The Royal Institution

Why Are Sea Levels Rising? With Oceanographer John Englander #shorts #science #sealevels

In a short explainer, oceanographer John Englander breaks down the physics behind rising seas, using a simple ice‑cube demonstration to illustrate why melting ice matters. He notes that ice floats because it expands before freezing, making it about 9‑10 % less dense than water. When glaciers or ice sheets that rest on land reach the ocean and calve into icebergs, their subsequent melt adds fresh water to the sea, directly raising the water level. A comparable contribution comes from thermal expansion: as the ocean warms, water volume increases, accounting for roughly 4‑10 cm of rise over the past century. Englander emphasizes that thermal expansion has supplied about half of the observed sea‑level increase, a figure he illustrates with the “ice cube in a glass” analogy. He also points out that the century‑long temperature rise of about one degree Celsius has already driven this expansion. The combined effect of continued glacier melt and accelerating thermal expansion means future sea‑level rise will outpace current trends, heightening risks for coastal infrastructure, real‑estate markets, and climate‑adaptation planning worldwide.