This highlighted that a backup, alternative, or redundant supply system is necessary for the USAP. The appropriate choices can both result in efficiencies in the present system and enable new major science by virtue of the developed logistics plus net USAP energy savings that can then be applied to science.

First, it is widely recognized that although the approach is not new, the most cost-effective manner to transport the large amount of fuel and cargo required for the USAP, with acceptable risk, is through shipborne delivery to the principal point of use and redistribution (i.e., McMurdo Station). The tonnage that USAP requires to be delivered to McMurdo Station makes annual air delivery of the total both impractical on several grounds and unrealistically expensive. Hence, it can be assumed that barring an as-yet-unprecedented crisis, fuel and at least a major share of cargo will be delivered there by sea. Also, there is no alternative deep-water harbor within hundreds of miles. Thus, if a ship with fuel or cargo destined for McMurdo Station cannot reach the pier, the USAP must contend with unloading the fuel or cargo onto shelf (glacial) ice or onto sea ice. Consequently, the preferred mode for shipborne logistics support remains to provide tankers and cargo ships, escorted to the pier by an icebreaker capable of opening the supply channel through the ice.

This mode of resupply, however, contains the single point of potential failure in the present system. If alternatives could be developed to accommodate an occasional year in which very heavy ice conditions preclude fuel delivery, the vulnerability of the resupply system would be lessened. It should be noted, however, that the heaviest ice years near McMurdo Station have recently occurred consecutively, not randomly. The presence of large icebergs kept sea ice in the McMurdo region, allowing it to grow very thick and hard in places beginning in 2000. Yet there remains the possibility that in any year the icebreaker(s) used to support the McMurdo break-in could be unavailable (e.g., damaged), the entry to the channel to McMurdo Station could be blocked by an iceberg, or other circumstances could prevent a complete seaborne resupply.

If one annual fuel delivery is missed, or deliberately skipped, the fuel storage capacity at McMurdo Station must be sufficient to supply the USAP for at least a second year; thus, a scheme to supply more fuel than at present is required to create the reserve. This is not yet possible, but there are feasible fuel management scenarios that may provide a fuel reserve. For example, an NSF internal study indicates that if total fuel storage at McMurdo Station is increased from the present 9.5 million gallons to 16 million gallons (neither unreasonable nor unduly expensive), and a tanker is used with 20 percent greater capacity than the one used at present, and if fuel reserves were employed on a one-time basis, the USAP could endure one missed annual delivery of fuel only three years after completion of the larger tank farm.

Another step in reducing the risk to the USAP from the dependence on annual delivery to McMurdo Station is through investing in resources to produce a paradigm shift in the South Pole Station supply chain logistics and methodology, with a goal to significantly reduce, if not eliminate, the single point of potential failure related to operating all South Pole Station logistics through McMurdo Station. At present, NSF is investigating the construction of a hard surface processed snow runway at South Pole Station capable of receiving heavy-lift wheeled aircraft—for example, directly from New Zealand or South America. This option appears to be relatively inexpensive and may take only a few years to construct. It also appears feasible to develop a safe, efficient ground-based traverse capability between various key points (e.g., McMurdo Station, South Pole Station, and an ice shelf or sea-ice edge) for support of both science and logistics missions of the USAP. The NSF reported that the proof-of-concept ground traverse between McMurdo Station and South Pole Station has now been completed.

These logistical changes would also allow existing resources to be used to support new expeditionary science and other program priorities. For example, a large number of valuable LC-130 aircraft flight hours—currently expended on fuel, cargo, and personnel transport flights between McMurdo and South Pole Stations—could be used to access parts of Antarctica that are now difficult or impossible for USAP to support by air from McMurdo Station.

In addition, other options may help reduce the portion of fuel and cargo required to be delivered directly to McMurdo Station. If the icebreaker(s) used to break in to McMurdo did not require refueling from the fuel delivered to McMurdo, the same fuel tanker used today could supply sufficient extra fuel to rapidly build a reserve, as long as the fuel storage capacity at McMurdo is increased. The present Polar class icebreakers require refueling in the Antarctic to maintain icebreaking capability because they do not have sufficient seawater ballast capacity to keep the hull at the depth needed to break heavy ice unless they are nearly fully fueled. NSF reports that it is examining the feasibility of these and similar measures, related to the systems under its purview.

Logically, it may appear that the present dependence on Polar class icebreakers would be eliminated by moving all USAP logistics to a base that did not require breaking heavy ice. An Antarctic coastal base must, however, offer more than simply a location accessible by sea. Major additional considerations include depth of the harbor, weather at key times of the year, suitability of local terrain for locating buildings and storage facilities, support for aircraft, relation to USAP science support and other missions, and so forth. While it is true that McMurdo Station and Scott Base (New Zealand station) are the only present-day Antarctic stations that require Polar class icebreakers for austral summer access, it should be recognized that these are the only Antarctic bases in the Ross Sea sector and also that their location is well chosen. For example, their location within the southwestern Ross Sea is particularly important because this area



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