Analysis of organic species stored in ice cores provides a unique opportunity to obtain information about the environment of the past. Because of the trace nature of the organic components of interest, studying these species in molecular level detail within ice cores can be an analytical challenge. Using Fourier transform ion cyclotron resonance mass spectrometry with electrospray ionization, we have characterized, at an unprecedented molecular level, the organic material in an ice core collected from Franz Josef Land (Russia). Several thousand distinct molecular species are identified and provide clues to the principal sources of the organic matter. Humic-like substances have been identified in both modern and ancient ice, despite the remote marine setting of the ice field. Species containing sulfur heteroatoms are far more abundant in the modern ice, indicating that anthropogenic sulfur emissions are also present in the high--molecular weight organic compounds preserved in ice.