Seasonal variations of the mesospheric Fe layer at Rothera, Antarctica (67.5°S, 68.0°W)

The maximum Fe abundance occurs in late autumn (early May) at Rothera, rather than in midwinter. A secondary Fe enhancement occurs 6 months later in late spring (October–November) prior to the formation of polar mesospheric cloud (PMC) layers in summer.

The midsummer Fe layer is 3 km lower at Rothera because Fe depletion by PMC layers near the mesopause is not as extensive or as complete as at the South Pole. These observations are modeled satisfactorily using a mesospheric one-dimensional Fe chemistry model driven by a general circulation model and including a detailed micrometeoroid flux and ablation model. Our study shows that the autumnal maximum in the Fe abundance is caused primarily by the seasonal temperature maximum in the mesopause region, reinforced by the seasonal peak in the meteor input function (MIF).