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The duration of seasonal winter ice cover has declined in many mid- and high-latitude regions around the world as climate continues to warm. We obtained data on lake ice breakup dates, air temperature, precipitation, and large-scale climate oscillations for 152 lakes across the northern hemisphere from 1951 to 2014. Ninety-seven percent of study lakes exhibited earlier ice breakup trends. Forty-six percent of the variation in ice breakup trends was driven by spring air temperatures and elevation across the northern hemisphere. However, changes in ice breakup have not always been in a gradual or linear pattern. Using the sequential T-test analysis of regime shifts, we found evidence of abrupt changes in mean ice breakup for 53% of lakes with shift years identified between 1970 and 2002. Concurrently, we found abrupt changes in mean spring and winter air temperatures, winter precipitation, and large-scale climate oscillations that occurred either the same year or 1 yr prior. Earlier ice breakup and the shortening of the ice season will have consequences for winter heritage, local economies, and lake ecosystems around the world.