~*-jnr~> .- VOL. XI, NO. 2 DECEMBER 1964 EDITOR: JAN HAHN Published quarterly and distributed to the Associates, to Marine libraries and universities around the world, to other educational institutions, to major city public- libraries and to other organizations and publications. Library of Congress Catalogue Card Number: 59-34518 HENRY B. BIGELOW Founder Chairman NOEL B. MCLEAN Chairman, Board of Trustees PAUL M. FYE President and Director COLUMBUS O'D. ISELIN H. 8. Bigelow Oceanographer BOSTWICK H. KETCHUM Associate Director of Biology and Chemistry The Woods Hole Oceanographic Institution Woods Hole, Massachusetts VOL. XI, No. 2, December 1964 ca/cftfes on! Caryn Shave w. E carry this letter not only because it is a fine example of many received from children who find our drift bottles, but also because Caryn Shave was named after our former research vessel 'Caryn' (shown on the cover). Her father, David W. Shave, M.D., now a psychiatrist, served as a sailor on our ship and later as a biochemist. There are at least two girls named after the ship; the other is Caryn Shonting whose father, David Shonting, Ph.D., sailed on the ship as an under- graduate student and is now engaged in oceanography at the U.S. Naval Ordnance Station, Newport, R. I. "Now Listen, I told you . . ." Editorial VOL. XI, No. 2, December 1964 A. HE news of the Free-Corer (page 2) is rather exciting. Sediment coring at best is hard and dirty work. The new method, described as 'elegant' by the authors, not only is all that, but also takes away a lot of the dirty work. New instruments and methods always are interesting. It is, perhaps, not surprising that many instruments in general use to-day were developed at our Institution. The bathythermograph, the Stetson gravity corer, the GEK, the Salinometer, the PGR and the seismic "boomer" are but a few examples, all at one time or another described in 'Oceanus 1 . There seems to be no doubt that the Free-Corer will join the list of the new tools originating at Woods Hole and widely used by oceanographers around the world. NEW INSTRUMENT K. N. SACHS. JR. "It is an e r ie feeling to throw an instrument the corer by V. T. BOWEN and P. L. SACHS 'URING the year just past the Insti- tution has acquired a new and exciting tool for bottom sampling: the Free Corer. Development of this was sparked by dis- cussions at sea during 'Chain's' work about the Equator in 1963.* The desira- bility of freely released instrument pack- ages were illustrated to us by the rugged topography encountered and by the multiple (often conflicting!) scientific programs of that cruise. On return to Woods Hole, P. L. Sachs of our staff, and S. O. Raymond of Benthos Company (working initially under development contract from the Institution), set about constructing and testing a free-release device to collect cores of bottom sedi- ment. The story of that development, with its vicissitudes and surprises, is too long to be outlined here; it is enough to say that by summer 1964, a reliable and convenient model was in production. We have just returned from our first extensive use of these devices in our geological study of the Mid-Atlantic Ridge between 22 and 23 N, and 45 and 46 40' W on 'Chain' cruise 44. The device consists of a heavy, dis- posable coring unit, and a light recov- erable assembly of glass floats, and plastic liner tube. Dropped free from the : 'See: ('Chain' 35), Oceanus, Vol. IX, No. 4, June 1963. over the side without a string attached!" Free-Corer RUBBER BAND HOLLOW RUBBER BALL Hfl 30cm O.D. SHEET STEEL SHELL FLOAT RELEASE CAST IRON BALLAST WIRE moving ship, the corer quickly reaches a velocity of about 425 meters per minute; it is balanced so that it falls with nose straight down. At the bottom it drives deep into the sediment, forcing a column of undisturbed sediment into the liner- tube, and at the same time, forcing up the outside of the barrel, the pilot weight which has so far held down the trip-lever holding the floats in place. As this weight rises to release the trip-lever, the floats are freed and begin to rise - - now con- nected by two meters of nylon line to the top of the liner-tube. The tug exerted when the floats come to the end of this tether, is enough to break the column of sediment at the bottom of the tube, and withdraw the sediment-filled liner from the steel coring tube. Now the floats and core rise freely to the surface, leaving the coring unit behind in the bottom. An electronic flash in one of the glass spheres provides a long-distance signal of the whereabouts of the floating unit, which is then picked up by the ship. The Free-Corer on its way down, and back at the sea surface, after having dropped its outer casing. The hollow spheres are made of plexiglass, the sphere containing the electronic flash unit is made of two halves whose surfaces have been carefully ground and lubricated with silicons oil to provide a seal. The spheres have been successsfully tested to pressures of 670 Kg/cm 2 , (about 9500 Ibs. per square inch) corresponding to depths of about 6400 meters. EMPTY GLASS SPHERE \ I ' \ // / GLASS SPHERE WITH ELECTRONIC FLASH INSIDE SPACER RING Elegant! In addition to being quick and easy and to having a kind of elegance not often involved in sediment sampling, this operation has proved to have a large number of advantages. Two of these are outstanding in that they permit scientific results not really previously possible, when using wire-lowered sediment corers. To illustrate these, a brief description of conventional gravity coring may be helpful: "gravity coring" is the term used for operations in which the only force helping drive the core tube into the sediment is that of gravity. Once the site to be cored is selected, the ship is brought about into the wind, so that drift will not force the wire under the hull; the corer is then lowered at the end of a 5/32 or 3/16" steel wire rope, at a rate usually about 120 meters per minute; when the corer is just a few meters (25 or so) above the bottom, the wire is allowed to fall free, and the corer strikes the bottom at a velocity often exceeding 250 meters per minute. During this entire period the ship is moving laterally in response to wind and current. This lateral move- ment continues during retrieval of the core. In a 4,000 meter lowering, in the trade-wind belt, for instance, total drift may well approach three-quarters of a mile. Adding to this the dislocation in- volved in positioning the ship before lowering, total displacement from the previous track often exceeds one mile. In making, as one often wishes to do, a careful survey of the bottom topography in areas of rugged relief, an accompany- ing series of sediment samples would be most illuminating. Because of the track dislocations involved in wire-line sam- pling one can obtain samples only in conjunction with rather imprecisely posi- tioned bathymetry; a good trace of the bottom topography requires an uninter- rupted run of the vessel. With the Free- Corer this presents no problem; the vessel makes its bathymetric run, dropping Free-Corers either at regular intervals, or in connection with the relief as revealed on the echo-sounder (about five minutes is needed to rig the next Free-Corer after a release). Then at the end of a suitable length of run, the vessel returns to retrieve the samples. Each core can be related precisely to its place on the PGR chart of the bottom topography. When samples are desired from abrupt features, such as the tops of pinnacles, the bottoms of narrow valleys or spaced along slopes of sharp relief, wire-line methods have proved time consuming in the extreme, or quite impractical. With the Free-Corer such sampling is straight forward; the falling velocity is so high compared to the horizontal components imparted either from the movement of the vessel or by currents, that the sampler can be dropped on a selected target with an accuracy exceeding the precision with which we can "see" the target. On the cruise just past, we easily cored the tops of mountains only a few hundred meters across, and the bottom of one valley 4800 meters deep, and with a flat sedi- ment filled basin no more than 600 meters across. Of twenty-four drops, twenty-three were recovered: a propor- tion exceeding our wildest hopes. Powerful tool In the present model the core tube is 6.6 cm inside diameter, and 1.2 meters in length. The very high impact velocity of the Free-Corer has resulted both in longer cores, of the same sediment, than obtained with much heavier wire-line corers, and in sediment columns showing much less smearing along the walls of the tube. We have little doubt that the length of core obtained can be easily increased, at cost of very slight change in ease of handling. The high velocity of impact doubtlessly can be thanked for our most unexpected core: about 12 cm of good quality chalk consisting largely of the skeletons of Foraminifera ce- mented into a soft but solid rock! This was the sample obtained from the top of a sharply pointed peak rising more than half a mile above the adjacent hills and valleys. When it is realized that the Free-Corer not merely had to penetrate enough to cut out its sample, but to fix the 192 cm disposable section no more than 20 off vertical (beyond this angle, the liner-tube catches, and cannot be pulled free); it becomes apparent we have a really powerful tool! Those night watches can be long and arduous! Six Free-Corers are ready to be launched over the side of the R.V. 'Chain' as J. Burke "takes five," waiting for the command from the top deck laboratory where his watchmate is monitoring the ocean bottom topog- raphy by watching the Precision Graphic Recorder of the echo-sounder. The Precision Graphic Recorder here used to check the position of a camera above the ocean bottom is a pre- cision timing device developed at the Institution to make echo-sounding more accurate. The prototype of the PGR was discussed under "New Instru- ments," Oceanus, Vol. Ill, No. 2 Winter 1955. Our precise bathymetric surveys have been made possible oy the PGR. WRIGHT DR. BOWEN is a Senior Scientist on our staff. He also is a Lecturer in Zoology at Yale University. MR. SACHS is a geologist working with Dr. Bowen. Landbirds often come on board our ships even when we are hundreds of miles from land. These arctic snow buntings came on board the 'Erika Dan' when we were south of Iceland and rode all the way until we were just north of the British Isles. Some birdwatcher in Scotland or in the Hebrides may have had quite a surprise! Dutch Ship Returns Pigeon Lost in Storm T, HE bugler aboard the Dutch destroyer 'Amsterdam' sounded the V.I. P. call. Officers and sailors saluted and stood at attention. Up the steps came a London plasterer named Bill Bush, dressed in overalls and a sports jacket. "Your pigeon, sir," said Lieut. Comdr. Henk Smeets, "is plump and well, and the most popular V.I. P. we ever had." Three weeks ago Mr. Bush's racing pigeon, Pamela, landed on the destroyer after being released from Guernsey to fly back to Mr. Bush's loft in London. Storms blew her 210 miles off course. The crew got in touch with the Dutch Embassy in London, who got in touch with the British Navy. When the destroyer anchored in London, Mr. Bush picked up Pamela. (From an AP Dispatch in the New York Times, 19 Nov. '64.) The article 'Freak Ocean Waves,' by L. Draper, published in the May 1964 issue (Vol. X, 4) was reprinted in the November issue of "Science Digest," The Hearst Corp., N. Y. 40 120 "Reprinted with permission. Copyright 1963 by Scientific American. Inc. All rights reserved." THE MID-ATLANTIC RIDGE follows generally the S-shape of the Atlantic Basin. Lateral ridges also are shown. Islands that have active volcanoes are represented by black triangles. Numbers behind the islands indicate age in millions of years. 2O WEGENER FAULT ISLAND (10) ICELAND CABOT FAULT MADEIRA-(90?) BERMUDA (36) -^BAHAMAS (120) CAPE VERDE ISLANDS (150).: ST. PETER AND ST PAUL'S ROCKS (?) FERNANDO POO-"' __ PRINCIPE FERNANDO DE NORONHA (120) ^ANNOBON *ASCENSION(1) -ST. HELENA (20?) fc- TRINDADE(?) ^TRISTAN DA CUNHA (1) "GOUGH/- ISLAND (20?) NIGHTINGALE (18)'-.. ^FALKLAND ISLANDS (1.100?) \ ABOUVET INLAND (1) THE MID-ATLANTIC RIDGE Youthful Key to an Old Ocean by R. M. PRATT Jhe center of the ocean basin with its earthquake and volcanic activity appears to be a 'young' feature. L HE study of the Mid-Atlantic Ridge may be considered to have started with the discovery of the Azores in 1427 by the Portuguese pilot Diogo de Silves. The Azores, like St. Peter and Paul Rocks, Ascension, Tristan da Cunha, Gough and Bouvet Islands, are but surface expressions of the great submarine mountain range ex- tending the length of the Atlantic Ocean. Early recognition that the ridge was con- tinuous down the middle of the Atlantic is indicated by Lt. Maury on his chart of the North Atlantic in 1854; and we learn (Agassiz, 1888) that in 1859 Berryman, on the U.S.S. 'Arctic,' sounded across the North Atlantic from Newfoundland to Ireland with the objective of verifying the existence of a submarine ridge, along which it was proposed to lay a telegraph cable. Even today, one of the best sur- veyed portions of the ridge, appropriately called the Faraday Hills, lies along the cable route between Newfoundland and Ireland. 1990 fathoms A sfeep slope (5043'N, 2947'W) on the side of the rift or median valley in the Mid-Atlantic Ridge. Sessile organisms, including hydrozoa, sponges, and coral, are particularly noticeable. The photograph shows that such animal life occurs wherever something solid is available that the organisms can attach to. Nearby dredge hauls recovered basaltic rocks. The fine sediment drifting down over the rock is globigerina ooze the characteristic surface sediment in areas away from land and land-derived sediment. In this photograph the 7-inch-wide compass gives some idea of the scale and orientation of the slope. 10 Mid-Atlantic Ridge The overall continuity of the Mid- Atlantic Ridge was known in the late 1800's as indicated by the following pass- age from Agassiz*: "The South Atlantic is shut off from its northern area by a ridge extending from St. Peter and Paul Rocks to Ascension, at a depth of about 2,000 fathoms. The Challenger Ridge runs nearly north and south, leaving a free communication between the Antarctic Ocean and the eastern and western basins of the South Atlantic. The North Atlantic is subdivided into an eastern and western basin at a depth of about 1,500 fathoms by the Dolfin Rise, which follows in a general way the course of the S-shaped Atlantic basin." And again in the classic summary by Murray and Hjortf. "The most striking feature of the Atlantic Ocean is certainly the low central ridge (dividing the ocean into eastern and western basins), which was until recently supposed to be continuous from Iceland -Three Cruises of the 'Blake,' 1888. p. 242. vThe Depths of the Ocean, 1912, p. 135. through both the North and South Atlantic as far as latitude 40S, but is now known to be discontinuous in the neighborhood of the equator: (Romanche Trench)". t They also describe in some detail the influence of the Mid-Atlantic Ridge on the hydrology and the distribution of various organisms. The Meteor Expedi- tion in 1925-1927 worked over the South Atlantic portion of the Ridge and obtained for the first time numerous echo sounding records across it, showing the true com- plexity of the topography and, incident- ally, the Medianal Valley or central rift. The era of modern research on the Mid-Atlantic Ridge was initiated in 1947 and 1948 by Maurice Ewing on our Research Vessel 'Atlantis\ Since then numerous expeditions from the Lament Geological Laboratory and Woods Hole and from England, Germany and Russia have intensively studied various portions of the Ridge. iSee also ('Chain' 17) Oceanus, Vol. VIII, No. 1, Sept. 1961. SSee: National Geographic, September 1948 and November 1949. A DREDGE HAUL from the Ridge on board the R.V. 'Atlantis' in 1947. From left to to right: Drs. D. Ericson, F. Press and M. Ewing (kneeling). 11 Mid-Atlantic Ridge The accompanying illustration shows the topography of the Ridge made on three recent trans-Atlantic cruises of the R/V 'Chain' in which the writer partici- pated. Care was taken to obtain the best possible navigation track and high- resolution echo soundings (using a Pre- cision Graphic Recorder) to assure that none of the abrupt depressions or scarps were missed. The objectives of the study were to see to what extent individual features on the ridge could be correlated along the ridge axis on closely spaced profiles and to try to deliniate specific topographic features with coring and dredging operations. The northern survey made in July of 1960 ('Chain' 13) consists of three crossings about ten miles apart, the fourth crossing is 40 miles north and was made after a run following up the axis of the central rift. The depth of 2,200 fathoms is about the maximum reported for the central rift in the North Atlantic. On the east side of the rift a mountain with a minimum depth of 330 fathoms was located and surveyed. This appears to be the minimum depth re- corded along this section of the Ridge. Deep rift The deep prominent rift in this area is a northward extension of the Medianal Valley described by Hill (1960) but is south of the area described by Dietrich (1959) in which no evidence of a central rift was noted. A comparison of the records of this survey with a crossing of the U.S.C.G. 'Yamacraw,' (cruise 10) to the north indicates that tranverse faulting has probably deplaced the axis of the ridge about 50 miles to the west and explains the northward termination of the valley. A dredge haul in the rift recovered a number of pieces of volcanic glass and fine-grained basalt mixed with globigerina ooze. In the dredge, the rock had the appearance of bombs lying on top of the ooze, indicating possible recent submarine volcanism. Other dredge hauls from the nearby ridge crest recovered an assort- ment of coarse gabbro, basalt, gneiss, and quartzite pebbles some of which are quite obviously ice rafted. The accompanying photograph, taken nearby, is typical of many taken along the ridge. DR. PRATT has been with the Institution for five years. He is principally interested in relating the topography of the ocean bottom to the geological history of the ocean basin. The second survey was made by the 'Chain' (cruise 7) in 1959, southwest of the Azores. In this area there is no prominent central rift and it is difficult to imagine topographic patterns that might follow through from section to section. Dredge hauls during this survey failed to recover any rock. The third ridge survey was made in 1961 ('Chain' 21) at about latitude 29 N. Several other tracks of Woods Hole ships pass over the ridge in this vicinity, giving a relatively complete picture of the topog- raphy. A minimum depth of about 750 fathoms and a maximum of about 1,880 fathoms was found in the axial part of the ridge. An axial valley or sorts can be connected between the sections but it is certainly not as well-defined as the valley in the northern survey area. Five dredge hauls recovered basaltic type rocks in this area and numerous cores and photographs were taken. BIG JENNY A VETERAN. The vane of this bottom camera shows that it has been lowered many times in the Tyrrhenian Sea, in the Puerto Rico Trench, over the Mid-Atlantic Ridge, in the Mediterranean Sea and during the search for the submarine 'Thresher'. V 12 ,,', .' ' ' ^> TOPOGRAPHY of the Ridge made during three recent cruises to see how individual features could be correlated along the Ridge-axis on closely spaced profiles. The central valley or rift is clearly shown. 13 Mid-Atlantic Ridge Our crossings of the Mid-Atlantic Ridge have been made with the idea of correlating ridge features from section to section and dredging and photographing these features. Little can be added to the general description of the ridge although it is becoming apparent that the secondary features of the ridge may not be linear but a vast complex of seamounts, some of which we can study directly as the oceanic islands. From our observations it appears that the rift features are subsidiary to the volcanism and general uplift, and trans- verse faults are as prominent in some areas as the much publicized medianal rift zone. Why is the Mid-Atlantic Ridge of such great interest? It has been known for over a hundred years that this great topo- graphic feature extended down the center of the Atlantic. It is the very fact that it is in the very center of the ocean, where the deepest part should logically be, that makes it of such great interest. Geologic thought until very recently has assumed that the ocean basins are permanent, primordial features on the earth's surface which are gradually being encroached upon by cyclic waves of sedimentation from the continents. All this has changed: | AXIS OF CROSS SECTIONS 35W |331 |30W. I 5ON |3,-W |Z9W. J29W. 28* Cross sech'ons of the Mid-Atlantic Ridge, showing the central valley or rift. Circles on the track chart indicate the structural axis of the Ridge, which appears to be displaced (by a fault?) in the northernmost section. (A). 14 we find that in the Atlantic Ocean the center of earthquake and volcanic activity coincides with the central ridge from Jan Mayen and Iceland to Tristan da Cunha and Bouvet Island. The deepest basins with the oldest sediments lie near the continents. Thus, it is becoming clear to those of us who study the history of the earth by examining the ocean bottom first that it is the center of the ocean basin that is young and active rather than the edges. In fact, the Mid-Atlantic Ridge appears to be the expression of a great upwelling convective current in the earth's mantle, and rather than the oldest, it is probably the youngest part of the Atlantic Ocean floor. Dr. Harry Hess of Princeton pictures the ocean floor as constantly renewing itself along the Mid-Atlantic Ridge and then sliding out laterally to either side. This explains the equal separation of the Continents from the Ridge axis, which, as Dr. Hess explains, are carried passively on the spreading convective cells. Every time our ships make observations on the Mid-Atlantic Ridge we add to our knowl- edge of the origin and basic structure of the ocean basin and thus of the Earth. 36' W. 35' 34' 33* 32* 31* 3O* 29* 28* XIS OF CROSS SECTIONS SPOT DEPTHS FROM CHARTS BC 04ION S BC 03ION AIH 13 22 JULY. 19*0 52N.| |28W MIO-ATLANTIC RIDGE CROSS SECTIONS FROM CHAIN No. 13 8 YAMACflAWHa. 10 SHOWING THE CENTRAL VALLEY OR RIFT CAMERA LOWER DEPTHS IN FATHOMS BASED ON 8OO FMS/SEd (UNCORRECTED) 3. STRUCTURAL AXIS OF MID-ATLANTIC RIDGE HAIN 13 19 JULY. I960 INDEX MAR Depths are in fathoms, uncorrected for the speed of sound in seawater. Locations of dredge hauls, camera lov/erings and heat probes also are indicated on this trackchart. 15 % Nof a nuclear explosion but a typical cumulonimbus with anvil top. These clouds form thunder and hail storms and also are the driving mechanism in a hurricane. Practical weather modification is still a dream for the future. Schemes to change our climate appear in the Sunday Supplements but are not yet science a long chain of reasoning goes between cause and effect which is not yet based soundly on physical laws or testable by measurements, as science requires. 16 Tlie Ocean as a Laboratory for Weather Modification EXPERIMENTS MALKUS by JOANNE S. MALKUS The energies involved in the motions of air and sea are stupendous. Just one large thundercloud releases as much energy as a hydrogen bomb, while a hurricane may expend the equivalent of 100 or more such bombs per hour. If man's puny resources are to alter these forces, he must learn much more than he knows now about their machinery - - for a head-on or random attack will surely not succeed. He must pinpoint Achilles heels, or instabilities, where a relatively small cause may trigger a loaded gun, or better yet a chain reaction - - and the links in the chain must be accurately pre- dictable in advance - - we must not, for example, set out to destroy a hurricane and discover too late that we have intensi- fied it instead. How are we to approach the two-fold practical and scientific goal of weather modification? This article centers around some of the first concrete steps in this direction namely, real experiments which alter phenomena in the actual atmosphere by a man-made cause creating predictable and measurable con- sequences. Thus the word "experiment" should be heavily underlined in the title. 17 Atmosphere The experiments are very small and modest ones compared to the grandiose Sunday Supplement schemes. Neverthe- less, they cost several hundred thousand dollars and involve the precise coordina- tion of six specially equipped aircraft in a maneuver which is just barely possible operationally. Powerful tool These experiments only involve two classes of atmospheric phenomena - - a certain type of clouds that we call cumulus clouds and the tropical hurricane. They are not designed to make rain from the clouds, or to tame the furious winds of the storm - - they may not even help us find a later way to these objectives, although surely we may hope so. But they do have two important positive features - first, they have already been carried out and are not just Sunday Supplement speculation. Secondly, they probably pro- vide the most hopeful and powerful tool available to learn more about a class of atmospheric phenomena that is both vitally important to planetary science and to human life. Cumulus clouds are responsible for a large fraction of the world's rainfall and water resources, particularly in the water- starved tropics. Furthermore cumulus clouds can become dangerous and destruc- tive - - under the right conditions they can become 50,000 feet tall and cause thunderstorms, hail, tornadoes, and turbu- lence intense enough to rip airplanes apart. In this giant form they provide the driving power of the tropical hurricane which is probably the worst menace that the atmosphere can concoct. So we need to study cumulus clouds. Like people, they have a life cycle - - they are born, they grow up, and eventually age and die. But, unlike people, the bigger they are, the longer they live. Small ones may last only five to ten minutes; larger ones may enjoy an active life lasting 20 minutes. The giants, or cumulonimbus, as we call them, can sometimes retain their vigor an hour or more. But at all times their natural existence is a struggle - a near balance-between the forces of growth and those of destruction. From this near-balance comes the potential power of our experiment, which consists of pulling a small trigger to set off a large reaction which is measurable; and hopefully predictable using the laws of physics and mathematics. A typical good sized cumulus cloud in the tropical ocean. The tops are at about 20,000 feet. 18 W-57 Profile view of the cumulus cloud seeding experiment. The seeding plane is a Navy A38. (Second from the top). The ofher aircraft are fully instrumented observing planes from the U.S. Weather Bureau. MONITORING AIRCRAFT COMMAND ^AIRCRAFT Plan view shows how the command aircraft flies a box around the area while the three observing planes record cloud properties, such as temperature, water content and ice nuclei. For several reasons the tropical oceans provide the best laboratory for weather modification experiments. In the first place, they produce cumulus clouds day and night. Secondly, the tropical oceans breed hurricanes, which are probably the most hopeful large-scale storm to experi- ment upon. Thirdly, I predict that if practical weather modification ever does become a reality, the oceans are almost certain to be involved somewhere hence we must use every opportunity to learn more of how the air and sea interact, or affect each other. Figure 1 shows a typical tropical oceanic cumulus cloud, which would normally stop growing at about 20 - - 25,000 feet where there is often a stable dry layer acting as a lid against its further growth. Explode clouds What we are going to do is to design an experiment to explode this cloud. Actually, we figured out a way to double the growth forces so that they win over the destructive forces and cause the cloud to become not only a giant, but a rather abnormal giant as well. We do this by dropping 25 silver iodide smoke genera- tors into the cloud from an airplane flying across its top. We will design the experi- ment so that other aircraft will fly through the cloud at several levels both before and after the seeding with silver iodide bombs, so that the predicted chain of events from cause to effect can precisely be tested by measurements. In order to make this experiment as nearly as possible a controlled experiment, ideally we also have to study identical clouds which are not seeded and compare their develop- ment to the seeded clouds. Fortunately, the tropical oceans produce so many clouds that we believe we were able to select control clouds which behaved just as the seeded clouds would have if we had left them in peace. But now we must explain how this experiment works - - in fact, we must learn something of how a cumulus cloud works in order to understand how we can explode one and what we can hope to learn from causing the explosion. In other words, years of cumulus study had to pre- cede this experiment. We must ask first what makes this cumulus cloud grow, and what normally stops its growth at about 20 - - 25,000 feet. Clouds are chimneys of rising moist air which cool by their rising motion and condense water vapor into the drops that make the cloud visible. Condensation of water from vapor to liquid releases heat - - the released heat makes the cloud warmer and hence less dense than its surroundings - - so that it is buoyant like a cork held under water. It is buoyancy that is the lifeblood of a cloud and it stops growing and dies when it runs out of buoyancy. 19 Afmospfiere This cloud would normally run out of buoyancy at 20 - - 25,000 feet because of a stable dry layer there which acts as a lid. But what would happen if we could invent a way to give it more buoyancy at that critical point? Might we give it enough vigor to break through the lid, above which there is nothing much more to stop its growth until it hits the stratosphere? Well, that is just exactly the idea - - that is, in fact what the silver iodide does to the cloud. Cloud physics To see how 75 pounds of silver idodide can double the growth forces of this cloud, and thus allow it to burst its head through the restraining lid, we shall have to explain a little cloud physics. The main fact about cloud physics is that water does not always freeze at 32F or 0C. In clouds water is often found in a liquid state at -40C and is commonly still liquid at -20C; even this temperature is way above the top of this cloud, so that we can expect to find its drops all in a "super- cooled" state in its upper half - - that is, these drops are below freezing tempera- ture but not frozen. But water does not like to stay in a supercooled state and will try to freeze into ice crystals or snow flakes if given an opportunity. The best opportunity for freezing is provided when some ice crystals are put into a super- cooled cloud. Once ice crystals are present, the supercooled water will all freeze in a hurry. This is how cloud seed- ing with dry ice works. The dry ice makes some ice crystals, which then set off a chain reaction. But what about silver iodide? Oddly enough, silver iodide has a crystal structure so near that of ice that water is fooled - - ice crystals grow onto the silver iodide crystals, which splinter and multi- ply - - the drops evaporate and grow as more ice crystals etc. and the whole cloud top is turned from water into ice in two or three minutes. How does this double the growth forces and give the cloud the required shot-in-the-arm? Well, freezing releases heat also - - the so-called latent heat of fusion, about 80 calories per gram of water frozen. It is easily shown that freezing the normal water content of a cloud like this, which is about 2 grams of water per cubic meter of air, will increase the cloud temperature by about 1 Centigrade. That does not sound like much --.but the cloud is naturally only about 1 C warmer than its surroundings anyway - so we can, by freezing its water, double its tempera- ture excess - - and that means double its buoyancy or growth force. x A o Seeded Cloud Locations U.S.S. Randolph Aug. 17, 1963 Curacao San Juan, PR. "* Location of the August 1963 cumulus seed- ing experiment, the aircraft were stationed in Puerto Rico. By fortunate coincidence the aircraft carrier 'Randolp' made an upper air sounding A . Other upper air soundings were made at Puerto Rico and Curacao . Difficult operation All these facts about cloud physics have been well known for sometime - the reason that the experiment was not performed before August 1963 is because it is technically and operationally so difficult. The whole cloud has to be filled with silver iodide particles to turn the water to ice suddenly - - this required the development of pyrotechnic genera- tors, which were invented at the Naval Ordnance Test Station at China Lake, California. This requires one aircraft. Secondly, the cloud properties must be measured before and several times after seeding - - this requires at least two, or better, three specially instrumented air- craft. All this demands delicate coordi- nation. 20 "Explosion" of seeded cloud on August 29, 1963. The top two photographs show the first phase. Left: at time of seeding. Right: minutes later. Below: the second nine In the center: One of the silver iodide pyrotechnic generators used to produce silver iodide smoke in the selected clouds. phase. Left: 19 minutes after seeding. Right: 38 minutes after seeding. The most important aircraft is the so-called Command Plane, which directs the other airplanes by watching them on its radar. This was a Navy Super- Constellation, the same type as are used for defense radar picket planes. I rode in this aircraft and selected the clouds and took pictures of them as the Command Plane flew around each cloud in a box pattern and traced the cloud's development on its many radars. The aircraft were all based in Puerto Rico. We had only four days for the experiment last summer but by some miracle, it worked on all four days. Eleven clouds were studied, six were seeded and five examined as controls. Four of the six seeded clouds exploded - - that is, they grew 10 20,000 feet taller than their neighbors and expanded enormously in the horizontal. They also enjoyed at least twice the normal lifespan. Two clouds were seeded improperly or too late and died, and all five control clouds died without growth or extension of their life cycle. The above is an example of an exploded cloud taken from a series of 10 koda- chrome slides. I took these pictures at known intervals, from the Command Plane as it executed its box around the cloud. It is important to note that the explosion consists of two phases - - the first phase is vertical development and the second horizontal. In the first phase the cloud tower that was actually seeded grows from under 20 to over 40,000 feet, expending somewhat but not hugely. In the second phase the whole cloud body explodes horizontally to about four to five limes its original diameter. What we have here is a rather spec- tacular development of an abnormal giant cloud. But to make this demonstration a valuable scientific experiment, we have to do two things: first, show the explosion is reproducible from the same cause and not an accidental freak of nature. I already mentioned that this repetition was achieved on four successive days - - some students at U.C.L.A. are now working on specifying the conditions under which 21 II 6 KM S to SW In the first phase of explosion a seeded cloud grows mostly verti- cally. Traced from actual aerial photographs at 4-5 minute intervals. In the second phase of explosion the cloud grows horizontally. The original diameter of the seeded cloud has almost doubled. Tracing from photographs; the last outline is 38 minutes after the seeding. 6 km SW to NW SEEDED CLOUD AUG. 20 12 10 3'-'- 2 6 10 14 RATES OF RISE (m/sec.) ) I 2 3 TEMP EXCESS C Numerical model of the effect of seeding. The solid curve on the left shows the rate of rise of the cloud tower when not seeded. The other curves show various calculated effects of seeding, as explained in the text. The circles show the observed rate of rise calculated from photographs. On the right: temperature excess (proportional to buoyancy) of cloud tower over the outside air. Solid curve, unseeded. 'Railroad track'-, seeded without expanding. Dotted x-ed: seeded with one-third expansion. A schematic before and after picture of seeded cloud is shown in the center. Tempera- tures are in-cloud temperatures. The silver-iodide is assumed to turn all supercooled water into ice between 4C. and 8C. 22 this experiment will be a success - - they turn out to be fairly specialized, but would occur on about 4 - - 8 days in each month at a given place in the tropics. Secondly, we have to demonstrate, using the laws of physics and mathematics, that the seeding caused the cloud's explosion - in other words, we have to develop quantitatively the chain of events between cause and effect. Calculations It would take too long to explain the laws and equations that were used - - 1 will show briefly the results of the calcula- tion to give a rough idea of what was done and why. The physical laws give us equations for the rate of rise of the cloud, its temperature excess over the outside air, and how much water it contains. Let us first look at these as calculated for the natural or unmolested cloud (Pg. 22). This cloud tops at about 22,000 feet. All these graphs are derived from theoretical cal- culations but they are compared with the aircraft measurements before seeding and in the control cloud. Now we seed the theoretical cloud and see what happens. Each curve takes account of a different effect of the seeding alone and in com- binations. The dashed curve just adds the heat of freezing. The railroad track curve adds also the factor of increased rainfall, which lightens the load of water the tower has to carry. The dotted curve adds the heat and takes into account the tower's expansion and the x-ed curve combines all effects of the seeding. The observed rate of rise lay between the dashed and x-ed curves. Thus we have an experiment in more senses than one, in that we have a way of checking our cloud theories by computing growth curves based on differ- ent hypothesis as to which factors are important in cloud growth and testing these by comparison with our observations on both seeded and unseeded clouds. Clearly the potential of this experiment has just barely begun to be exploited we have just scratched the surface of what can be done and learned. Schematic hurricane model showing typical cloud distribution relative to the direction of motion. The top view shows how this would be seen on radar. Below is a vertical cross section along line at right angles to the direction of motion. Atmosphere A related experiment involves applying the same seeding techniques to the tropical hurricane. Huge cumulus towers run the heat engine that drives the tropical hurri- cane. Our illustration shows how these clouds are arranged in a typical hurricane. The primary energy releasing cell (cloud chimney) is located in the area enclosed by the broken line. We designed and carried out an experiment dropping much larger silver iodide generators into this primary energy cell of two hurricanes, in an attempt to disrupt the linkage between the clouds and the stability of the air circulation swirling around the storm center. In other words, we postulated an Achilles heel of the storm and tested the postulate by the experiment. However, a hurricane is a much more difficult object for a good experiment than a 'simple' tropical cumulus cloud. This is not because they are more dangerous to fly in, or many hundreds of thousands of times more energetic, but because unlike cumu- lus clouds, which are well-behaved normally, hurricanes behave very badly. They undergo fantastically large natural RADAR SPIRAL RAINBANDS LEFT SIDE RIGHT SIDE EUJPrimary Energy Cll ("Hot Towert") E23Convective Cloudi CD Ahottratui 23 changes for no apparent reason so that one cannot easily prove that what he did led to what was observed subse- quently. Furthermore, it is obviously impossible to select an identical hurricane to run a control on because no two hurricanes in history have been identical. However, it is gratifying that at last the mighty hurricane is subject to experimen- tation - - that this is so gives man some reduction in his awe of them and the hope someday to cope with their destructiveness. Probably more exciting to the scientist, however, is the more modest cumulus experiment. The earth sciences, such as meteorology and oceanography have up till now differed from physics in that con- trolled experiments on natural phenom- ena were largely unfeasible, and we had to content ourselves with observing what nature chose to perform, or to make small, not quite adequate models in a laboratory. We think that our cloud experiment is promising because it is a step in convert- ing meteorology from a purely observa- tional science. Acknowledgments: The writer expresses her gratitude to her colleague Dr. R. H. Simpson of the U.S. Weather Bureau who conceived and directed Project Stormfury, under which the work described in this article was carried out. Project Stormfury is an Inter-Agency program between the U.S. Weather Bureau and U.S. Navy, partially supported by the National Science Foundation. DR. MALKUS is Professor of Meteor- ology at the University of California, Los Angeles, and has been on our staff for many years. See also: "Special issue on Meteorology," Oceanus, Vol. IV, No. 3, Spring '56, and; "The Ocean as the Atmosphere's Fuel Supply," by Joanne S. Malkus, Oceanus, Vol. VI, No. 4, June '60. Recenf books Jackson, D. F. (Editor), "Algae and Man," Proceedings of the NATO Advanced Study Institute, Plenum Press, New York, 1964. $14.50. An interesting, international account, including the effects of algae, both beneficial and detrimental, on the human (and animal) organism. Buehr, W., "World Beneath the Waves,", W. W. Norton & Co., Inc., New York, 1964. $3.25. An interesting book for young children with fine illustrations by the author, many of them based on photographs and drawings supplied by us. Long, Capt. E. John, "Ocean Sciences," U.S. Naval Institute, Annapolis, Maryland, 1964. $10.00. A series of articles, written by 18 authors, mostly administrators. Of interest to oceanographers to know what Washington thinks of their respective fields. The chapter: "Oceanography and Government" is "must" reading. Miller, R. L. (Editor), "Papers in Marine Geology," Shepard Commemorative Volume, The Macmillan Co., New York, 1964. $20.00. 24 papers describing contemporary processes, marine ecology, properties of sediments, submarine arch- aelogy, regional studies and studies of the earth's history. Raymond, J. E. G., "Plankton and Productivity in the Oceans," The Macmillan Co., New York, 1963. A Pergamon Press Book. A splendid textbook on primary production, long needed, which properly points out that knowledge of others aspects of oceanography are needed to study marine biology. 24 MBL/WHOI LIBRARY III I I UH 17ZJ P Recent books Wiist, G., "Stratification and Circulation in the Antillean-Caribbean Basins," Part one, Columbia University Press, New York & London, 1964. $15.00. Dr. Wust, of "Meteor" fame, continues to produce prolifically. As this book arrived when we went to press, it will be discussed in a future issue. Wiegel, R. L., "Oceanographical Engineering," Prentice Hall Inc., 1964. $18.00. Largely devoted to ocean waves, this book should be of great value to engineers having to deal with shore installations as well as ship construction. Damien, R., "Albert kr, Prince Souverain de Monaco," Institute de Valois, Paris, 1964. Price unknown (in French). At long last a biography of the Prince among oceaTnographers. Illustrated with photographs taken aboard the 'Princess Alice 1 and the 'Hirondelle IT. Strangely enough, there scarcely are any biographies of oceanographers. This one is worth reading. Jagersten, G., "Life in the Sea," Basic Books, New York, $10.00. A beautiful book of photographs by Lennart Nilson, made meaningful by the comments of Professor Jagersten. Will make a fine Christmas present. Hahn, J., "A Reader's Guide to Oceanography," Woods Hole Oceanographic Institution, 1964. A completely revised and enlarged edition of this popular Guide is available, please send a stamped, self-addressed, long envelope. Copies in bulk: 10 cents each. We have printed some 27,000 copies of this Guide since 1960! Marine geology of the Gulf of California, a symposium. American Association of Petroleum Geologists. Memoir 3. Edited by T. H. van Amid, and G. G. Shor, Jr. 408 p., illus., $9.00. T J. HE Gulf of California is a narrow inland sea between the Mexican coast and the peninsula of Baja California. It was first circumnavigated in' 1539 by Francisco de Ulloa who named it Mar Bermejo, the Vermilion Sea, because of the reddish color of the muddy waters of the Colorado estuary. The sea floor of this narrow trough is characterized by a chain of deep basins, some of which have oceanic depths, separated by narrow and steep walled ridges, a few of which extend above sea level to form islands. The Gulf of California is believed to have been formed by the separation of the Baja California peninsula from the Mexican mainland. Memoir 3 just published by the American Association of Petroleum Geologists deals with the oceanography, physiography, structure, sediments, geo- logic history and biogeography of this unique region. Written by 22 leading marine scientists, most of them from Scripps Institution of Oceanography, it presents a comprehensive picture of the geology and biology of the Gulf. The editors and publishers of this book deserve a vote of thanks for a job well done. It will make a valuable addition to the library of all those interested in the sea. The excellent color bottom topography charts alone would make this a valuable book. It is also one of the few texts pub- lished in recent years available at a reasonable price, an unheard thing in this age of $20-30 textbooks. The only minor criticisms that the reviewer has is the absence of a section summarizing all the data presented, and that the only con- tinuous seismic data presented is for the southern tip of the Gulf and that no surveys were made of the more complex areas in the center of the Gulf. E. Uchupi Contents VOL. XI, No. 2, Dec. 1964 Articles THE FREE-CORER fay V. T. Bowen and P. L. Sachs THE MID-ATLANTIC RIDGE YOUTHFUL KEY TO AN OLD OCEAN by K. M. Pratt 9 THE OCEAN AS A LABORATORY FOR WEATHER MODIFICATION EXPERIMENTS 16 by Joanne S. Malkus Features NAMESAKES OF THE R.V. -CARYN 1 LANDBIRDS AT SEA BOOK REVIEW INSIDE FRONT COVER 7 23 Published by the OGEANOGRAPHIC INSTITUTION ~*