Figure 2 shows the surface temperature over the shelf. The temperature in the shallow areas is quite uniform and between 29 and 30 °C in Guatemala and west to 94°W in Mexico. From there and further westwards to Salina Cruz, a two degrees gradient was observed along the coast, and indicated inflow of colder surface water from the north. The dominating wind direction off Salina Cruz was from north to north-west.
Some lifting of deeper water masses seems to have occurred since the previous survey when also the discontinuity layer was reported more shallow than during the first two surveys. Using the 1 ml/l oxygen limit as an indicator of deeper water masses the variation in bottom depth of this limit is as follows (in meters):
|
Section\Period |
March |
June |
September |
December |
|
Champerico |
90 |
120 |
75 |
60 |
|
San Marco |
75 |
100 |
80 |
75 |
|
Salina Cruz |
|
90 |
95 |
60 |
