Wintry tales, magical water and ice swimming in Finland

____________________________________________________________________________________________

Until a few seconds before it happened I wasn't sure I had the guts to go through with it. But then I did.

Listen to this article on the SCIENCE OF TRAVEL podcast



In this episode

  • How are the seasons caused?
  • What effect does the tilting of the earth have?
  • What is the anomaly of water?
  • Why is ice less dense than water?
  • What happens when water freezes?
  • Why do lakes freeze over?
  • Why can we bath in ice holes?
____________________________________________________________________________________________

Until a few seconds before it happened I wasn't sure I had the guts to go through with it. But then I did.

Accompanied by fellow exchange students I left the 80 °C (176 °F) sauna, only dressed with a bikini, and left the humid heat. I stepped out into the dry, sub-zero January winter air, the temperature was -24 °C (-11 °F), and headed towards a snow-blanketed, frozen lake. My hot feet stuck to the freezing ground, as I was quickly walking to the snow-covered, frozen lake in Finnish Lakeland. That's when I saw it. The ice hole.

Bathing in an ice hole in a Finnish Lake after going to the sauna is a truly awakening experience. But why do lakes freeze over and why is there liquid water beneath it? Find out in this blog post at the Science of Travel Blog

I was already cold. I had been since leaving the sauna. Should I really bath in the dark, cold water? I knew I'd regret it my entire life if I chickened out now. I watched my fellow exchange students get in and out of the hole one after the other. Eventually, it was my turn. Now or never.

I dipped my toe into the water. Then I immersed my legs, my stomach, my chest. Someone snapped a photo (the photo I sent you if you're on the email list), and then I left the icy water again. And I felt amazing. Tingly. Warm. We went back to the sauna. And then we repeated it. After heating up in the sauna, I glided into the ice hole another 3-4 times. It felt energizing, wild, raw. 

Why do Finnish lakes, or generally lakes in higher latitudes, so very north or very south on Earth, freeze at all? In other words: why does it get so cold on Earth? Or even simpler: Why do we have winter once a year on each hemisphere? And back to the Finnish lake: why does the ice swim on top of the liquid water? Why can we dig a hole into a frozen lake only to find liquid water beneath it?

Usually, with other materials, when that material is in a solid state, the density is higher than that of the liquid equivalent. Why don't lakes freeze from the ground upwards, but from the surface downwards?

You'll get the answer to these questions and learn why water is utterly special in today's episode.
 
Hey there, this is Daniela, I'm the host of the Science of Travel podcast and founder of EarthyMe and EarthyUniversity, the online course platform for travelers. Welcome back to the show, and, if you're new: welcome!! I'm happy you found your way here.


Like what you're reading? Subscribe to the STORIES OF EARTH newsletter for more sophisticated content

Winter

Winter is a season (you don't say!!). One of four we can enjoy here on Earth. The other seasons are spring, summer and fall. Winter is experienced differently depending on the location, the latitude. The farther away from the equator, the more extreme winter gets and the more typical characteristics of winter are reflected in changing flora, temperatures, weather, climate, and daylight.

In Hawai'i, winter means bigger waves and slightly cooler temperatures. In the Caribbean, not much changes. In Germany, winter means rainy or sometimes snowy days. In the northeastern USA winter sometimes brings blizzards, but California stays mostly pleasant throughout the year and never gets really really cold.

Winter turns Scandinavia into a winterwonderland.

Winter polarizes people. Some hate it, some love it. Some escape it, some seek it. To me, winter means being myself. I love winter. I was born in winter. I feel safe in winter. Every morning I look out the window with the faintest, the slightest hope of snow. More often than not I get disappointed. Where I live, snow in winter is becoming rarer and rarer. Winter is fun, is cozy, is warmth and cold. It's crisp air, flying hair, runny noses, red cheeks, hot beverages, crackling fires, silence, moody, overcast and clear blue skies. Winter is snow and ice. Winter allows the world to turn it down a notch. The outgoing, extroverted days of summer have passed. It is time to retreat to home. To close the doors. It is an invitation to unwind, to turn inward, to reflect. As an introvert, I feel like winter is my permission to be who I am. Summertime pressure is over. In winter, I can unfold.

In 2016, from January to April, I spent four months as an exchange student in Finnish Lakeland. When people asked why I'd chosen Finland as my destination, during Finnish winter, when it is cold and dark, I told them that was exactly why I had chosen Finland. 

But why is Finland dark in winter? And why is it so cold? I will specifically answer these and many more questions in the brand new online course about Finland at EarthyUniversity.


For now, we'll keep it general and ask the elephant-in-the-room question: Why do we have winter on Earth? Or more broadly:

Why do we have seasons? How are the seasons caused?

The crux is the tilt of the Earth's axis, also called obliquity. As you most likely know the Earth has an almost spherical shape and spins. It spins counterclockwise (from west to east). One spin takes about 24 hours and this is what we call a day.

Every spinning object spins around an axis. Earth's axis is not entirely vertical. If it was, we wouldn't have seasons in higher latitudes. The temperatures would be almost the same throughout the year at every place, as is the case at the equator. At the equator, the intensity of the sun's rays does not change much over the course of a year, as its position relative to the sun stays the same.

But again, Earth's axis is tilted about 23.44° in reference to the vertical line perpendicular to the Earth's orbit, which is called orbital axis. This is probably a bit hard to understand by just listening to it. So I'm trying to explain this a little more in detail:

The Earth moves around the sun in a circular motion. Earth’s path around the sun, its trajectory, is called orbit. Earth's orbit currently is elliptical. You can imagine the orbit as a flat, elliptical disc with the sun in the center. From this disc, you have to imagine a vertical line with a right angle to the disc. This vertical line is our reference line. From this vertical line we will measure an angle between the Earth's axis and this vertical line. This angle is 23.44° and this means Earth is tilted away from the sun sometimes and towards the sun sometimes. This has implications for the seasons.

Let's walk through it, starting with northern summer. During northern summer, the northern hemisphere is angeled towards the sun, as the Earth's axis is tilted towards the sun. The northern hemisphere receives more solar radiation and energy, because it is closer to the sun than the southern hemisphere, where it is winter now.

As the summer months pass by and the Earth revolves on its orbit around the sun, the position of the Earth's axis does not change. The axis' tilt is constant – but this isn't entirely true, because the Earth's axis moves around over very long time scales. However, we will not consider long-term obliquity changes or axial precession in this podcast episode. For us, the Earth's axis tilt is fixed, which means that the northern hemisphere now transitions from summer to fall, as the axis does not face the sun directly.

Earth continues on its orbit and by the time it reaches the position where the axis points away from the sun, Earth now has completed half a revolution around the sun and winter has arrived on the northern hemisphere and summer has arrived on the southern hemisphere. Countries north of the equator (northern hemisphere) are farther away from the sun and countries south of the equator (southern hemisphere) are closer to the sun. Now, the southern hemisphere is exposed to higher intensity sun rays.

If you need visuals to grasp this better (which I did too when I first learned about the seasons), have a look at the image below.

As the Earth moves further on its orbit, it transitions from winter to spring and finally back to summer, when the Earth's axis is tilted towards the sun (northern summer). This entire cycle is called a year. It takes the Earth approximately 365 ¼ days to orbit the sun once.

Why we have seasons. Credit: NOAA


What happens when water freezes?

Winter has arrived on the northern hemisphere (let's stay on the northern hemisphere now to not complicate things, but all explanations for northern winter are equally applicable to southern winter as well). In winter (on the northern hemisphere), temperatures drop as a result of reduced solar radiation. Earth's axis is tilted away from the sun. 

As the temperature sinks below 0 °C (32 °F), water freezes. This is the freezing point of water, you know that. Water does not always freeze at 0 °C (32 °F), it depends on the pressure. For now, I'm assuming air pressure at the Earth's surface of about 1,013.3 hPa which is the normal, average air pressure at the Earth's surface at sea level.

What then happens, at the freezing point of water, is marvelous. Liquid water turns into its solid state known as ice. Snow, by the way, is a bunch of ice crystals falling from the sky and accumulating on the ground. Here's the first cool part about freezing water: ice. Ice is a hexagonal crystal. You've probably seen the beautifully shaped ice crystal before, here is an image:

Ice crystals, frostwork at a window during winter at the Finnish Lakeland

It's important to know that ice forms crystals, because this has implications for the second cool part about freezing water: as the water freezes, its volume expands. The volume expands because the water's atoms become arragend along a specific crystalline structure which requires more space.

Let me explain a bit further: One water molecule consists of two hydrogen atoms and one oxygen atom. As the water cools down and transitions from liquid to solid, it has to organize its atoms. It does so by creating the crystal lattice. Imagine it like this: when transitioning from liquid water to ice, the water takes its atoms and places them in the shape of a ring with six corners and six sides. Each corner is occupied by one oxygen atom. This shape is called a hexagon. This hexagonal ring takes up more space because it contains voids, large gaps, where no atoms are located. As a consequence, fewer ice molecules (water molecules) fit inside a defined volume, which means the overall density is lower. Therefore, ice is less dense than the unstructured water molecules in the liquid state. In the liquid state, the gaps between water molecues are smaller, because water molecules, in the liquid state, are not organized on a lattice. That's why they can be closer together and the gaps are smaller. More atoms, or water molecules, fit inside a defined volume, which means the density is higher.

When water freezes, it becomes less dense and increases its volume, hence, expands, because its atoms get arranged on a hexagonal crystal lattice. Water becoming less dense and increasing its volume when freezing is quite unusual. We wouldn't necessarily expect that. Many materials gain density and reduce their volume when they enter the solid state, so when they freeze, as the temperature sinks. Not water it doesn't. That's why ice floats on the surface. That's why ice cubes don't fit their small containers after freezing. That's why glas bottles filled with water break in the freezer. That's why icebergs swim, too. You already knew that. You knew that ice is less dense than water. But now you know why: the famous anomaly of water is the cause.

In a nutshell: The anomaly of water

So let's recap: The anomaly of water describes water's counter-intuitive, extraordinary behaviour when changing phases from liquid to solid or vice versa. Water has its highest density (and lowest volume) at about 4 °C (39.2 °F). This means water at the bottom of lakes or the deep ocean is about 4 °C (39.2 °F) warm. Why? Because dense substances sink below less dense substances. This means: water decreases density, expands its volume, if the temperature is higher or lower than 4 °C (39.2 °F), because, again, water has its highest density at 4 °C (39.2 °F).

This implies that upon the melting of ice, the water contracts when heated. So again, we just learned that when water freezes to ice, it expands; and the other around, when ice melts, it contracts. This is, rather unusual again, and this is called negative thermal expansion, because most materials expand when heated (not contract).

To wrap up: For the Finnish Lake I took a dip in this means that warmer water sinks to the bottom and cooler water rises to the surface, because of the density anomaly we just learned about. When the mercury drops below the freezing point, the lake will start to freeze from the surface down where the coldest water is located, leaving the deeper water strata (layers) in a liquid state – because the warmer water is below the ice.

I adore Finland and can't help but talk about it in a new online course for travelers:


That's it for today. If you liked this episode or article, subscribe to the STORIES OF EARTH LETTER. I'm slowly abandoning Instagram and other social media channels, so be sure to subscribe as email is my favorite and only place I send updates for new podcast episodes and the travel courses at EarthyUniversity.
__________________________________________________________________________________________________
About the author

Daniela is convinced that by gaining deep insights into planet Earth and travel destinations you’ll create meaningful, grounding and memorable life and travel experiences. She explains fundamental geological processes that form and shape landscapes and combines these insights with philosophical and philanthropical views in her online courses, articles, podcast and e-letter. She holds two bachelor's degrees in geosciences (B.Sc.) and business administration with tourism (B.A.). She is the owner and founder of EarthyMe, EarthyUniversity and the Science of Travel blog and podcast and the Stories of Earth Letter.

 

__________________________________________________________________________________________________


__________________________________________________________________________________________________

Credits
1. Images

Banner: Daniela in Mikkeli, Daniela Dägele

Ice crystals on window: Daniela Dägele

Seasons graphicChanging seasons | National Oceanic and Atmospheric Administration (noaa.gov)

2. Text and further reading

season | National Geographic Society

weather records: List of weather records - WikipediaLowest temperature recorded on Earth - Wikipedia

What are your thoughts?

Please note, comments must be approved before they are published

/* -- Responsive video embed -- */ .responsive-video { padding-bottom: 56.25%; /* for 16:9 ratio */ padding-top: 25px; position: relative; height: 0; } .responsive-video iframe, .responsive-video object, .responsive-video embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }