What are the main contributors to observed sea level rise in the modern era?

• A. Thermal expansion due to warming and loss of land ice from glaciers and ice sheets.
• B. Only loss of land ice.
• C. Sea level rise is not related to warming.
• D. Only thermal expansion.

Answer: (A)

Two processes drive observed sea level rise in the modern era: thermal expansion of seawater as it warms, and the addition of water from melting land ice such as glaciers and ice sheets. When ocean temperatures rise, seawater expands, increasing volume and raising global sea level. At the same time, glaciers and the major ice sheets in Greenland and Antarctica lose mass, with that meltwater flowing into oceans and contributing to sea level rise. Together, these two mechanisms account for most of the recent rise, both tied to global warming from human activities.

Why the other ideas don’t fit: focusing only on land ice ignores the substantial contribution from warmer water expanding, while focusing only on thermal expansion misses the ongoing input from melting land ice. And it's incorrect to say sea level rise isn’t related to warming, since both expansion and melt are direct responses to higher temperatures.