In stark contrast to last winter's weeks' long cold-box-like weather, warming conditions at Apostle Islands National Lakeshore have prompted officials to close their "ice caves" for the season after just nine days.

Last winter the shoreline caves draped with ice were open to the public for 10 weeks, luring an estimated 138,000 visitors and generating some $10 million in area revenues. This year, the ice caves opened to visitors on February 28, but deterioriating ice conditions on Lake Superior prompted lakeshore Superintendent Bob Krumenaker to close the caves Monday night at 7 p.m.

The decision came in the face of a weather forecast that included up to gale-force winds and temperatures in the 40s and 50s for the next week or more.

"Ice is beginning to melt and the risk of ice formations falling raises safety concerns," a lakeshore release said.

Though running only nine days, nearly 36,000 people were able to visit the ice caves this winter. This past weekend brought out more than 17,000 visitors, the lakeshore reported.

"This has been an amazing boon to the regional economy and although we would love this to continue for another month, the safety of the visitor always comes first," said Bayfield Chamber of Commerce and Visitor Bureau Executive Director David Eades.  "Although the sea caves will not be accessible again until summer, there are still plenty of other winter activities to enjoy in the area."