Coastal Processes in Iceland

Iceland, as a whole, is growing. The near constant vulcanism on the island adds more and more land, almost every year.
The existing land is also uplifting. Pressure from large ice sheets is being removed as glaciers here recede due to global warming. The crust is rebounding, like a sponge that is compressed and then released. This uplift is outpacing sea level rise. In some areas there is 35mm/yr of uplift vs. 3.2mm/yr sea level rise.    
Iceland's rebound  vs. sea level increase. This change in height is having a dramatic effect on the erosion of these areas of Iceland's shores. Contrary to what you might think, the rate of erosion is decreasing due to the uplift. There is a mathematical rule, known as The Brunn Rule of Erosion (Brunn, 1983) which states that if sea-level rises by (a) there will be coastal erosion (s) equal to:
   s = la/h . (h) equals the maximum depth of exchange of material between the nearshore and offshore, and (l) is the length of the profile of exchange. Iceland's rebound is equal in effect to a decrease in the sea level. In areas of the southeast coast of the island, which are experiencing the most dramatic uplift, erosion has equaled approx. 8m/yr over the last century. in other areas which are not being uplifted, the erosion is closer to 10m/yr. Coastal Erosion Near Jökulsá River.

Despite this small bright spot, the changes brought about by the melting glaciers are not positive. An increase in the flow of the rivers which carry glacial melt to the sea is causing those rivers to erode more of the coast. River deltas are being pushed further and further inland as more powerful currents remove sediments more rapidly. The main component of these deltas is clastic material washed down the glaciers from past eruptions.





Near the town of VÍk the last major eruption, that of the volcano Katla, happened in 1918. The washout from this eruption extended the coastline by approx. 5-6 hundred meters, from 1918 until 1971. Since that time the shore has re-eroded 350-450 meters (an average of 11.25m/yr), and is as about the same as it was before the eruption.
 (at right: VÍk's shoreline from 1904-present)
Sediment transport off Iceland's shore.

The Icelandic people are not sitting idly waiting for calamity to strike. There are seawalls, dykes, and beach replenishment projects going on all over the island. coast adapt report They have established what they call a "defense line", sea defense structures in an area still inland enough that several decades of predicted erosion will pass before the sea will be in contact with this "line".