By Hannah Richter , Science.  Excerpt: In 2022, something shocking happened to the Hektoria Glacier, a small river of ice that slips into the sea near the tip of the Antarctic Peninsula. Over 16 months, it retreated by 25 kilometers, and it lost a whopping 8 kilometers in just two of those months—the fastest glacial retreat in the modern record. Now, after  a forensic analysis of the event reported today in  Nature Geoscience , researchers say they have identified the worrisome mechanisms behind it: a combination of glacial earthquakes and a swath of thinned ice popping afloat and breaking apart in a geological instant. If the same processes were to occur at larger Antarctic glaciers, they could rapidly accelerate the retreat of ice sheets and raise global sea levels, says Jeremy Bassis, a glaciologist at the University of Michigan. The study is “telling us that those worst-case scenarios are maybe not as implausible as some people might have thought.” ...[Jeremy] Bassis ...