To cancel A/B as you are drifting on a windy contaminated runway,DO NOT SWICTH OFF the A/B manually but use Manual braking.
90% N1 reverse...must be a hell of a short and contaminated runway...
The point made by Centaurus is valid. The autobrake system can be disarmed by moving the selector switch to the Off position. Or by moving the speed brake lever to the down detent. Or advancing the forward thrust lever(s) after touch down. Or: applying manual brakes.
The FCTM states the brakes should be released if the aircraft starts drifting sideways on a slippery runway. By applying manual brakes to disarm the autobrakes you are momentarily applying more brake pressure which contradicts the requirement to release the brakes. There can also be a period where the pilot is unsure if indeed he has applied sufficient foot pressure to disarm the autobrakes. A close eye on the autobrake disarmed light is vital to confirm that the disarming has taken place.
The main thing is to get the autobrakes disarmed promptly and of all the choices under the circumstances it would be logical to use the autobrake selector to the Off position.
Braking efficiency may be greatly reduced on a slippery runway, leaving only the spoilers and reverse thrust to do their work in reducing the landing roll distance. Reverse in particular is more efficient if used at high speed which means immediately on touch down. See FCTM under heading of Reverse Thrust operation. It states: "Maintain reverse thrust as required,
up to the maximum, until the airspeed approaches 60 knots".
On a slippery performance limiting runway it is good airmanship to use full reverse thrust until you know for sure the aircraft will safely stop considering the reduced braking efficiency associated with slippery surfaces