If all the earth's surface water vanished, would most of us die of anoxia?

In My Humble Opinion
21

Here’s the Wikipedia page for Elevation, which has a nice histogram of the land surface. Note that the horizontal axis represents area, so that area on the graph represents volume. You need to find the elevation above sea level where there is as much atmosphere below that elevation but above sea level, as there is water below sea level, but above the ocean floor.

The mean ocean depth is about 4 km. If the land were all at sea level, that elevation would be the 9,000 feet (about 2740 meters) I calculated earlier. If there were 4 km cliffs right near all the shores, then that elevation would be 4 km. The true land height closer to sea level than to 4 km, so the new air pressure at what is now sea level will be closer to the air pressure at 2740 meters than to the air pressure at 4 km.

(That histogram also lists the highest permanent human settlement as being at 5.1 km, or 16,728 feet. They’ll be dead, but that suggests Denver might be OK.)

22

billfish78 the reason for O2 supplementation is for when the human body has not been given TIME for physiologic acclimation. You have probably heard of athletes (runners and cyclists in particular) who will train at high altitudes before a race at ~sea-level or such. Extra red blood cells, hemoglobin and whatever else it is exactly that allows persons to live in upper Himalayas, but a plane gets you there faster than acclimation. See where I am going with this? I lived near Sun Valley, ID for a decade and my brother was in at Fort Ord, California doing Infantry for 7 years - a bad-ass hiker, basically, and he lugged a Dragon around, too. Strong, tall guy. When he visited one year, we went Elk hunting north of Stanley and hiked up many ridges of 8-9000’. I pounded him into the ground, while chain-smoking and drinking beer. He got so winded I had to carry his rifle down, LOL. He arrived less than 12 hours earlier by plane, and I enjoyed the hell out of that day. I also treated (X-ray) a lot of ski injuries from sea level folk who fainted at top of lift when they first started exerting themselves. Almost predictable.

23

Disregarding all the scientific blabber, my answer to the OP would be: “No, they would die of dehydration”

24

I put the histogram in LibreOffice, and made lines to approximate Elevation Vs. surface area. The ends of the lines were
Area, feet
0.015, 3100
0.045, 1200
0.857, 500
0.710, 0

Using that, I get that 85.7% of the Earth has an elevation of less than 500 meters, 95.5% has an elevation less than 1200 meters, and 98.5% has an elevation below 3100 meters.

Working in volume units of meterEarth_Surface_Area, the amount of water removed is 0.714000[sup][1][/sup] = 2840*. The volume of atmosphere below 500 metes is 390, the volume between 500 and 1200 is 694, and the volume between 1200 and 3100 is 1843. That sums to 2867, which is about the amount of water removed, so current sea level will be about the same pressure as an elevation of 3100 meters, or about 10,000 feet[sup][2][/sup].

[1] More precisely, the mean ocean depth is… somewhere between 3680 meters and 4,267 meters? WTF, science?

[2] The OP didn’t mention if ice in Antarctica and Greenland disappears as well, and that histogram doesn’t say whether ice is counted as land or water, so that might change +/- 80 meters, or 260 feet.