Paleo Slide Set: Polar Ice Cores Calcium Concentrations While ECM data can provide many important insights regarding past climate, 41 other analyses provide even more compelling paleoclimatological data. Calcium concentrations, like ECM, serve as a proxy measurement of dust flux onto the ice sheet. Glacial periods are marked by high calcium concentrations, while warmer periods are notable for very low calcium concentrations. As you can see from this slide and the previous one, the climatic regime underwent extremely rapid transitions during the period from 18,000 to 10,000 yr B. P. Photo Credits: Graphic by Thomas Andrews. Data from Paul Mayewski and others. University of New Hampshire.