Model set-up and other boundary conditions.

<p>The tectonic boundary conditions (black) consist of a 50 mm/yr indentation of a rigid block at the southern boundary and fixed (<i>v</i>_<i>x</i> = <i>v</i>_<i>y</i> = 0) elsewhere. Vertical isostatic motions are allowed at the entire boundary (zero slope and zero momentum across the boundary). The harder block in red has 3 times higher viscosity than the rest of the model domain. The orographic precipitation model is controlled by a constant velocity and direction of incoming humid air (blue arrows). The initial topography is set flat and 35 m above sea level, with an additional random noise between ±5 m. In the text, the positive-<i>y</i> direction is referred to as ‘north’, and the positive-<i>x</i> direction is named ‘east’.