Mark C. Urban, University of Connecticut (IMAGE) University of Connecticut Caption Mark Urban, associate professor of ecology and evolutionary biology at the University of Connecticut, stands under a sheet of aufeis in Alaska. These ice sheets form over Arctic underground springs but have become less prevalent with global warming. Credit Mark Urban, Photo Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.