64 



iiially by the end of winter to a uniform temperature of 30° to 

 32° F. from surface to bottom, and such temperatures as these are 

 indistin<ruishable from those farther north and in the Arctic. The 

 winter of 11)23-24, liowever, chilled the water column in the above 

 locality to a minimum of only 35° to 38° F., and this rare circum- 

 stance! due undoubtedly to a mild winter, not to occur here again 

 probably for many years, permitted the thermal contrast between 

 local and arctic water. In other words, since we possess evidence 

 wliich attributes the 37° to 38° temperatures, found from surface to 

 bottom in the central part of the Bank, as the minimum of local 

 cooling, how then could the leg of icy water extending southward 

 on the east side of the Bank have acquired a still lower temperature 

 of 32° ? This latter body of water must have been transported here 

 from a northern source — an Arctic invasion — which is outlined as 

 strikingly as if chalked on a blackboard. The resemblance between 

 the position and shape of the shaded area of arctic water on chart 

 F and tlie normal distribution of arctic w^ater as shown on sketch 

 10, page 150, International Ice Observation and Patrol Bulletin 

 No. 11. for 1923, is astonishingly close, thus corroborating previous 

 evidence accumulated during the past four or five years. 



The northern edge of warm Atlantic water south of the Grand 

 Bank between the forty-eighth and fifty-eighth meridians lay be- 

 tween the forty-first and forty-second parallels, a position which 

 has been found normal for this time of year. (See charts I and G, 

 Bulletins No. 10 and 11, respectively.) The ''cold-wall" between 

 the forty-seventh and forty-eighth meridians changed course 

 abruptly to the north, and we found Atlantic water warmer than 55° 

 as far north and west as latitude 44° 30' north, longitude 46° 20' 

 west, and it will be noted on chart F that the shaded isotherm for 35° 

 presents a shoulder-like form at this aforementioned northern and 

 western point. Also the isotherms for 45°, 40°, 35°, and 32° plainly 

 indicate a tendency upon the part of the warm Atlantic water to 

 force its way inshore between the forty-fourth and forty-fifth paral- 

 lels. Such a tendency has been previously described ^ wherein warm 

 and salty Atlantic water tends to work inshore up the submarine 

 valley, which exists at this place in the ocean bottom. Further 

 evidence of this phenomenon was experienced by the patrol ship 

 while cruising northward along the eastern edge of the Grand Bank 

 on March 25. On that date, at 11.45 a. m., sixtieth meridian time, a 

 well-defined tide-rip was observed extending in a general east-north- 

 easterly direction from the continental edge. Just before crossing 

 this wall observations were made of the surface which disclosed a 



» Smith, Kdward H. : International Ice Observation and Ice Tatrol Service, 1923, U. S. 

 ('. C. Hull. No. 11. pp. i;{!)-140. 



