Turner Pass is incorrectly marked on Topo maps. It is the col just east of Pt 2119 at the base of Madeline's North West Ridge.
From Turners Bivouac the best route is to climb up to the upper Madeline Snowfield at around 2200 metres altitude and traverse in a northerly direction to the pass, across exposed snow slopes. The pass can also be reached by descending off the northern end of the main Madeline Snowfield, and sidling above the lower Age Glacier to the base of a prominent couloir, which leads to the pass.
The first crossing reached the Donne Glacier by descending a narrow gully directly below the pass. This may potentially still be feasible, perhaps when well filled with snow, but a better route crosses the snowfield on the north side of Madeline before angling back west down a slab ramp to about 1600 metres altitude, and then sidling back east below bluffs to the tussock slopes above the Donne Lake outlet.
First crossing: Samuel Turner and Party, 1921.
Ascent to Turner Pass from Donne Lake as described: Ruari Macfarlane, Tom Riley, Mark Watson, March 2021.