Future Loss of Arctic Sea-Ice Cover Could Contribute to the Substantial Decrease in California’s Rainfall

Arctic Sea-Ice
Arctic sea-ice changes drive precipitation decreases over California. Arctic sea-ice loss induces high-latitude changes. These changes trigger tropical circulation and convection responses. Decreased convection and decreased upper level divergence in the tropical Pacific Ocean then drive a northward propagating Rossby wavetrain, with anticyclonic flow forming in the North Pacific Ocean. The result? The flow steers the wet tropical air masses away from California. Image courtesy of Kathy Seibert, Lawrence Livermore National Laboratory

The Science

Arctic sea-ice loss of the magnitude expected in the next few decades could substantially impact California’s rainfall. It could also exacerbate future California droughts. Scientists at Lawrence Livermore National Laboratory developed a novel way to isolate the impacts of high latitude sea-ice loss.

The Impact

Earlier studies suggest that California’s drought has a human-made component arising from increased temperatures. Scientists expect to see more droughts. This study highlights yet another pathway by which human activities could affect future droughts over California—Arctic sea-ice loss. The study also suggests the need for better sea-ice data. The ability of Earth system models to estimate precipitation changes over California may be linked to how well future sea-ice changes are simulated.

Summary

The dramatic Arctic sea-ice loss observed over the satellite era has intensified debate into whether these high-latitude changes are affecting larger weather and climate patterns. Many previous attempts to demonstrate statistically significant remote responses to sea-ice changes have been hindered by factors such as large high-latitude variability and short observational datasets. In this study, researchers developed a new modeling framework, involving sea-ice physics parameter perturbations, to isolate the climate response arising from changes in Arctic sea-ice cover alone.

The model simulations indicate that the loss of Arctic sea-ice cover drives the formation of a high-pressure ridge in the North Pacific—much like the ridges that have been pushing the winter storm systems away from California during the 2012-2016 drought. In a two-step teleconnection, sea-ice changes lead to reorganization of tropical convection that in turn triggers an anticyclonic response over the North Pacific, resulting in significant drying over California. The mechanism behind this teleconnection appears to be robust to the source of high-latitude sea ice changes: the research shows that Antarctic sea-ice loss can also trigger substantial precipitation changes over California.

This research indicates that substantial loss of high-latitude sea-ice cover is highly likely to have significant far-field effects. Such loss can impact California’s precipitation through atmospheric teleconnections involving tropical convection changes.