Nature News: The albedo effect affects the warming of Earth’s atmosphere

published November 9, 2020

Lonesome Lake with ice cover. photo by Sue Pike

I was up in the mountains this weekend hiking up to North Kinsman Mountain via Lonesome Lake. It was so warm for November. Even though we had packs full of winter gear, even though we started early, a warm breeze had begun to blow and we were down to T-shirts and shorts within the first mile.

This is a beautiful little lake nestled in among the mountains at around 3,000 feet. When we got there, it was still mostly covered with ice. There was even ice and old snow along the shaded parts of the trail. I was struck by how warm it was in the surrounding woods and rocky outcroppings, yet cold by the water.

I am about to teach a big climate unit in my freshman Integrated Earth Science class.   Earth’s energy budget is a big part of this, so the sun and its interaction with the Earth have been on my mind. Walking through this dramatic change in air temperature made me realize that I was experiencing the albedo effect. 

Albedo is the fraction of incoming solar radiation reflected back (instead of being absorbed) by an object. The term “albedo” comes from the Latin for whiteness. The albedo effect is a measure of how much of the sun’s energy is reflected back into space. This is one of many factors that affect the warming of the atmosphere. Solar radiation passes through our atmosphere, strikes the ground and is either reflected back into space or absorbed and re-radiated as heat. So a surface with high albedo that reflects a lot of the solar radiation warms the atmosphere less (if at all) than a surface with low albedo that absorbs solar radiation and transforms it into heat.

Lonesome lake near Mt Kinsmen in the White Mountains. The ice kept this area cooler-albedo! -Sue Pike

When I realized what I was feeling, I got so excited. It was like I was walking through one of my science class experiments. I really wished my students were there with me so we could experience albedo together. Walking through the forest, or further up the mountain, the incoming solar radiation (short wavelength energy) was being absorbed by the dark green forest and granite and changed into longer wavelength energy (heat).  The atmosphere was heating up and we felt warmer. By the lake, that incoming solar radiation was reflecting off the ice, bouncing off at the same wavelength, there was no conversion to heat and so the immediate area was cooler. I can talk about this phenomenon in class, but imagine how cool it would be (pun intended) to be standing next to a big ice-covered lake mirror and make this connection.

Why care about albedo? It is a huge regulator of Earth’s climate. Understanding albedo helps us understand why we are experiencing accelerated warming of the poles. As temperatures warm and ice melts, the open ocean with its low albedo replaces ice cover that has a high albedo, increasing the amount of solar radiation transformed into heat, increasing the temperature. This is a positive feedback loop that only ends when the ice disappears. We are, in effect, rapidly losing a giant northern mirror that reflects solar radiation back into space before it can be turned to heat.

Examples of climate feedbacks, like albedo, are all around us. I guess this is obvious, but it hasn’t always been so to me. Until I learned what albedo was I wouldn’t have recognized what I was experiencing on that hike. I wouldn’t have gotten so excited. This, for me, is one of my biggest motivators as a teacher and a learner. The more we understand the science that underlies the world around us, the better we can appreciate it, which might just motivate us to protect it. 

Ice is Magic

published Feb 5, 2020 in the York Weekly, Portsmouth Herald and Foster’s Daily and online at seacoastonline.com

I spent almost the entire first semester last year having my freshmen STEM class run experiments about ice. Every morning, when I walk my dog, we follow a path along the river and observe the ice, marvel at the huge slabs of ice that are carried downstream and stacked like pancakes in some places, crunch our way over the paper-thin ice that coated the hummocks of the floodplain after the last brief thaw, watch dangling orbs of ice form in the waterfall that spills down to feed the river. I, like so many others, am obsessed with ice.

If you think about it, ice formation on a pond or lake is fairly straightforward. As the water gets colder, it gets denser and starts to sink. Liquid water reaches its maximum density at 4 °C (39.2 °F), after that it continues to get colder and freeze solid, but as it freezes, it becomes less dense and floats to the surface and we end up with ice-covered lakes.

Ice slabs pile up in Little River

At first, the ice is paper-thin, fragile sheets that crumble in your hand. As winter’s cold progresses, the ice gets thicker and thicker as more ice is added from the bottom. As long as the pond or lake is deep enough, there should always be at least some liquid water underneath the ice. This is very helpful to the animals that live in the pond or lake. They can survive in the liquid water near the bottom until the spring thaw.

Now, think about a river or stream in which the water is constantly moving. All of that turbulence makes it difficult for a nice sheet of ice to form. On cold winter nights, the surface water of a river cools, crystals of ice form and start to grow. The constant water movement keeps the crystals from growing together into a solid sheet, instead you get a slushy mixture of water and ice called frazil ice. You can see this floating on the top of a river in early winter, or instead of floating on top, because the crystals are so small, they can easily be carried by the turbulence down to the bottom of the river.

Ice slab close-up with river behind it

As temperatures continue to drop, the frazil ice can start to join together at the surface and form round plates of ice with upturned edges (from the plates bumping together). This is called pancake ice. Or, what was more common on my river, ice will start to form along the edges of the river. Ice forms more easily along the edges because there is typically less water movement and the temperature of the shallow water on the edge cools faster. This is called border or shore ice. Border ice will generally enlarge toward the middle of the river until the ice from both sides meet.

Border ice forms along a small stream

Another interesting way a river can freeze is when the frazil ice that is transported to the bottom of the river attaches to the streambed and builds from the bottom up. This is called anchor ice. Anchor ice can grow very rapidly and block the flow of a river or stream causing local flooding. If there is particularly low flow of water along the bottom, an enormous amount of anchor ice can build up. This can be extremely harmful to aquatic life because the anchor ice can physically lift up parts of the streambed and move it downstream, movement akin to the action of a bulldozer, killing small fish and aquatic invertebrates (like dragonfly or caddisfly larvae) that live in the streambed, or freezing fish eggs that were waiting for spring to hatch.

I thought I first fell in love with ice in some dramatic location, perhaps when I crossed Lake Champlain on the ferry one cold winter’s night and watched the prow cut through the ice and listened to it grind against the hull of the boat, or when I was travelling as a National Geographic Grosvenor Teacher Fellow in the Arctic Ocean and witnessed firsthand the ethereal beauty of icebergs and the vast expanses of pack ice in the polar sea. But watching the beautiful, ever-mutable ice along my little river this winter has made me realize that I’ve loved ice since I was a kid watching icicles dangle from the gutters of my house, that no matter where you find it, ice is magic.

In winter’s cold, the subnivean zone is abuzz

Published January 21 2020 The York Weekly, Portsmouth Herald and Foster’s Daily and at seacoastonline.com Titled ‘Nature News’

The subnivean zone lies between the snow and the earth.

This winter has been troublesome; a few weeks ago it was so cold my pipes froze, then it we climbed to unseasonably warm temperatures, then some more snow, and now, very cold again-my pipes continue to freeze. One thing that makes me happy is that we have a nice layer of snow on the ground, insulation that is is vital to the survival of many of the plants and small mammals, even microscopic life forms, that are essential parts of our Northern ecosystem. So, for many, the recent snow was welcome relief from the cold.

While the surface seems empty, underneath, at the interface between ground and snow, a veritable city is rising. Old leaves and branches hold the snow up, creating an open space. The ground also radiates heat, warming the overlying snow, which instead of melting sublimates (when a solid turns into a gas without first becoming a liquid) directly into water vapor. Both of these processes leave a space between the snow and the ground, called the subnivean zone.

The word “subnivean” comes from the Latin for under (sub) the snow (nivean) and is a scientific term referring to the open passageways that form under deep snow.

Six or more inches of snow are all that are needed to trap the earth’s heat and allow a subnivean zone to form. This zone remains humid because of the transformation of snow into moist water vapor and is capped by a layer of ice that acts as an insulating roof. The temperature of the subnivean zone is generally a constant 32 degrees, protecting species that would otherwise freeze.

The most common inhabitants of the subnivean are mice and voles — they make tunnels under the snow connecting sleeping areas and sources of food. Red squirrels also burrow into the subnivean to stash food. Entrance holes to these networks allow carbon dioxide to escape. Carbon dioxide is released when these animals breathe and by the ground itself. Without the entrance holes to serve as ventilation shafts, carbon dioxide could build up to lethal levels.

While the subnivean zone provides protection for mice and voles, it is also the hunting ground for the short-tailed weasel (or ermine), a weasel that, except for its black-tipped tail, turns snowy white in the winter. This small weasel, just the right size to live and hunt in the tunnels under the snow, is a major predator upon small rodents.

All you need is about 6 inches of snow to allow the subnivean space to form

Recent research has unearthed a whole new category of inhabitants of the subnivean zone — microbes that are proving to be important players in the cycling of both nitrogen and carbon dioxide between the earth and the atmosphere. A deep snowpack with an active subnivean zone appears to encourage a healthy microbial population that, through respiration, releases significant amounts of carbon dioxide into the atmosphere. Studies suggest that as much as half of the carbon taken up by plants in the summer is released back into the atmosphere by microbes in winter (Paul Brooks, University of Colorado Boulder). At the same time these microbes, by processing and storing nitrogen, fertilize the soil as the snow melts.

Without a healthy snowpack, without these snowpack microbes, plants don’t do as well come spring. While these microbes may be releasing a lot of carbon into the atmosphere during the winter, they are also necessary for healthy plant growth — plants that will absorb carbon dioxide throughout the growing season.

For all these reasons, it seems to me, a nice deep snow, serving as an insulating blanket on the earth, is a welcome part of our northern winter.

Nature News: New England forests will have to evolve with climate

published January 15 2020 in the York Weekly, Foster’s Daily and the Portsmouth Herald and on seacoastonline.com

Dryad emerging from an old dead tree. Dryads protect and die with their trees. I wonder what they are thinking as our forests succumb to climate change-who do they go after? All of us who use fossil fuels?

This past weekend was unseasonably warm. Record-breaking in fact, for New England, with temperatures a good 7 or 8 degrees warmer than past records.

It seemed like everyone was out taking advantage of the balmy weather to take a walk in the woods. I headed up a side trail on Blue Job Mountain and while working my way up a slushy streambank looked across a clearing and saw something I had never seen before. There, in an old broken-off tree stump was a figure, made of wood, that looked to be climbing out of the tree.

The tree must have been felled relatively recently because the wood was still a bright orange-brown, a splash of color surrounded by the snow-covered pines and oaks. It looked raw and newly exposed. Sunlight hadn’t gotten to it yet (ultraviolet rays break down the cellulose in wood, bleaching out the color, giving it a silvery gray sheen). This figure that I, rationally, knew was just a random carving of the wood into human form, looked back at me. I knew it was just wood, but it still was magical. I could see how people from many different backgrounds, from all over the world, have believed that there are spirits that inhabit trees, so for a moment I believed a wood spirit was looking back at me.

Trees have lives that follow vastly different time scales from ours. They usually live much longer than we do and don’t move as we do. They are root-bound. They only move by reproducing, by sending their seeds out ahead of them into new territory. This warm weather was a reminder to me of their vulnerability. How is the rapid warming of our Earth going to affect the forests of New England?

A little over ten thousand years ago, the glaciers were receding and trees were re-colonizing New England. Slowly their seeds were carried or blown north and slowly they colonized the newly formed earth. This is a process called succession. When there is no dirt (as when glaciers had scoured all the dirt from the land), first lichens and mosses colonize bare rock, break into it and build soil. Then grasses and small plants move in, followed by shrubs, followed by fast-growing, light-loving trees, followed finally by the trees of a mature forest – the beech and maple, pine and oak of our temperate, deciduous forests.

Now, as conditions shift, as it warms, many of these trees need to move north or die. According to Mass Audubon’s “Effects of Climate Change on Woods & Forests,” a general rule of thumb is that “most tree species can colonize habitat beyond their existing range at a rate of 100 km in a 100 years (about 62 miles per 100 years). Some species will be able to move that fast, but warming temperatures will likely require forests to shift by 400 to 600 km (about 250 to 370 miles) by 2100, a rate faster than most species can tolerate.”

One of my favorite types of tree spirits are the Dryads. I first read about these as a child in the classic Bullfinch’s “Mythology.” According to Bullfinch, Dryads are nymphs or spirits, bound to particular trees, caretakers of the trees.

“Dryads or Hamadryads, were believed to perish with the trees which had been their abode and with which they had come into existence. It was therefore an impious act wantonly to destroy a tree.” I guess the caretaking days of my Dryad were over. Her tree had been felled by age or a wind storm. Perhaps that is why she was stepping out of the tree?

Susan Pike, a researcher and an environmental sciences and biology teacher at St. Thomas Aquinas High School, welcomes your ideas for future column topics. She may be reached at spike3116@gmail.com. Read more of her Nature News columns online.

Chickadee-dee-dees!

published Dec 25, 2019 the York Weekly, Portsmouth Herald, Foster’s Daily and seacoastonline.com

I think if you ask any New Englander to name the top three birds at their feeder, the chickadee would be on everyone’s list. I also think that of any of the common bird calls in our forest, the chickadee’s is the one most of us could easily identify. These tiny, round birds with a black cap and bib that contrasts with its white cheeks are found all over the northern parts of the United States and up into the middle of Canada.

black-capped chickadee

When not living in the suburbs you can find them in deciduous and mixed forest, almost any kind of open woodlands, as well as thickets. When we clear forests for agriculture or development, we are increasing the amount of forest edge – a habitat type that chickadees love (unlike something like an ovenbird that requires deep woods for nesting).

The black-capped chickadee (Poecile atricapillus) is one of seven species of chickadees found in the United States. They all have similar body shapes with sometimes subtle differences in color or streaking on their heads. For example, the boreal chickadee (the other New England chickadee) has a brown cap and cinnamon flanks and a more northerly range, preferring the boreal forests of Canada and the mountains of New England.

Chickadees probably do so well with humans due to their flexibility and curiosity. They are highly social birds that are quick to explore new environments and take advantage of resources (they will usually be the first bird to use a new feeder). According to the Cornell Lab of Ornithology, one study found that “every autumn black-capped chickadees allow brain neurons containing old information to die, replacing them with new neurons so they can adapt to changes in their social flocks and environment even with their tiny brains.” They really do have tiny brains, which makes their ability to memorize that much more remarkable. They often hide food for later use and can remember thousands of hiding places!

Try listening to their calls. They actually have a very complex language, much more than the obvious chickadee-dee-dee. They can communicate information about other flocks, predators and foraging information. For example, they add ”-dees” to their chickadee call to indicate higher threat levels.

From the number that show up at my feeder every day one, wouldn’t know that we are in the middle of a mass extinction of birds. A recent Science Magazine article recently reported that there has been a 29% decline in birds in the United States over the past 50 years (that’s almost 3 billion fewer birds on the North American continent today compared to 1970!). While chickadees aren’t considered endangered, or even threatened at this point, their distribution is expected to shift and their numbers decline due to ongoing climate change. A 2017 report by Massachusetts Audubon predicted that by 2050 the black-capped chickadee population is likely to disappear from coastal areas of Massachusetts and decline substantially throughout southern New England as rising temperatures push their range to the north.

For now, if you want to attract chickadees to your backyard, provide feeders (they are one of the easiest birds to attract to a feeder), black-oil sunflower seeds and suet will do the trick, and some standing dead trees for cavity nesting sites (they also like nest boxes).

While chickadees are around all year, I think of them as winter birds. Watching them at my feeder as snow lightly falls is a wonderful way to welcome winter in New England.

Susan Pike, a researcher and an environmental sciences and biology teacher at St. Thomas Aquinas High School, welcomes your ideas for future column topics. She may be reached at spike3116@gmail.com. Read more of her Nature News columns online.