mean reported by Karaulovsky and Sigaev (see footnote 
2). From these earlier reports, it appears that the 
temperature peaked at 7°C in 1955, declined to a low of 
4.3°C in 1966, and has fluctuated between 6.1° and 6.5°C 
since 1970. 
Figure 7 illustrates the changes in proportions of bot- 
tom water covered by various TCI’s for the entire Gulf. 
Although some years had the same or nearly the same 
mean observed temperature, the TCI’s were often quite 
variable. For example, during the spring cruises of 1970- 
72, the observed means varied by only 0.1°C, but the per- 
centage of water in the coldest and warmest TCI’s (solid 
bars in histogram) varied by factors of about 2 and 13, 
respectively). The 6°-8°C TCI dominated in all years 
while the 4°-6°C TCI remained the most consistent dur- 
ing the study period. The general warming trend is 
characterized by a rather progressive decrease of water 
<4°C near shore with a corresponding increase of water 
>8°C mostly in the eastern basin of the Gulf (Fig. 2). No 
water<4°C was evident in 1974, while a small amount of 
water <2°C contributed to the coldest index which was 
observed in 1968. 
PERCENT 
BOTTOM -WATER TEMP °C 
Figure 7.—Percentages of temperature-class intervals (TCI’s) in the 
Gulf of Maine during the spring, 1968-75. (Dotted circles represent 
the observed mean bottom-water temperatures; solid bars emphasize 
temperature extremes.) 
Subareas of the Gulf of Maine—Spring.—Adjusted 
indices of the annual mean bottom-water temperature 
for the Gulf by subareas of one-degree longitude are sum- 
marized in Figure 8. Analysis by subareas reveals an in- 
crease in the frequency and magnitude of oscillations 
between years with an overall warming trend indicated 
for each subarea. Subareas | and IV had the lowest and 
highest bottom temperatures, respectively, during all 
years. This is associated with differences in bathymetry 
as Subarea I has the most shoal water and nearly all of 
Subarea IV is greater than 200 m deep. The relative 
shoalness of Subarea I is also reflected in the large tem- 
perature variability between years, especially the in- 
creases between 1969 and 1970 (+1.5°C), and between 
BOTTOM - WATER TEMP °C 
Spring — 
GULF OF MAINE 
1968 69 70 71 72 73 74 75 
Figure 8.—Adjusted mean bottom-water temperatures in the Gulf of 
Maine in subareas I-V during the spring, 1968-75. 
1973 and 1974 (+1.0°C), and the decreases between 1970 
and 1971 (—0.6°C) and between 1971 and 1972 (—0.7°C). 
A temperature increase was noted in all subareas in 1968- 
70 with the sharpest rise between 1969 and 1970. In no 
year was a decrease observed for all five subareas. 
The 8-yr means and annual anomalies are sum- 
marized in Table 2 and show that all subareas had 
negative values in 1968 and 1969 and positive values in 
1974 and 1975, but a mixture of values in the intervening 
years. 
Comparison of the Gulf by subarea again shows how 
years of similar mean temperatures can have vastly dif- 
ferent TCI’s (Fig. 9). In Subarea I the observed means 
were all 5°C in 1970, 1974, and 1975, but the TCI’s in 
1970 were about 20% each for the 2°-4°C and 6°-8°C in- 
tervals, and 60% for the 4°-6°C interval, while 1974 and 
1975 were both nearly 100% for the 4°-6°C interval. Con- 
versely, a deep stable subarea like IV had very similar 
TCI percentages when the spring means were similar and 
clearly shows the decrease in coldest and increase in 
warmest TCI’s as the warming trend progressed. 
Table 2.—Mean bottom-water temperatures and anomalies for Gulf of Maine, spring 1968-75. Adjusted 
values are shown in parentheses. 
Subarea Mean 1968 1969 1970 1971 1972 1973 1974 1975 
4. -1.5 = 67, . = - .2 5 mg 
(4.1) (E13) (- .5), (1.0) (+ =S)PE( 23) (= 24) -6) (+ <5) 
II EoD) peaTM AOS Earns: sasiiuml igi imera dk)  oatat) 
(5-8) (-).9) (- .7) (#27) (+ 64) (0) (2) (2) (#5) 
on2uenit=ts -. tee Doel Marie AC Sarg) 3 
(Get) aN (CTE O) Rn (=e 24) (F286) (tees) 0) (tO) rahe 2) eel) 
70s -. - 
(629) (aor) (=s 24) en 
v 6.0 -1.0 -1.0 
7 
(S29) al(=i39) (=e 
Vitec) (ea). dee 
