Alaska, Featured, Science

El Niño, La Niña, and Alaska Temperatures

Typical La Niña winters in North America. Image courtesy of NOAA climate.gov. Drawn by Fiona Martin.

By Allison Sayer for Seward City News –

It doesn’t take a climate scientist to tell that this winter in Southcentral Alaska has been colder than the past two winters. The Kenai Peninsula is buried in snow, and much of the interior has experienced the prolonged cold the old timers reminisce about. Does this have anything to do with the global change from El Niño to La Niña? After years of exceptionally warm Pacific ocean temperatures, will the ocean finally return to normal? And what about climate change? If the world is getting warmer, why is this winter shaping up to be colder than last winter?

The terms El Niño and La Niña get thrown around quite a bit, but what do they really mean? El Niño and La Niña describe “SST anomalies” in the central and eastern tropical ocean that persist over a period of months. SST is simply an acronym for sea surface temperature. Anomalies are differences between current temperatures and a multiyear average. The averages are subdivided by months to account for seasonal differences.

For example, a January SST anomaly of -2.2 degrees means the sea surface temperature is 2.2 degrees cooler than the long term average January sea surface temperature.

So why do climate scientists pay so much attention to the SST anomalies in the central and eastern tropical ocean? And why do the anomalies have to persist for months to create El Niño or La Niña? What does this have to do with us?

Diagram showing warm, moist air rising and cool, dry air falling during El Niño. Diagram courtesy of NOAA Climate.gov, drawing by Fiona Martin.

During El Niño, warmer than average Eastern Equatorial Pacific sea surface temperatures cause warm air to rise off the sea surface. This air displaces the air above it. If the temperature difference (a.k.a. SST anomaly) persists for a long enough time, it sets a circulation pattern in motion that continues around the world. Different parts of the globe experience different effects.

The typical El Niño pattern for much of Alaska is a trend towards warmer temperatures.

So, does that mean that the warm weather Alaska experienced last year was the result of El Niño and not climate change? No. 2016 was the warmest year ever recorded in Alaska, warmer than any of the other El Niño periods that had come before. El Niño and climate change worked together to create these conditions.   

La Niña Began in 2016

In late 2016, NOAA scientists announced the world was officially in a La Niña cycle. During La Niña, cooler than average Eastern Equatorial Pacific sea surface temperatures persist for a months-long period of time. This creates a different effect on circulation patterns.

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Most of Alaska can usually expect cooler weather during a La Niña cycle than during El Niño, with the exception of the Arctic. If the typical La Niña trend holds true, this winter should continue to be cool in much of the state. However, the current La Niña is “weak.” It may not have as strong an effect on our climate all the way up in Alaska as other factors that originate closer to home. Also, NOAA scientists expect conditions to become “ENSO Neutral,” neither El Niño nor La Niña, within a month or two.

Global Surface Temperature Anomalies, 1980-present. El Niño conditions are colored in red, La Niña in blue. Figure courtesy of NOAA.

If this winter is cooler than last winter, does that mean we can stop worrying about climate change? No. La Niña years are cooler than El Niño years. But the average La Niña temperatures all over the world are still rising. If we want to know whether climate change is also influencing our temperature, we need to compare this La Niña year specifically to other La Niña years. 

What about sea surface temperatures? What about The Blob?

“The Blob” was a mass of warm water trapped in the North Pacific that gained attention in 2013. The warm water depressed food chain productivity by reducing nutrient flow through ecosystems. It had other serious ecological and economic effects including increased frequency of toxic algae and jellyfish blooms. The effects in Alaska are still being studied, but the Blob is a likely suspect in widespread seabird die offs and 2016 fishery failures.

The Blob was not simply the result of higher average air temperatures. Unusual wind patterns created a warm water reservoir that flowed quickly towards the poles when the winds changed. A lack of sea-stirring storms over the Pacific prevented the warm water from being displaced. Once The Blob started, El Niño reinforced the warming trend in the northern Pacific ocean by continuing to influence the flow of warm water towards the North Pacific.

It seems like The Blob is really gone, and will stay away at least for now. It also seems like global weather patterns are not going to work to create a new Blob right away.

Sea Surface Temperature Anomalies, Oct-Dec 2016. Image courtesy of NOAA.

Even with The Blob and El Niño gone, predictions for Alaska sea surface temperatures are mixed. The surface temperature in the Gulf of Alaska was still between 1.5 and 2 degrees C above average in December 2016. While interior Alaska has been good and cold this winter, Arctic Alaska has remained warm. It was 36 degrees in Barrow on New Year’s Day, 2017. Alaska has less sea ice than ever, a factor that will make the ocean warmer. The impacts of climate change on global temperatures will continue.

There is a lot of hope for 2017 to bring Alaska a more “normal” climate, or at least for temperatures to be less extreme than they were in 2016. I will eagerly watch to see what happens. If you are interested in learning more about climate issues, climate.gov has a wealth of information.

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