Arctic Sea Ice Variability and Its Influence on the Midlatitude Circulation and Hydrologic Cycle

Arctic sea ice plays an important role in our global climate system. In addition to its local impact within the Arctic, the variability of Arctic sea ice could also impact the Northern Hemisphere midlatitudes. It is important to understand this influence in the midlatitude circulation and hydrologic cycle to help enhance predictions for future climate.

     In order to determine how different areas of arctic sea ice affect the midlatitude circulation and hydrologic cycle, we make use of monthly sea ice concentration (SIC) data from the National Snow and Ice Data Center (25km*25km), monthly zonal velocity at 250 hPa from the ERA-Interim reanalysis, and monthly precipitation data from the Global Perception Climatology Project during 1979-2015. First, we remove the linear trend for all variables to focus on year-to-year variability. For the Barents Kara Sea (BKS, 70-82 N and 15-100 E), the SIC variability is found to be the largest during August-November and correlation coefficients are calculated between precipitation and SIC averaged over the BKS and over August-November, and similarly for zonal velocity. For the Bering and Chukchi Seas (50-82 N and 170 E-160 W), correlation coefficients are also calculated but with SIC averaged over August-October during which the SIC variability is the largest in this region. Statistical significance is evaluated via a simple Student’s t-test using the 95% confidence interval.

     From the correlation analysis, with lower-than-normal BKS SIC, the following results are found. A statistically significant drying tendency is seen over the Nordic Sea as well over the Arctic Ocean and close to the Siberian Coast. A wet tendency is found in the Northern Russia area. These results of the hydrologic cycle largely follow the results of the zonal flow, which shifts northward in the North Atlantic Ocean. The results are also found consistent in months from December to March of the subsequent year. Results from the Bering and Chukchi Seas include, with lower-than-normal SIC, a significant wet tendency over Alaska and Western/Central Europe. Again the effects of SIC variability are found to persist until the following March.

     In summary, we find statistically significant response of the hydrologic cycle as a result of Arctic sea ice variability from observations. The response of the hydrologic cycle mainly follows the jet response. The response in the midlatitudes is also found to persist for about four months following the sea ice variability. This suggests the use of sea ice information to help improve the prediction of precipitation in winter and early spring. Possible mechanism related to troposphere-stratosphere interaction has been proposed in other studies.