Currents in Eyjafjörður were examined in the summer of 1992 using current meters on both sides of the mouth of the fjord where the bottom depth is 105 m. The current meters that were placed at 15 and 85 m depth measure the current speed and direction and they stayed there from the middle of July to the end of August. Inflow to the fjord occurs on the west side of the fjord but the outflow on the east side. The reason for this is that the ocean currents are affected by the Coriolis force which has the effect in the northern hemisphere to deflect everything that moves to the right of the direction it is moving in. The Coriolis force is caused by the rotation of the Earth around its axis.

The North Icelandic Irminger Current that flows eastwards over the continental shelf north of Iceland is thus deflected into the fjords and bays on their western side. The saline water that enters the fjords seems to generally stay on west side of the fjord all the way to the head of the fjord. This is seen in the distribution of salinity where the isolines are mostly along the fjord with higher salinity in the west and lower in the east. Seawater entering the fjord in the west stays at the western coast where the salinity is relatively high but along its path it is mixed with freshwater from the rivers and the salinity decreases until the water eventually flows out on the eastern side.

One example of this circulation that is easy to see with the naked eye occurs during spring floods in the rivers. Eyjafjarðará during the spring flood brings with it a lot of sediments coloring the river. When it discharges into the fjord it immediately turns to the right and hugs the eastern side of the fjord as is easily seen due to the color of river water.

Steingrímur Jónsson

Straummælingar á 85 m dýpi sitt hvoru megin í mynni fjarðarins. Ferlarnir sýna hraða og stefnu straumanna. Straumarnir eru inn fjörðinn vestanmegin (blár ferill) og út fjörðinn austanmegin (rauð lína). Hver gulur punktur táknar upphaf nýs dags (gögn frá Hafrannsóknastofnuninni). Straummælingar á 85 m dýpi sitt hvoru megin í mynni fjarðarins. Ferlarnir sýna hraða og stefnu straumanna. Straumarnir eru inn fjörðinn vestanmegin (blár ferill) og út fjörðinn austanmegin (rauð lína). Hver gulur punktur táknar upphaf nýs dags (gögn frá Hafrannsóknastofnuninni).

Jafnseltulínur á 5 metra dýpi í júní 1992. Sjórinn er ferskari austan megin (grænt og gult) (gögn frá Hafrannsóknastofnuninni). Jafnseltulínur á 5 metra dýpi í júní 1992. Sjórinn er ferskari austan megin (grænt og gult) (gögn frá Hafrannsóknastofnuninni).