The rapid melting of the Greenland Ice Sheet is part of a “positive feedback loop” with potentially catastrophic impacts from climate change. (Source: NASA)
The Arctic and Antarctic regions have been bellwethers for climate change for decades, as both the north and south polar regions have been warming at nearly four times the average global rate.
This Arctic amplification, as it’s known in the Northern Hemisphere, is linked to the melting of the Greenland Ice Sheet, which has accelerated over the last couple of decades with no slowdown in sight. And Greenland still has a lot of ice left to melt—at least for the time being. If all the ice were to melt on the Greenland Ice Sheet, sea levels would rise by 7 meters!
What’s going on
As highly reflective polar ice and snow melt, they expose a darker surface underneath them (water or land), which then absorbs solar radiation rather than reflecting it back to space. The absorption of heat energy at the earth’s surface further warms the atmosphere, which causes more ice and snow to melt in an increasingly rapid cycle. The additional moisture in the atmosphere from higher temperatures and the evaporation of melted ice also contributes to the warming process because water vapor is a very efficient greenhouse gas.
This whole sequence is an example of a positive feedback loop: global warming melts ice, thus reinforcing global warming, which amplifies ice loss. In its most extreme state, some believe it could lead to a runaway greenhouse effect where atmospheric temperatures soar to more than 900° C and boil the oceans away—but not for another 3 billion years. Still, there’s nothing positive about this positive feedback loop when it comes to our climate and environment, even now.
A 2017 research study noted that the last 47 years of data has uncovered dramatic change in nine different indicators, such as an increasingly fast hydrological cycle (precipitation, evaporation, precipitation) and reduced ice thickness. On Greenland, the melting ice is uncovering permafrost, which is soil (land mass) that has been frozen year-round for the last 3 million years.
Before the permafrost was frozen, plants grew and animals thrived there. When those life forms died, their carbon-based molecules (carbon dioxide and methane, to name two) were trapped in the soil, a phenomenon called a carbon sink. But as the permafrost starts to melt, that trapped carbon and water are released, further exacerbating climate change worldwide by releasing greenhouse gases.
An estimated 50% of the world’s carbon trapped in soil exists in the Arctic. The thawing, collapsing permafrost also affects the health of boreal forests in Arctic-adjacent areas and the other plants and the animals in those ecosystems, which could further impact the extent and capacities of carbon sinks in the region.
A weaker polar vortex
The Arctic amplification has also contributed to extreme weather farther south. As noted in a previous blog, the polar vortex, which is in the stratosphere—above where weather actually occurs—has been exhibiting weak states for longer periods of time during (boreal) winter over the last 40 years of available data. These weak states are manifested as polar and arctic air shifting farther south, contributing to intense snowstorms in the U.S., Europe, and Asia.
It's worth noting that the southward movement of that cold air also means additional warmth in the Arctic and a reduced ability to build ice back up during the winter before melting begins in earnest again in the warm season. This is another part of the insidious positive feedback loop mentioned earlier.
The resulting decrease in the pole-to-equator temperature gradient is also likely influencing the large planetary-scale waves in the atmosphere responsible for transporting weather systems across the mid latitudes. Not only do these waves act as tracks for weather systems, but the waves themselves also move.
Some studies have noted that as the Arctic continues to warm and the temperature difference between Canada and the Caribbean continues to decrease, these waves will become more frequently trapped. As the waves are unable to move as quickly around the globe, they’ll become more intense. The net result is that weather systems can impact the same area for longer periods of time. That can mean more numerous and more intense storms, floods, heat waves, wildfires—and cold and snow as well, at least for the time being. These slowing waves may also be impacting the speed with which tropical cyclones move and may have contributed to the record precipitation amounts from hurricanes Harvey (2017) and Florence (2018).
By now everyone should be concerned about the global warming that’s changing our climate. And we should be particularly concerned about regional warming in the Arctic, because it’s changing our world in unprecedented ways.