Operation Deepfreeze has been so thoroughly publicized that it makes an Antarctic expedition sound no more hazardous than a tourist’s world cruise. The truth is that the notoriously bad Antarctic weather, low temperatures, and difficulties in communications, logistics, and navigation severely challenge the best men and equipment available. And for the naval aviators of Operation deepfreeze there is an additional hazard, that peculiar polar phenomenon known as a “white-out.”
The effect of white-out is a complete loss of shadow and of horizon definition. Depth perception and visual perspective rapidly approach the vanishing point. Some aviators caught in a white-out may also experience acute vertigo. Aerial existence during this meteorological condition has often been likened, with surprisingly little exaggeration, to “flying in a bowl of milk.”
White-out occurs when a uniform overcast exists over a completely snow-covered surface or featureless ice field. The hazard is present in both polar regions and generally considered to be most prevalent during the spring and fall seasons when the light source is low to the horizon and the twilight element is present. The general scene is one of uniform greyness devoid of any feature or contrast although both elements would normally be present.
White-out occurs also during polar summers when continuous daylight prevails, but ordinarily a denser overcast must exist.
The aviation hazard is that the pilot cannot tell when he will encounter the phenomena. So long as shadow and different colored objects such as multi-hued ice fields, exposed rock or land or open water streaks are visible, the hazard is not evident. Yet loss of depth and horizon perception may instantly occur, particularly if the pilot’s ground progress abruptly takes him over a uniform overcast white surface such as crossing a glacial shelf when flying inland from a partially open water area.
The only immediate remedy is for the pilot to shift flight operations from visual to instrument means of reference.
This remedy is unfortunately not available to helicopter pilots whose aircraft, to date, has not been properly instrumented because of the peculiarities of rotary wing flight. As helicopters are a vital part of any military polar operations, the problem is a grave one and involves a greater risk than that encountered by conventional aircraft pilots. Of necessity, the helicopter pilot must attempt to land immediately, and this limits him to flights of low altitude and short range during periods white-outs may be expected. Much of the Antarctic continent that exploring aviators must fly over is as yet uncharted, hence, the land elevations are unknown. With the loss of horizon and depth perception ability and the absence of shadow or feature, serious risk of collision with the terrain exists. This risk is even greater for helicopter pilots because of the lower flight altitudes involved. Radar altimeters can assist the conventional aircraft, but the helicopter is without this valuable aid. The seriousness of the hazard is supported by the fact that all aircraft lost on naval Antarctic operations prior to 1956 crashed from causes directly attributable to white-out. The well-publicized PBM Mariner crash at Cape Dart in 1946 during Operation highjump was a white-out casualty as was the helicopter crash of the succeeding year’s ice breaker expedition and that of the USS Atka cruise, completed in April, 1955. The Atka was on a preliminary reconnaissance cruise in support of Operation Deepfreeze and lost a helicopter in a white-out.
The hazard is attendant even around ordinarily well defined areas. During aircraft landing operations, with a white-out existent, surface objects lack normal clarity and tend to have a diffused and distorted appearance if visible at all. This lack of definition is serious, for a pilot’s depth perception is all important during the final few moments of any aircraft landing.
Surface personnel are also handicapped by white-outs. Distance definition becomes extremely difficult or impossible. Documented reports reveal that experienced polar travellers operating in white-out conditions find it impossible to determine whether a dark object is a mountain many miles away or a candy wrapper or other small dark object perhaps only fifty feet away. Many a polar traveller has experienced the eerie sensation of looking down at his feet and being able to see his foot gear yet being unable to distinguish the surface on which he stands. The next step may plunge him over an ice cliff or bring him into collision with a raised object. Explorers have reported actually walking into the side of a camp building while being under the distinct mental impression that the building was yet some distance away.
Admiral Peary stated of his travels over the polar ocean en route to the North Pole that “We experienced that condition, of a hazy atmosphere in which the light is equal everywhere. All relief is destroyed, and it is impossible to see for any distance.” Colonel Joe Fletcher, U. S. Air Force, discoverer of the ice islands in the Arctic Ocean, says of the Admiral’s remarks that “it was an apt description. We found that when thick clouds obscured the sun no shadows were cast to reveal hummocks, drifts, and depressions in the snow. Everywhere there was only whiteness . . . small dark objects were visible at a surprising distance and often appeared many times their actual size.”
Thus, overland travellers face the hazard of losing themselves and their equipment down holes or crevasses they might otherwise discern. During the Ronne Antarctic Research Expedition (RARE 1946-1948) the author participated in the rescue of an expedition member who walked over the edge of a some sixty-foot ice shelf and fell into the newly frozen sea. The rescuers themselves narrowly avoided tumbling over the shelf edge which was ordinarily quite evident even during periods of winter darkness. It is interesting to note that the normal “sixth sense” which warns of danger or the presence of obstruction or depth is lacking to one witnessing a white-out.
The problem is evident in Arctic regions also but to a lesser degree because of the greater amounts of exposed land which afford some contrast. It is most pronounced in the Arctic over frozen water areas and over the polar ice cap. The Antarctic however, with its some six and a quarter million square miles, is generally ice covered. Little exposed land is evident even in the Palmerland section which is closest to civilization, lying due south of Cape Horn. Hence the Antarctic white-out problem is an acute and real one.
The question then arises, what can be done about it all? First, if at all possible, one should avoid operations during periods when white-out conditions might reasonably be expected or forecasted. If travelling personnel are reasonably secure at a site, they should remain so until conditions improve, which will be heralded by the breakup of the overcast.
Preliminary results of attempting to forecast the necessary overcast attendant to white-out indicate some degree of success, but lack of polar weather data and unreliable electronic communications seriously hamper the forecaster. Co-incidentally, the periods of poorest radio reception occur when white- out conditions seem to be most favorable. It appears that the use of colored lenses in the form of sun glasses or goggles affords a measure of relief provided the white-out has not reached an advanced stage. The author prefers using amber lenses—available through normal military supply sources—but has observed or experienced partial relief using green (light and/or dark), blue, rose, smoky black and even night adaptation, red lenses. The choice of color however, should be a matter of individual preference thus necessitating the provision of multi-colored lens kits so that users may vary their color choice to meet varying conditions. In any case, colored lenses should be instantly available to personnel for white-out relief as well as for use to reduce eye strain or avoid “snow blindness,” caused by the intense glare normal to polar regions and to an even greater degree during white-outs. Some observers believe that the light intensity is even “magnified” or increased during whiteout, stating that the light reflects and reflects in all directions independent of the normal laws of reflection, refraction, and polarization, which during white-out seem to be inoperative. It should be pointed out that, insofar as is presently known, loss of vision resulting from extreme glare or snow blindness is not directly related to the loss of perception attendant to white-out. Glare and snow blinded personnel actually suffer a temporary loss of vision while white-out victims maintain their optic senses but in a confused way. It is, of course, possible for these hazards to be present in combined form. Such a victim is indeed in a bad way!
The causes of white-out conditions are also independent of somewhat similar conditions noted during dense “sea smokes” or “ice fogs.” The former being an evaporation type cloud which saturates the air mass directly over open water streaks (leads) in ice fields and the latter being an ice crystal accumulation caused by sublimation occurring over a uniform freezing ice field. Further precautionary steps or aids, other than immobilization and use of colored lens, would be the use of colored signal panels or paints with fluorescent qualities and colored chemical smokes. The colored smoke grenade type of approximately fifteen minutes duration is of great assistance to aviators particularly when landing on skiis on a flat open surface. A half dozen grenades dropped from a moderate height preparatory to landing, or set off by surface parties at fixed sites, will give the pilot both color contrast and wind data. Further, the smoke tends to stain the snow surface as it drifts over it thus outlining the surface contour highlights and affording a greater area of contrast. Using instrument flight approach techniques involving a controlled rate of descent, the author and others of his acquaintance has effected numerous safe ski landings. Similar techniques are used for wheel landings on a prepared ice surface. Here the contrast may be improved by marking the snow runways outline with colored, discarded oil drums or packing boxes.
In the above cases, however, the white-out was not of an advanced nature. By reference to advanced white-out, it is intended that the reader should consider the amount of light present such as twilight or cloud obscuration and the altitude and density of the overcast plus the presence of possible light precipitation or blowing snow. A uniform overcast of only two hundred feet thickness at an altitude of from 3,000 feet to 10,000 feet in an otherwise cloudless sky will produce a moderate white-out, whereas a more severe case exists when the overcast is of the nature of several thousand feet thick with a base of about 1,500 feet and with a light precipitation present. The advanced stage is more prevalent when overcast bases are between 1000 and 2500 feet rather than at greater heights which produce less severe white-outs for the horizon range is, of course, greater in the latter case. As stated, the presence of blowing snow, precipitation, or statically suspended ice crystals markedly increase the hazard. The presence of precipitation is mentioned as an additional light reduction complication and is not to be considered as a basic element of the white- out problem, as such precipitation constitutes a physical obstruction to vision, but its presence does further reduce the amount of light available as seen beneath the overcast. Normal forecasting techniques can generally predict the presence of these atmospheric particles however.
The problem from an aviation standpoint is further complicated if a pilot has been flying over the overcast for a prolonged period of time and is both glare-conscious and physically fatigued. He must make his landing let down to critically low altitudes for Ground Controlled Approach (by radar), or other type of instrument-landing procedure, and is suddenly presented with a lack of perception contrast when he “breaks out” rather than a view of familiar landmarks he might otherwise expect to see. Surface personnel looking toward a distinct background such as a distant mountain range might not be aware of the white-out whereas the pilot making an approach away from the dark background toward an ice plain would be acutely white-out conscious. Pilot reports indicate that vertigo is an attendant sensation often resulting in varied degrees of nausea or retching—this at critically low, final approach altitudes!
It appears that in spite of more than seven years additional research and experience, my statement and that of my senior colleague of the Ronne Antarctic Research Expedition still holds true as originally published in Guide to Stonington Island Aviation Meteorology Technical Report #3, ONR, 1948. At that time Lieutenant H. C. Peterson, U. S. Marine Corps Reserve, expedition physicist, and I, climatologist, stated that “the meteorologist should recognize that a solid overcast —regardless of visibility underneath it— constitutes a real flying hazard since perception of snow covered terrain features is usually destroyed. Most dangerous conditions arise with a low ceiling, a solid overcast, and a sort of diffuse stratiform mist reducing visibility and whitening the sky. Less serious reduction of depth perception occurs with high, thin overcasts.”
It is only fair to point out that there are two major differences of opinion existing on the subject. Serious polar-experienced people support divergent views, although the author is not in accord with them. They are now presented for consideration.
It is held that colored lenses cannot be safely worn by pilot personnel because of the need to scan flight instruments. As a naval aviator, the author has consistently worn colored lenses during all phases of polar flight operations, including night flying, and considers amber lenses to be a decided asset. Many other pilot colleagues including those of the U. S. Air Force, Royal Canadian Air Force, and the Danish Air Force concur in the use of amber or colored lenses during most phases of polar flight operations.
The further preference for amber or yellow color is supported by the fact that most buildings of the Joint U. S.-Canadian Arctic Weather Station network are painted a bright yellow or orange color. Experiments of orange and black checkerboard effects proved unsatisfactory. Operation Deepfreeze aircraft are painted a brilliant, luminescent, international orange, and numerous items of survival gear and outer clothing are similarly colored. In contrast, however, numerous Arctic military installations are constructed with unpainted exterior aluminum panels. These have proven to be unsatisfactory from a visibility standpoint, but mass production standardization requirements dictate their continued use as they are a successful basic Arctic shelter.
These observations are independent of those related to the need for colored lenses for the alternate problem of glare reduction and the prevention of snow blindness. The colored lens view is further supported by many ice-cap travellers, frozen Arctic water area researchers, and Arctic coastal construction groups.
The second divergent view sets forth the belief that the basic white-out factors are temperature, wind, and the moisture content of the snow surface. This view excludes the overcast factor but holds that as temperatures lower, the surface snow tends to “dry out.” Winds blowing across the surface aid the drying process and have a tendency to set the surface snow in motion, thus causing it to assume the texture of a fine powder. With increasing wind velocity, the powder snow is carried aloft, causing a loss of horizon definition. This view holds further that winds in excess of 25 knots are necessary to set up the white-out condition, and, if the snow surface is “wet,” winds will not powder the snow and carry it aloft regardless of their velocity. Note that this view requires the presence of moderate wind velocities, thus precluding a calm white-out. Such is not the case, however, for many extensive white-outs occur with little or no surface air movement.
The author believes that the broader view embracing the uniform overcast and unbroken white surface elements is the more realistic approach and submits that the “snow aloft” theory is of less frequent occurrence. It is more properly classified by the international special weather report group as an obstruction to vision in the form of blowing snow rather than as a true whiteout. The snow aloft theory is, in essence, local in nature and subject to glacial foehn winds or other moving air sources perhaps confined to local areas, whereas the overcast theory can be envisaged on a semi-continental or otherwise large scale basis.
In closing, it is noted that the U. S. Army Engineers Snow Ice and Permafrost Research Establishment of Wilmette, Illinois, has recently conducted independent white-out studies on the Greenland Ice Cap. Their reports are as yet unpublished, but discussion with SIPRE representatives in 1954 indicated that they would investigate all approaches to the problem.
One of the objectives of Operation Deepfreeze will be to continue further study and to gather observations and data that may result in greater alleviation of this hazard. The International Geophysical Year (IGY) will involve more than forty nations, including the United States, and many will send units to the Antarctic during 1956-1957. We can hope that such an aggregation of scientific talent and their subsequently published reports may yet provide an answer to this most vexing of polar problems.