They live in some of the most inaccessible waters on Earth, where ocean temperatures hover around freezing. And because they move through areas that humans rarely reach, they have been able to help researchers with a very special task.
Equipped with sensors, six narwhals from the Scoresby Sound region, the world's largest fjord system on Greenland's east coast, collected data during their natural movements. This provided researchers from the University of Copenhagen, the Greenland Institute of Natural Resources and other institutions with entirely new data that would otherwise have been impossible to obtain.
"The narwhals have been in parts of the fjords where very few measurements have been taken before. And there, 300 kilometres from the coast, we find traces of Atlantic water. It is completely new that we can show this," says Mads Peter Heide-Jørgensen, Professor at the Greenland Institute of Natural Resources.
The water in the fjord system is a mixture of cold Polar Water originating in the Arctic and warmer, more saline Atlantic Intermediate Water from the Atlantic Ocean.
But the region has long been one of the major blind spots on the oceanographic map. Where research vessels often must turn back, narwhals can continue swimming.
"Now we suddenly have measurements from places we can use in our models, giving us a much more complete picture of the ocean. It is absolutely fantastic to use the animals in this way," says Susanne Ditlevsen, Professor at the Department of Mathematical Sciences.
Warm water accelerates glacier melting
In the study, which has just been published in the scientific journal Science Advances, the researchers combined the narwhal measurements with historical oceanographic data from the World Ocean Database (WOD) for the Scoresby Sound region.
"We used the two large datasets to build a robust model showing how temperature, salinity and depth are related. The models show that the layer consisting of Atlantic water has become thicker, while the upper layer of Polar Water has become thinner," says Susanne Ditlevsen.
The researchers show that warm Atlantic Intermediate Water now reaches deep basins in front of glaciers hundreds of kilometres into the fjord systems.
"This is the water that helps melt the glaciers. We show how the warm water can contribute to accelerating the rate at which glaciers lose ice," says Mads Peter Heide-Jørgensen.
Helping predict climate change
For the researchers, the results are not only about ocean conditions in East Greenland. They can also help improve the climate models used to predict future climate change.
Melting from Greenland's glaciers and ice sheet is an important factor in climate research. When glaciers melt, large volumes of freshwater are released into the ocean, which can influence ocean circulation and climate patterns far beyond the Arctic.
"In the large climate models used to predict future climate change, glacier melt plays a major role. That is why it is crucial that we improve our understanding of it, particularly because Greenland contains so much ice," says Susanne Ditlevsen.
[[ Fact box 1: How the narwhals helped the researchers
- Six narwhals were equipped with CTD sensors that measured ocean temperature, salinity and depth.
- The narwhals were captured and tagged by local hunters near Scoresby Sound in East Greenland.
- The sensors remained attached for between 85 and 332 days, collecting a total of 2,060 oceanographic profiles between 2017 and 2020.
- Measurements were collected to depths of more than 1,500 metres.
- The narwhals were able to gather data in areas that research vessels rarely or never reach because of sea ice and difficult access.
Fact box 2: About the study
- The new narwhal measurements were combined with more than 2,200 historical oceanographic profiles from the World Ocean Database.
- The study shows that warm, saline Atlantic Intermediate Water penetrates farther into East Greenland fjords than previously documented.
- Ocean temperatures in the region increased by around 0.047 degree Celsius per year between 1960 and 2021.
- The researchers find that the layer of Atlantic water is becoming thicker while the layer of Polar Water is becoming thinner.
- The results can contribute to improved estimates of glacier melt in future climate models.
- The study was funded in part by the Danish Ministry of Climate, Energy and Utilities, the Danish Ministry of the Environment (DANCEA) and the Greenland Institute of Natural Resources.
- Read the study ]]
