The sea ice in the arctic and antarctic regions of the earth is an especially sensitive indicator of the earth's climate, and in particular, the current overall atmospheric temperature of the planet. It was recently reported to have reached a new low. Our guest, NASA's Walt Meier explains why this is the case and which processes govern the increase or decrease of the ice. We then discuss how the ice mass is measured based on satellite and how its thickness is estimated based mostly on in-situ measurements. We cover climate modeling and its connection to sea ice and conclude with an outlook on future research.