Joe MacGregor is a glaciologist and geophysicist interested in the past, present and future flow of ice sheets. He seeks to understand why ice sheets flow more quickly in some areas than in others, how this flow evolves over time and how we can better observe the controls upon ice flow. These are critical concerns for Earth’s two remaining ice sheets in Greenland and Antarctica, along with ice masses elsewhere in the Solar System. With a diverse set of collaborators at NASA and partner institutions, his current research synthesizes observations from a variety of methods, including airborne radar sounding (e.g., Operation IceBridge), satellite remote sensing (e.g., Landsat, MODIS, InSAR), ground-based surveys (e.g., ice core chemistry, borehole thermometry) and laboratory measurements (e.g., dielectric spectroscopy) to better understand ice sheets.