Icebergs in the northern oceans have received much attention at the hands of many intelligent writers, but comparatively little has been published in recent years concerning the ice in the southern and Antarctic oceans. It appears from what has been written on the subject that there are years of few or no icebergs, followed by a period of years of a great accession of bergs. Such a period of remarkable frequency of bergs is that of 1891-1895, and with this period, or rather the period from 1888 to 1895, the present essay and its accompanying charts especially deal.
It is not necessary to dwell upon the importance of the ice problem, or the risks and perils of the navigator in the southern oceans, due to the immense floating islands and also to the detached pieces of ice, which are in themselves sufficiently large to do serious damage to the staunchest vessels afloat.
If we could have the testimony of those brave and gallant navigators who have left port in noble ships, and who have neither returned nor left any traces as a basis for speculation as to their fate, we would probably, in many instances, learn of a sudden shock, of the rending, falling masses of ice, the rushing of water, and the quick engulfment of the vessel and crew. The collision with a gigantic iceberg occurs so suddenly and with such terrific force as to appall the bravest.
As in the northern hemisphere the origin of icebergs is in the polar regions, principally in Greenland, so in the southern hemisphere their place of formation is in the Antarctic lands, concerning which we know only a "few discontinuous coast-lines." Reasoning as to their formation, by analogy, from our observations in Arctic regions, we may suppose them to be formed in a similar manner in the south polar regions; that is, from the large glaciers that are formed on sloping lands by the accumulation of falling snows and congealing rain and fog.
These glaciers, "of so imposing and magnificent an aspect, in spite of their apparent immobility, have a descending movement, slow and continuous," toward the sea, and "protruding their margin into the water until the stability of the mass and buoyancy become neutralized and the margin breaks off, or calves, as it is termed," and casts those huge masses of freshwater ice adrift into the "great Antarctic drift current, so called in the Pacific, as well as in the Atlantic and Indian oceans."
"This great body of water moves toward the east between 40° and 60° south, with a constancy similar to that of the prevailing westerly winds. It is especially noticeable in the Pacific between 45° and 55° south, and from Tasmania and the south point of Stewart Island (New Zealand) to about 118° W., where a portion breaks off and forms the Menton current, which moves to the N.E., towards St. Ambrose Islands. The greater part, however, of the main current continues to the eastward, as far as about 85° west, where the southern branch divides into two currents between 42° and 47° south, one bearing to the northeast, forming the Chili current, and the other tends to the E.S.E. and S.E., toward the Gulf of Penas and Straits of Magellan, and forms the Cape Horn current."
Borne away upon Antarctic currents, the icebergs drift into lower latitudes and melt in warmer water. The icebergs which leave the Antarctic continent at 63° or 65° S. "experience little change by the melting process until the 60th parallel is reached." It is commonly thought that they melt most rapidly under water, and "the change of center of mass and shifting of berg into new positions of equilibrium, undermining, fracture, etc., causes irregular and fantastical shapes." This change of center of mass and the exposure to view of new surfaces is probably often due to the loosening and letting go of huge rocks, boulders and stones imbedded in the berg, since "icebergs, like glaciers, are great transporting agents," bearing away to the deep sea these solid substances.
It is difficult to arrive at the average size of these bergs, as they are reported of all sizes, up to 800 or 1000 feet in height and up to several miles in length. The shapes of the bergs are also reported as being of almost every conceivable form, but in the southern oceans the bergs, as a rule, do not have so frequently the towering spires that are often a characteristic of those seen in the northern oceans, but are comparatively flat-topped.
The icy barriers have been reported to have the appearance of vast chalk cliffs, and "it is a question whether the discontinuous coast-lines constitute parts of a continent, or whether they are, like the coast of Greenland, portions of an archipelago, smothered under an overload of frozen snow which conceals their insularity." "It is calculated that the center of the polar ice-cap must be three miles deep, and may be twelve miles deep, and the material of this ice mountain being viscous, its base must spread out under the crushing pressure of the weight of its center." "This extrusive movement thus set up is supposed to thrust the ice cliffs off the land at the rate of a quarter of a mile per annum."
Mr. Findlay explains the difference in appearance of icebergs in northern and southern oceans as follows: "In the north they are formed on a limited space of land, chiefly Greenland, and here the land ice reaches the sea down narrow fiords in the form of glaciers, literally rivers of ice, whose outflow into the sea is constantly disrupted, and in the spring the masses drift southward in every variety of size and figure except the tabular. In the south, on the contrary, the whole of the south pole appears to be encircled with land covered with this tremendous icy mantle, without any inlet into its interior, as in the case of the Arctic regions, unless there should be such south of Cape Horn, and thus there is no influx of warm water which can penetrate into the rear of the icy barrier (as is the case in Baffin's Bay and around Spitzbergen) to dissolve and drift it out in a similar way."
The motion of an iceberg is a compromise motion of wind, surface current and undercurrent. The southerly gales in the Antarctic region, due to the cold air caused by the presence of glacial formations settling down and squashing out, is probably the greatest factor in causing a strong surface current, which has much to do with the northern movement of the berg.
Drifting to lower latitudes through the effects of currents and winds, "as the distance from their birthplace increases, they are found in all stages of decay. Some apparently retain their original form until they reach comparatively low latitudes, and others appear to have changed entirely," having overturned, as some say, but more frequently broken up. In connection with this breaking-up of bergs, and illustrative of large numbers of bergs sometimes seen, and of the danger from loose ice in passing to the leeward of a berg, and the unreliability of the thermometer as an indicator of the nearness of ice, the following extract is given from the report received at the Hydrographic Office from Captain A. John Miller, British bark Lindores Abbey, from Portland, Oregon, to Galway: "February 8, 1893, at 6.30 P.M., in latitude 50° 50' S., longitude 48° 17' W., we saw a large iceberg about a point on the port bow; from the fore-topgallant yard we could see several others ahead and on the starboard bow; at 8 P.M. we were up to the front one and could then see a number of others. We were favored with very clear weather and a steady breeze from W.S.W. to W.N.W., going about 7 ½ knots an hour, steering N.N.E.; during the night and all next day we were passing through between these large bergs, which we could see on both sides as far as the eye could reach, some of them over a mile long, and ranging from 150 to 200 feet in height. From 1 P.M. to 4 P.M. (three hours) I counted 63 large bergs, besides numbers of small ones. While passing some of them we heard them crack and saw pieces falling off them, the noise being like the report of artillery firing; while passing close to leeward of the large bergs there was always a lot of loose ice, large enough to be very dangerous to ships in the dark, as it was almost flush with the water and difficult to see at night; when right to leeward of the icebergs we invariably got a strong gust of wind off of them, just like squalls off highlands, strong enough to make us lower our royals sometimes; at 8 o'clock on the evening of the 9th of February we passed the last large iceberg, having been just 24 hours among them, and having sailed about 180 miles through them in a northeasterly direction. At 5.30 next morning we passed three small pieces of ice, but saw none during the night, nor have we seen any since. While passing through this vast field of ice there was no perceptible change in temperature of either air or water, the thermometer showing air 46° F., water 44° F. It was a grand sight, especially at sunrise, and one never to be forgotten by those on board."
As to size of icebergs sighted in the southern oceans, Chief Officer Cummings, of British bark Beechwood, reports to the Hydrographic Office that "on the 6th of December, 1893, they met with a number of icebergs in lat. 40° 43' S., long. 42° 28' W. Through these navigation was extremely difficult. Great precaution was taken at night, sail was shortened during the night, an incessant lookout kept to prevent collision with any of these frightful obstructions to clear sailing. On December 7th, lat. 47° 7' S., long. 41° 44' W., other bergs were encountered, necessitating renewed vigilance. On the same day a monster berg hove in sight. It was a mighty mountain of ice, moving slowly in solitary grandeur among the great Atlantic waste." Captain Mansus, master of the Beechwood, and Mr. Cummings, chief officer, estimated the length of this appalling mass of ice to be 15 to 20 miles, and its height 300 to 400 feet. The captain of the Drumcraig also reports to the Hydrographic Office that "on December 29th, 1892, in lat. 49° 34' S., long. 45° 53' W., he sighted a large ice island fully 300 feet high and 25 or 30 miles long." These dimensions are wonderful, but not of more than half the horizontal dimensions of the body of ice which Mr. Towson tells "was passed by 21 ships during the five months of December, 1854, and January, February, March and April, 1855, floating from lat. 44° S., long. 28° W., to lat. 40° S., long. 20° W., with a height not exceeding 300 feet, but of horizontal dimensions of 60 by 40 miles. It was reported to be of the form of a hook, the longer shank of which was 60 miles, the shorter 40 miles, and embayed between these mountains of ice was a space of water 40 miles across." When we consider that only about one-ninth of the mass of an iceberg is above water we wonder at their magnitude and source, and yet we can more readily imagine their source when we recall the fact that "Sir James Ross followed the line of the enormous ice cliffs in the Antarctic regions for 450 miles and more, which had an unvarying height and character, calculated to be upwards of 1000 feet in thickness." Similarly, Capt. Wilkes "in some places sailed for more than 50 miles together along a straight and perpendicular wall of ice from 150 to 200 feet in height."
Among the Hydrographic Office files is an interesting report from Captain Doan, of the American ship Francis, which I give in full:
"February 16, 1893, at noon, lat. 51° 01' S., 49° 15' W., we passed between two large icebergs, about 15 miles apart, and saw to the S.S.E. of us another very large berg several hundred feet high and a mile or more in length. Put the ship under easy sail for the night. At 1 A.M., 2.30 A.M. and 4 A.M. passed large bergs. Weather cloudy and misty. Wind hauling to N.W. Soon after 4 A.M. it began to get daylight, when we saw before us an immense barrier of ice, extending from N.W. to S.E., as far as we could see from aloft. Some of the floating glaciers were miles in length and from three to five hundred feet high. Stood to within a mile of the track, but seeing no safe passage through the barrier, we wore ship to southwestward at 5 A.M. We now saw icebergs all about us. Temperature of air and water from 47° to 50°. At noon wore ship to northward, passing a number of large and small bergs. At 3 P.M. saw the barrier again, to leeward, still continuing its line from N.W. to S.E. and as impenetrable as before. Stood on till 5.30 P.M., and as the ice was visible to N.W. (2 points off weather bow), as far as we could see from aloft, we again put the ship on the southern tack. Wind hauling to S.W. and steadily increasing to a moderate gale. Now having the ice fields for a lee shore was anything but pleasant to contemplate during the long night watches. February 18th, midnight, wore ship to W.N.W. Reefed upper foretopsail, furled upper mizzen. Rough sea. At daylight we saw a berg ahead about one mile long and three or four hundred feet high. It was perfectly level on top, and its sides and ends were as perpendicular and clean cut as the blocks of ice taken from our lakes and rivers at home. It is also apparent that these immense pieces of ice are in the same condition as when first broken from the main glacier, as the irregular angles of the smaller bergs indicated that they had turned over occasionally. At 11 A.M. saw the dreaded barrier again, still extending to N.W. At noon our position was lat. 50° 29' S., long. 47° 12' W. Found we had a very strong N.E. current setting us towards the ice, adding another factor to the manifold dangers by which we were surrounded.
"At 1 P.M. judged we could see the end of the barrier to the N.W., or about 1 ½ points off our bow. Gave the good ship all the sail she could bear and pushed her through a very large and turbulent sea, caused partly by the deflection of the strong N.E. current against the large mass of ice under water (the pack being from two to four miles to leeward).
"We now had the satisfaction of seeing the ship steadily draw past the last fearful piece of this gigantic ice field, which we found by careful measurement by the patent log was just six miles long and, as near as we could judge, it was three or four miles wide. This would give an unbroken area of 18 or 20 square miles, between three and four hundred feet above the sea. (At 4.15 P.M. passed the N.W. point of ice, lat. 50° 13' S., long. 47° 23' W. Saw the ice extending away to N.E., but no more in our vicinity.)
"Too much notice cannot be given to our mercantile marine of this great danger that lies directly in the fair way of vessels bound eastward around Cape Horn, as it will doubtless take years before such a mountain of ice (such as I have described) to be destroyed, and that was only one of many more that we saw in this ice field, extending from lat. 50° 13' to 51° S., long. 46° 45' to 47° 23' W., and how much beyond I am willing to leave to some other navigator to tell."
Referring again to indications of approach to ice, many ways have been suggested; especial reliance upon the thermometer is often advised, but while in many instances this would no doubt prove useful, yet we have some reports showing that the thermometer cannot always be relied upon to indicate the proximity of ice. Besides the report previously referred to, we also have the following from Captain McMillan, of the British ship Dudhope: "Careful thermometric observations of air and water were regularly taken, but our approach to ice, always from windward, was not once indicated by any appreciable change of temperature in either air or water. On passing to leeward of the bergs a fall of a few degrees was generally observed in the air. On one occasion we passed within a cable's length of a berg and found the temperature to be the same there as at several miles distance. This would go to show that in thick weather, or in any other, even temperature and thermometer at normal height should not be accepted as a reliable guarantee of immunity from ice. Care and a most vigilant outlook are the only reliable safeguards. To depend on the thermometer would mean disaster, as I am convinced that a ship would be too close to the ice to extricate herself by the time the thermometer would indicate its presence."
As has already been stated, there are years of very few or no icebergs, and then years when great numbers are reported. In the year 1832 the southern ocean was so covered with icebergs that a number of whaling vessels, bound round Cape Horn, encountering them, put back to Valparaiso to await a more favorable season, because it appeared too dangerous to undertake the voyage. Again in 1854 there was a great accumulation of icebergs, and now during the past few years, notably 1892 and 1893, there has been another notable output from the great berg factories of the Antarctic regions. During the intervals between these periods there have been very few bergs reported. What causes this occasional great accession of bergs? Some authorities offer as a probable explanation the breaking off of the ice margin by volcanic eruptions, and others that earthquakes cause numerous pieces of the glacier to become detached and set adrift as icebergs, and others that unusual heavy annual snowfall is favorable for increase in number of bergs. The rapidity of glacier movement seems usually to regulate the number of bergs cast off. If the ice at the bottom of the glacier moves so slow that the melting of the margin on coming in contact with the salt water equals the advance, then we would have no icebergs, except perhaps those breaking off from the upper part of the outer margin, and these would be comparatively small.
In order to obtain facts for study, charts have been compiled from reports deposited in the Hydrographic Office, Department of the Navy. Through the courtesy of Commander C.D. Sigsbee, Hydrographer, I was permitted to use the files of the office. Out of several thousand meteorological reports examined, 307 reports of ice in the southern oceans were found, and upon these the charts are based. For the years 1892, 1893, 1894, and 1895 a large number of reports was found, especially in 1893 and 1895; while in the other years, notably 1888, only one or two reports of icebergs sighted were found, although about the same number of reports of vessels going over approximately the same route was carefully examined. The conclusion from this is that during the years 1888, 1889 and 1890 there were comparatively few icebergs in the southern oceans.
There are two charts, one representing the seasonal iceberg limits, together with approximate sailing routes to various points, and the other showing by different colors the icebergs reported in the different seasons throughout the period under discussion. It must be understood that the routes do not by any means represent the various routes taken by vessels whose course is determined by the direction of the wind. On the seasonal chart the icebergs plotted in red are those sighted in June, July and August; in blue, for September, October and November; in green, for December, January and February; in yellow, for March, April and May.
The charts deal entirely with icebergs and not with other forms of ice, such as field ice or ice floes. They give a graphic presentation of reports of icebergs seen during the different seasons, and convey a general idea of the number and positions of icebergs. The chart of limits may serve as a "practical guide to mariners as a warning in approaching the regions where especial vigilance is essentially required." On the chart of icebergs the positions of bergs are plotted as nearly as practicable as reported, and when too numerous to plot, the number is given, or, if no number, but "numerous," or "large number of bergs," is reported; the letter "L" is placed by the side of a berg in the color corresponding to the color used for that season. In a few instances, where bergs are reported as "fast breaking up" or "rotten-looking," a note is made on the chart.
From plotting upon the chart the icebergs reported in the months of December, January and February during the years from 1891-1895, distinguishing by symbols the bergs seen in different years, it has been found that the greatest number was reported in 1893 and 1895, with a smaller number in 1892 and 1894, and the smallest number in 1891. We find groups of bergs south of Cape Horn, east and northeast of the Falkland Islands, and south of Africa, and a line of bergs stretching to the eastward near the 45th parallel, with the most easterly one, in January, 1892, on the 75th meridian east, while to the west of Cape Horn, in 1892, we find a line of bergs extending along near the 55th parallel from 100° W. to 135° W. The greatest frequency is in December and January, and the lowest latitude reached is in December and January, 1893 and 1895.
From a similar chart for March, April and May, the months of March and April, 1893, have the greatest number, with no reports for 1888, 1889 or 1894. The principal group is east and northeast of Falkland Islands, and is entirely for the years 1893 and 1894, while the group for 1895, south of the Horn, has become much smaller. The most easterly report is in 32" 30' E, and 42° 30' N., and the most westerly one is near the 50th parallel and 135th meridian west.
On a chart for the southern winter season, June, July and August, we find all the years under discussion represented except 1888 and 1889, with the greatest number in 1892. There is a group immediately south and near Cape Horn, and another large group between 40° S. and 45° S. and 30° W. and 40° W., and still another large group between 40° S. and 45° S. and 25° E. and 30° E. There is also a line of bergs reported in July, 1895, extending from 44° E. to 67° E., near the 45th parallel. There is a small group reported in the same month and year near the 55th parallel and 160th meridian W. A large group of bergs was reported in July, 1892, in the remarkably low latitude of 37° S. and near 42° W.
On a chart for September, October and November we find a large group of bergs south of Cape Horn, and it is seen that this group is made up entirely of bergs sighted in 1895, with the exception of two bergs reported in November, 1891. East and northeast of the Falkland Islands we find all the years represented except 1891 and 1894, with only one report each for 1888, 1889 and 1890. Near the 40th parallel, and from 0° to 5° E., there is a large number reported in 1893 as "low, rotten-looking bergs, fast going to pieces." This is the only season in which we have any bergs sighted in 1888. The chart for this season is remarkable for the years represented, as well as the east and west limits. Bergs were reported in 1893 at 180° W., and in the unusually low latitude for that part of the ocean of 42° S., near which position 78 icebergs were reported. We also find a group in 1893 near the 45th parallel and 160th meridian E.
The accompanying "Chart of Ice Limits for the Four Seasons" shows the northern limits reached by the ice in the different seasons; the limit for December, January and February is shown in green; for March, April and May, in yellow; for June, July and August, in red; and for September, October and November in blue. The broken black lines indicate approximately the sailing routes to various points. The ice-limit lines are shown only where ice has been reported during the season considered. From this chart it appears that the greatest northern limit reached in the South Atlantic for the period under discussion was in the season of June, July and August, reaching to about 37° S., near the 20th meridian W. This limit is nearer the equator than the usual summer limit of the northern ice, as we find by an inspection of the ice charts published on the North Atlantic Pilot Chart for June, 1894, covering a period of seven years, that the lowest southern limit is 40° N., and near the 50th meridian. A few bergs are shown in the chart of limits north of Falkland Islands, and are not enclosed within the limits shown. It is an unusual position for bergs, but the surface current near the islands shows that they might easily have been drifted to the position shown.
In July, 1895, a number of bergs were reported between the Cape of Good Hope and Australia, but none reported after that, except one berg in November near 45° S. and 50° E. This sudden disappearance of the bergs may have been caused by rapidly breaking up, but probably by having been driven by heavy winds causing a strong set of the current toward higher latitude and out of the track of vessels.
An inspection of the chart would seem to show that the bergs are formed at several different special parts of the Antarctic Continent, and are then, by the compromise force of wind, surface current and undercurrent, drifted northward, then northeasterly, and then easterly. If we should be fortunate enough to get reports for the years under discussion from higher latitudes it might be possible to trace back, from the group of bergs, to the Antarctic lands, and find the approximate place of formation of these groups.
The life of a berg in the southern oceans is probably much longer than that of one in the northern ocean, since they are larger and more compact, and as we have seen, drifts to lower latitudes in the South Atlantic than those in the North Atlantic. Mr. Towson states that "in January, 1850, an iceberg was within sight of the Cape" (Good Hope), "and that in April, 1828, and in August, September and October, 1840, there were several icebergs in this locality." This is an unusual position for bergs, being 34° S. The northern limits of icebergs for the years of which this paper treats reach farther north over the whole southern ocean generally than at any period for which similar deductions have been found. Some of the bergs sighted in the South Atlantic during this period have been reported as being earth-stained and discolored. This may have been due to the iceberg "exposing the side of some old crevasse, into which debris from a surface moraine has fallen."
To show the remarkable drift of pieces of these southern icebergs, the following extract is taken from a report received at the Hydrographic Office from the master of the brig Dochra: "On April 30, 1894, latitude 26° 30' S., longitude 25° 40' W., at 10 A.M,, observed a piece of ice twelve feet long, four feet wide and four feet high; it was very white and seemed perforated. We passed quite near it; the sea was smooth and several people saw it."
It is to be hoped that the renewed interest in Antarctic exploration, now manifest in Europe, will bear good results, and that the bold explorers sent out will solve the question of the origin and nature of these gigantic ice masses. Knowing this, it will remain for shipmasters faithfully to report all ice sighted, together with observations of wind, weather, temperature of sea-water and air, currents, etc., before we can fully trace the history of the ice mass from the time of its first formation till it finally disappears in the waters of the temperate zones.
In the preparation of this essay, and in addition to the large number of ships' logs, I have consulted the following books, charts, etc.: "Antarctic Explorations," G.F. Griffiths, Smithsonian Report, 1890; "Glacial Geology," Prof. James Geikie, F.R.S., Smithsonian Report, 1890; "Deep-sea Deposits," A. Daubree, Smithsonian Report, 1893; "South Pacific Ocean Directory," fifth edition, A. G. Findlay, London, 1884; "Icebergs in the Southern Ocean," H. C. Russel, Sydney, 1895; "A Popular Treatise on the Winds," Ferrel, New York, 1893; "Theory of Winds," Capt. Charles Wilkes, Philadelphia, 1856; "American Practical Navigator," Bowditch, revised edition, Bureau of Navigation, Navy Department, Washington, D.C., 1896; "Climate and Time," Croll, Edinburgh, 1885; "Encyclopedia Britannica"; "International Ice and DereHct Code of Signals"; "The Liverpool Mercantile Service Association Reporter, 1895"; North Atlantic Pilot Charts for June, July and August, 1894; " Report of Ice and Ice Movements in the North Atlantic Ocean," Ensign Hugh Rodman, U.S.N., Hydrographic Office, Washington, 1890; "Memoir of Danger and Ice in the North Atlantic Ocean," Bureau of Navigation, Navy Department, Washington, 1888; "Report of Ice and Ice Movements in Bering Sea and the Arctic Basin," Ensign Edward Simpson, U.S.N., Hydrographic Office, Washington, 1890; various reports on file at the Hydrographic Office, Navy Department, Washington, D.C.