548 
BULLETIN OF THE BUREAU OF FISHERIES 
It is probable that vernal warming followed a similar course, at first, in the 
coastal zone in 1921, with the indraft of warmer and salter water from offshore main- 
taining the winter status of cold surface stratum and warmer bottom water into the 
first week of March. In 1925, however (p. 1004) , warming from above and from below 
raised the temperature of the whole column in Massachusetts Bay at a more nearly 
equal rate from the middle of February until late in March, whereas in Ipswich Bay the 
surface warmed the more rapidly from the beginning. In 1920, however, the surface 
was already fractionally warmer than the 20 to 40 meter stratum as early as March 
4 (p. 524), and it may be that in any year when an extremely severe winter chills the 
upper 100 meters or so of the gulf to an abnormal degree the surface at once com- 
mences to warm after the grip of winter is released, whereas in more normal years 
the surface temperature may be expected to remain almost stationary for a brief 
period during late February and early March. In 1924, when a foot or so of snow 
fell on March 11 and 12, followed by several days of freezing weather, the surface 
had warmed to only 2.2° at a station 8 miles off Gloucester {Halcyon station 10652) 
by March 19, with about 1.8° at depths of 40 and 70 meters. 
The progressive warming of Massachusetts Bay is illustrated for a warm April 
by the Fish Hawk stations for 1925, when the mean surface temperature rose from 
2° on March 10 to about 4.6° on April 4 to 8. A definite regional differentiation 
also had developed, with the surface warmest (5° to 5.4°) in Cape Cod Bay, where it 
had been coldest during the preceding months. Thus, the relationship characteristic 
of winter (coldest next the land) was now definitely reversed, so to continue through 
the spring (fig. 22) and summer. At the 40-meter level, however, the bay still con- 
tinued slightly warmer at its mouth (3.2° to 3.9°, Fish Hawk stations 30 to 33 and 
34) than in Cape Cod Bay or near the Plymouth shore (2.9° and 2.6°, stations 6a 
and 10), evidence that the indraft of offshore water continued to exert more influence 
on the temperature of the deeper strata (up to the 7th or 8th of April in that year) 
than did solar warming from above. This was not the case in Ipswich Bay, how- 
ever, where the 40-meter temperature was almost precisely the same on April 7 (2.4° 
to 2.8°) as it had been on March 10 (2.5° to 2.7°), though the surface had warmed 
from 3.35°-3.6° to 4.2°-4.9° during the interval. 
By April 21 to 23 the mean temperature of the surface of Massachusetts Bay 
had risen to 5.2° (4° to 6.8° at the individual stations, fig. 22) and the 40-meter 
temperature to a mean value of about 3.8°, but virtually no change had yet taken 
place in the temperature of the bottom water at depths greater than 60 meters, a 
constancy illustrated by the following table. In 1920, also, the inner part of the bay 
was actually slightly colder at 40 meters on April 20 (1.58°) than it had been on 
April 6 to 9 (2.2°-2.4° at stations 20089 and 20090), evidence of some upwelling of 
the colder water from below. 
Fish Hawk stations 
Apr. 7 and 8, 1925 
Apr. 21 to 23, 1925 
No. 33 _. 
Meters 
80 
84 
112 
Degrees 
2.91 
3.11 
2.9 
Meters 
60 
80 
84 
Degrees 
3.06 
2.92 
2.7 
No. 30 - 
No. 31 
