Atmospheric river shifts in response to Holocene forcings and their impact on millennial-scale hydroclimate changes

Abstract:

The hydroclimate of extratropical regions has changed substantially since the mid-Holocene, as indicated by many paleoclimate proxies. Insolation changes are the main forcing ultimately driving these hydroclimate changes on millennial time scales. But the response of atmospheric rivers—the synoptic process primarily responsible for atmospheric moisture transport in the extratropics—to insolation changes has not been explored in detail. We present results from climate model simulations of the early and mid Holocene, in conjunction with an atmospheric river detection method optimized for climate change studies, that explore the annual and seasonal response of atmospheric rivers to insolation changes. We find that changes in the average latitude and intensity of landfalling atmospheric rivers largely explain precipitation differences between the Holocene and preindustrial reconstructed from proxies. We also explore their relationship to the background climate state.