N PS ARCHIVE 1965 CERES, R. mmWBL , imSIi m $S!2 THE SEASONAL VARIATION OF PERMANENT CUU:-rR'JI"S VYSlKfN SAFMsJ RAY CERES ■ -■'■.■ ,J ■ :-v. ■..:•■.■• ■ ft fliiiHHiil i' v-,, ■...■■:.;■ .■'.','.■ -i,'! .... .■ ■: in ■>'-&■;■'■■■'■■■.•■■::": flKiHH HaMSSssag*Hft fe«S»*« s^ THE SEASONAL VARIATION OF PERMANENT CURRENTS WITHIN BAFFIN BAY ***** Robert L. Ceres THE SEASONAL VARIATION OF PERMANENT CURRENTS WITHIN BAFFIN BAY by Robert L. Ceres Lieutenant, United States Navy Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE United States Naval Postgraduate School Monterey, California 1 9 6 S DUDLEY KNOX LIBRARY NAVAL POSTGRADUATE SCHOOL MONTEREY, CA 93943-5101 THE SEASONAL VARIATION OF PERMANENT CURRENTS WITHIN BAFFIN BAY by Robert L. Ceres This work is accepted as fulfilling the thesis requirements for the degree of MASTER OF SCIENCE from the United States Naval Postgraduate School I ABSTRACT The seasonal variation of permanent currents within Baffin Bay is investigated. A model based on physical reason- ing is developed, whereby the speed of surface currents may be calculated during winter months, when observations are not available due to ice coverage. Verification is made where possi- ble utilizing late fall, and early spring data. Limitations, applications, and variability of results are discussed. Two important applications are: first, to add to the oceanographic knowledge of the Baffin Bay area, and second, to provide an additional input to computer programs already in existence for forecasting the drift of sea ice within Baffin Bay. 11 TABLE OF CONTENTS Section Title Page 1. Introduction 1 2 . Background 3 3 . Wintertime Regime 5 4. Application 19 5. Limitations 23 6. Current Profile Study 25 7 . Verification 29 8. Conclusions 33 9. Bibliography 34 Appendix A 35 in LIST OF ILLUSTRATIONS Figure Page 1. Summertime Surface Circulation Pattern M- Baffin Bay 2. Wind Driven Velocity Profile (Schematic) 8 3 . Winter Profiles within the Friction Layer 11 M-. Transition from Summer to Winter Profile 18 5. Mean Seasonal Variation of Surface Currents 20 Within Baffin Bay 6. Spring and Fall Velocity Profiles 22 7. Ice Edge; forecast and observed 30 June II and 16, 1953 8. Small Scale Forecast of Ice Lead 31 June 30, July 1, 1960 9. Ice Edge; forecast and observed 32 May 12 and 17, 1959 IV 1. Introduction Numerous oceanographic cruises have been made into Baffin Bay in recent years primarily by Canadian and United States oceano- graphic vessels. The purposes of these cruises are to extend man's knowledge of this region, and to explore its commercial and military potential. This research, and other traffic as well, is hindered in large part by the yearly cycle of winter ice growth which generally leaves Baffin Bay accessible to shipping only dur- ing the short summer season, July through September. Thus, while a great deal is known about Baffin Bay during these summer months, the winter oceanographic regime is almost totally unexplored. It is, then, the first intent of this paper to consider one aspect of this winter regime, that is, the surface circulation pattern. One important aspect of extending knowledge of this area is the problem of forecasting the drift of sea ice. The purpose and usefulness of such forecasts is well established; they are present- ly being made in the Baffin Bay area on a routine basis by hand calculation. Both the Fleet Weather Facility, Monterey, California, and the U. S. Naval Oceanographic Office, are in the process of developing computer programs to accomplish this task; and, more specifically, Knodle (1) in 1964 developed a computer program for forecasting the wind drift of sea ice. Verification of test data utilizing this program indicated that, if the additional input of permanent currents could be introduced into the program, the accur- acy of results might be significantly improved. This input of permanent currents would be in the form of vectors at grid points of any scale desired and would be added vectorially to the present output, which considers only wind effects. While this final step of programming was not completed in this paper, the basic data for its completion are developed and examined in some detail, together with a discussion of the variability of the currents and the limitations of the methods employed. 2 . Background The first extensive attempt to determine the circulation pattern in Baffin Bay was made in 1928 • and,while much has been done since that time, the work of Kiilerich (1939) (2) on the Danish Godthaab expedition of 1928, still stands as the most authoritative account of the summertime surface currents that exist within the Bay. The results of this work, as modified by the more recent observations, is shown in figure 1. Exhaustive descriptive accounts of this region are available from any number of sources (3, M-) ; so only a few distinctive features which are pertinent to the problem at hand will be mentioned. Again, with reference to figure 1, it should be noted that Baffin Bay is largely an isolated body of water with limited exchange taking place through the narrow channels to the north, and across the Davis Strait to the south. A ridge there forms a definite sill, with a limiting depth of less than 730m. The continental shelf is narrow on both the Greenland and Canadian sides of the bay, with steep slopes falling off rapidly into the one large basin, whose depths are in excess of 2000m. The circulation is cyclonic with one small gyral to the immedi- ate north of Davis Strait and one large gyral centered over the Baffin Basin. Mean velocities are shown in cm/sec. Various clima to logical atlases show that. from mid-November through late May, Baffin Bay is virtually ice-bound; and thus in the following section a model is presented to show how the surface current, at any given location within Baffin Bay, is diminished with the advent of total ice coverage. 3 . Wintertime Regime Due to the fact that no winter measurements have been made, this section is devoted to the development of a model, which. when applied, will describe the wintertime variation of the surface currents within Baffin Bay. Two assumptions will be made initially" first, that the summertime circulation is primarily maintained by the wind, and further, that the contribution made to the surface circulation from the Artie Basin and the North Atlantic is at a maximum during the summer, decreasing to a minimum by mid-winter. The latter part of this first assumption will be discussed in section 6. The former, is justified qualitatively on the basis of climatological wind data, and descriptive accounts of the area. For example, mean sea pres- sure charts for the summer months show Baffin Bay to be under the influence of a cold low pressure center. Further, the Polar Basin is under the influence of a cold high which contributes to steady easterly winds across the northern portion of Baffin Bay throughout the summer. The second assumption is that, once Baffin Bay becomes completely ice covered, no wind stress is transmitted through the ice. In other words, the contribution the wind makes towards main- taining the current is zero. Naturally, there will be some shifting of the ice due to tides, freezing effects, etc.; but in the mean the ice will be, for all practical purposes, stationary. If the assumptions above hold, the only real forces acting to alter the basic currents are first, the force of friction be- tween ice and water, and second, the frictional forces between the sea floor and the water. The latter is assumed to be rela- tively small and is not considered in this model. This is reason- able when one considers that the continental shelf is narrow, and that several investigators, including Kiilerich, found the deep- basin water to be near motionless. Further, if one assumes that the energy gained from currents entering the bay, is approximately equal to bottom and boundary losses, then the omission of these losses is further justified, at least qualitatively. The fundamental winter relationship can now be seen: the energy of the currents is diminished at the rate at which energy is dissipated by frictional stress between ice and water. If this rate is known, together with the vertical distribution of velocity, it follows that the rate at which the current velocity decreases can be calculated. In order to find this rate, first let the stress be given by where k = coefficient of friction between ice and water, u = surface current velocity, defined to be the current found a few meters beneath the sea surface, and ©w = density of the water at the same level The rate of work per unit area is "£u> which is to be equated to a rate of energy dissipation per unit area: ^U- " ~$E t*a . &y* ) T = tangential stress between air and ice /{ = eddy viscosity coefficient, Oou = density of the air, oo = cosind, where «> is the angular velocity of the earth's rotation, and (D = latitude, -nL = coefficient of friction between air and water A = the wind factor, V = the wind velocity, and aK , dW) U.} are as previously defined 10 From (b) and (c) is obtained Ai= ' -L -Jy • which when substituted into (a) yields Finally, solving (c) for V and substituting into the above 9 fb^NlL. where N^ff £ffl jfofo. ' With sufficient accuracy ^ = 2x10 , and on the basis of studies r-.2 by several authors, A = 1.27x10 . Substituting these, and other known values, into the above expression yields kK = i+7 3U (4) where Ar\ is in meters if u is in meters/sec. In the above development the tangential stress T operating on the sea surface was caused by wind. Shuleikin concluded, how- ever, that with ice coverage the frictional layer would also be present, but would be generated by the surface friction between ice and water. Further, he concludes that the numerical value of the coefficient N will not vary perceptibly because "it is known that the turbulent regime affecting the value &K becomes established under the influence of any velocity of the surface current u, independent of whether this velocity is generated by the tangential stress of wind origin, or by the stress caused by the friction of ice on the water". Thus, in thte model equation (4) will be used to relate u and An 11 With the magnitude of the currents that we are dealing with^ it is easily seen that this depth of friction will rarely exceed fifty or sixty meters' and within this thin upper layer it can be assumed with a good degree of accuracy that where t) w is the density of the water a few meters beneath the surface, and (?) is the mean density within the friction layer. The numerical value of the coefficient of friction, kw, has been investigated in some detail by several authors, and in part- icular by Brown and Crary (6) , Fukutomi (7) , and Shuleikin (S) . The values varied with location and with the age of the ice. Wittman and MacDowell (8) modified ShulekinTs coefficients for use specifically in Baffin Bay, and Knodle (1) concluded after further investigation, that a mean value of .013 was the best approximation. This value of J^ then will be used for this model. Now, from equation (4) and the density approximation above * equation (3) takes the form, la3 - \ ('.'■ ■' '■'■I < <-/.> M; ''V C5) It will be shown in the following paragraphs that the expression pti. -4- <. U. J> J may be treated, with some approximation, solely as a function of the surface velocity, u, if it is assumed that the shape of the velocity profile, once established, does not alter significantly. While the wind-driven profiles given in appendix A show a great variety of shape, it should be noted that the greatest 12 variability occurs when the currents are weak and in shallow water. Profiles associated with stronger currents in deep water (i.e., from S to 10 cm/sec. at the surface) show a definite uniformity of shape. It is argued here that most of the profile variability comes about as the result of non-uniform influences, such as wind gradients at the surface, summer run-off, inflowing currents, tides, or internal waves, and that these disturbing in- fluences are either totally absent or at a minimum during the winter season. Considering the above, we will now construct a model for the current velocity profile. First, it is assumed that during the winter, the frictional component of the velocity (VV) is analogous to that given by Ekman; then (e) \ff« -n*e-,,v* where, u ^ = velocity found at the depth of friction, and VrCz) = frictional component of the velocity found at depth i within the friction layer. Further, it is assumed that. due to the proximity of land within Baffin Bay, there is no rotation of this frictional component with depth. It follows that: (f) u* - u± - %W , where ua = the magnitude of the Current found at depth ^. within the friction layer. If, for example, at the time the ice becomes stationary, the depth of friction is found at 50m, then. by equation (4) , u ^ may be calculated and a velocity profile plotted (see figure 3) . 13 11+ Several comments are needed concerning this profile. First, the velocity at a = bh is the proper velocity to give the rela- tion between u and &\\ , i.e., Lr\ = 473u i . Second, equations (e) and (f) are being utilized as the winter profile model since no direct and detailed profile studies for flow beneath stationary ice were available to the author. Finally, the introduction of this profile necessitates redefining u, the surface current velocity, as will become apparent in the following paragraphs . — *r To find the relation between the surface velocity u and u in the friction layer, several velocity profiles were constructed utiliz- ing equations (e) , (f) , and (4) for assumed values of uA , from 12 cm/sec to M- cm/sec. For ease of computation each profile was approximated by a straight line as shown in figure 3. The velocity gradient with depth could then be treated as a constant (du/da = C) , and (a) TL = «V + 0 ^fi- (h) U.a="- and u for each velocity profile approximation, two important conclusions were reached! first, that the quantity (JOL +JS ^ ^ i and secondly, that the same expression can be described in terms of the surface current velocity u, again without significant loss of accuracy where the constant ki equals 2.32. If equation (5) is modified in accordance with equation (5a). then MM u\ = - fa (i Ctf £] m u ^ . (6) With the rapid decrease in current velocity near the ice surface associated with the winter profile of figure 3, it becomes appar- ent that u no longer adequately defines the velocity within the friction layer, but rather that CV^k is the representative current velocity. Utilizing the same winter profiles as in the above development of u , it was found that the approximation U.^ = 3.18ur was quite accurate, providing the range of velocity profiles chosen is not too large. That is, within the range utilized, 4-12 cm/sec for u^ , the accuracy is quite good, and would be the range of values expected for the major portion of Baffin Bay, Hence, if we define u = u^ , and substitute the above approximation into equation 6, then its solution is where 16 It is seen then, that at the time the ice becomes stationary the current velocity u of equation (7) represents the current found at the depth of friction, and that this depth will decrease as the winter season progresses approaching the surface by the time of spring ice break -tp (see figure 4) . Thus, u at the depth of frict- ion is applicable only during the time the ice is stationary, while u several meters beneath the sea surface (i.e., at 5m) is applicable for the remainder of the year. Thus, equation (7), shows the time variation of the current at depth th , where u(t0) represents the current at the initial time of ice coverage and is known if the assumption is made that the current velocities of figure 1 are representative of u ,L at the time the ice becomes stationary. Hence, we may calculate the current at any time u(t) between initial ice coverages and the time of break- up of the ice . The application of this equation is discussed in the following section, and a curve showing the seasonal variation of the surface current is developed utilizing this equation. The transition from the summer to the winter profile, is be- lieved to take place within a short time after the ice becomes sta- tionary. This is analogous, for example, to tidal currents near bottom, as given by Defant (9 ). In this transition period the K. E. loss is confined almost entirely to the friction layer, and the re- duction of K. E. with depth does not occur until after the winter profile becomes established. This transition period is shown schemat- ically in figure 4, together with a profile, say several months later. 17 u inrrL-- nm,- Schematic velocity profiles showing transition and decline of u vs . a . ice initially becomes stationary t-, : several hrs . later tp: several months later (Note - not to scale) FIGURE 4 18 *+. Application In this section the application of equation (7) developed in the previous section will be discussed, together with a qualita- tive treatment of the spring and summer current build-up, thus completing the mean yearly cycle. Two facets of equation (7) must be dealt with prior to its application. First, the time the ice becomes stationary and the time break-up of the ice occurs must be determined; and, second, the value of (^discussed briefly in section 3, needs to be calcul- ated. The latter will be treated first. Recall that C = LNM/&K and that the assumption has been made that kinetic energy is dissi- pated from the surface to the level of no motion nearly uniformly. This implies that the level of no motion descends with time . By equation (M-) it is seen that the depth of friction &h is a function Of the surface current velocity u and thus is likewise a function of time (see figure 4). Hence, a profile study was under- taken, one purpose of which was to investigate the variation of these quantities (see appendix A) . From it, some approximations could be made. From the fall data, it was estimated that the level of no motion in deep water occurred at approximately 1000m and3as previously discussed, bJ\ = 50m. Only a very few spring soundings were available to the author, and only one in deep water. The velocity profile constructed from them is as shown in figure 5, together with a fall velocity profile taken at approximately the 19 U (cm /sec) 0 100 200- 300 400 Z Cm) 500^ 600- 700 eoo 900 1000 ^•zero u to ref. L at 1500m Spring and Fall Velocity Profiles At: Lat. 69° 30'N, Long. 62° 40 TW (constructed from data contained in (10) & (12) ) FIGURE 5 Decrease in u to zero at ref. L. at 1200m 20 samfe location. While this indeed is sketchy information, both the spring and the fall profiles ^ in this instance, lend support to earlier assumptions, and in particular to the assumption that an energy loss is dissipated with depth nearly uniformly. From this profile it was estimated that at the time of break-up of the ice LNM = 500m and kn = 20m. Thus, C varies from the fall to the spring only from 20 to 25; a mean value of 22.5 is chosen for C in equation (7) . The span of time during which this model would be applicable was determined on the basis of climatological data to be from October through April. The limitations of utilizing these dates are discussed in section 5; however, they should be approximately correct for an average year. Now all the quantities of equation (7) are known, and u(t) may be calculated utilizing the velocities of figure 1 as u(t0) . The expression from equation (7) g. »M»l*^f represents the fraction of the summer time current velocity and may be plotted versus time with tQ = 0 on 1 October and t (in seconds) up to 1 May. The plot is shown by the solid line portion of figure 6 . The assumed spring and summer build-up of the current is shown by the dashed portion of figure 6 . This build-up was handled in a purely qualitative fashion due to time limitations. Now, figures 1 and 6 together permit determination of the mean current velocity for any time during the year or location within Baffin Bay. 21 ■*-> a. R \ \ CD 3 \ < \ = \ O >» \ x L \M V X c . 3 ^ \ -> \ X \ (0 7 TT '2 > / *£ co / °c0 j L * J. a. 1 '< c c j o — • — »♦— CO r to ft ZCQ UJ 1 °> .- co , in / - ■> durin appi . to Z) /t U. 05 C L. A of time lod el is C -01 -> eason Currc / < / 3 9 *- eriod ich rr (j to •Q 00 u u c co / ° 0. x: cot / ** : : / > o "2 2c/) / / +j j o 1 j 1 1 jL ■o Q- ■ to §ss^ss$^ o eg 0 V) ( t a jnBu ass) uoi;e|n dj|o lie; l<>% ' 22 S. Limitations There are three major limitations to the winter-time model developed in the preceding sections which require discussion. First, the assumption was made, based on climatological data, that the ice cover became approximately stationary on 1 October, and that break-up occurred on 1 May. This statement implies that 'these times occur simultaneously throughout the Bay, when in fact the freezing and break-up occur over a period of time with vary- ing locations . An attempt was made to divide Baffin Bay in four approximately equal areas and develop separate curves similar to figure 6 for each quadrant. This trial was abandoned jhowever, as it introduced more uncertainties and complications into the pro- blem, and these disadvantages seemed to outweigh whatever benefits might be derived. For example, a declining current in one quadrant would certainly effect the next quadrant into which the current was flowing. No ready solution to this problem is proposed; it is felt that whatever modification is introduced would lead to only small changes in figure 6. The use of climatological data also implies that any one year is like the next, and this obviously is not the case. Figure 6 could, however, be quite easily reconstructed, based on information from local reconnaissance flights for any given year. The second major limitation concerns the variation in the summer time build-up of currents. Evidence indicates that this 23 variation in some years might be large. For example, in 1964- residual ice was observed in Melville Bugt throughout the summer, because the mean pressure patterns normally associated with this season were displaced enough from their normal positions that the winds, which normally would advect ice out of Baffin Bay and con- tribute to the current build-up, were simply not present- During such an anomolous year, the model would obviously not work. How- ever, this unusual situation is a rarity. The final limitation concerns the sum of the approximations and assumptions made in the development of the model itself. While these assumptions and approximations have all been discussed individually and justified, the cumulative effects could be addi- tive and result in serious error. Particularly in the assumption of the shape of winter velocity profile and in the treatment of C=LNM/a|-\ could large errors arise. However, in the absence of winter data, it is not possible to assign a number to this cumula- tive error. In section 7, verification of a forecast utilizing this model is quite good. This in itself is not proof that all the approximations and assumptions are valid, but it does at least lend support. 24 6. Current Profile Study In order to verify the assumptions made in earlier sections, as well as to verify figures 1 and 6, an attempt was made to ob- tain the published results from the latest fall and earliest spring oceanographic cruises that had been made into Baffin Bay. These data were received from the Bedford Institute of Oceano- graphy, Darthmouth, N.S., via the Canadian Oceanographic Data Center (10, 11) . Utilizing the standard techniques of computing and summing dynamic height anomolies, a number of velocity profiles was constructed. These profiles, together with their locations, are shown in appendix A. While, in large part, this study failed to yield the verification that was hoped for, some interesting ob- servations can be made. The remainder of this section is devoted to a discussion of what was hoped to be gained by this study, whether success or failure was met, and whenever possible why. First, it was hoped that the shape of the velocity profiles, at least for the fall data, would fit the preconceived notion of a wind-driven velocity profile (see figure 2) . While in a number of instances, particularly in deep water, this was the case, a great variety of shapes resulted. While causes for variability were mentioned briefly in section 3 (tides, internal waves, etc.), it is believed by the author that a major limitation of the dynamic method of computing currents is that oceanographic station data can- not be taken simultaneously (that is, with only one ship) . For the 25 profiles shown in appendix A, a lapse time of from two to six hours occurred between adjacent stations; if reorientation of the dynamic topography were to take place during this interval, distortion in the magnitude of the currbnt at a given depth would occur. It was hoped, secondly, that the level of no motion could be firmly established for the spring and the fall, as various investi- gators, and particularly Kiilerich, had stated that this level will vary from season to season, perhaps even irregularly from place to place. While some substantiation of the figures used in this model were gained from this study (see figure 5) , it can be noted from appendix A that this level cannot be fixed with confidence. Here also, one must be careful to distinguish between the reference level and the level of no motion. For this study, the reference level was chosen in every instance at the greatest depth that the adjacent soundings would permit. However, in some instances the soundings did not approach the bottom* and, hence, the profiles give only a velocity that is relative to whatever current exists at this reference level. This of course means also that the true level of no motion could be at quite a different depth from that implied by the profiles . One of the initial assumptions made was that exchange of water between Baffin Bay and the bodies of water to the North and South was at a maximum during the summer, decreasing to a minimum by mid-winter. As can be seen from appendix A, only the exchange across Davis Strait 26 could be examined. While the assumption made cannot be validated on the basis of this study, it is interesting to note that, if the assumed level of no motion is correct, outflow greatly exceeded in- flow in both seasons with no inflow occurring with the fall data, and very little with the spring data. From previous calculations of current flow across Davis Strait, Dunbar (4) had stated that the volume transport is approximately in the ratio of 2 to 1 with outflow being twice as great. He concluded therefore, that Baffin Bay received its waters in approximately equal quantities from the north and the south, but failed to consider runoff, which on the basis of this study would appear to make an important contribution. Hence, while the ratio of 2 to 1 would appear to be an underestima- tion, if , in fact, water does enter Baffin Bay in approximately equal quantities from the North and South, one could draw the tenta- tive conclusion that the amount of water entering Baffin Bay is small during all seasons. On the basis of the fall data, an effort was made to validate the current velocities given in figure 1. Of the twenty-five fall velocity profiles plotted in appendix A, fourteen, or 56%?were in good agreement with figure 1, that is. within + 3cm/sec at the sur- face. One further limitation of the dynamic anomoly technique is that it gives only that component of the current which is normal to a lijn^ drawn between adjacent stations. This surely accounts in large part for the variation from figure 1 in several of the profiles 27 The remainder^ however, and some are the exact opposite of what one would expect, can only be explained in terms of the limita- tions of the methods employed outlined in previous paragraphs. In conclusion, there was only fair agreement between the obser- vations and figure 1, with no consistent error being observed that would indicate that it should be changed. A verification of figure 6 was hoped to be accomplished on the basis of the spring data. These data, however, due to ice coverage were restricted primarily to Labrador waters, with only eight soundings taken within Baffin Bay. Of these eight, all but one showed a definite decrease in the velocity as the model predicts. The verification presented in the next section is an- other test of the model, and of figure 6. 28 7. Verification In Section 1, it was stated that one of the primary reasons for investigating the seasonal variation of the permanent cur- rents within Baffin Bay was that the results of the study could be used as an additional input to Knodle's computer program for forecasting the wind drift of ice, developed specifically for Baffin Bay. In this section, the results of Knodle's three veri- fication runs are shown in figures 7, 8, and 9, together with a modified forecast which includes the effects of permanent currents. This latter forecast was arrived at by adding to the wind-drift calculations of Knodle's, hand calculated, advection of the ice edge by currents in accordance with figures 1 and 6. While this is a laborious and time consuming task, the results were gratify- ing; and the job would be a simple one for the computer. As can be seen, there was indeed a significant improvement over Knodle's results in each of the three cases. One might con- clude, however, that the magnitude of the currents was too small, or5in effect, that figure 6 overestimates the winter seasonal de- cline of the current. It is possible that melting might account for a large part of the remaining error. It is concluded on the * basis of the foregoing that, while figures 1 and 6 may be altered in the light of later findings, their use in forecasting the drift of sea ice within Baffin Bay tends to improve the drift forecasts. 29 obse rved-T^ BAFFIN BAY EENLAND — Input Obse rved Forecast (Kno die) Forecast (Modified for permanent c u rrents ) .0 Limit of ice edge 0 Hand 16 June 1953 // FIGURE 7 30 31 r=» i nput observed f o recast ( K nodle) forecast (modif i ed for permanent currents) I f DAVIS Limit of ice edge 12and17 May 1959 FIGURE 9 32 8. Conclusion In the preceding sections, a model has been developed which predicts- the winter decline of the permanent currents within Baffin Bay. In the absence of winter data, it was necessary to make a number of assumptions, on the basis of physical reasoning, about the nature of the flow. The spring and summer build-up was handled qualitatively thus completing the yearly cycle. A limited verification of the results was obtained. It is concluded that, despite the limitations of the model, steps have been taken toward adding to the oceanographic knowledge of the Baffin Bay area and providing the basic material for a com- puter input to forecasting the component of sea ice associated with permanent currents. Finally, it is recommended that the re- sults of this paper be combined with the results of Knodle . It is felt that there would result a fully operational program, far faster and more accurate than is presently done by hand calculation. 33 9 . BIBLIOGRAPHY 1. Knodle, W. C, A Computer Program For Forecasting the Wind Drift of Sea Ice. U. S. Naval Postgraduate School, May 1964. 2. Kiilerich, A. B., The Godthaab Expedition 1928. Kobenhaven, C. A. Reitzels Forlag. 1939. 3. Oceanogr. Mar. Biol. Ann. Rev., 1964, 2, 45-75 Publ. George Allen and Unwin Ltd., London. Physical Oceano- graphy in Arctic Canada by AJEL Collin and Mw J.Dunbar. 4. Canadian Fisheries Research Board Bulletin (1949-52) Bulletin #88. Eastern Arctic Waters by M,JJJunbar 5. Shuleikin, V. V. Fizika Moria (Physics of the Sea) Moscow, 1953. 6. Browne, I. and Crary, A. P., The Movement of Ice in the Arctic Ocean. Arctic Sea Ice Conference, Easton, Md., Feb. 1958. 7. Fukutomi, T. On the Steady Drift Current and Steady Drift of Sea Ice, Due to Wind in the Frozen Sea. Low Temperature Science Research :abpratpru. Hokkaido University. Study of Sea Ice, report #14. October, 1948. #123. 8. U. S. Naval Oceanographic Office. Manual of Short-term Sea Ice Forecasting, by W. I. Wittmann and G. P. Mac Dowell, July 1963: SP - 82. 9. Defant, A. Volume II of Physical Oceanography. The Macmillan Company New York, 1961. 10. Eastern Arctic -- I960; Data Record #18. Canadian Oceanographic Data Centre 1964. 11. ICNAF Norwestlant - 2 Survey Canada, Data Record #14. Canadian Oceanographic Data Centre 1964. 12. Report of the International Ice Patrol Service in the North Atlantic Ocean. Season of 1962. Bulletin #48. U. S. Government Printing Office, Washington. 1963. 34 APPENDIX A VELOCITY PROFILES On the following pages are shown the velocity profiles as constructed from the data contained in (EO) and (11), together with the locations for the fall profiles (figure A. Sept. 17 - 24- , 1960) and the spring profiles (figure B. June 1 to 11, 1963). The computations were made in accordance with the Sandstrom- Holland-Hansen method of computing currents. It is assumed that the reader has some familiarity with the technique, so that only ■ a brief outline will be required here. 1. Dynamic height anomolies were computed for the standard levels and summed upwards from the reference level (R.L.) to the surface in accordance with: l\0 ~ ) , v Ap was with the specific volume anomoly 0 . The R.L. picked in all cases at the maximum depth that adjacent soundings would allow. Relative currents for each level were computed by the formula: where W|= current found at a given level W^ = current found at the reference level assumed equal to zero OcecLn Oc&a_n Sto..A J^ ^ R.L. I W«. ■ O 35 The results of these computations, as stated, are shown in the following pages together with other pertinent data such as the depth of the water, the time the sounding was taken, etc. 36 FIGURE A Fall Data: 17 to 22 Sept. 1960 Location of Ocean Stations 57 through 89 . Direction of surface current between stations as indicated 37 i ^^™" ™T"™ 1 ™^™ ^^^ ^T^ ^^^ K ^2r\ 47V. i / '•51 /* > GREENLAND c ) \J K V27 1 V X V \ ' \ ' © ^J \ 1 1 I ill i i i I I I /l -i ^^^ 60 55 50 FIGURE B Spring Data: 1 to 11 June 1963 Location of Ocean Stations 24 through 27, and 41 through 51. Direction of surface current between stations as indicated 38 CD i O CD O CD i CD ID ■v G) ID i 00 ID CD- ID ft z O i- i< W _) U. O OH Q_ >- u o _l LU > z O LU i— , , ^ < UJ 3 ■ u o u_ _l 1 >— ' Q. UJ o C\J CD o CD m o 0) CD Q 2 J O o o O u: LU. O o o CJ m ID in in ££ h 2 in CM * S cp o c\j m m f\\ ^r d m K T— ^; o d 10 z o> 00 0) o ,- , ,z in lO CD ID - Q i i 00 i 0) i o (-• 1- in in ill (0 0_ < UJ i- i/) ^ 39 i+O VELOCITY PROFILES AT STATION 67-68, 68-69,69-70,70-71 -UCCM./SEC.) - 6 e 10 S TA 69-70 • U. r^~ ■STA 68-69 : fi ? f J § *- -STA 67-68 STA 70-71 Z(M) SEPT. 1 9, 1960 STATION NO. G.M.T. REF.L.(M) DE PTH (M) 67 68 61 83 1 75 544 68 69 8 3 12.1 700 1392 69 70 12.1 16.5 1500 2062 70 71 16.5 23.0 2000 2309 LOCATION. SEE FIG J RE A 41 VELOCITY PROFILES AT STATION 73-74,74-7 5,75-76,76-77,7 7-78 ■IKCM./SEC.) * STA 7 3-74- SEPT 20-21 , 1960 STATION NO. G.M.T. REF. L. (M ) DE PTH (M) LOCAT I ON 7 3-74 11.8 -15.6 700 1 504 SEE FIGUR E A . 74 -7 5 15.6-19.3 700 2080 75-76 19.3-23.6 7 00 150 6 76 "77 23.6 -2.0 500 777 77 -78 2.0 "4.3 100 350 42 VELOCITY PROFILES AT STATION 80-81, 81-82,82-83,83-84 -U(CM/S EC) — STA 80-81 V -STA 82-83 SEPT 21-22, 1960 STATION NO G.M.T. REF. L. (M ) DE PTH (M ) 80-81 18 3 -22 75 681 81 "82 22 -2.6 ■1200 1415 82-83 26-8.2 12 00 1525 83 -84 - i 200 904 LOCATION : SEE F, - Fi 43 VELOCITY PROFILES AT STATION 85-86,86-87,87-8 8 ,88-89 ST A 85 -8 6 STA. 86-8 7 U(CM /SEC) 2 4 SEPT. 23-24 ,1960 STA* NO. \'0 G.M.T. REF L.(M) DEPTH(M) 85-86 5.8-9.9 75 139 86-87 9.9-15.7 125 389 87-88 1 5.7- 208 500 576 88-89 208- 0.2 150 361 LOCATION:SEE FIGURE A J 44 VELOCITY PROFILES AT STATION 24-25 , 25-26 26-27 -IKCM/SEO- STA 25-26- Z(M) STA 24-25 JUNE 1 -2 STATION 1963 NO. G M. T 14.4 18.8 REF. L. (M) DE PTH(M) 24 25 1200 1527 25 26 188 22 8 1000 1308 26 27 22.8 02.2 1000 11 61 LOCATION : SEE FIGURE B M-5 VELOCITY PROFILES AT STATION 41-42,42-43,43-44 ,44-45 ,45-46 10 U(CM/SEO- 2 STA 45-46 _£ STA 43-44' ST A 41-42- STA 44-45 100 Z(M) (STA 42-43:ZERO) 200 300 <) JUNE 10.1963 STA NO. G. M.T. REFL.(M) DEPTH(M) 41-42 1.6-3.5 30 49 42-43 3.5-6.2 30 79 4 3-44 6.2-8.5 75 133 44-45 8.5-10.7 125 253 45-46 10.7-14.8 300 514 LOCATION: SEE FIGURE B 46 VELOCITY PROFILES AT STATION 47-48 48-49 49-50 50-51 U(CM/SEC ) ► 0 2 4 i i_ STA 4 7-43 Z(M) 100 200 STA 50-51 STA4 9-50 -STA 4 6-4 9 JUNE 11 1963 STA. NO. G. M. T. REE L.(M) DEPTH(M) 47-48 3.3-5.2 175 223 4 8-49 5.2-8.2 100 149 49-50 8.2-10.5 50 88 50-51 10.5-12.6 30 52 LOCATION: SEE FIGURE B 47 BlUOE 4 AUO - 1691? „4-UH- L Thesis C33838 Cere aJ!;e sfasonal vari- ation of permanent currents wi nl 79938 thin Baffin <-4 .c C WIDER 16 9] Thesis C33838 Ceres 79338 The seasonal vari- ation of permanent currents within Baffin Bay.