SPICER—Wearing ice-covered boots and wiping away icicles from beards and noses, a crew of about 40 people were busy Wednesday harvesting massive ice blocks from Green Lake. Prized for the crystal-clear ice that reflects a blue hue as the sun filters through the bitter cold air, the 573-pound blocks of Green Lake ice will be the jewels used to build a 70-foot-tall ice castle in St. Paul for the Winter Carnival. St. Paul’s annual winter celebration will be extended an extra week this year—from