One of the biggest threats from climate change is sea level rise. Heightened sea levels threaten coastal communities, which are home to 39% of the population. A number of factors contribute to sea level rise, but one of the biggest contributors is melting land ice from countries like Greenland. Melting land ice is problematic because, unlike sea ice, it is not already part of the ocean system. Think of it like a full glass of water – if ice is already in the glass, its melting does not cause the glass to overflow. The volume of the ice is already accounted for, and as it melts, the volume does not change. However, if you add ice to the full glass, there is more water volume, and the glass will overflow.
Once land ice starts to melt, it becomes more likely that this ice will continue to melt. This is because of something called the ice-albedo feedback.
Let’s define some of these terms before we get into the nitty-gritty.
Albedo is a measure of how reflective a surface is, on a scale from 0 (absorbs all sunlight) to 1 (reflects all sunlight). Darker surfaces have lower albedo values, while lighter surfaces have higher albedo. For example, old asphalt has an albedo of about 0.1, while fresh snow has an albedo of about 0.75.
A feedback, also known as a feedback loop, is a process where one step affects the rest of the process. Feedback loops can be positive, meaning that the process intensifies; or negative, meaning that the process diminishes. Ice-albedo feedback is a positive feedback.
As land ice melts, the color of the surface becomes darker. Ice is whiter than the pools of water that form in it, as shown in the image above. Because darker surfaces have lower albedo, or absorb more solar radiation, they are hotter than lighter surfaces. Think of walking barefoot in summer – stepping on a blacktop is much more painful than a light-colored sidewalk. As the darker surface get hotter, it becomes much easier for the surrounding ice to melt. This is why ice-albedo is a positive feedback. Ice melts, the surface gets warmer, more ice melts, causing the surface to warm, so on and so forth.
Melting land ice and the effect of the ice-albedo feedback may seem like too big of a problem to solve. However, individual efforts can have an impact! One way to conserve energy is to always un-plug your phone and/or laptop chargers before you leave the house for the day. Did you know your chargers use energy when they’re plugged in, regardless of whether there’s a gadget on the other end? Unplugging them goes a long way in not only saving energy that is commonly generated by harmful fossil fuels, but it will also save you money on your energy bill.
To learn more about Earth’s climate and how it is changing, visit https://www.globalweatherclimatecenter.com/climate
©2018 Meteorologist Margaret Orr
Photo from NASA Earth Observatory