GED Science TestEarth and Space ScienceMedium
A climate scientist is analyzing data on global ocean temperatures and sea levels over the past century. They observe a consistent trend of rising ocean temperatures and an accompanying increase in sea levels. Which primary factor directly contributes to the rise in sea levels as ocean temperatures increase?
- AIncreased precipitation over oceans.
- BSubduction of oceanic crust.
- CThermal expansion of seawater.
- DMelting of sea ice.
Show answer & explanationAnswer & explanation
Correct answer: C. Thermal expansion of seawater.
As ocean temperatures rise, seawater expands in volume (thermal expansion). This expansion is a significant contributor to global sea-level rise, distinct from the addition of water from melting land ice.
Why the other options are wrong
- A. Increased precipitation over oceans would have a minor, temporary effect, not a primary long-term driver.
- B. Subduction is a tectonic process that occurs over geological timescales and does not directly relate to temperature-driven sea level rise.
- D. Melting sea ice does not directly raise sea levels because it is already displacing water.
Thermal Expansion (Seawater)
The increase in the volume of seawater as its temperature rises, contributing significantly to global sea-level rise.
- Water expands when heated, even slightly.
- Accounts for a substantial portion of observed sea-level rise.
- Distinct from the addition of water from melting glaciers and ice sheets.
Memory trick: Warm Water, Wider World, Waving Goodbye to Shores.