The coupled interaction of ocean surface waves and sea ice is important in determining the thermodynamic and dynamic properties of sea ice and its relationship to the ocean and atmosphere. Wave-ice interactions create the marginal ice zone (MIZ), a region critically important for ecology, transportation, and the polar energy budget. Typically, the MIZ is defined using satellite products as those regions where sea ice concentration is between 15% and 80%. Here we present a new technique to observe ocean surface waves in sea ice, leveraging NASA’s ICESat-2 satellite laser altimeter, and produce maps of wave-affected sea ice regions in both hemispheres. Defining a new wave-based metric for MIZ extent, we find that compared to a concentration-based metric, wave-based MIZ estimates are smaller. Further, the wave-affected MIZ makes up a larger fraction of sea ice extent in winter than in summer, opposite to the seasonal cycle of concentration-based MIZ. Link.