variability, and branched runs in which a QBO is imposed in runs previously devoid of a QBO. Each CMIP6 model underestimates the Holton-Tan effect (HTE), the weakening of the polar vortex with QBO easterlies in the lower stratosphere. To establish why, 850 Kelvin potential vorticity (PV) maps are used to study zonal asymmetries in the teleconnection. The QBO initiates the HTE by promoting equatorward (poleward) intrusion of high (low) PV over mid-latitude Asia (60°E-120°E). The presence of the PV intrusion in a model response is highly correlated with polar cap warming and the HTE. Models with stronger 10 hPa QBO amplitudes generally include the PV intrusion.