Winds are one of the main causes of ocean currents, especially in shallow waters. The wind exerts a force on the sea surface and moves the surface layer. Indirect effects of the wind are also important as the wind can create pressure differences by moving the water around.

This pressure difference is felt through the whole water column and thus affects currents at all depths. Winds also affect the vertical mixing of water which is important for the growth of the phytoplankton in the ocean.

Wind measurements were made in Hrísey in 1992-1993. There are three main wind directions. Northerly winds are most frequent, but south-south-easterly winds from the inner parts of the fjord as well as south-westerly winds from Svarfaðardalur are also common. This shows that the wind direction is governed largely by the topography, especially the mountains that shelter the fjord from various wind directions, but the wind is channeled through the valleys.

The wind direction in Grimsey for the same period reveals a much more uniform distribution arising from the fact that Grímsey is far from land and there the influence of topography is not felt. Still some wind directions are more common than others but they are determined by the larger scale weather systems of the region.

Steingrímur Jónsson

Tíðni vindátta í Hrísey og Grímsey. 0° tákna að vindur blási úr norðri, 90° úr austri o.s.frv. Fyrir Grímsey er tíðnin einungis reiknuð á 30° fresti en á 10° fristi fyrir Hrísey (gögn frá Veðurstofu Íslands). Tíðni vindátta í Hrísey og Grímsey. 0° tákna að vindur blási úr norðri, 90° úr austri o.s.frv. Fyrir Grímsey er tíðnin einungis reiknuð á 30° fresti en á 10° fristi fyrir Hrísey (gögn frá Veðurstofu Íslands).