Gradient 3 measures the north/south wind com- 

 ponent along the eastern slope of the Grand 

 Banks which is partially responsible for deter- 

 mining the speed at which icebergs will drift 

 south in this area. Gradient 4 is a measurement 

 of the influence of westerly, or easterly, winds 

 along the northern slope of the Grand Banks. 

 These winds are important in determining ice- 

 berg drift toward or away from the Newfound- 

 land coast and into or out of the core of the 

 Labrador Current. If the westerly winds are too 

 strong or persistent when the bergs reach the 

 northeast corner of the Grand Banks, they may 

 be carried over Flemish Cap and deteriorate rap- 

 idly as they are pushed into the warmer waters 

 of the North Atlantic Current. Gradients 5 and 

 6 provide a preseason indication of the potential 

 for iceberg drifts south and west in Davis Strait. 



The 1976 pressure gradient statistics are shown 

 graphically in Figure 32 in comparison with their 

 1946-1975 averages. Gradients 1 and 2 show 

 above normal southerly flows throughout the 

 season, with lulls in the December. January and 

 April positions of each graph before normalizing 

 or going slightly below normal in July. This 

 provided a great impetus for southerly iceberg 

 drift during the season. Icebergs did not reach 

 gradient areas 3 and 4 until early March. From 

 then until mid- June, the gradient pressure rose 

 to slightly above normal, thereby increasing 

 southerly flow slightly. Gradient 4 shows a pre- 

 dominant easterly wind flow until mid-June, 

 which kept the bergs drifting mainly in the Lab- 

 rador Current along the eastern slope of the 

 Grand Banks. Gradients 5 and 6 combined show 

 a general south-easterly flow, from September 

 through November, then changing to a predomi- 

 nant northerly flow inhibiting berg movement 

 into the Davis Straits until February when both 

 gradients basically normalized. 



Air temperatures throughout the season were 

 normal with the exception of northern Labrador 

 and Baffin Island where temperatures fell to ap- 

 proximately 6-8°F below normal in January and 

 February. A frost degree day, as used in Figure 

 33, is denned as one day at a temperature of one 

 fahrenheit degree below 32°F i.e. one day at 

 20°F would be 12 frost degree days). Similarly, 

 a melting degree day is one day at a temperature 

 of one fahrenheit degree above 32. All stations 

 illustrated showed slightly above normal frost 



degree days and slightly below normal melt de- 

 gree days. These near normal temperatures com- 

 bined with the far less than normal southern 

 expanse of sea ice this year were in a large pari 

 responsible for limiting the number of icebergs 

 that survived to reach the Grand Banks region, 

 resulting in a relatively light season. 



Figures 34 and 35 depict sea surface tempera- 

 ture (°C) contours for two representative periods 

 during 1976. Contours provided by the Meteorol- 

 ogy and Oceanography Office (MP^TOC) of Ca- 

 nadian Maritime Command (MARCOM) have 

 been modified by additional data received by Ice 

 Patrol from merchant shipping and Airborne' 

 Radiation Thermometer (ART) surveys. Since 

 the latter part of the 1974 ice season. Ice Patrol 

 observers have been using the ART to record sea 

 surface temperatures while conducting aerial ice 

 reconnaissance. The operational use of the ART 

 has been described in Appendix C of the 1974 Ice 

 Patrol Bulletin (CG-188-29) and is discussed 

 further in Appendix E of this Bulletin. The 

 late April temperatures in 1976 were just slightly 

 warmer than normal and early July sea surface 

 temperatures were approximately 1°C below nor- 

 mal. This corresponds well with the melt degree 

 day records for St. John's presented in Figure 33 

 showing April's accumulation greater than nor- 

 mal and both June and July's below normal. 



The following iceberg melt table was developed 

 from observations made by Lenczyk (1962-1964). 

 The International Ice Patrol uses this table to 

 predict the complete melt of various sized ice- 

 bergs. 



43 



