Northern hemisphere ice sheets and planetary waves: A strong feedback mechanism

We carried out a statistical analysis of the relation between the net mass balance of high‐latitude glaciers and 500 mb height deviations of the seasonal mean atmosphere. Mass‐balance series of 23 glaciers and ice caps were used, ranging in length from 8 to 30 yr. Considering the sample as a whole, it appeared that the only significant predictor for mass balance variations is the summer anomaly of the 500mb height. Except for a few individual glaciers, correlations with mean vorticity and meridional wind component turned out to be insignificant. To investigate the potential feedback between ice‐age ice sheets and planetary waves, we used a stationary two‐layer atmospheric model to calculate the response to the CLIMAP (1976) ice‐sheet topography for 18,000 YBP. Combining the result with the statistical analysis reveals that the feedback is important: the planetary‐wave pattern forced by the ice sheets leads to deviations of the equilibrium‐line altitude of about 500m.