An international research team lead by the Cnr Institute of Polar Sciences and Marine Sciences with the contribution of the University of Cambridge has reconstructed the recent history of warming at the gate of the Arctic Ocean - a region called the Strait of Fram - between the Greenland and Svalbard. The paper, published in Science Advances, defines for the first time the onset of warming and infer a further increase in the future due to climate change
The Arctic Ocean began to warm rapidly in the early twentieth century, decades earlier than hitherto documented by modern experimental measurements. The news comes from an international research group lead by the Institute of Polar Sciences Sciences (Cnr-Isp) and Marine Sciences (Cnr-Ismar) of the National Research Council of Italy with the contribution of the University of Cambridge. The cause is a phenomenon long known as 'Atlantification', that is a progressive intrusion of Atlantic waters (hot and salty) into the Arctic domain (cold and fresh). The work, published in the journal Science Advances, identifies for the first time the historical dating of this phenomenon.
“Arctic Atlantication is progressively accelerating, however, before our study we did not have a historical understanding of this process, as satellite observations are limited to roughly the last 40 years. This change in the water properties preceded the warming documented by satellites and in situ measurements,” explains Tommaso Tesi, leader of the paper and researcher at Cnr-Isp.
For the study, the research team examined a region at the entrance to the Arctic Ocean, along the eastern part of the Fram Strait, between Greenland and Svalbard. “We analyzed a marine sedimentary record - our 'time machine' - looking for diagnostic signs of Atlantification, such as changes in temperature and salinity,” continues Tesi. “By 'reading' the chemical signatures found in marine microorganisms, we have seen that since the beginning of the 20th century, ocean temperatures have increased by about 2 degrees Celsius, while sea ice has retreated and salinity has increased. In fact, when we examined the entire time span of 800 years, our temperature and salinity records were quite constant, when we came to examine the beginning of the twentieth century, we found a marked change in these parameters.”
“All the oceans in the world are warming due to climate change, but the Arctic Ocean, the smallest and shallowest of the oceans, is warming faster than all of them. The rate of warming in the Arctic is more than double the global average, due to the thawing of sea and land ice,” said Francesco Muschitiello, co-author of the article and researcher in the Department of Geography at the University of Cambridge. “We compared our results with ocean circulation at lower latitudes and found that there is a strong correlation with the slowing of dense water formation in the Labrador Sea (a region of the North Atlantic Ocean that lies between the Labrador Peninsula and southern Greenland). In a future warming scenario, deep circulation in this subpolar region is expected to further decrease due to the thawing of the Greenland ice sheet. Our findings imply that we may expect further Arctic Atlantification in the future due to climate change.”
The results of the new Science Advances study are not yet covered in current climate models, and this poses a problem in outlining future trends. “Climate simulations generally do not reproduce this type of warming in the Arctic Ocean, which means that there is an incomplete understanding of the mechanisms that drive the Atlantification," concludes Tesi. “We rely on these simulations to project future climate change, but the lack of signs of early warming in the Arctic Ocean is a missing piece of the puzzle.”
The research was made possible thanks to the Base Dirigibile Italia, a permanent infrastructure in the Arctic managed by the Cnr-Isp (https://www.isp.cnr.it/index.php/it/infrastructure/stazioni-di-ricerca/stazione-artico - airship-italy.
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- Tesi Tommaso et al. 'Rapid Atlantification along the Fram Strait at the beginning of the 20th century.' Science Advances (2021)