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原文传递 Polar Icebreakers in a Changing World: An Assessment of U.S. Needs.

题名：	Polar Icebreakers in a Changing World: An Assessment of U.S. Needs.
关键词：	polar regions,icebreakers/arctic ocean, antarctic ocean, economic development, scientific research, sea ice, coast guard ships, missions, marine transportation/
摘要：	The United States has enduring national and strategic interests in the Arctic and Antarctic, and the importance of these regions is growing with time. In the north, the United States has territory and citizens above the Arctic Circle, creating significant national interests. In the south, the United States maintains three year-round scientific stations to assert U.S. presence and ensure U.S. leadership among the nations that are signatories to the Antarctic Treaty. The United States uses this leadership to ensure that the Antarctic Treaty area, comprising all land and waters below 60 degrees South latitude, is preserved for peaceful purposes and scientific research. Antarctica is an ice-covered continent surrounded by an ocean, parts of which are seasonally ice covered. The central Arctic Ocean is perpetually ice covered, and in the winter ice extends along the northwestern Alaskan coast and south through the Bering Strait. Asserting national interests and achieving national purposes in both polar regions requires polar icebreakers, ships capable of operating in a variety of challenging ice conditions. Over the past several decades, the U.S. government has supported its polar interests with a fleet of four icebreakers. Three of these, including the world's most powerful nonnuclear icebreakers, POLAR SEA and POLAR STAR, and the modern research icebreaker HEALY, have been operated by the U.S. Coast Guard. These three ships are designed to support U.S. Coast Guard missions and to support science. / Supplementary Notes: Prepared in cooperation with National Research Council, Washington, DC. Polar Research Board. Sponsored by Department of Transportation, Washington, DC. / Availability Note: Order this product from NTIS by: phone at 1-800-553-NTIS (U.S. customers); (703)605-6000 (other countries); fax at (703)605-6900; and email at orders@ntis.gov. NTIS is located at 5285 Port Royal Road, Springfield, VA, 22161, USA.
报告类型：	科技报告