Vessel Traffic Overview

Updated:October 9, 2009 14:51

Link to website on marine traffic in the Aleutians:   Live Ships Map - AIS - Vessel Traffic and Positions

Notice: Vessel positions may be up to one hour old or incomplete. Data is provided for informational reasons only and is not related by any means to the safety of navigation. All rights reserved. No part of MarineTraffic may be copied, reproduced or retransmitted in any material and form or by any other means, without the prior written permission of the Scientific Head and the University of the Aegean.

Several recent incidents involving freight vessels in transit near the Aleutian Islands have focused attention on the oil spill risk posed by vessels operating within the productive fishing grounds and sensitive wildlife habitats of Alaska’s Aleutian chain. In December 2004, the M/V Selendang Ayu lost power, drifted aground, and broke apart near Unalaska Island, spilling an estimated 335,000 gallons of intermediate fuel oil and marine diesel oil. Approximately seven years earlier, another freighter, the M/V Kuroshima, ran aground at Unalaska Island and spilled approximately 40,000 gallons of Bunker C fuel oil. In July 2006, the car carrier M/V Cougar Ace capsized while transferring ballast approximately 200 nautical miles southwest of the Aleutians and was ultimately towed to an anchorage on Unalaska Island.

While the Cougar Ace incident did not result in a significant spill, it was the third major freight vessel casualty in the vicinity of the Aleutian Islands in less than a decade. After the Kuroshima incident, the State of Alaska passed a law requiring nontank vessels greater than 400 gross tons that call on Alaska ports to file oil spill contingency plans with the state. The federal government has recently followed suit with a law requiring oil spill contingency plans for nontank vessels calling at US ports. However, the Selendang Ayu was engaged in innocent passage through Alaska waters, while transiting the North Pacific great circle route from Seattle to China. The Cougar Ace was in international waters transiting the southern great circle route, well south of the Aleutians. These vessels were therefore exempt from State and federal oil spill planning requirements.

At the time of the Selendang Ayu casualty, it was known that vessels passed through the Aleutians on trans-Pacific voyages between East Asia and North America ports. The number and type of vessels using this trade route was not known. This report characterizes the type and amount of vessel traffic moving to, from, within and through the Aleutians Subarea. This includes available data regarding:

• The number, size, and type of vessels that transit the great circle route between the coastal ports of North America and East Asia ports, and the general type and quantity of fuel oil capacity.
• The number, type, and size of vessels calling at Aleutian ports.
• Type and quantity of oil transported as cargo to and through the Aleutians Subarea.
• Current tugboat traffic in the Aleutians, particularly with regard to tugs that may be able to come to the aid of a stricken vessel.

The Northern Great Circle route of the North Pacific Ocean

A great circle is the shortest distance between two points on a sphere. Vessels transiting an ocean between two continents may follow a great circle route because it is the shortest distance, or they may deviate from the great circle route where favorable weather and sea states allow for faster travel.

On many map projections a great circle route is not a straight line. Figure 1 shows a gnomonic map projection of the North Pacific where the great circle route is a straight line. As seen on this map, a great circle route from Yokohama, Japan to Seattle passes through Unimak Pass and the Aleutian Islands. Figure 2 shows this same route on a Mercator projection where, because the map is flat and the earth is curved, the route appears as a “great circle,” or more accurately, a semi-circle.