DEOE-, 1922. MONTHLY WEA4THER REVIEW. SOME METEOROLOGICAL ASPECTS OF THE ICE PATROL WORK IN THE NORTH ATLANTIC. By Lieut. (Junior Grade) EDWARD H. S Y ~H . pJ. S. Coast Guard, Cambridge, Mass., Jan. 10,lQZl 629 Next spring will complete 10 years of ice patrol service in the north Atlantic. During this period scientific investigation of the ice regions has been carried 011 with the object of increasing our general howledge of these regions, and also of securing a more effective mana e- ment of the patrol. Up to within a few gears the te- havior of ice in the Atlantic was a inatter of conjecture. To-day charts are available showing the drift of bergs from the time of leaving the Labrador coast, the courses followed by these bergs being as carefully plotted as the ‘track of a ship. Conditions are subject to inucli varia- tion from year to year. Some years produce large quan- tities of ice; other ears bring scarcely n a y . In some drifts far south. Until now little time has been devoted to this aspect of the problem. The causes oE rnriations in oceanic circulation, and similarly the behavior of ice from year to year, may be attributed to several factors. The meteorological aspects affecting the movements of ice dl be considered later, but before takin u that matter a brief description of the Internationltl %e Satrol Service ma be interesting. constitutes a groat menace to steamships plying between Europe and the United States. In the days of slow steamers most of the vessels followed a rent circle them throu h the ice zone a lar e portion of the penr. agreements have been entered into whereby definite routes have been established to the southwnrd of the normal ice zone. If the ice zone were Cued nothing further would be required to assure reasonable safety along the routes, but, as reviously indicated, the limits of the ice fields season, and consequently a vessel might sail on a course that was clear at the tune of her departure but collide with ice which had drifted into her path when she reached the vicinity of the Newfoundland Banks. The establishment of the ice patrol followed directly the Titanic disaster, when the then largest shi afloat was sunk on the night of April 14, 1912, by strging an iceberg off the tail of the Great Bank of Newfoundland. In November, 1913, an international convention met at London, and amon other subjects discussed the prac- to esta t lish a permanent International Ice Patrol Service and the United States Government was in- vited to undertake the management of the service; the expense to be divided among the signatory powers in proportion to the amounts of thew respective ship tonnages. The work has two aspects: First, and of the utmost importance, is the determination of the variable limiting lines of menacing ice, and the dissemination of the information for the guidance of ship ing; secondly, and ographical and meteorological observatlons as will de- tarrmne the causa of these variations, thereby increas- ing our knowledge to insure means of greater safety for life at sea. years the ice is he1 B up in high latitudes: in others it Ice whic K drifts south. into the. Atlantic el-erv spring course between the two continental ports, w a ich carried Since the a d vent of the large and f ast passenger steamers and the i ergs vary considerably in location as well as in ticabilit of patrol k mg the ice regions. It was agreed coordinately with the first,js the ma El ‘ng of such ocean- with the southern, eastern, and western limits of ice as they vary in position throughout the season, and to broadcast this information to all approachin ships. that a thorough knowledge of ice movements is abso- lutely nec,essary. In conjunction with its scouting. duty, the ice patrol secures scientific observations relatmg to the area. Daily reports also are foiwarded to the United States Weather Bureau. Previous scientific investigation of the vicinity of the Newfoundland Banks is negligible, except for the Murray and Hjort expedi- tion on the Michael Sars, 1912, and the Scotia cruise, 1813, Mttthews. Vessels’ logs possess a large amount of data, but it is not easily accessible and is limited to the ocean surface. No true picture of oceanographicd conditions can be obtained without consideration of the subsurface. The three great ocean currents in the northwest Atlantic are well known, viz, the East Greenland, the Labrador, and the Gulf Stream. The East Greenland current is an overflow from the north polar basin of an accumulated mass of fresh water which has been discharged from northern Eurasian rivers and augmented during the summer by the water from melted ocean ice. The escape is southward past Jan Mayen along the east coast of Greenland, where the current bears. great masses of sea ice. The number of bergs is comparatively smal heavy , due to the scarcity of glaciers along the east coast. The East Greenland Current rounds Cape Farewell and continues northward along the west coast of Greenland to 65’ N., where it begins to throw off branches west- ward to the Labrador Current. From 70’ N. a northerly current is found alon the coast as far as Cape York, southerly current. The polar drift, which has its source north of Smith’s Sound, is made up of two branches, an eastern branch, consisting of the current just described, and a western branch which flows southward close to the American coast, being augmented by tributaries from Lancaster Sound, Jones Sound, etc. In Davis Strait the east and west branches join, forming the Labrador Current. Tracin the Labrador Current in its southern extension we fin % it floods the northern part of the Great New- foundland Bank, a small branch esca es to the westward Greater uantities s read eastward in expansive surface layers, w ?I ile the mi dle branch continues its flow along the east slope of the Great Bank. When the polar cur- rents are swelled, arctic water spreads in over the Bank and across the southern end,. otherwise the area over the Bank resents a characteristic identity that is at no time engulzd by either Labrador Current or Gulf Stream. The Labrador Current flows southwesterly around the I t can be seen froni this duty as brie f f y described where it turns sharpy B south in the east branch of a through the “Gully” under the Ne wp oundland headland. 630 MONTHLY WEATHER REVIEW. DEGEMBEB, 1922 Tail of the Bank and im in es on the Gulf Stream which ZS flowing east ast the Faif. The Gulf Stream, after it passes the Ban!, spreads out in fan shape into several swirling bands and ex ansive ocean drifts. Upon meet- arrested, then turned in toward the Stream, and lastly pulled along in an easterl flow parallel with the Stream, water at the Tail of the Bank in t e form of varied mixing eddies. The statement that the Labrador Current is. arrested in its flow and turned back parallel to the Gulf Stream is at variance with the views of many authorities who claim that the Labrador Current sweeps southwesterly across the Great Bank and continues as a cold current with a set down the east coast of the United States as far as Cape Hatteras. Another fact which has been brou h t out by the oceanographical work of the ice the Labrador Current upon meeting the Gulf Stream dives beneath the latter, emerging to the southward. The evidence gathered by the patrol forbids such a view. On the contrary, the tendency of the polar water to spread out on the surface is quite pronounced. One ocean current may dive beneath another at some places in the world, but such is not the case here. In the consideration of ice, it is necessary to make a distinction between field ice and berg ice. Field ice, formed by frozen Arctic sea water, is under the con- trol of the winds and the surface currents. I t is the first ice to drift south, puttin in an appearanc.e as early covers the entire area between the Newfoundland coast and the 43d In March and Axil it is noted In low latitudes it is quickly melted and is by no means as dangerous as icebergs. eat source of icebergs is the laciers on the west When released by the breaking up of the field ice in summer the bergs are drifted around by ocean currents until they succeed in entering the Labrador Current. They first a pear during March, drifting south along the June, bergs constitute a menace to steamships in this vicinity. As stated above, the oceanic circulation and niove- ments of ice are subject to continual variations which are attributed to several underlying factors, viz: (a) Meteorological conditions over the north Atlantic and Arctic regions, (6) the hydrodynamics of the Atlantic and Arctic basins, Cc) variations in solar energy. In re- viewin some of the literature upon the subject,’ there is potential possessed by large bodies of water of similar character. The theory, briefly stated, is that the basic principle of oceanic circulation originates in the physical changes in water which manifests themselves in move- ments of a certain kind of a water mass from the region in which it abounds to the region where it is scarce. The volume and velocity of the induced current thus established will be governed by the supply and demand. Meteorological changes are factors in oceanic circulation which cause variations according as they increase or ing the Gulf Stream, t K e Labrador Current is frictionally with a consequent inter d igitation of olar and tropical f patro 5 is the lack of evidence to support the belief that as January and February. !i t the latter date it often most frequent P y on the southern part of t L e Great Bank. coast o Y Greenland, from the region o !? Disko northward. east side o P the Great Bank. During April, May, and arallel. The a mo 8; ern tendency to stress the importance of the 1 Sandstrom W.: “Canadian Fisherics Expeditim. 1914-1915.” pp. 221-291. Pettemxm ‘0.: “Connection bet\veen Hydrograp:licaI and h;etoornlogical Phe- Dlclsdm, E. N.: 86The &mlatlon Gf th