Major Ice Break-Out In Antarctica Expected

Press, Volume CVI, Issue 31230, 30 November 1966, Page 10

Major Ice Break-Out In Antarctica Expected

{Special Crspdt. N.Z.P.A.)

SCOTT BASE,

Nov. 28.

A major break-out of Antarctic ice in McMurdo Sound is expected this summer. Already there is more open water than usual, and most of the remaining ice is only a year old.

Since the New Zealand scientific station, Scott Base, was built 10 years ago, the McMurdo Ice Shelf fronting the base remained stable until the 1964-1965 summer. This ice was 100 feet and more thick, but two summers ago the McMurdo break-out extended further than usual, easing pressure on the ice in front of Scott Base, and allowing huge slabs to drift seawards from the coast.

Again, last summer, the

break-out followed a similar pattern, then broke further into the permanent ice shelf, exceeding the record noted by Scott’s expedition in the 19101911 summer.

Edge at Cape Evans

The starkly defined ice edge, where the liquid black sea swells against the solid white ice, is now at Cape Evans. Here McMurdo Sound is 40 miles wide, and for a distance along Ross Island ice clings to the coast then

swings in a great arc across the sound to the Prince Albert Mountains of the Victoria Land coast From this ice edge It is 25 miles south to Scott Base and the nearby break-out line—beyond which the 130,000 square mile Ross Ice Shelf pushes seawards at the rate of over half a mile a year. Its sea edge remains close to Cape Crozier. Some of this shelf deflects east-

wards, giving the McMurdo Ice Shelf a movement of just over 250 feet a year.

In front of Scott Base at present the annual sea ice is only eight feet thick. On it is an airstrip for supply aircraft arriving from Christchurch and “highways” from both McMurdo Station and Scott Base cross the ice. Vehicles and bulldozers haul laden sledges to and from the aircraft. However, this ice will soon be unsafe and by early next year will most likely be open water. An accurate prediction of the break-out is not possible,

so a constant watch has to be kept on the ice. Weaknesses, melt holes and cracks, are already showing and in front of Scott Base, seals have pushed up through the ice earlier than usual. Once this ice is considered unsafe, vehicles will have to go around the edge of Ross Island to an alternative airstrip on the permanent ice shelf. From around the Antarctic Continent other scientific stations report that more sea ice than normal broke away from coastal areas during October.

Away to the north of McMurdo Sound at the United States Hallett Station, ice has broken free in the bay. Similar early break-outs have occurred at Japan’s Showa Station (south of South Africa), and Australia’s Wilkes Station (south of Australia). Scott’s Moorings

On his first Antarctic expedition, Scott moored his ship, Discovery, in Winter Quarters Bay (now the location of the United States McMurdo Station) early in February, 1902. Pram Point, where Scott Base is built, was so named because some of the expedition went there in a pram dinghy. The following summer the break-out stopped many miles north of the Discovery anchorage, and, unable to be freed, the ship and expedition had to remain another year in Antarctica.

Since man began permanently occupying the McMurdo Sound area 10 years ago, the break-out has been creeping further south each season. Some theories attribute this to the effect of ice breakers causing a premature breakout in November; yet the extensive natural break-out recorded in Scott’s diary was only slightly exceeded last season.

In a study of theMcMurdo Sound ice break-out, Mr A. J.

Heine (Antarctic Division, New Zealand Department of Scientific and Industrial Research) writes that the main factor affecting break-out around the southern end of Ross Island is a combination of heavy sea swell, followed by strong winds from the south. The sea hinges ice up and down, then floats it away from the shelf, particularly where there are already weakening cracks. “Further north of McMurdo Sound these ice slabs jostle together as pack ice and subdue the power of the swell on the ice edge. “Although complete weather observations are made, no correlation is noticeable between these records and ice break-out patterns,” says Mr Heine.

When the ice broke away from in front of Scott Base last summer 70 to 80 knot southerlies whipped sea spray over the Base buildings, which are 25 yards from the coast.

Salt Corrosion

Humidity in Antarctica is so low that metals do not need protection from rust and now salt spray has corroded copper and steel fittings, particularly between outside instruments and the science laboratory. The Antarctic Division superintendent, Mr R. B. Thomson, has decided that some sea rescue equipment be installed at Scott Base this summer. “There is a full range of mountain and crevasse rescue equipment at the base, but now the open water is a new hazard to be prepared for,” said Mr Thomson. Scott Base leader, Mr C. M. Clark (Christchurch), said that when open sea appears in front of the base, buoys and rope will be mounted near the coast. Sea water freezs about 28.5 degrees F., depending on its salinity. It is said a person

loses consciousness after two-and-a-half minutes immersion in near to freezing sea water, and death follows soon afterwards.

The sketch map shows the southern portion of Ross Island, and the approximate ice edge of last summer's record break-out It is 25 miles from Scott Base to the nearest tip of White Island. The photograph shows the meeting of the McMurdo Ice Shelf and the sea.