Forty-seven days of hourly sea level and atmospheric pressure data collected in 1848 at Port Leopold, N.W.T., are analyzed using modern time series computation techniques. Tidal analysis reveals a mixed tide but mainly semi-diurnal. A detailed analysis of the tidal data reveals that the time-keeping of the record was as good as today's standard. A high correlation between hourly sea level and atmospheric pressure data demonstrates the inverse barometric effect.Key words: Arctic, sea level, tide, ice cover, free oscillation, lowpass, scatter diagram, time series, Resolute, Port LeopoldMots cl&eacute;s: Arctique, Niveau de la mer, mar&eacute;e, couvert de glace, oscillation libre, goulet, diagramme de dispersion, series chronologiques, Resolute, Port L&eacute;opol

Barber, F.G.

Bolduc, P.-A.

Taylor, J.D.

English

University of Calgary Journal Hosting

VOL. 39, NO. 3 (SEPTEMBER 1986) P. 264-266 ARCTIC Sea Level  at Port Leopold, N. W.T., in 1848 P.-A. BOLDUC,’ J.D. TAYLOR’ and F.G. BARBER’ (Received 8 May  1985;  accepted in revised  form 2 January 1986) ABSTRACT.  Forty-seven  days of hourly  sea  level  and  atmospheric  pressure  data  collected  in  1848  at  Port  Leopold,  N. W .T., are  analyzed  using  modem time  series  computation  techniques.  Tidal  analysis  reveals  a  mixed  tide  but  mainly  semi-diurnal.  A  detailed  analysis of  the  tidal  data  reveals  that  the time-keeping of the  record  was  as good as  today’s  standard.  A  high  correlation  between  hourly  sea  level and  atmospheric  pressure  data  demonstrates  the inverse  barometric  effect. Key  words:  Arctic,  sea  level, tide, ice  cover,  free  oscillation,  lowpass,  scatter  diagram,  time  series,  Resolute,  Port  Leopold RESUMk. Les donndes  horaires,  pour 47 jours, du niveau  de  la  mer  et  de  la  pression  atmosphdrique,  recueillies  en  1848 ?I Port Uopold,  (T.N.-0), sont analysdes ?I I’aide  des  mdthodes  modernes  de  calcul  sur  les  sdries  chronologiques.  L’analyse  de  la  marde  rdvble  la  presence  d’une  marde  mixte,  mais principalement  semi-diurne.  L’analyse dttaillte de  la  marde  indique  que  la  prdcision  du  temps  utilisde  alors  est  aussi  bonne  que  celle  d’aujourd’hui. L’effet  baromttrique  inverse  est dbmontr6 par une  corrdlation  dlevde  entre  les  donndes  du  niveau  de  la  mer  et  celles  de  la  pression  atmosphdrique. Mots  clds:  Arctique,  niveau  de  la  mer, a te, couvert  de  glace,  oscillation libre, goulet,  diagramme  de  dispersion,  series  chronologiques,  Resolute,  Port Ltopold In September  1848  Her  Majesty’s  ships  Enterprize  and  Investi- gator  entered  the  harbour of Port Leopold,  in  latitude 74”N. and longitude 91°W., for  the  purpose  of  establishing  there  a d pBt of provisions,  and of extending,  in  boats,  the  examination  of  the north, south,  and  west  coasts of North  Somerset,  in  search of the  missing  expedition  under  the  command of Sir  John  Franklin. No sooner,  however,  were  the  ships  anchored,  than  a  heavy  pack of ice  was  driven  down  upon,  and  completely  closed  the harbour’s  mouth,  and  this  effectually  preventing  their  egress, they  were  compelled  there  to  pass  the  winter  of  1848-49. [Ross, 18541 Traditionally naval  forces of  world  nation states have allocated ship time to duties close to or directly related  to science. Perhaps the foremost  example  is  that of HMS Beagle and the studies of Darwin (Stoddart, 1983), but  there  are others. It may  be  argued that  much  of  this  work  is a form of self-preservation, as it is in  hydrography and oceanography, for it behooves the mariner to know as much as possible about the water on which he travels. Likely  it  was  such  concern  that  led  Captain Sir James Clark  Ross to understand  more  about he changes of depth that occurred  in  Port  Leopold (Fig. 1) during  the enforced stay of his two ships. That is, his  concern for the safety of his ships led  him FIG. I .  Port Leopold  is  a  relatively small indentation (5.5 x 2.5 km) on  northeast Somerset  Island  facing  Prince  Regent  Inlet  and is about  170 km from Resolute. to ascertain by observation “the amount of irregularities” in the tide there, and he soon perceived a connection between the irregularities and variations of  atmospheric pressure. In particu- lar he  mentioned  the  records of 9 and  20  November as evidence for such irregularity, but “occasioned by a heavy gale of wind,” each of two  days’ duration. For  the  nine  months  they were locked in ice each ship carried out a similar program. According to Ross  (1 854:287): At  the  exact  hour of mean  time  the  heights of the  tide  and of the mercury  in  the  barometer  were  taken;  the  former by the  quarter- master,  and  the  latter by  the  officer of the  watch,  who  immedi- ately  entered  both  observations  in  the  meteorological  journal, . . . Ross had made extensive tide  observations in the course of his explorations - i.e., in New Zealand, Cape Horn and the Falkland  Islands (p. 296), so he  likely  had a practised eye for irregularities in a record. Of course he lacked modern time- keeping (radio was  not  yet available), making  it  seem possible that  the  precision i his data with  regard to time  might  have  been rather  less  than  now.  As  shown below, we were able to determine that  the  extent of systematic error in time was  not greater  than  anticipated in modem tidal data. Port Leopold, “once a favourite harbour for exploring expe- ditions and  whalers”  (Dunbar  and Greenaway, 1956), is rela- tively shallow, 20 m at  he mouth, and without apparent particular bathymetric feature, although it has not yet been adequately  surveyed.  Each  winter it is covered with fast ice  that probably  attains a maximum  thickness of about 2 m. It is  known that an ice cover can influence long waves such as tides, particularly  in  areas  where  depth  is limited, but  not  in areas as freely connected to the  ocean as Port  Leopold  appears to be; for example, at nearby  Resolute it was  not possible to discern an influence of the  ice cover on the main tidal constituents (Godin and Barber, 1980). The tide at the port is “mixed: mainly semidiurnal” (Dohler, 1964), with  higher  high  water following lower low water; large  tides  range  up to 2.5 m. The amplitude of M2  appears to be about 60 cm and  that of K1 about 27 cm; the ratio (01 +Kl)/(M2+S2) is 0.51. In Ross’s time series, i.e., the 47 days of  hourly tide pole  and barometer observations (Fig. 2), there are a number of values  that appear to be  the result of error, perhaps of transcription, and while the corrections to some  values  appear obvious, for the work here we adhere to the ‘Depatment of  Fisheries  and  Oceans,  Ocean  Science  and  Surveys, 1202-200 Kent St., Ottawa,  Ontario,  Canada  K1A OE6 @The  Arctic  Institute  of North America NOTES 55 1 Barometer  r 55 \t 5 0  4 5 1  v 40 - 0 10 20 30 Por t   Leopo 1-XI t o  17-XI1, t 45 I 4 0  40 50 I d  1848 16 16 12 I I I I I , 12 . -  Tide  Pole 0 10 20  30 40 50 Days FIG. 2. Time  series  of the 47  days (1 November-17  December 1848) of hourly  tide pole  and  barometer  readings  at  Port  Leopold  tabulated  by Ross (1854). Royal Society account. From correspondence with Dr. D.E. Cartwright of the  Bidston  Observatory it seems  that  while  some of Ross’s data, e.g., sea temperature, are still available, the hourly  values of sea  level  from either ship are  not. We  had “in hand” an  examination of recent Resolute tidal data and  eventually  reduced  a  length  of data there similar to that for Port Leopold but for 1975. In this, in addition to the semidiurnal  and  diurnal constituents, we  were able to identify others including the lunar monthly (Mm), lunar fortnightly (Mf), ter-monthly (9-day and 7-day), several shallow-water constituents and a  short-period free oscillation of the harbour. A similar free oscillation of Port  Leopold  probably also occurs but cannot  be  discerned in hourly data; nevertheless, variance in the Port  Leopold  spectrum (Fig. 3)  at 0.0305 cph  (period of about 33 h) has been tentatively identified as the gravest mode of co-oscillation of parts of the  system  and the exterior ocean, as in Helmholtz  resonance.  That  it  is  not  seen in the Resolute spec- trum  suggests  that  Barrow Strait acts as a  connecting  channel to the exterior ocean (the current is variable  in  the channel, but  sea level  is  not) and supports  the  Helmholtz resonance conjecture. Through  simple  application of well-known formulae to a  variety Port   Leopo I d 1-X I t o  17-X II, 1848 SEY I D I URNAL .- 0.00 0.05 0.10  0.15 0.20  0.25 0.30 265 of average  configurations of depth, surface area, area of channel cross section, etc., it is possible to derive  a  number of periods of free oscillation close to that observed. For example, with Barrow Strait as  a channel, a co-oscillation of parts of the Parry Channel  system  can be contrived to give a  gravest  period of oscillation close to 33 h. Although  the  level of noise in Ross’s data appears low, it is not  as  low as at Resolute. This could be due to the method of observation, which  could  contribute to non-systematic error in both time and level, or, more likely, due to the errors of transcription  noted above. As well, that shallow-water constitu- ents are  not  clearly  seen  in the Port  Leopold  material  may  be related-to the level of noise, but  it  is possible that  the  thickness ofthe  ice cover has  an  influence. At Resolute, for example, in late winter data some of these constituents are better  defined  than in early  winter data, while at another  location (Tuktoyaktuk) some shallow  water constituents are stronger  when  an  ice cover is  in place (Barber et al . ,  1984). Interestingly, there  is  less  power at longer periods  in the Port Leopold spectrum - e.g., very little, if any, lunar monthly (Mm), rather less lunar  fortnightly (Mf), no ter-monthly (9-day) and little quarter-monthly (7-day) - but it is  known  that these components  may  vary in strength over time. More significantly perhaps, their relative smallness indicates that the tide pole remained  securely fixed to the  sea floor and  that  an alteration of reference level  did  not  occur over the interval of the spectrum; on 18 December  the  pole  was  dislodged (Ross, 1854:287). While further consideration of Ross’s  time-keeping  seemed trivial, it did appear necessary that we assure ourselves that serious error in time  did  not exist, recognizing  that  he  could have  achieved  a  precision of about  a  second  a day (Landes, 1983). We applied several methods of spectral analysis, of which that of .Vanicek (1971) eventually proved applicable. This showed that Ross’s time-keeping was as good, perhaps better, than  that at Resolute  and of the order of  4 sec.day or less; Ross’s  clock  and  the  Resolute  clock  appear to have  been fast. In  a  postscript (p. 296)  Ross  acknowledged  that  his  was  not the first observation of the  inverse  barometer effect (in  1966 Roden  noted  that  the  first  observation of the  inverse  barometer effect.is that of N. Gissler in 1747), but we can understand Ross’s attention, for “at low spring-tides” the keels of his vessels “sometimes rested  on  the ground.” And although  it  is not clear from  his account, there  can be little doubt that  ‘during the  period of observation  of  the data he  had  in  process  a di gram similar to that of Figure 4, which  would  of course have  provided 0 10 20 30 40 50 I I I I I Low pass pressure  ( inverted) -40 - -45 22 21 20 I LOW pass water  level  a 10 20 30 40 50 I I I I I I Days Frequency - cyc/hour FIG. 4. The lowpass of the pressure and the lowpass of the sea level data so RG. 3. Spectral analysis of the 47  days ( 1  November-17  December 1848)  of tide presented that each has the same vertical range and with the pressure (upper) pole  readings at  Port Leopold.  (This is  an unsmoothed  power  spectrum  produced  curve  inverted. (In the lowpass  all  waves of a period shorter  than one day  have using the  fast  Fourier  transform technique.)  been  fil red out.) 266 NOTES him  with a strong  indication of  an inverse relationship between pressure  and  daily  mean sea level (the lowpass), i.e., between pressure  and  sea  level  after  the daily tides  have  been removed. Apparently it was the “first few days’ observations” that engaged  him (p. 285), but  again it is not clear to which  record  he was referring, for the program of observation was begun in September. In  any event, the first few days of the November portion of the  record  indicate  such a relationship rather clearly. Further visual comparison  reveals  several other occasions of marked inverse correlation, e.g., around  days 10, 35 and 40. It seems likely, too, that he produced a scatter plot of the lowpass values, i.e., pressure versus sea level. We found in simple  regression of the  lowpass of pressure on the lowpass  of sea level a strong inverse correlation (r=-0.76). In further confirmation  we  carried  out a cross-spectrum analysis between the  two  lowpass  time series that shows (Fig. 5) that the coher- ence between  the  lowpassed  water level and  pressure  is ignifi- cantly large’over almost the entire frequency  range from zero to 1 cycle-day. As  well  the  phase  difference  between  the two series is close to 180” over the entire range. Thus the  strong  negative correlation is  well confirmed. t -904 t -180 I I I I I I I I 1 I ”/ 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 2! L 0 0 0.2 0.0 I, I I I I I I I I I I 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Frequency - cyc/day FIG. 5. Cross-spectrum  between  the  lowpass  of  the ti& pole  and  lowpass  of barometer  with  significance levels. Ross  also  commented  that  mean  sea level increased during the  period of observations “to the  middle of July” (p. 287), which  seems  somewhat unusual, for in the  Arctic  sea level is generally lowest in spring and highest in autumn (Lisitzin, 1974). The long-term record at Resolute supports the latter generalization, but  in at least one year (1968) sea level there appears to have  increased over most  of  the year, so that in this respect  Ross’s data may  not  be  unusual.  What  seems  unusual  is that  Ross  appears  to  have  determined  from  the outset to  obtain barometer  readings in conjunction  with  the  sea level observa- tions, although he Jeemed to suggest (p. 296) that he had previously  noted in other  areas  an influence of the  atmosphere on sea  level - i.e., it seems  likely  that  he  was  testing  an earlier formed notion about sea level and atmospheric pressure. He may  even  have  considered  the  likelihood  that  the invers  barom- eter effect is  best  seen  at  high latitude. The installation of the tide pole could have been achieved easily enough, and we suspect that the routine of hourly observations was not that onerous. That this  early  time series in arctic waters  happens  to have  occurred  at a Canadian site is, we think, a happy one. That the  numbers  were  printed by the  Royal Society and so became available for “crunching” by modem  methods  is  even happier. REFERENCES BARBER, F.G., TAYLOR, J.D., BOLDUC, P.A., and MURTY, T.S. 1984. Influence of ice  cover  on  resonance  phenomena  in  Tuktoyaktuk Hrbour. In: McTieman, T.J., and Demchuk, B.E., eds. Science, Technology and Arctic Hydrocarbon  Exploration:  The  Beaufort  Experience.  34th  Alaska  Science Conference. Sept. 20-Oct. 1, 1983, Whitehorse. Yukon Department of Economic  Development.  302-326. DOHLER, G. 1964. Tides in  Canadian  waters.  Ottawa:  Canadian  Hydrographic DUNBAR, M., and  GREENAWAY,  K.R. 1956. Arctic  Canada  from  the air. Service. 14 p. Canada  Defence  Research  Board. 541 p. GODIN, G., and  BARBER, F.G. 1980. Variability of  the tide at some sites in the  Canadian  arctic.  Arctic  33:30-37. LANDES,  D.S. 1983. Revolution  in  time:  clocks  and  the  making  of  the  modem world. Harvard MA: The  Belknap Press. 482  p. LISITZEN, E. 1974. Sea-level changes. Elsevier Oceanography Series 8. 286 p. RODEN, G.I. 1966. Low-frequency sea level oscillations along the Pacific coast  of North America. Journal of  Geophysical  Research  71:4755-4776. ROSS, J.C. 1854. On the  effect of the pressure of the  atmosphere  on  the  mean level  of  the  ocean.  Transactions  Royal  Society  144:285-2%. STODDART, D.R. 1983.  Grandeur  in this view of life:  Darwin  and  the Ocean world.  Bulletin  Marine  Science 33521-527. VANICEK, P. 1971. Further development and properties of the spectral analysis by least-squares.  Astrophysics  and Space Science 12:lO-33. 

Sea Level at Port Leopold, N.W.T. in 1848

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Sea Level at Port Leopold, N.W.T. in 1848

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