Interaction between Arctic sea ice and cloud-related variables in ERA40 Reanalysis and CCSM3

Recent observations of the Arctic reveal a shift towards a warmer and less icy state, leading to many questions concerning future conditions. Among these questions are the influence of clouds and their “accomplices” (e.g., water vapor and radiation) on amplifying or dampening the loss of Arctic sea ice. In an effort to evaluate the cloud/sea-ice interactions, compositing techniques are applied to the ECMWF ERA40 Reanalysis dataset and the CCSM3's modern and 2xCO2 runs. By assessing Reanalysis data, observed relationships can be identified and serve as a basis to evaluate co-variability amongst the modeled data.

Autumn appears to produce the most robust relationships. During most of autumn, areas of anomalously low sea ice concentrations exhibit increased upward surface latent heat flux and increased boundary layer height. These relationships also exist during the summer, however no clear sea ice/cloud relationships exist in this season. During autumn, low and middle cloud cover increases over areas of higher sea ice concentration. Late autumn shows a shift of this relationship to the eastern seas, where freeze up occurs later. These relationships are similar in the CCSM3 modern run. Whereas low cloud cover may be driven more locally based upon surface conditions (e.g., sea ice concentration), middle cloud cover may be influenced locally and through turbulent transport of temperature and moisture aloft.