alarm clock on shabbat

Question

Situation: one uses an electricity-powered alarm clock with an LED (LCD?) display. When the alarm goes off in the morning, it will continue buzzing at a very high decibel/volume --until it is shut off. Question: If one forgets to switch the alarm off before shabbat, such that it will keep buzzing/beeping (loud enough to be heardthroughout the house) until motzaei shabbat, is there any permitted way to switch it off? Paranthetically, Before it sounds off at the pre-set time, switching it off means switching a small green "lite" in the corner of the screen. (I was thinking along the lines of pessik reshe d'la niha leh bid'rabbanan with a shinui [or kil'ahar yad] so as not to disrupt the oneg shabbat -- that's 5 "snifim letzaref lehattir.") Thank you!