Warm North Atlantic Ocean promotes extreme winters in US and Europe

Apr 01, 2014

The extreme cold weather observed across Europe and the east coast of the US in recent winters could be partly down to natural, long-term variations in sea surface temperatures, according to a new study published today.

Researchers from the University of California Irvine have shown that a phenomenon known as the Atlantic Multidecadal Oscillation (AMO)—a natural pattern of variation in North Atlantic temperatures that switches between a positive and negative phase every 60-70 years—can affect an atmospheric circulation pattern, known as the North Atlantic Oscillation (NAO), that influences the temperature and precipitation over the Northern Hemisphere in winter.

When the AMO is in its positive phase and the sea are warmer, the study has shown that the main effect in winter is to promote the negative phase of the NAO which leads to "blocking" episodes over the North Atlantic sector, allowing systems to exist over the eastern US and Europe.

The results have been published today, Wednesday 2 April, in IOP Publishing's journal Environmental Research Letters.

To arrive at their results, the researchers combined observations from the past century with climate simulations of the atmospheric response to the AMO.

According to their observations, sea surface temperatures in the Atlantic can be up to 1.5 °C warmer in the Gulf Stream region during the positive phase of the AMO compared to the negative, colder phase. The climate simulations suggest that these specific anomalies in can play a predominant role in promoting the change in the NAO.

Lead authors of the study Yannick Peings and Gudrun Magnusdottir said: "Our results indicate that the main effect of the positive AMO in winter is to promote the occurrence of the negative phase of the NAO. A negative NAO in winter usually goes hand-in-hand with cold weather in the eastern US and north-western Europe."

The observations also suggest that it takes around 10-15 years before the positive phase of AMO has any significant effect on the NAO. The reason for this lag is unknown; however, an explanation might be that AMO phases take time to develop fully.

As the AMO has been in a positive phase since the early 1990s, it may have contributed to the extreme winters that both the US and Europe have experienced in recent years.

The researchers warn, however, that the future evolution of the AMO remains uncertain, with many factors potentially affecting how it interacts with atmospheric circulation patterns, such as Arctic sea ice loss, changes in solar radiation, volcanic eruptions and concentrations of greenhouse gases in the atmosphere.

The AMO also shows strong variability from one year to the next in addition to the changes seen every 60

Explore further: Study suggests autumn Arctic sea ice can be used to predict European winter weather

More information: 'Forcing of wintertime atmospheric circulation by the multidecadal fluctuations of the North Atlantic ocean' Yannick Peings and Gudrun Magnusdottir 2014 Environ. Res. Lett. 9 034018. iopscience.iop.org/1748-9326/9/3/034016/article

add to favorites email to friend print save as pdf

Related Stories

The Atlantic Ocean dances with the sun and volcanoes

Mar 31, 2014

Natural fluctuations in the ocean temperature in the North Atlantic have a significant impact on the climate in the northern hemisphere. These fluctuations are the result of a complex dance between the forces ...

European fisheries flip with long-term ocean cycle

Apr 17, 2013

A sudden switch from herring to sardines in the English Channel in the 1930s was due to a long-term ocean cycle called the Atlantic Multidecadal Oscillation (AMO), an international study shows. This is the ...

Cold winters mean more pollution

Feb 22, 2011

Differences in air pressure over the North Atlantic have meant that the last two winters in Gothenburg, Sweden, have been extremely cold. This has led to the air in Gothenburg being more polluted with nitrogen ...

Recommended for you

Hopes, fears, doubts surround Cuba's oil future

21 hours ago

One of the most prolific oil and gas basins on the planet sits just off Cuba's northwest coast, and the thaw in relations with the United States is giving rise to hopes that Cuba can now get in on the action.

New challenges for ocean acidification research

Dec 19, 2014

Over the past decade, ocean acidification has received growing recognition not only in the scientific area. Decision-makers, stakeholders, and the general public are becoming increasingly aware of "the other carbon dioxide ...

Compromises lead to climate change deal

Dec 19, 2014

Earlier this month, delegates from the various states that make up the UN met in Lima, Peru, to agree on a framework for the Climate Change Conference that is scheduled to take place in Paris next year. For ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.