Empirical constraints on ice cliff calving.

Ice cliffs taller than 15 meters are rare at Earth's ice sheet margins, and their calving rates are higher than current models predict, but runaway retreat is unlikely.

• Why it matters: Understanding the maximum height and calving behavior of ice cliffs is crucial for predicting ice sheet stability and sea level rise, yet tall cliffs are rarely observed.
• What they did: The study measured 15,330 ice cliffs using laser altimetry and analyzed how cliff height relates to mélange thickness, water depth, and crevassing, revealing key factors influencing calving.
• The result: Tall cliffs calve more rapidly than models assume, but processes like dynamic thinning and retreat into low-gradient regions prevent runaway retreat, indicating that projections may underestimate subannual calving rates.