Losing a giant needle in a haystack … or sand dune

I just read in New Scientist that apparently climate change leads to bigger sand dunes.  I non-scientifically figured that seems kinda obvious really.  Less plants and more erosion would likely result in more dunes – and some of them would probably be bigger than normal.

But apparently it’s not that simple.  Sand dunes have a habit of collapsing after they reach a certain height, so more of them doesn’t necessarily mean bigger ones:

“Once the dune becomes big enough to interact with the boundary layer [the lowest layer of the atmosphere] it creates waves in the air. These waves feed back and interact with the sand below, keeping a lid on the dune size,” explains co-author Brad Murray of Duke University in Durham, North Carolina.

Warmer air increases the thickness of the boundary layer, which explains why Earth’s largest dunes are found inland, in the hottest part of the desert. It also suggests that if global warming heats the planet in the right place, then dunes could get bigger.

The biggest sand dunes in the world are half a kilometre tall.  That would put NZ’s tallest building, the Sky Tower, about 170 metres underground if it were to encounter sucha dune.  (A silver lining to a sand storm cloud?)

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