PBS高端访谈:缅因州神奇的冰湖（在线收听）

And, finally, a very different story about ice. A small community outside Portland, Maine, got a lot of attention this week for a particularly frosty and rare natural phenomenon. The NewsHour's Julia Griffin, with the help of Maine Public Television, explains.

JULIA GRIFFIN: The icy oddity in Westbrook, Maine, this week made bystanders stop to take a second look. It wasn't the moon, or an alien spacecraft, but a huge circular disc of ice spinning ever-so-slightly in the Presumpscot River. Residents saw the disc form slowly over the course of a few days.

CATHI SAWTELLE, Local Resident: About a week or so ago, I noticed this small round piece of ice. And it would be swirling counterclockwise, just slowly.

JULIA GRIFFIN: Since then, the disc ballooned to more than 300 feet across, rotating like a giant Lazy Susan.

LYNDA ADAMS, Westbrook City Councillor: I think the ducks and the seagulls are enjoying the natural amusement ride going on in the middle of the river. It's been great.

JULIA GRIFFIN: It isn't the first time spinning ice circles have been spotted in the river, but it is the biggest anyone in Westbrook can recall.

TED SCAMBOS, University of Colorado at Boulder: It's a spectacular version of this. I don't think I have heard of any of them that are as large as the one near Westbrook.

JULIA GRIFFIN: Ted Scambos is a senior research scientist at the University of Colorado at Boulder. He said ice discs are rare because they require the right combination of temperature, river shape and water speed.

TED SCAMBOS: What you need is an area that has freezing conditions, but just barely freezing conditions, and a river with the right kind of bend in it, so that you get a large eddy that's almost circular.

JULIA GRIFFIN: And in those conditions, small pieces of ice can begin to solidify into a solid plate.

TED SCAMBOS: And once they do, they're going to get, sort of, shaved a little bit as they go around the riverbank each time, and that's what makes that perfect circle.

JULIA GRIFFIN: But, just like ice itself, the disc's movement froze Wednesday, a development that didn't surprise scientists like Scambos.

TED SCAMBOS: These things are very ephemeral, and it's great that people are appreciating it while it's happening, because it won't last long. They either break up by melting or they freeze up harder to the bank and then break up in pieces later on.

JULIA GRIFFIN: And that might happen sooner than Westbrook residents would like. While a paddle boarder managed to free the disk late Thursday, allowing it to spin again, a winter storm expected this weekend could break it apart or bury it in snow. For the PBS NewsHour, I'm Julia Griffin.

JUDY WOODRUFF: A spinning story.

最后，我们来介绍一个与冰有关的故事。位于缅因州波特兰外部的一个小社群本周获得了公众的关注，起因是这里出现了罕见的自然结霜现象。下面请听我台记者茱莉亚·格里芬从缅因公共电台发回的报道。

茱莉亚·格里芬：本周，缅因州出现的异常结霜现象让路人驻足。这既不是月亮，也不是什么外星航天器，而是普利桑普斯科特河上方盘旋的一个大冰盘。市民看到这个冰盘是在几天的时间里形成的。

凯茜，当地市民：大概一周前，我就注意到了这个小小的圆形冰状体。它当时在慢速做逆时针旋转。

茱莉亚·格里芬：从那时起，这个圆盘就开始扩大，直到成为300多英尺的样子，旋转起来俨如大块头的餐桌圆盘。

琳达·亚当斯，韦斯特布鲁克市议员：我觉得鸭子和海鸥们都在享受大自然的这一匠心之笔，在河中央嬉戏玩耍，景象实在美妙。

茱莉亚·格里芬：这不是河上第一次出现旋转的冰盘，但这绝对是韦斯特布鲁克目前为止最大的一次。

泰德，博尔德的科罗拉多大学：这景象让人叹为观止。我从未听闻韦斯特布鲁克附近有这么大的冰盘出现。

茱莉亚·格里芬：泰德是博尔德科罗拉多大学的一名高级研究员。他表示，冰盘本身就已经很罕见了，因为它们形成需要合适的温度、河谷形态、水速。

泰德：需要整片区域达到结冰的温度，但不能低于结冰的温度太多。河流也要有合适的曲度，这样会有近乎圆形的大涡流。

茱莉亚·格里芬：符合了这些条件，小片的冰才能凝固成固态的圆盘。

泰德：冰盘形成后，圆盘在每次经过河堤的时候形状都会有所削减，这样就会形成正圆形。

茱莉亚·格里芬：但跟冰的相同点是——这个圆盘每周三都会停止移动。这样的景象也在泰德等科学家的意料之中。

泰德：这些现象都是暂时的，大家能欣赏这样的现象是好事，毕竟这也不会持续很长的时间。冰盘最后都会融化分解，或者结冰扩张到河岸上，然后分裂成碎片。

茱莉亚·格里芬：结局出现的时间可能比韦斯特布鲁克希望的要早。虽然周四晚上冰盘得以再次旋转，但本周末的冬季暴风雪可能将其撕裂或者埋在雪中。感谢收听茱莉亚·格里芬发回的《新闻一小时》。

朱迪·伍德拉夫：感谢您的精彩分享。