The Persian Gulf averages about 35 metres in depth and the seabed between Abu Dhabi and Qatar is even shallower, being mostly less than 15 metres deep. For thousands of years the Ur-Shatt (a confluence of the Tigris-Euphrates Rivers) provided fresh water to the Gulf, as it flowed through the Strait of Hormuz into the Gulf of Oman. Bathymetric data suggests there were two palaeo-basins in the Persian Gulf. The central basin may have approached an area of 20,000 km2, comparable at its fullest extent to lakes such as Lake Malawi in Africa. Between 12,000 and 9,000 years ago much of the Gulf’s floor was not covered by water, only being flooded by the sea after 8,000 years BP.[27]
It sounds like a really big area, most of the Persian Gulf, that was flooded. Maybe it was gradual over a few hundred years. Maybe some sort of natural dam suddenly burst.
The Missoula flood, which I mentioned above, was catastrophic - the Columbia River had been dammed by a glacier, which caused an inland sea (Glacial Lake Missoula) to form stretching from central Washington all the way to western Montana. When that glacier gave way, the lake drained into the Pacific over the course of about 2-3 weeks, with 400 million cubic feet of water (about ten times the flow of every river that exists on Earth today combined) flowing every hour at a speed of 45 MPH.
I don’t know if there’s any archaeological evidence for such a flood happening in the Persian Gulf, but as I said there is Native American oral tradition about the Missoula flood, so if there was one, the story certainly could’ve survived. I personally lean toward the idea that the Mideast flood myth had more to do with the fact that annual river flooding was central to ancient agriculture there, though.
There’s a controversial but non-crackpot hypothesis that the biblical narrative of the deluge has its roots in a catastrophic inflow of Mediterranean water into the Black Sea, which had previously been a large inland lake, in the 6th or 7th millennium BC. This would have occurred over the course of a year.
During the LGM the Persian Gulf was a lush river valley. It would have had abundant wetlands and good hunting. I think that’s where the ancestors of the Sumerians came from. They attributed their origin to a place in the Gulf named Dilmun. It was probably the island of Bahrain, which would have been a mountain during the LGM and the focus of any cult that worshiped in high places. This would explain why the origins of the Sumerians are so mysterious and why they can’t be connected with any other people: their original homeland was drowned.
There are many deluge myths. In ancient times, for most observers, the “whole world” was what you could see from one horizon to another, maybe with a couple days walk in either direction. So a flood doesn’t have to be particularly large for observers to conclude that it covered the whole world. Or, that since an observed flood nearly covered the whole world, then maybe in the past there was a bigger one that actually did cover the whole world.
None of this requires that an Ice Age come to an end, it could be just once-in-a-millennium combination of extremely heavy snowfall in the mountains and a very warm spring season. It sounds unlikely, but at any given time, there’s a “once in a lifetime” weather event happening somewhere on the globe. The world is a big place, lots of moving parts, lots of ins and outs.