Ice-Shelf Mystery

Press, Volume CII, Issue 30302, 30 November 1963, Page 12

Ice-Shelf Mystery

The mystery of fish, sponges, and other bottomliving creatures found dead on top of the ice of the McMurdo ice-shelf remains a mystery, because the theory which has been supposed to explain it is not borne out by investigation, Mr A. J Gow. a New Zealander working at McMurdo station for the United States Army Cold Regions Research and Engineering Laboratory, told a reporter of “The Press." The phenomenon was first noticed by a member of Scott's expedition, who found several large headless fish Since then, many kinds of bottom-living creatures have been seen, including some still attached to pebbles. No report has ever been made of similar occurrences in any other part of Antarctica, however—or anywhere else in the world, for that matter Some of the fish species found on the ice are not known from living -pecimens. Material from some of the creatures found on the shelf has been subjected to carbon--14 dating, but the ages found —of the order of two millennia—are quite unreliable because of some factor in the Antarctic environment which Introduces a margin of error of about the same size. The theory commonly held up to now assumes that the c-eatures came up through the ice. When ice forms on the sea-bed. fish and other animals are trapped and frozen into it Over the years, the ice at the surface progressively disappears through sublimation or melting and evaporation, so the ice from below makes its way to the top. carrying the trapped creatures with it Mr Gow's work in his coldlaboratory at McMurdo station, however, has convinced him that this explanation is untrue, for he has identified the ice of the iceshelf on which the creatures have been found as glacial ice. originating on land—not sea-ice as ’he theory would require. Glacial ice has a characteristic structure in which the ice-crvstals have b«en aliened through shearice stre’-ses which develop di-ine movement: sea-ice s'”'w* little or no such alignment and. in addition, has

brine enclosures which, even if they eventually disappear, leave their mark in the icestructure. Mr Gow can at present suggest no alternative theory for the presence of the creatures, but thinks the phenomenon may have some connexion with the vertical crevices in the ice which are found off most of the beaches in the area. Professor D. E. Wohlschlag, of Stanford University, California, however, who. is the leader of a team investigating the fauna of the sea beneath the ice of McMurdo Sound, still defends the original theory. Photographs of ice forming on the sea-bed show what is probably the start of the process by which the creatures are brought to the surface, he says.