North Pacific ENSO Teleconnection to Mediterranean Climates of North America in Late Cretaceous Greenhouse

The El Niño-Southern Oscillation (ENSO) influences the world through its teleconnection. Forced by global warming and rising atmospheric CO2 levels, the evolution of ENSO is still under debate. ENSO records in deep-time greenhouse climates can enhance the understanding of ENSO and its teleconnection under global warming.

This research analyzes Earth System Model (ESM) outputs of Late Cretaceous to show ENSO teleconnection between North Pacific and Mediterranean Climate region of North America (MCNA) under greenhouse gas and paleogeographic forcing. ESM outputs show 2.1-3.2-year ENSO-band cycles in both sea surface temperature (SST) and precipitation in MCNA, which are consistent with records from high-resolution sedimentary archives. The simulated ENSO teleconnection to Late Cretaceous MCNA is more influenced by the Subtropical High than the Aleutian Low. This is thought to be related to paleogeographic forcing, where a closed polar-ward seaway results in a warmer sub-polar Pacific and a more robust Aleutian Low over it. Consequently, under the remote forcing of ENSO, the Subtropical High shifts the Westerlies longitudinally, leading to alterations in both moisture and thermal transportation, which in turn changes the winter precipitation of MCNA.

This study reveals that ENSO teleconnections remain robust under Late Cretaceous greenhouse climates, and in comparison with today, forcing from the subtropics played a more significant role in affecting the evolution of North American climate.