#Decadal2022: North Atlantic marine climate in recent decades

The Fourth Symposium on Decadal Variability of the North Atlantic and its Marine Ecosystems: 2010–2019 kicks off in Bergen, Norway.
Published: 20 June 2022

​​​​Climate variability and change are impacting the distributions and productivity of marine species in the North Atlantic. Monitoring and predicting the effects of climate change on the distribution of habitats, and the marine species that occupy them is critical for resource management. 

Beginning today in Bergen, Norway, the Fourth Symposium on Decadal Variability of the North Atlantic and its Marine Ecosystems: 2010–2019​ is part of a series of decadal symposiums organized by ICES, where researchers gather to review the variability of North Atlantic environmental conditions and marine ecosystems over the past decade. Researchers aim to understand the relationship between ecosystem components and how they influence the distribution, abundance and productivity of living marine resources. In addition, researchers will review recent advances in sub-decadal forecasts of ecosystem change.

The symposium provides a forum to highlight key ICES working group activities, allowing scientists, from multiple disciplines to network, build relationships and share their scientific understanding of marine ecosystems.

We will take a closer look at three of the keynote lectures from the symposium this week, beginning with Karin Margretha Húsgarð Larsenand her talk, North Atlantic marine climate in recent decades.

Marine climate in the North Atlantic Ocean​

Karin Margretha Húsgarð LarsenHavstovan Faroe Marine Research Institute, opened the conference with a keynote lecture in Theme Session 1: Ocean climate and physical environment in the North Atlantic and their linkages to changing marine ecosystem that explored the marine climate in the North Atlantic Ocean, with a focus on the Subpolar Gyre, the Greenland-Scotland Ridge, and the Norwegian Sea areas. 

In the recent decade, Larsen explains that two events dominated the marine climate in the Subpolar Gyre. During the 2014/15 winter, extreme cooling occurred in the Irminger Sea, resulting in very low-temperature anomalies over large areas of the Subpolar Gyre. This event was termed “The Cold Blob”. In 2015, stronger atmospheric forcing over the Subpolar region in form of stronger winds and increased heat loss, mainly over the Irminger Sea, resulted in a stronger Subpolar Gyre, which expanded eastward. The atmospheric forcing also led to a stronger freshwater flux from the New Foundland shelf into the Subpolar Gyre and increased precipitation. Together these events resulted in an extreme freshening in the eastern part of the Gyre with exceptionally fresh water in the Iceland Basin. 

Despite the increased cooling, the temperature of the Atlantic Water crossing the Greenland-Scotland Ridge remained relatively high and a de-coupling between temperature and salinity thus occurred. This de-coupling is also evident in the Norwegian Sea where the upper layers have experienced a warming and freshening trend since 2011. In the Norwegian Basin, more than 60% of the warming is explained by reduced ocean heat loss to the atmosphere, while the freshening mainly is due to the inflow of fresher Atlantic Water. 

We might speculate, said Larsen, whether the de-coupling between temperature and salinity might affect the deep water formation in and downstream of the Norwegian Sea, but hitherto the exchanges of Atlantic Water and Overflow Water across the Greenland-Scotland Ridge have remained stable. The Norwegian Sea also receives an inflow of Modified East Icelandic Water (MEIW) from the East Icelandic Current, but this inflow apparently was low during 2005–2017. 

In recent years, the presence of MEIW in the southern part of the Norwegian basin seems to have increased and this might impact the marine climate in the Norwegian Sea in the coming years. Both MEIW and Subpolar Gyre waters are rich in nutrients and are therefore important for the marine ecosystems downstream and on nearby shelves. On the other hand, silicate concentrations in Arctic Waters entering the Subpolar region have been declining for several years and this trend is expected to impact the phytoplankton growth and composition in marine ecosystems in the region. 

The Fourth Symposium on Decadal Variability of the North Atlantic and its Marine Ecosystems: 2010–2019​ runs from 20–22 June 2022 in Bergen, Norway.


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#Decadal2022: North Atlantic marine climate in recent decades

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