The ocean temperature around Iceland has never been higher than in the summer of 2010 since the Icelandic Marine Research Institute first began measuring the heat and salt level of seawater in 1970.
A seabird cliff on Grímsey island. Photo by Páll Stefánsson.
The temperature began increasing rapidly after 1996, by 1-2°C in the uppermost levels of seawater off the southern and western coast—a development which should have occurred over 100 years, Morgunbladid reports.
The salt level in the seawater around Iceland has increased at the same time, which indicates where it originates. “The theory is that it’s coming in increased quantity from the ocean to the south and east,” said oceanographer Hédinn Valdimarsson.
In the north the ocean temperature is not increasing as rapidly yet shallow waters off the northern coast are becoming warmer too, indicating a similar development as in the south and west.
Valdimarsson pointed out that this might be part of a natural fluctuation. There was a period of warmth in the ocean between 1925 and 1964, after which it cooled again. The problem is that there isn’t enough information to make reliable forecasts.
Among the possible consequences of this development is the drop in sandeels around the coastline, which is the main food for seabirds like puffins and Arctic terns.
Capelin. Sandeels look similar but are even smaller. Contrary to the sandeel stock, the presence of capelin is increasing in Icelandic waters. Photo by Bjarni Brynjólfsson.
“I am not especially optimistic,” said Valur Bogason, a biologist at the Marine Research Institute, of the fish stock’s possible recovery. “There has to be a good recurrence of the stock, preferably for two or three years in a row, for a retroversion to occur.”
There are various theories as to why sandeels are decreasing in such significant numbers. Bogason and his colleague Kristján Lilliendahl, who have studied the condition of the sandeel stock since 2006, believe it is an interplay between increased exploitation by other animals and environmental factors.
The theories include the growth of the haddock stock; the fish feeds on sandeels and its roe, increased presence of mackerel in Icelandic waters which are known to eat sandeels and might also compete with sandeels on krill and lack of oxygen on the ocean floor due to increased density of algae around the Westman Islands.
None of these theories have been proven but Bogason and Lilliendahl believe that “something special” occurred around the Westman Islands and Vík.
It appears that the sandeel stock off the Westman Islands suffered a significant shock which almost wiped it out. The condition was especially poor in 2006 and 2007.
The situation improved somewhat the following year, especially off Vík, but it is still severe off the Westman Islands where the largest puffin colony in the world relies on sufficient supply of sandeels.
Click here to read more about the condition of puffins and Arctic terns.