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 Larsen, and her talk, North Atlantic marine climate in recent decades.
Marine climate in the North Atlantic Ocean
Karin Margretha Húsgarð Larsen, Havstovan 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.
