This paper analyzes severe, broadband, radio frequency interference (RFI) signatures that are commonly observed in L-band ALOS PALSAR images acquired close to the North American Arctic coast. These RFI signals are caused by military over-the-horizon radar systems. We introduce the specifics of the interfering signals and demonstrate that standard RFI Filters used in the operational ALOS PALSAR processor are insufficient to remove their influence. A new approach for filtering the identified RF interferences is presented and its performance is analyzed by a cross comparison with reference methods. The capabilities of the new correction method are emphasized by presenting several processing results, A statistical and geographical analysis of the strength and distribution of observed RFI signatures is shown, indicating widespread contamination of imagery across the American Arctic coast.