Please make sure you’ve read the previous 13 chapters of this story on this website before reading this one, in order to get the most from it.

During several parts of this saga, Return to the Andes, I’ve alluded to the fact that South America can be a very cold place, and now I’m going to explain just what I mean by that. Most of us who live in the temperate zone of the Northern Hemisphere feel that ours is a cold part of the world. I can say from experience that those of us who live in the mid-latitudes, between 30 and 60 degrees north, think of South America as a hot place (think Amazon basin), and find it hard to imagine that it could possibly match the winter cold of the great interior land-masses of North America or Eurasia. But I’d like to approach this subject from a different angle, one that may give you a new perspective on how weather works south of the equator.

You might think “Hey, the world’s divided into two equal parts, the Northern Hemisphere and the Southern Hemisphere, right? Both halves get the same amount of sunlight in the course of a year, so why should there be any difference in the overall temperature between the two?” Well, let’s look at a few facts. We all know that almost 70% of our planet’s surface is ocean, leaving barely 30% as land. So? Let’s take it a step further. Of all earth’s land, 68% of it lies north of the equator, leaving merely 32% to the south. And in the Southern Hemisphere, not counting Antarctica, most of that land lies within 30 degrees of the equator. If you look at a globe, at the Southern Hemisphere, and see where the land-masses are, you’ll see something interesting. Most of the globe between 30 degrees south and Antarctica is covered by water. Oh sure, there are a few exceptions, but they’re pretty minor – let’s see what they are.

The tip of South Africa barely reaches 35 degrees; the southern shores of Australia touch 40 degrees; the North Island of New Zealand also reaches the 40-degree mark. Below 40 degrees south latitude, the only land we have is Tasmania, the South Island of New Zealand, and that long thin part of South America known as Patagonia. Sure, there are a few other bits of land south of that 40-degree mark, but they are tiny, insignificant little islands. So, that huge cold southern ocean is what governs the climate of Patagonia, but in order to understand how it does that, we need to study more about our planet’s weather patterns in general.

You’ve probably heard of the doldrums – kind of an odd word, used by mariners for centuries. It’s a wide band of unreliable winds and a lot of thunderstorms, spanning a region of about 10 degrees both north and south of the equator. Northeast trade winds from the north and southeast trade winds from the south feed this area, moving towards each other, and this causes the atmosphere to rise, causing a belt of low pressure around the equator. All this rising air flows to the north and to the south, then drops again in the subtropics at around 30 degrees south and north latitudes. As this air sinks, it causes belts of high pressure called subtropical highs, which are found at both the southern and northern edges of the tropics. Let’s take it a step further.

On the earth’s surface, moving even farther away from the equator, we find a zone called the mid-latitudes, between 30 and 60 degrees of latitude. This is a very active belt of winds which move across the planet from west to east. Are you still with me? This is an important part of the explanation, and I really am going somewhere with all of this. If we move towards the poles from these westerly winds, we will encounter an area of low-pressure that surrounds both poles at around 60 degrees latitude, called circumpolar troughs. When storms from the mid-latitudes reach these troughs, they would normally be broken up and die. In the Northern Hemisphere, the huge land masses of Europe, Asia and North America break up the circumpolar trough into the Aleutian Low in the North Pacific Ocean and the Icelandic Low in the Atlantic Ocean, and when storms reach these areas they die a natural death. However, in the Southern Hemisphere, in the circumpolar trough that surrounds Antarctica, conditions are very different – there are no such land masses to act as obstacles. At 60 degrees south, we find the only place on earth where a line of latitude runs all the way around our planet without hitting any dry land.

This is such an important fact, that the ocean can flow freely (remember, the winds blow from west to east down there) continuously around the globe at 60 degrees south – this keeps the ocean of those far southerly latitudes very cold. In the Northern Hemisphere, those huge land masses of North America and Eurasia act as dams, and permit ocean currents such as the Japan Current and the Gulf Stream to rush warm waters from the tropics far to the north. Those warm currents help keep the average annual temperature of the Northern Hemisphere almost 2 degrees F. warmer than the Southern Hemisphere, and that, Folks, is huge. No such warm currents disturb the cold ocean temperatures of those high southern latitudes.

Okay, I’m almost done with this explanation, so bear with me a little longer. 

Air wants to move from the subtropical high pressure at 30 degrees towards the circumpolar low pressure at 60 degrees, and this air is greatly helped along by the Coriolus effect of the spinning earth. The larger the temperature difference between 30 degrees and 60 degrees, the stronger the pressure forces will be and the stronger the corresponding winds will be. Since the temperature difference between 30 and 60 degrees is greater in the Southern Hemisphere, that is where the strongest west winds blow on planet Earth. What start as warm and cold fronts in the Southern Hemisphere quickly lose their individual characteristics and adopt the character of the ocean below them – wet and cold. These storm bands of cool, moist air get sucked toward the circumpolar trough around Antarctica, which causes a series of wet storms to get sucked over the Andes, and the horrible weather in the mountains can last for weeks on end.

The Andes in Patagonia act as a ramp, and the air rises suddenly, cooling it even more and condensing its moisture into clouds, rain or snow. Over countless years, all of this precipitation has formed the glaciers and huge ice caps of the Patagonian Andes. One more thing – once this air passes over the crest of the mountains, it can accelerate as it plunges down the other side, giving it tremendous force. Remember the outrageous wind effects I described in the previous chapter in Torres del Paine? You may have heard of the “Roaring Forties” when describing the belt of strong winds at that latitude. Well, how about the “Furious Fifties” and the “Screaming Sixties”? Both terms are apt for the Southern Hemisphere. Bottom line, Folks, is that, if you’re lucky, a good spell of weather in Patagonia might last 48 hours, rarely longer.

In the Northern Hemisphere, in North America, we find a few small glaciers in Mexico, almost none in the U.S. Rocky Mountains and a few in the Cascades. Only once we move north of the 49th parallel do we find more in the Canadian Rockies and the Coast Range. The Columbia Icefield, at 52 degrees north, contains a decent chunk of glacier, the largest in the Rockies, but even it covers a mere 125 square miles. However, we need to travel to 58.3 degrees north latitude before we find glaciers calving icebergs into the ocean, and even farther north to find the same in Greenland and Scandanavia. Remember that number, 58.3, because I’m now going to tell you a few things that may shock you.

In Patagonia today, you can find icebergs breaking off of glaciers directly into the ocean at 48.3 degrees of latitude. That is a full TEN degrees closer to the equator than in the Northern Hemisphere. To put that in perspective, if you were to see the same thing happening in North America, you’d have to see it halfway between Vancouver, British Columbia and Seattle, Washington. Unthinkable, unheard-of and impossible. Instead, you’d need to travel 700 air miles farther north, almost to the Yukon border, to see such a thing occurring. See what I mean? This is a great example of how much colder South America can be than North America.

Let’s look at another example. There are some huge ice fields in Patagonia, three in particular I’d like to mention. Farthest south is the one that lies to the southwest of the Isla Grande de Tierra del Fuego, and is included within Parque Nacional Alberto de Agostini in Chile. It includes the Cordillera Darwin, a mind-boggling area of permanent ice and snow. This rugged ice field is 70 miles in length, very hard to reach and boasts some of the world’s worst weather. The fact that it sits at 55 degrees latitude makes it a very remote, cold place indeed, and being at the southernmost tip of the Andes – well, you’d just expect a lot of ice there, and many of its glaciers flow right into the ocean. Truth be told, it’s more of a spidery-looking thing as opposed to a broad ice sheet. Although I think that this ice field is one of the most outrageous you could ever hope to visit and climb in, it’s not the most exciting one I want to show you.

There’s another called the Northern Patagonian Ice Field, or Hielo Norte. It lies entirely within the boundaries of Laguna San Rafael National Park, much closer to the equator than the previous ice field I just mentioned. It sits between 46.3 and 47.6 degrees latitude and covers 1,600 square miles. Now this one is a true ice sheet, and 28 different major exit glaciers and countless minor ones feed rivers and lakes around its perimeter. It too lies entirely within Chile. Here’s how big it is – if you plunked it down on to the area of Seattle, Washington in the USA, it would cover a distance from Everett in the north all the way down to Centralia in the south, about 20 miles south of Olympia, at the same latitude. Pretty hard to imagine an ice sheet that big in Washington state, right? The first north-south crossing of this ice field wasn’t even completed until 1973, it is so daunting.

But I’ve saved the best for last, Folks, and this one is a real blockbuster. It’s the paterfamilias of them all – the Southern Patagonian Ice Field, or Hielo Sur. Covering a massive 4,775 square miles, this monster stretches 220 air miles from north to south. 78% of its area lies within Chile, the other 22% in Argentina. Both Fitzroy and Torres del Paine sit on the eastern edge of this huge ice sheet. A few hardy explorers have crossed it from west to east, or east to west, but only one intrepid party has ever traveled its north-south length, in 1998. Given its horrible weather, that would be a lengthy and dangerous undertaking. This huge mass of ice feeds dozens of large glaciers – among them are the Upsala, the Viedma and the Perito Moreno, as well as the Bruggen Glacier, the largest in area and the longest in the Southern Hemisphere outside of Antarctica. This amazing ice field even contains two active volcanoes.

So, thanks for bearing with me. I hope this somewhat lengthy explanation has shown you how South America really is, in many ways, a colder place than North America. If you live in the Northern Hemisphere and have never visited South American to see this glaciation, it may be hard to accept how dramatic it is, but trust me, it’s true.

Please stay tuned for the next installment of this story, Part 15.

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