Sledding and ice fishing on the Han River may become history as the river running through Seoul is less likely to freeze during winter due to climate change.

The river froze over for as long as 80 days in the 1900s, but due to climate change the period was shortened to an average of 14.5 days in the 2000s, the Seoul Metropolitan Government said Friday in a report on the Han River history.

This year, the river first froze on Jan. 14, a day later than usual and 12 days later than last year.

Last year’s winter marked the longest cold spell in recent years.

“The river starts to freeze on Jan. 13 on average and beging thawing on Feb. 5, but the effects of city life such as warm water released from homes and buildings, and vehicle exhaust gas make the river less likely to freeze,” said a city official.

With the weather getting milder, the river is covered with thin ice, making it dangerous to step on, officials warned.

“Citizens often ask us whether they may sled on the river when the river gets frozen. We rather recommend going to a riverside sleigh park near Ttukseom,” said the official.

The whole surface used to freeze as thick as 30 to 50 centimeters, but nowadays it doesn’t freeze as much, with the ice only around 5 to 10 centimeters thick, he said.

He added that many citizens are keen on the frozen river.

But, he advised citizens to take caution, saying that the point of measure by the weather agency is different from the frozen spots seen by citizens.

Whether the river is frozen solid or not is determined by how thick the river freezes under the Han River Bridge. This is the last spot to be frozen as the river in that area is deep with swift-flowing torrents, the report said.

The spot has been the standard point of measuring the frozen state of the river since the Korea Meteorological Administration started to compile related records in 1906.

By Lee Woo-young  (wylee@heraldcorp.com)