DUBLIN – Iceland’s volcano has produced a 1,000-mile-wide ash cloud off the west coast of Ireland that will force western Irish airports to close today.

The Irish Aviation Authority said shifting winds, currently coming from the north, had bundled recent days of erupted ash into a massive cloud that is growing both in width and height by the hour.

Eurocontrol, which determines the air routes that airliners can use in and around Europe, says the ash accumulation is posing a new navigational obstacle — because the cloud is gradually climbing to 35,000 feet and into the typical cruising altitude of trans-Atlantic aircraft. Until recent days, the ash had remained below 20,000 feet.

The Irish Aviation Authority said the engine-wrecking ash would skirt Ireland’s western shores today, forcing a half-dozen airports to ground flights.

The latest alert came hours after British and Irish authorities declared the all-clear after much of the same ash was blown southwest from Scotland through Ireland in mid-week, closing airports along the way.