It's hard to imagine the North Pole not being covered with snow at any given time, but according scientists, there was a point millions of years ago when the Arctic was virtually ice-free during summers and the temperature of the ocean's surface ranged from 4 to 9 degrees Celsius (7.2 to 16.2 degrees Fahrenheit).

Researchers from various scientific organizations, including the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI) in Germany, examined several sediment samples collected from the Lomonosov Ridge in the Arctic Ocean in order to shed light on the climate history of the region.

By analyzing microfossils known as dinoflagellates that were included in the earth samples, the researchers were able to determine that the lower part of the sediment core was made up of deposits that were six to eight million years old. This meant that the samples are from the late Miocene period.

The researchers also made use of "climate indicators," which allowed them to reconstruct the type of climate that existed in the central Arctic Ocean during the time.

They discovered that six to 10 million years ago, the Artic and its surrounding ocean were not covered in ice during summertime. This contradicts earlier notion that the region had always been blanketed in dense sea ice all year round throughout its long history.

Biomarkers In The Sediment

In their study, the researchers looked for specific organic compounds in the sediments samples that served as biomarkers for their analysis. These compounds were produced by organisms that existed in the Arctic Ocean during the period and had been preserved in the deposits.

According to Dr. Ruediger Stein, a geologist from the AWI and lead author of the climate study, the first set of biomarkers they examined came from carbonaceous algae, which lived in the surface of the ocean. This provided them with information on the conditions of the water's surface during summers in the Arctic.

Molecules collected from the carbonaceous algae allowed them to determine that the temperature of the Arctic Ocean's surface during the late Miocene period was somewhere between 4 and 9 degrees Celsius (7.2 to 16.2 degrees Fahrenheit).

Since these values are well beyond zero, Stein said it is more likely that summers in Arctic didn't include the formation of ice.

The second set of biomarkers the researchers analyzed, however, indicated that the Arctic Ocean was still covered in sea ice during other parts of the year. In fact, the ocean still experienced considerable ice buildup during spring and winter time six to 10 million years ago much like it does today.

The findings of the international climate study are featured in the journal Nature Communications.

Photo: NASA Goddard Space Flight Center | Flickr 

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