Why do sea levels rise when the planet warms?

When the ocean absorbs heat, water expands, which increases sea level even before any ice melts. Warming also causes glaciers and ice sheets on land to lose mass, adding water to the sea. Since the late 19th century, global mean sea level has risen by over 20 centimetres, with the rate accelerating in recent decades. Satellite records since 1993 show a faster rise than the long-term historical average. Coastal communities are affected by higher storm surges, saltwater intrusion, and more frequent flooding.