Sep 18, 2014
In recent years, the retreat of sea ice in the Arctic has been linked to cold winters in Eurasia and North America. Now a study by a team from Japan indicates that a northwards shift of the Gulf Stream could trigger planetary waves that cause cold weather in Eurasia, bring warmth to the Barents Sea and decrease sea-ice extent.
“The relationship between atmospheric forcing in the North Atlantic and sea-ice variability over the Barents Sea remains uncertain,” Kazutoshi Sato of the Graduate University for Advanced Studies, Tokyo and Japan Agency for Marine-Earth Science and Technology told environmentalresearchweb. “Therefore, we investigated the impact of the Gulf Stream heating anomaly on the atmospheric circulation from the North Atlantic to Eurasia.”
Sato and colleagues found that a “warm Arctic and cold Siberia” pattern was indeed linked to forcing by the Gulf Stream. A poleward shift in the Gulf Stream alters atmospheric convection in the region and affects the jet stream, they discovered. The result is meandering westerly winds that create high pressures over the Eurasian coast, reducing warm air transport and bringing extreme cold weather events to Eurasia. At the same time, the Gulf-Stream-induced atmospheric changes increase southerly winds over the Barents Sea, boosting temperatures and forcing sea ice to drift north.
“The remote atmospheric response from the Gulf Stream would be amplified over the Barents Sea region via interacting with the sea-ice anomaly, promoting the warm Arctic and cold Eurasian pattern,” writes the team in Environmental Research Letters (ERL).
To carry out the analysis, the researchers employed six-hourly data from the Climate Forecast System Reanalysis, along with a linear baroclinic model. Observations of daily mean surface air temperature during December at Bear Island, part of the Svalbard archipelago, enabled the team to compare years with particularly warm and particularly cold winters. The linear baroclinic model revealed the atmospheric response to heating anomalies in areas such as the Barents Sea.
“Our model results showed that a change in condensational heating over the Gulf Stream directly induces a cold anomaly over western Eurasia,” said Sato. “In addition, the southerly winds cause sea-ice decline over the Barents Sea by its northward drift, supporting previous studies focusing on the relationship between the sea-ice retreat over the Barents Sea and warming/cooling over the Arctic/Eurasia.”
As they write in ERL, the team believes that the impact from the Gulf Stream should be considered for a thorough understanding of change in the Barents Sea and the consequent cooling over the continent.
“Today, a linkage between the Arctic and mid-latitudes becomes a hot topic not only scientifically but also socioeconomically,” said Sato in a press release. “Therefore, the role of mid-latitude oceans, e.g. the Gulf Stream, Kuroshio [in the Pacific], should be investigated more than ever towards the better understanding of future projections by improving the modelling of global ocean circulation as well as processes of sea-sea interaction.”
Incorporating the effect of the polewards shift of the Gulf Stream could improve projections of climate once Arctic sea ice has reached low levels.
Now, Sato is researching sea-surface temperature variability over the Gulf Stream in other seasons. Examining temperatures during autumn could help predict Eurasian climate and Barents Sea ice reduction during winter. It’s possible that the polewards shift of the Gulf Stream could also cause extreme events in northern mid-latitudes during other seasons.
- Influence of the Gulf Stream on the Barents Sea ice retreat and Eurasian coldness during early winter Kazutoshi Satoet al. 2014 Environ. Res. Lett. 9 084009
- Graduate University for Advanced Studies
- Japan Agency for Marine-Earth Science and Technology
About the author
Liz Kalaugher is editor of environmentalresearchweb.