The Arctic ocean under pressure from the Atlantic

Monday 19 Dec 22


Colin Stedmon
DTU Aqua
+45 35 88 34 10
Warmer, less salty and more nutrient-rich water closer to the surface in the water off North East Greenland puts pressure on the ecosystem. The Arctic Ocean faces huge changes. 

New research results from the Artic show that the water off Northeast Greenland has changed massively in the last 20 years - the predominant layer of cold polar water is being displaced from below by water from the Atlantic Ocean.
This means warmer, less salty and more nutrient-rich water closer to the surface. Thus, an arctic ocean likely to face a shift in ecosystem structure and function.
Caroline V. B. Gjelstrup and Colin Stedmon, respectively PdD Student and Professor at DTU Aqua, are two of the researchers behind the study Vertical redistribution of principle water masses on the Northeast Greenland Shelf published in the science magazine Nature communications. 
When asked what the most surprising new finding in this study is, Colin Stedmon replies:
“For me it is the scales involved: The geographical coverage across the region. But also the vertical movement upwards of the interface between the water masses. This, together with other evidence, indicates considerable change in the region since the early 2000’s.”

Layer decreased by the size of Rundetårn

In the sea off Northeast Greenland waters are layered. At the bottom lies that which is most dense and is salty and comparatively warm (1-2C). This is covered by a layer of polar water from the Arctic Ocean which has temperatures close to freezing point of seawater and slightly lower salt content.

"The scales involved together with other evidence, indicates considerable change in the region since the early 2000’s."
Colin Stedmon, Professor, DTU Aqua

This layer of polar water acts as a cold shield separating surface waters, sea ice and in some places glaciers from the comparatively warmer saline water below. Without this insulating shield, winter sea ice would not form. 

“In the short run, the presence of warmer water at shallower depths will increase melting of glacial ice that protrudes into the sea in Northeast Greenland,” says Colin Stedmon.

Ocean life

The thickness of the polar water layer varies but usually it is on the order of 100-200 m meters. However, the layer is thinning both in the fjords and in coastal waters of Northeast Greenland:  

“In the longer perspective, the thinning of the polar water layer by more nutrient-rich water will most likely fertilize surface waters and change the structure of the food web in Northeast Greenland in a way already seen further south,” says Colin Stedmon.

The interface between the warm and cold water layers has migrated upwards on the order of 50 meters which is more than Rundetårn in København. So, the warm and nutrient-rich water from below is now becoming more accessible.

With ice melting faster and hereby more freshwater released into the sea water, ocean circulation will be affected and it will in turn in particular in this region affect our climate. 

On the other hand, with more nutrient-rich water, there is according to the scientists potential for the regions water to be more productive in terms of ocean life.

Photo: Nordgrønland, Colourbox