DATE2018-05-16 05:48:01
AUTHORSI Cvijanovic (1), BD Santer (2), DD Lucas (3), C Bonfils (4), JCH Chiang (5), S Zimermann (6)
  1. Lawrence Livermore National Laboratory , Livermore, USA
  2. Lawrence Livermore National Laboratory , Livermore, USA
  3. Lawrence Livermore National Laboratory , Livermore, USA
  4. Lawrence Livermore National Laboratory , Livermore, USA
  5. University California Berkeley, Berkeley, USA
  6. Lawrence Livermore National Laboratory , Livermore, USA
ABSTRACTDramatic loss of Arctic sea ice cover since the beginning of the satellite era has intensified the interest into whether these high latitude changes can significantly influence the weather and climate far from the Arctic. Many attempts to demonstrate statistically significant remote responses to sea ice changes have been hindered by factors such as large high latitude variability, relatively short observational datasets, and model limitations in adequately representing current sea ice changes. We sample uncertainty in sea ice physics parameters and variability in atmospheric initial conditions to obtain an ensemble of simulations with substantially different states of Arctic cover. This large ensemble isolates a robust, statistically significant climate response arising from changes in sea ice cover only. The key novelty of our setup is that unlike previous studies that impose artificial energy fluxes to achieve sea-ice loss, our sea-ice parameter perturbations allow for energy budget conservation. In this manner we are able to ensure that the observed atmospheric response really originates from the sea-ice changes and that it is not altered by spurious energy flux perturbations. Our results show link between Arctic sea-ice loss and the North Pacific geopotential ridge development. 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. These findings suggest that the ability of climate models to accurately estimate future precipitation changes over California is also linked to the fidelity with which future sea-ice changes are simulated. We conclude that sea-ice loss of the magnitude expected in the next decades could substantially impact California’s precipitation, thus highlighting another mechanism by which human-caused climate change could exacerbate future California droughts. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344aa