So in my opinion, scarves is pronounced as the dictionary has it: with a Short O or /a/.
But I believe that scarf and other "ar" words that are followed by voiceless consonants, are not actually pronounced by most people with a Short O or /a/. I think they are pronounced with a Short U as in fun. (a short U+R, to be exact).
I think we open our mouths less on a "ar" before a voiceless consonant. I can't find any data for this, but I feel it. Am I crazy, or have I been pronouncing scarf, lark, art, harp, etc wrong all these years?
I was born in the American Midwest.