Climate patterns

This story first appeared in print in the Winter 2020 issue of Revelstoke Mountaineer Magazine. Read the e-edition here:

Story by Jade Harvey

The deep blue is all-encompassing. Light penetrates in rays of soft gold down into this serene, enchanted place. There are aquatic creatures of every kind, iridescently glistening in the wavy shimmer from above.

Suddenly, there is movement below. Like a volcano erupting, up comes an intense rush of water towards the surface. An icy cold torrent … the Little Girl is awakening.

This little girl, isn’t your average child. She isn’t sweet or cute — one who is content to just be with her friends enjoying all those fun games little girls love to play. Instead, she’s looking to wreak climatic havoc on a global scale, throwing the Earth’s two hemispheres into disarray.

Let me introduce La Niña … or ‘the little girl’ in Spanish, a name given to this atmospheric and oceanic system by scientists, a system that can influence our climate for years at a time. But who is she and what does it all mean for us, and every other living thing on our fragile planet?

Our Earth’s climate is a complex, interconnected system which can be likened to a set of Russian nesting dolls. Using this analogy, the tiny doll at the very centre represents the main driving force behind our climate, which is planet Earth’s annual voyage around the sun.

Each of the multiple layers on top (the progressively larger dolls), represent interacting feedbacks in the cycle that enhance and spread the effects of the Sun’s energy, including wind patterns, oceanic currents, volcanic eruptions of gas, and the reflectivity of ice (known as albedo).

Much more recent (in terms of the Earth’s history) are human interactions — such as the burning of fossil fuels and deforestation, and these serve to exacerbate the climate-change problems we face.

Woven in to these feedbacks (several of those figurative dolls) are natural, global scale, short term cycles of changes in our atmospheric and oceanic currents — and these can dramatically affect our seasons.

The El Niño Southern Oscillation (ENSO) is one such cycle. Fluctuating between ‘cold’ (La Niña) and ‘warm’ (El Niño) phases, this pattern changes the atmospheric pressure (responsible for winds) and sea-surface temperatures (responsible for driving ocean currents), thereby affecting rainfall and temperature in differing ways across the globe. La Niña is characterized by lower than normal air pressure over the Western Pacific, and low-pressure zones invariably generate storms.

So how does the allegorical Little Girl in this tale work her magic?

Let’s take a long bath, relax and find out … and our bathtub in this case is the entire South Pacific Ocean.

In order to understand the shift into La Niña, we need first to understand the standard conditions in the Pacific Ocean.

Normally, strong trade winds blow westward across the tropical Pacific (the area between the Tropic of Cancer (23N°), covering the equator and down to the Tropic of Capricorn (23S°) like a giant belt around the centre of Earth.

These trade winds occur due to the Coriolis effect, which means that as our planet spins anti-clockwise on its axis, the winds created at the equator by the Sun’s energy are whipped around the Earth’s surface — thereby causing large-scale winds that move from East to West in the tropics (and West to East up North, where, of course, we are).

Going back to that relaxing South Pacific bath, we’ve all turned on the hot taps and now our feet are too hot! So now we have to move the water back and forth with our hands to even out the temperature in the bath tub.

The shifting (dominant) trade winds are driven by those changes in atmospheric pressure, (like when we use our hands to mix the hot and cold water in the bathtub), and this contributes to the entire ocean basin between South America and Australia sloshing back and forth.

As the warm water sloshes towards Australia (our hot feet), cooler, more nutrient rich water gets sucked up in ocean currents off the coast of North and South America (at the other end of the bath). This process is known as upwelling and it is super important for the health of the ocean’s ecosystems.

Warmer water creates the conditions for more condensation, more clouds and ultimately more precipitation over the tropical Pacific. These conditions have a knock-on effect and cause changes in Northern Hemisphere atmospheric circulation.

The subtropical jet stream — a giant, global spanning, invisible river of wind in the sky that is usually centred over Mexico, gets shifted up, hovering right above us here in Canada. This wind moves from West to East delivering us that warm, wet air, all the way from the Ocean, over the Coast Mountains to the Interior region.

It’s where we get our snow from … and, this winter, the meteorologists are expecting more. Much more!

We’ve been observing this three- to five-year cycle (from data collected by ships) since at least the beginning of the 21st century. Climatic proxy (estimation) techniques put this natural phenomenon as occurring for many centuries.

El Niño can be devastating for ocean ecosystems and fishing in the Pacific Ocean off the coast of South America. Fish populations die or migrate as they seek the cold, nutrient-rich water in the euphoric zone (upper layer of the ocean.) These nitrates and phosphate nutrients are the basis for photosynthesis (food production from the sun) for phytoplankton, which in turn are the basis of the food chain for EVERYTHING in the ocean.

So, if the western Pacific Ocean could express its feelings, it would be pretty happy right now. That’s not to say the Little Girl is all good.  Research at Colorado State University suggests that the chance for continental US and the Caribbean Islands to experience hurricane activity increases substantially during La Niña.

In a study completed in BC, La Niña winters were shown to experience more avalanches due to increased snowfall, with a higher percentage of dry rather than wet avalanches. Any increase in avalanches places a higher stress on infrastructure, transport and community efforts to cope with snow.

Then, for added complexity in 2020, we have an ongoing global pandemic where transport connections plus the flow of goods and services and essential health care systems are all being impacted — resulting in a recipe for big trouble.

It has been noted that touring gear is selling out across the province, with more people looking to access the backcountry should commercial skiing get shut down. As many may be tempted to venture out without the knowledge and skills to do so safely, it could be that the Little Girl’s visit (La Niña) might result in more havoc than ever.

As the cooling in this southern place spreads, the sky above catches ahold of the flow. They grip each other tightly travelling vast distances across the surface, pushing the powerful river of the sky North, north to the land of bears and whales and mountains.

The river sucks its moisture from the great Pacific, winding across the expansive landscape until it is lifted up and over the mountains and it can bear the wet, heavy load no more. Frozen in this high place, it sheds in sheets of soft white. Covering the land in the thickest, soft, blanket ever seen. The Little Girl laughs. Her powers know no limits.