Which statement about oceans is correct?

Question

BlackTom AI · Accepted Answer

Earth’s ocean area relative to the planet and the comparative warming of ocean surface versus land are the two key facts here.

Relevant knowledge points:
- Earth’s total surface area ≈ 510 million km²; global ocean area ≈ 361 million km². 
- Water has a much higher heat capacity than land and is subject to vertical mixing and evaporative cooling, so ocean surface temperatures respond more slowly to radiative forcing than land surface air temperatures.
- Observations show land has warmed more (rate and magnitude) than the ocean surface over recent decades, even though the oceans have absorbed the majority of excess heat into deeper layers.

Step-by-step reasoning and calculation:
1. Compute ocean fraction: ocean area / total area = 361 million km² ÷ 510 million km² = 0.7078 ≈ 71%. This yields the commonly quoted 71% ocean coverage of Earth’s surface.
2. Explain temperature behavior: because water’s specific heat (~4184 J·kg⁻¹·K⁻¹) is far larger than that of typical soils and because ocean surface temperatures are moderated by mixing into deeper waters and by evaporation, the same added energy produces a smaller change in sea-surface temperature than in land-surface/air temperature. Empirically, global mean near-surface air temperature over land has increased substantially more than sea-surface temperature in observational records.

Why the statement is correct:
- The numerical fraction (≈71%) is supported by area data and the physical explanation (higher heat capacity, mixing, evaporation) explains why ocean surface temperatures have increased less than land temperatures, even though oceans store most of the added heat at depth.

Why common alternative claims would be wrong:
- Saying oceans cover much less than 71% is contradicted by area data.
- Claiming ocean surface temperatures have increased more than land ignores the physical heat-capacity and observational evidence showing land warms faster.
- Claiming oceans are cooling contradicts long-term measured warming (especially in the upper ocean layers).

Conclusion: The provided statement is correct: oceans make up about 71% of Earth’s surface and their surface temperatures have increased less than those of land.

Which statement about oceans is correct?单项选择题

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