Sea Ice Insulates the Ocean Beneath It


By Sue Pike / yorkweekly@seacoastonline.com
Posted Jan 2, 2018 at 3:44 PMUpdated Jan 2, 2018 at 3:44 PM
Sea Ice-pancake ice to be exact-in a local harbor

We have had a cold past week -- temperatures hovering down around 0 degrees Fahrenheit. It’s amazing to me that birds and other animals can tolerate these conditions with such seeming equanimity. Ducks hang out in icy water. And while wild birds prefer open water to drink, they can get what they need from snow or any food that has some water content (like insects and wild fruits) - but I worry anyway and sporadically put out little dishes of water around the bird feeders, which probably aren’t much help since they freeze so quickly. Kids are skating on the local ponds and the stream out back is gurgling under a bubble-strewn cover of ice, icicles dangling down into the rushing water beneath.
Salt water has a lower freezing point than fresh, but with these sub-zero temperatures it too is freezing over. Chunks of ice are accumulating in the harbor, pushed up against the dock and shore by waves and wind - seeing this, I can pretend I am looking down from an icebreaker pushing through sea ice near the north pole.
Sea ice can take on different forms and has different names to suit -- brash ice, grease ice, ice cakes, pancake ice. The sea ice I saw in the harbor was pancake ice, so named because it is roundish (like a pancake) with upturned edges. Pancake ice forms in rough seas. As the seawater begins to freeze, it forms tiny, millimeter-wide crystals called frazil. This thickening slush on top of the water (sometimes called grease ice) starts to solidify into sheets. Waves break the sheets apart and the edges of these smaller sheets (the pancakes) start to roll up as the pancakes collide with each other. These collisions also produce keels on the bottoms of the pancakes.
While sea ice isn’t common down here in the Gulf of Maine, up in the Arctic the seasonal ebb and flow of sea ice plays a fundamental role in the health of polar ecosystems and of our planet. Without it local conditions, even global conditions, will change. For example, as sea ice forms, salt is expelled from the mix -- this increases the salinity of the water causing it to sink down to the ocean floor. This sinking water flows along the ocean floor back to the equator as part of the global currents of water that move heat around our planet. The sinking water also mixes the water column resulting in nutrients rising to the surface. The sea ice dampens wave action near coastlines, protecting them from erosion. The loss of sea ice in the Arctic is causing coastlines to erode at an accelerated rate. Just as ice forms an insulating layer over our local ponds, sea ice insulates the ocean beneath it -- trapping heat (the ocean stores a lot of heat, which it gradually releases over the winter) under the ice. That layer of sea ice results in colder and drier conditions.
While sea ice might help to insulate the ocean beneath, it is also very reflective and has a net cooling effect on global temperatures. Sea ice has high albedo -- meaning it reflects a good amount of incoming solar energy back into space, helping to cool the planet. Because of global warming, the amount of Arctic sea ice has been diminishing, which in turn accelerates global warming. Because there is less ice to reflect incoming solar radiation and more open water to absorb it, the northern seas warm more quickly, more solar radiation is absorbed by the planet, and so the rate of global warming increases.
Sea ice is also vital to polar food webs. We’ve all seen photos of polar bears stranded and starving on tiny clumps of sea ice, unable to hunt for seals. Arctic sea ice, which is fast disappearing, is a critical habitat for a variety of large well-known animals like polar bears, seals, and penguins. But what most of us forget about are the little things -- for example, when sea ice melts in the summer it releases nutrients into the water that feed phytoplankton which in turn feed everything else in the polar seas.
The sea ice showing up in our local harbors is just a taste of that expanse of ice that is rapidly diminishing up north. Since satellites first started recording Arctic sea ice, it has lost more than half its volume -- it is getting thinner and covering less area every year.

Comments

Post a Comment

Popular posts from this blog

Image
NATURE NEWS 'Dead crabs' on beach are often just old exoskeletons Rock crab exuvia  Seapoint Beach Kittery Pt ME When my kids were little, one of their favorite things to do at the beach was to go crabbing - nothing official, no crab pots or bait, just their hands turning over rocks. As they got older they graduated to string with a hot dog off the dock. They’d always let the crabs go. They went crabbing because crabs are cool little animals, are fun to "race" and are a little scary to handle.  My kids learned early on the right way to pick them up to avoid getting pinched. The crab-related question I get most often is about all those dead crabs that wash up on the beach, their little bodies tangled in the wrack-line. The amazing answer to that question (at least to me) is that more often than not those aren’t dead crabs but rather their shed exoskeletons. Crabs belong to a group of invertebrates (arthropods) that have rigid exoskeletons, which provide
Read more

Yellow-bellied sapsuckers

Image
Nature News: Yellow-bellied sapsuckers really have yellow bellies Published May 22 2019  seacoastonline.com/Portsmouth Herald/the York Weekly/Fosters Daily Female yellow-bellied sapsucker lacks red throat.  Sue Pike photo I had hummingbirds show up in my yard well before many of the flowers had bloomed - usually once the quince bloom you can count on seeing ruby-throated hummingbirds shortly thereafter. This year the hummingbirds were first. While I don’t know for sure where they were getting their sugar supply (perhaps hummingbird feeders) an interesting fun fact is that hummingbirds will often follow yellow-bellied sapsuckers in their migration north. According to the Cornell Lab of Ornithology” “The sapwells made by Yellow-bellied Sapsuckers attract hummingbirds, which also feed off the sap flowing from the tree. In some parts of Canada, Ruby-throated Hummingbirds rely so much on sapwells that they time their spring migration with the arrival of sapsuckers. Other birds as we
Read more
Image
Nature News Puffballs: Mushrooms that house powdery spores By  Sue Pike yorkweekly@seacoastonline.com I really like puffballs, not the huge football-sized ones that are starting to show up in the lawns around my house (those are very cool) but rather the smaller, ping-pong sized ones that grow in the woods. The ones that ask you to touch them and shoot a puff of spores up and out into the world. Puffballs are an interesting group of mushrooms (the Gasteromycetes) that instead of exposing their gills and forcibly expelling spores into the wind, rely upon external forces to release and disperse the spores from the mushroom. Puffballs, as the name suggests, are typically spherical, ball-shaped or often pear-shaped mushroom that houses a mass of powdery spores inside. Most fungi that we typically call mushrooms are the reproductive part of a much larger underground network of cells (the mycelium), long strands of branching, thread-like hyphae that inhabit the soil or rotti
Read more