A spar-type platform includes a hull defining a centerwell extending downward to a keel. The hull includes a reduced diameter neck portion for diverting ice flow. Adjustable ballast tanks allow the hull to be moved between a ballasted down position defining an upper water line, and a ballasted up position defined by a lower water line. A riser a support buoy is disposed in the keel. Risers extend through the centerwell, each having an upper portion extending upward from the support buoy and a lower portion supported in the support buoy. A disconnect system detachably connects the support buoy to the hull and the upper portion of each riser to the lower portion thereof, whereby the hull and the upper portion of each riser are selectively detachable from the buoy and the lower portion of each riser for movement to avoid a collision with a floating object.