Study: Arctic Ocean Began Warming Decades Before Global Warming Took Hold

An international team of scientists has shown that the Arctic Ocean began warming as early as the start of the 20th century.

An international team of researchers has shown that the Arctic Ocean began warming from the early 20th century — this happened decades earlier than previously believed, the scientists noted.  

This is due to warmer water flowing into the fragile polar ecosystem from the Atlantic Ocean.

The international team reconstructed the recent history of ocean warming at the "entrance" to the Arctic Ocean, in an area known as the Fram Strait, between Greenland and Svalbard.

Using chemical signatures found in marine microorganisms, the researchers identified a phenomenon called Atlantification: the Arctic Ocean began to warm rapidly in the early last century, when warmer and saltier waters poured in from the Atlantic.

This change, which likely preceded the warming, is documented by modern instrumental measurements. Since 1900, the ocean temperature has risen by about 2 degrees Celsius, while sea ice has retreated and salinity has increased.

The results show a link with the North Atlantic that is much stronger than previously thought. This link can shape Arctic climate variability, which may have important consequences for sea ice retreat and global sea level rise as polar ice sheets continue to melt.

As the Arctic Ocean becomes warmer, it causes ice to melt in the polar region, which in turn affects global sea level.

The researchers used geochemical and ecological data from ocean sediments to reconstruct changes in the properties of the water column over the past 800 years. They precisely dated the sediments using a combination of methods and looked for diagnostic signs of Atlantification, such as changes in temperature and salinity.

Tesi Tommaso
PhD, Institute of Polar Sciences, National Research Council in Bologna

When we looked at the entire 800-year timeline, our temperature and salinity records appear fairly constant. But suddenly, in the early 20th century, you get this marked change in temperature and salinity — it is really noticeable.

The researchers say their results also reveal a possible flaw in climate models, as they do not account for the early Atlantification of the early 20th century.