FY 1995
Variability of the atmospheric energy flux across 70°N computed from the GFDL data set
Overland, J.E., and P. Turet
In The Polar Oceans and Their Role in Shaping the Global Environment, Nansen Centennial Volume, O.M. Johannessen, R.D. Muench, and J.E. Overland (eds.), AGU, Washington, D.C., Geophysical Monograph 85, doi: 10.1029/GM085p0313, 313–325 (1994) |
The primary energy balance for the arctic atmosphere is through northward advection of moist static energy--sensible heat, potential energy, and latent heat--balanced by long wave radiation to space. Energy flux from sea ice and marginal seas contributes perhaps 20-30% of the outgoing radiation north of 70°N in winter and absorbs a nearly equal amount during summer. Thorndike's toy model shows that extreme climate states with no ice growth or melt can occur by changing the latitudinal energy flux by ±20-30% out of an annual mean flux of 100 W m−2. We extend the previous work on latitudinal energy flux by Nakamura and Oort (NO) to a 25-year record and investigate temporal variability. Our annual latitudinal energy flux was 103 W m−2 compared to the NO value of 98 W m−2; this difference was from greater fluxes during the winter. We found that mean winter (NDJFM) energy flux was 121 W m−2 with a standard deviation of 11 W m−2. There were no large outliers in any year. An analysis of variance showed that interannual variability does not contribute towards explaining monthly variability of northward energy transport for the winter, summer or annual periods. Transient eddy flux of sensible heat into the arctic basin was the largest component of the total energy flux and is concentrated near the longitudes of the Greenland Sea (~10°W) and the Bering and Chukchi Seas (180°). There is a minimum in atmospheric heating north of Greenland, a known region of thick ice. While there was little interannual variability of energy flux across 70°N, there was considerable month-to-month variability and regional variability in poleward energy flux. Sea ice may play a role in storage and redistribution of energy in the arctic climate. |
