DEOE-, 1922. MONTHLY WEA4THERREVIEW. 629 SOME METEOROLOGICAL ASPECTS OF THE ICE PATROL WORK IN THE NORTH ATLANTIC. By Lieut. (Junior Grade) EDWARDH. SY~H. pJ. S. Coast Guard, Cambridge, Mass., Jan. 10,lQZl 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 with the southern, eastern, and western limits of ice as followed by these bergs being as carefully plotted as the they vary in position throughout the season, and to ‘track of a ship. Conditions are subject to inucli varia- broadcast this information to all approachin ships. tion from year to year. Some years produce large quan- It can be seen froni this duty as brieff y described tities of ice; other ears bring scarcely nay. In some that a thorough knowledge of ice movements is abso- years the ice is he1B up in high latitudes: in others it lutely nec,essary. In conjunction with its scouting. duty, drifts far south. Until now little time has been devoted the ice patrol secures scientific observations relatmg to to this aspect of the problem. The causes oE rnriations the area. Daily reports also are foiwarded to the in oceanic circulation, and similarly the behavior of ice United States Weather Bureau. Previous scientific from year to year, may be attributed to several factors. investigation of the vicinity of the Newfoundland Banks The meteorological aspects affecting the movements of is negligible, except for the Murray and Hjort expedi- ice dl be considered later, but before takin u that tion on the Michael Sars, 1912, and the Scotia cruise, matter a brief description of the Internationltl %e Satrol 1813, Mttthews. Vessels’ logs possess a large amount Service ma be interesting. of data, but it is not easily accessible and is limited to Ice whicK drifts south. into the. Atlantic el-erv spring the ocean surface. No true picture of oceanographicd constitutes a groat menace to steamships plying between conditions can be obtained without consideration of Europe and the United States. In the days of slow the subsurface. steamers most of the vessels followed a rent circle The three great ocean currents in the northwest Atlantic course between the two continental ports, wa ich carried are well known, viz, the East Greenland, the Labrador, them throu h the ice zone a lar e portion of the penr. and the Gulf Stream. The East Greenland current is an Since the ad vent of the large and fast passenger steamers overflow from the north polar basin of an accumulated agreements have been entered into whereby definite mass of fresh water which has been discharged from routes have been established to the southwnrd of the northern Eurasian rivers and augmented during the normal ice zone. summer by the water from melted ocean ice. The If the ice zone were Cued nothing further would be escape is southward past Jan Mayen along the east coast required to assure reasonable safety along the routes, of Greenland, where the current bears. great masses of but, as reviously indicated, the limits of the ice fields sea ice. The number of bergs is comparatively and the iergs vary considerably in location as well as in heavysmal , due to the scarcity of glaciers along the east coast. season, and consequently a vessel might sail on a course The East Greenland Current rounds Cape Farewell and that was clear at the tune of her departure but collide continues northward along the west coast of Greenland with ice which had drifted into her path when she to 65’ N., where it begins to throw off branches west- reached the vicinity of the Newfoundland Banks. ward to the Labrador Current. From 70’ N. a northerly The establishment of the ice patrol followed directly current is found alon the coast as far as Cape York, the Titanic disaster, when the then largest shi afloat where it turns sharpyB south in the east branch of a was sunk on the night of April 14, 1912, by strging an southerly current. iceberg off the tail of the Great Bank of Newfoundland. The polar drift, which has its source north of Smith’s In November, 1913, an international convention met at Sound, is made up of two branches, an eastern branch, London, and amon other subjects discussed the prac- consisting of the current just described, and a western ticabilit of patrolk mg the ice regions. It was agreed branch which flows southward close to the American to estat lish a permanent International Ice Patrol coast, being augmented by tributaries from Lancaster Service and the United States Government was in- Sound, Jones Sound, etc. In Davis Strait the east and vited to undertake the management of the service; the west branches join, forming the Labrador Current. expense to be divided among the signatory powers in Tracin the Labrador Current in its southern extension proportion to the amounts of thew respective ship we fin% it floods the northern part of the Great New- tonnages. foundland Bank, a small branch esca es to the westward The work has two aspects: First, and of the utmost through the “Gully” under the Newp oundland headland. importance, is the determination of the variable limiting Greater uantities s read eastward in expansive surface lines of menacing ice, and the dissemination of the layers, w?I ile the mi dle branch continues its flow along information for the guidance of ship ing; secondly, and the east slope of the Great Bank. When the polar cur- coordinately with the first,js the maEl ‘ng of such ocean- rents are swelled, arctic water spreads in over the Bank ographical and meteorological observatlons as will de- and across the southern end,. otherwise the area over the tarrmne the causa of these variations, thereby increas- Bank resents a characteristic identity that is at no time ing our knowledge to insure means of greater safety for engulzd by either Labrador Current or Gulf Stream. life at sea. The Labrador Current flows southwesterly around the Unauthenticated | Downloaded 09/29/21 11:35 AM UTC 630 MONTHLY WEATHER REVIEW. DEGEMBEB,1922 Tail of the Bank and im in es on the Gulf Stream which decrease dynamic forces. An axam le of this is a pre- ZS flowing east ast the Faif. The Gulf Stream, after it vailin off-shore wind across the Gup f Stream that tends passes the Ban!, spreads out in fan shape into several to us5 the surface layers of the Stream, from their nor- swirling bands and ex ansive ocean drifts. Upon meet- m$ course, but if this meteorological phenomenon be ing the Gulf Stream, tK e Labrador Current is frictionally removed, normal positions are resumed. arrested, then turned in toward the Stream, and lastly In the northwest Atlantic probably the underlying pulled along in an easterl flow parallel with the Stream, cause of the Labrador Current is hydrodynamic condi- with a consequent inter digitation of olar and tropical t.ions. Seasonal melting of the ice in northern regions water at the Tail of the Bank in tf e form of varied causes an escess accumulation of cold fresh water to mixing eddies. flood the surface between Greenland and North America. The statement that the Labrador Current is. arrested It seeks escape in a southward expansion on the warm in its flow and turned back parallel to the Gulf Stream saline water of the lower latitudes. is at variance with the views of many authorities who The variations in movements of the surface water claim that the Labrador Current sweeps southwesterly are greatly influenced by the circulation of the atmos- across the Great Bank and continues as a cold current phere. They follow directly from the seasonal changes. with a set down the east coast of the United States as The wind control is determined by the position, form, ’ far as Cape Hatteras. Another fact which has been and intensity of the whole north Atlantic high-pressure brou ht out by the oceanographical work of the ice area and by the cyclonic area to the northward. If the patro5 is the lack of evidence to support the belief that Icclandic ininimuiii lie to the westward in the Greenland the Labrador Current upon meeting the Gulf Stream region, during the months of December, January, and dives beneath the latter, emerging to the southward. February, the priocl when the field ice breaks loose, it The evidence gathered by the patrol forbids such a will cause revailing southwesterly winds which will re view. On the contrary, the tendency of the polar water tard the Lsrador Current and tend to hold the ice in the to spread out on the surface is quite pronounced. One higher lititudes. On the other hand, wind possessing a ocean current may dive beneath another at some places strong northerly coni onent will tend to augment the in the world, but such is not the case here. Labrador Current anB drift the ice south faster and in In the consideration of ice, it is necessary to make a greater quantity than otherwise. The normal seasonal distinction between field ice and berg ice. Field ice, increase in size and intensity of the north Atlantic high formed by frozen Arctic sea water, is under the con- during suininer causes strong southwesterly winds which trol of the winds and the surface currents.