7,000 Years Ago, This Ice Sheet Was Smaller. Scientists Think They Know Why. <img width="600" height="243" src="https://www.sciencealert.com/images/2019-07/processed/ThwaitesGlacierHittingPointOfIrreversibleMelting_600.jpg" alt=""/> Past instability warns of future risk. https://www.sciencealert.com/7000-years-ago-this-ice-sheet-was-smaller-scientists-think-they-know-why