WTN: acidity in Cal. Syrah question

I just opened for supper a 2009 Aldrich Browne Syrah from the Moriah Vyd. on Mendocino Ridge. I was struck immediately by the prickly acidity. I have seen this before with new world Syrah, both from USA and from Australia and now wondering what causes this. With brisk stirring, (my wife uses a whisk) this prickliness seems to disappate. The wine , otherwise, was quite enjoyable with good plum fruit and fine tannins. Is this a slightly incomplete fermentation? No bubbles were seen.

[David M. Bueker]

I have run into it enough that I asked a couple of wine makers. Consensus is trapped CO2 due to reductive wine making. It's definitely not refermentation.

Some of the Donkey and Goat Syrahs can exhibit this.

Aussie Shiraz sometimes has the same issue.