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926 GEOPHYSICS: J. KAPLAN PROC. N. A. S. veloped; but, both radiosondes and magnetic recorders were not available for use in many countries in the much increased numbers needed. This serious situation was relieved, only shortly before the Year began, by a generous grant from the Rocke- feller Foundation, which thereby greatly helped the whole enterprise. Many of the recorders have continued to be used on expeditions and at new permanent observa- tories since Polar Year II ended. In the coming Geophysical Year there will be further kinds and new means of observations, such as cosmic rays, geodetic observations of the moon, and rockets and rockoons (balloon-launched rockets) for exploring the upper atmosphere and the solar rays. The observations made during a Polar or Geophysical Year, however, when com- pleted, important though they are, only open a new phase of the enterprise-their analysis and discussion. After Polar Year II ended, another Rockefeller grant was made for these purposes and to set up a central library of archives and provide a bibliography of the whole undertaking. After La Cour's death in 1942, Fleming became the leader in these further organizing stages, which he brought to a formal conclusion at the end of 1950, with the co-operation of Laursen, of Denmark. The bibliography provides an impressive indication of the extent of the observations and the results of their analysis. But that harvest was not and still is not fully reaped; and even from Polar Year I there are useful gleanings yet to come. Let us bear these things in mind while we hear of the more widely branching plans prepared for the coming International Geophysical Year. * President, IUGG and President, ICSU Comit6 Sp6cial Ann6e G6ophysique Internationale. Present address: New York University, New York, New York. THE SCIENTIFIC PROGRAM OF THE INTERNATIONAL GEOPHYSICAL YEAR BY JOSEPH KAPLAN* UNIVERSITY OF CALIFORNIA AT LOS ANGELES The scientific program of the International Geophysical Year has several impor- tant general characteristicswhich willbedescribed before attentionis called to specific projects. With careful planning, thorough review, and international co-operation, it is hoped that significant advances will be made toward the solutions of some of our most puzzling geophysical problems. The dates as well as the places of obser- vation were selected with the above goal in mind. Because the sun is the key to many important geophysical processes, especially those related to weather and tele- communications, the period of observations was selected to coincide with the in- creased probability, as we approach the sunspot maximum, of occurrence of solar flares and other solar disturbances. The selection of the places of observations was also made with the sun and its increasing activity during this period as one of the determining factors. In addition to electromagnetic radiation, the sun emits high-speed particles, whose kinematics are intimately related to the earth's magnetic field. The incidence of solar electro- magnetic radiation on the earth also depends-on time and place. Consequently, Downloaded by guest on September 24, 2021 VOL. 40, 1954 GEOPHYSICS: J. KAPLAN 927 carefully planned world-wide observations are essential, and this is well illustrated by the north-south pole-to-pole chain of stations which is the principal feature of the proposed program in meteorology. Another important general characteristic of the program is the effort to achieve maximum results from a minimum program. Specific goals are set-for example, in the ionospheric program, which is based on our desire to understand ionospheric storms, the absorption of waves, and the motions in the upper atmosphere. Whenever man examines his physical environment carefully and systematically, the effect on the basic sciences of physics, chemistry, and mathematics is generally very significant. The way in which astronomy has so strongly guided the develop- ment of physics is perhaps the most striking example of this. In geophysics one example is the airglow, in which hitherto unobserved radiations due to OH were discovered relatively recently. The attempts to explain their origins led to a care- ful re-examination of the validity of some of the most fundamental problems in chemical kinetics of gaseous processes. The atmosphere, the solid earth, and the oceans are vast laboratories in which nature is constantly carrying on its remarkable experiments. Eleven fields of activity comprise the program: meteorology, latitude and longi- tude determinations, geomagnetism, gravity measurements, ionospheric physics, aurora and airglow, solar activity, cosmic rays, glaciology, oceanography, and rocket exploration of the upper atmosphere. These fields have close relationships: each is characterized by need for synoptic or epochal data, and the value of such data is enhanced markedly by obtaining it simultaneously in all the fields, per- mitting studies of the correlation of various geophysical events. A brief review of some of the fields in the program will suggest the nature of the problems to be stud- ied and of the method of approach. Glaciology. Glacier studies have given clear indications that we are now in a cycle of warming which began about 1900. This is no academic effect: if the in- dicated warming continues for another twenty-five to fifty years, the ice will melt out of the Arctic Ocean in the summer, making it navigable. Slow changes of climate have already begun to show a change of storm paths and redistribution of rainfall, rendering some areas previously well watered more arid and, in turn, bring- ing water to arid regions. The objectives of the United States glaciological efforts in the International Geophysical Year program will be twofold: (1) to extend the studies of glaciers on a world-wide basis in conjunction with similar efforts of other countries and (2) to co-ordinate the existing observations of glaciers with the varied world-wide efforts in other fields of geophysics in order to establish quantitative and qualitative indi- cations of long-term climatic variations affecting the world as a whole. The plan includes (a) assembly of all available data on the variation of glaciers, (b) analysis of the data obtained to determine the extent to which glacier variations are caused by climatic change, (c) study of the hydrological economy of specific glaciers with respect to meteorological factors, and (d) studies to establish, correlate, and trace climatic trends of the past and to improve future predictions by combining these findings with those of solar and atmospheric physics. Oceanography. As in the other fields of geophysics, the study of oceanography requires the conduct of many experiments and the taking of many measurements if Downloaded by guest on September 24, 2021 928 GEOPHYSICS: J. KAPLAN PROC. N. A. S. major problems are to be solved. These problems have to do with the nature of oceanic currents, temperature, composition and levels, and total water content. A major problem is the study of the annual cycle in sea level and the global water budget of the oceans. Although all available tide-gauge and temperature data have been studied, the problem remains unsolved because a minimum of twenty years of tide observations at a station is required to give a meaningful average, so that values in one area can be compared with values in another area taken at a different time. As much or more could be learned by synchronous measurements during one specific year. Simultaneous measurements of fluctuations in sea level are probably the most effective and the least expensive means of studying the "weather" of the oceans-i.e., the fluctuations in ocean currents with time. To be of value these observations must extend over vast ocean areas. In low latitudes the recorded seasonal changes in sea level are about what can be inferred from observed changes in temperature of the superficial layers, indicating a change in specific volume rather than in mass. In high latitudes there is also a change in mass. If these changes are associated with changes in currents, the currents at mid-latitude may be essentially confined to superficial layers, whereas at high latitudes they may extend to the very bottom and are there- fore not measurable by present standard techniques. Moreover, recorded sea level is lower by about half a foot in the Northern Hemisphere in northern spring and in the Southern Hemisphere in southern spring than in the respective fall seasons. From present data it cannot be determined whether this involves flow of water across the Equator or between the fringes of the ocean basins (where nearly all tide stations are located) and the central portions (where observations are inadequate). Such problems in oceanography are analogous to those in the meteorological program involving measurements of air flow across a meridian and across the Equa- tor. Similarly, the solution requires synchronous global measurements, which in- clude (a) observations and reduction of data from existing tide stations, (b) tem- porary tide gauges or surge recorders at some forty stations, with emphasis on is- lands and the Southern Hemisphere, particularly the antarctic, and (c) weekly temperature readings to depths of about 1,000 feet off shore from as many tide- gauge stations as possible. In addition to these tide and surge observations, a major study will be undertaken of the subantarctic oceans. The structure and dynamics of currents and other oceanic phenomena of this region, which are little known but are of great importance in several fields of geophysics, will be explored intensively. Geomagnetism.-Geomagnetism has various important relations and implications cutting across almost all areas of study in the physics of the atmosphere. In addi- tion to its own specific uses in surveying, navigation (including missile guidance), and exploration for minerals and petroleum, geomagnetism has broad and basic implications in the study of the ionosphere, radio-wave propagation, aurora, and cosmic rays, as well as in other fields of science.

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