Blue-Action Spring Newsletter 2020

 

Ocean circulation causes the largest freshening event for 120 years in eastern subpolar North Atlantic
 

The Atlantic Ocean overturning circulation is important to the climate system because it carries heat and carbon northward, and from the surface to the deep ocean. The high salinity of the subpolar North Atlantic is a prerequisite for overturning circulation, and strong freshening could herald a slowdown.

A new paper by Penny Holliday from the National Oceanography Centre et al. in Nature Communications show that the eastern subpolar North Atlantic underwent extreme freshening during 2012 to 2016, with a magnitude never seen before in 120 years of measurements. The cause was unusual winter wind patterns driving major changes in ocean circulation, including slowing of the North Atlantic Current and diversion of Arctic freshwater from the western boundary into the eastern basins.

They also showed that wind-driven routing of Arctic-origin freshwater intimately links conditions on the North West Atlantic shelf and slope region with the eastern subpolar basins. This reveals the importance of atmospheric forcing of intra-basin circulation in determining the salinity of the subpolar North Atlantic.

 

Synthesis and evaluation of historical meridional heat transport from midlatitudes to the Arctic
 

One of the key improvements to climate change and sea ice forecasts in the Arctic is to better understand the energy transport polewards. A recent paper by Yang Liu from the Netherlands E-science Centre and Blue-Action colleagues published results using reanalysis datasets to refine current knowledge of meridional energy transport.

The team used six atmosphere and ocean reanalysis datasets to compare the variability in Atmosphere Meridional Energy Transport (AMET) and Ocean Meridional Energy Transport (OMET). The results show how well the datasets agree with each other and the latest observation and modelling techniques. The Python work package used for the analysis is open source to the wider research community. 

 

Rapid Export of Waters Formed by Convection Near the Irminger Sea's Western Boundary
 

The deep ocean can regulate the Earth's climate by storing carbon and heat. At high latitudes, waters are cooled by the atmosphere and sink, but they can only be successfully stored in the deep ocean if they are exported toward the equator.

In a new study by Isabela Le Bras from Scripps Institution of Oceanography and colleagues from Blue-Action, they analyze new mooring observations in the Irminger Sea to investigate the cooling and export of high‐latitude waters. In addition to the well‐documented waters that are cooled in the center of the Irminger Sea, they find that saltier waters are cooled near the western boundary current. Both of these water types make it into boundary current and are exported. The observations are consistent with the dynamics of swirling eddy motions. The eddy transport process is more effective for the waters cooled near the boundary current, implying that cooling near boundary currents may be more important for the climate than has been appreciated to date.

The paper was recently highlighted by EOS here. 

 

The stratosphere, the layer of the atmosphere starting at about 10 km above the Earth's surface, can have a major impact on surface weather in winter, in particular during stratospheric extreme events, known as sudden stratospheric warmings. The tropospheric response is strongest in the North Atlantic and Europe; however, not all events exhibit the same surface response, which remains a major open research question.

In a new paper by Hilla Afargan-Gertsman from ETH Zurich et al., they analyse the changes in surface weather after 26 sudden stratospheric warming events. The results show that the anomalous weather patterns in the Pacific may contribute to the sign of the Atlantic response by propagation of synoptic storms from the East Pacific toward the Atlantic. The results of this study can potentially improve the understanding of the coupling between the stratosphere and surface weather and help to extend weather prediction timescales.

In focus: snow-making
 

Can we use climate models to support winter tourism?

A partnership between the University of Lapland and Rukakeskus Ltd, a ski resort company in Finland, is demonstrating the potential for Blue-Action research to support economic development for businesses.

Climate forecasting
Ruka is a Northern Finnish Ski resort that aims to become the most snow secure resort in Europe. Seasonal climate forecasting can help Ruka to anticipate its machine-made and stored snow requirements and to plan accordingly for the upcoming ski season. It can also provide Ruka with valuable information about changing weather patterns and future temperature trends.

Snow App
Blue-Action has co-designed a snow-making app that shows the latest climate predictions at a scale relevant to Ruka. The team at Ruka have many years of experience in making snow, and use the tool alongside their knowledge to decide on the optimum conditions to use the snow machines. A prototype of the app was used in Ruka over the 2019-2020 ski season, and the team will be analysing the results over the coming months to determine the added value of this climate service. Watch this space for further updates!

Future Events
 

Members of the Blue-Action team, including Ian Salter and Hjálmar Hátún from the Faroe Marine Research Institute, contributed to the Atlantic Ocean Research Alliance publication exploring the importance of the microorganisms within the marine environment. This roadmap explains the role this underexplored world plays in food, health and ecosystem integrity, and lays out suggestions for future research. 

Watch the video below to understand more about the project, and have a fantastic introduction to why we should care about ocean microbes!