ROYAL CARIBBEAN INTERNATIONAL will send the Empress of the Seas to Pullmantur, its Madrid-based sister brand, in spring 2008. Royal Caribbean said the Empress' last cruise with the line would be March 7; passengers booked on sailings after that date would be contacted by Royal Caribbean in order to transfer their booking to similar accommodations on another ship. The Empress was built in 1990 and refurbished in 2004; at 48,000 gross tons and 2,020 passengers it is Royal Caribbean's smallest ship