Volume

• Volume of the atmosphere: not really meaningful.
• Volume of Earth’s oceans: 1.335×10¹⁸ m³

Mass

• Mass of the atmosphere: 5.15×10¹⁸ Kg
• Mass of the oceans: ~1.4×10²¹ Kg
  • Average salinity: 0.035 Kg salt per Kg water, so 3.5% by mass.
• The oceans are 272x the mass of the atmosphere.

Specific Heat

• Specific heat of “air” at 250K is 1005 J/KgK
• Specific heat of ocean water is ~4000 J/KgK

Total Heat Capacity

• Total heat capacity of the atmosphere: 5.2×10²¹ J/K
• Total heat capacity of the oceans: 5.6×10²⁴ J/K
• The heat capacity of the oceans is ~1,077x the heat capacity of the atmosphere.

I think it’s interesting that the ocean is only 272x the mass of the atmosphere. That is knowable intuitively if you know the approximate pressure deep-sea subs deal with or know that 10m of water is equal to about 1 atmosphere of presure.

Another interesting scale to put in perspective is that the hydrosphere is about 0.023% of Earth’s total mass. So the Earth mass is about the mass of 4,300 oceans.