Less than a year after launching Guardian Australia, editor-in-chief Katharine Viner is moving to New York to take a similar role for Guardian US.

The appointment is one a series affecting Australian, UK and US operations. Emily Wilson – currently UK network editor of theguardian.com – moves to Sydney to replace Viner.

Launched last May on the back of an established local audience, Guardian Australia claims almost four million browsers in the country, and has grown its staff from three to more than 50 in two offices.

Viner says the launch was “the professional and journalistic experience of a lifetime”.

Commercial targets are being exceeded by almost 300 per cent and the publisher has established itself as part of the national conversation, not least because of its role in the release of leaked information that Australia had spied on Indonesian president Susilo Bambang Yudhoyono and his wife.

Now, she says, “there are no limits to what Guardian Australia can achieve”.

In New York, Viner takes over the US news operation built by Janine Gibson over the past three years, while Gibson moves to London as a deputy editor of Guardian News & Media and editor-in-chief of theguardian.com.

Editor-in-chief of Guardian News & Media Alan Rusbridger says she has done “a terrific job” in Australia, opening a brand new operation and quickly establishing the Guardian as a force to be reckoned with in Australian journalism: “She is a fantastic editor and, under her leadership, Guardian US will continue to go from strength to strength,” he says.

Viner and Wilson joined the Guardian within a couple of years of each other – Viner from the London Sunday Times in 1997, and Wilson as health editor in 1999 from the Daily Mail and Daily Mirror after a trainee role at the Bristol Evening Post.