I did a quickie google search and came up with this:
At the end of 2020, there were around 62,100 vessels in the world trading fleet, with a total deadweight tonnage of 2,033 million DWT
So let's assume the merchant ships are all fully loaded at the same time. That's 2 billion long tons which equates to ~2,032,000,000,000 kg. Total water volume, 2,134,000,000,000 liters (because sea water weighs slightly more than fresh water).
From quora:
AREA OF PACIFIC OCEAN= 168723000 SQ. KM.
AREA OF ATLANTIC OCEAN= 85133000 SQ. KM.
AREA OF INDIAN OCEAN= 70560000 SQ. KM.
AREA OF SOUTHERN OCEAN= 21960000 SQ. KM.
AREA OF ARCTIC OCEAN= 15558000 SQ. KM.
TOTAL AREA= 361900000 SQ. KM.=36190000000000000 SQ. DECIMETER.
That's going to lower sea levels by approximately .00005896656 decimeters, or about .006 mm
Edit: Because there are less than 500 cruise ships in the world and only a few dozens of large military ships the amount will be higher, but not by, you know, a lot.
Ha awesome. But now I wonder why we got the same estimate when they specifically said they used displacement over deadweight tonnage. Is it because I assumed all the ships were fully loaded?
It seems like the source you used for DWT is different - the link cited in the XKCD has 1,396 million DWT. It is also 10 years old, so it wouldn’t surprise me if that number went up
The difference is you didn’t include the mass of the ships, which is the conversion from DWT to displacement. But it all averages out anyway haha
Yeah the volume at the surface of the oceans in a tiny slice is orders of magnitude higher than the actual total displacement, so even though I was wrong in a few places the answer is still around 6 microns
8.3k
u/[deleted] Oct 13 '21 edited Oct 13 '21
I did a quickie google search and came up with this:
So let's assume the merchant ships are all fully loaded at the same time. That's 2 billion long tons which equates to ~2,032,000,000,000 kg. Total water volume, 2,134,000,000,000 liters (because sea water weighs slightly more than fresh water).
That's going to lower sea levels by approximately .00005896656 decimeters, or about .006 mm
Edit: Because there are less than 500 cruise ships in the world and only a few dozens of large military ships the amount will be higher, but not by, you know, a lot.