By SETH BORENSTEIN, AP Science Writer Canada's 4,000-year-old Milne Ice Shelf on the northwestern edge of Ellesmere Island had been the country's last intact ice shelf until the end of July when ice analyst Adrienne White of the Canadian Ice Service noticed that satellite photos showed that about 43% of it had broken off. She said it happened around July 30 or 31. Two giant icebergs formed along with