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As Scotland votes, high turnout makes result ‘unpredictable’

Scotland headed to the polls on Thursday, for a historic vote on whether the country should secede from Great Britain and become independent. The results are likely to have serious ramifications for currency markets, with the British pound expected to move sharply on the news.

And as the world waits for the Scottish polls to close, the specific question of just how many Scots are turning out to vote is our first clue as to how the results will shake out.

Recent polls have mostly shown about a 4 percent edge for those voting against independence. On Thursday, a final poll by market research company Ipsos MORI for the London Evening Standard predicted that Scotland will vote no, 53 percent to 47 percent. But a larger-than-anticipated turnout could indicate that a "yes" vote is a bit more likely than the polls imply.

Read MoreScotland vote affects US investors: Jim O'Neill

A whopping 97 percent of eligible voters are registered to vote. And according to The Scotsman, 18.5 percent of those registered had already voted by 10 a.m. local time, just three hours into the all-day vote.

Campaigners wave Scottish Saltires at a "Yes" campaign rally in Glasgow, Scotland, Sept. 17, 2014.
Dylan Martinez | Reuters
Campaigners wave Scottish Saltires at a "Yes" campaign rally in Glasgow, Scotland, Sept. 17, 2014.

"What we know today is that turnout has been extremely high in Scotland," Oliver Harvey, Deutsche Bank FX strategist, said on CNBC's "Futures Now" on Thursday. "They're talking about turnout of over 80 percent, which is exceptional for a U.K. election. And on the margin, that might suggest that there are some demographics at play, particularly 16- to 18-year-old voters that might be turning out. Which could, on the margin, suggest that this vote could be quite unpredictable."

Similarly, Jens Nordvig of Nomura summed up the situation in a Thursday note: "The recent polls around the Scottish referendum has shown the 'no' camp slightly in the lead. ... But the lead has been just a few percentage points, hence the outcome is no done deal."

Read MoreMarkets await Scottish vote—'be very much concerned'

Harvey would expect a "yes" outcome to be a boon for the U.S. dollar, as it will likely drive the British pound significantly lower.

"I think if you do get a 'yes' vote, that is going to be a surprise, and that's going to be a positive for the dollar, which has been trading quite well recently," he said. "This would be another positive dollar story."

Read MoreScotland vote worries its No. 3 industry: Whisky

However, that's far from what markets are expecting. The pound actually rose significantly against the dollar in Thursday trading, perhaps in reaction to that late poll result.

"Given the moves today in sterling, the market is probably 95 percent priced for a 'no' outcome," Harvey said.

—By CNBC's Alex Rosenberg

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