Glaciers are fascinating and important. They help to control water distribution and moderate Earth’s climate. Unfortunately, there is no doubt that most of the Earth’s glaciers are retreating due to climate change. These changes are expected to be harmful to humans, so mitigation strategies have been proposed and enacted. However, the effectiveness of these measures has been questioned and some pundits proclaim that a tipping point may already have been crossed. Luckily, new research on the global behavioural patterns of modern, retreating glaciers suggests that climate change mitigation efforts will have significant long-term benefits.
First some terminology on glaciers vs ice sheets. Both are formed from compressed snow that’s turned to ice. However, glaciers are much smaller than ice sheets, which typically cover entire continents; thus, ice sheets don’t care much about what the landscape is like below them. Glaciers, on the other hand, are constrained by the landscape, and typically flow through valleys. Glaciers sharpen the terrain; ice sheets flatten it. This post is only concerned with glaciers, because their small size makes them react faster to climatic changes. Thus, they are the canary in the coal mine (Figure 1).
Glacial retreat can be measured in several ways, most common methods are mass and area. A glacier’s mass balance is a description of changes in volume over time. (Units are usually metre water equivalent per year.) Area is simple: it measures what the glacier covers over time. To assess this, you can use lasers and satellites, but all you really need are some photographs (Figure 2).
Except for very few cases, Earth’s glaciers are melting and retreating (Zemp et al., 2015; Roe et al., 2017). Most of this retreat is caused by increased rates and intensity of summer melting (Zemp et al., 2015). For the past two centuries, most glaciers have been decreasing in area as well (Zemp et al., 2015); and these decreases have been exacerbated by human activity (Roe et al., 2017). One analysis shows that human activity accounts for ~35% of Earth’s glacial mass loss from 1851 to 2010 and that this increases to ~69% from 1991 to 2010 (Marzeion et al., 2014).
Impacts of ice loss:
Here is a short list of some impacts from the ongoing loss of Earth’s glacier ice:
- Glacial melt contributes to sea-level rise (Gregory et al., 2013).
- Loss or retreat of glaciers means no water for many people (e.g. Immerzeel et al., 2010).
- Glacier retreat sometimes diverts entire rivers (Shugar et al., 2017).
- Glaciers steepen the valleys they occupy and sometimes dam natural lakes. Thus, their retreat often causes landslides and catastrophic flooding.
- Occasionally, glacier loss can trigger increased earthquake activity.
- On a global scale, the loss of so much glacier ice decreases the planet’s albedo (its reflectivity). This forces Earth to absorb more solar radiation and exacerbates further climate change.
Discussion on glaciers and Climate change mitigation:
Here’s a sobering fact: for every kilogram of CO2 we emit, we lose about 15 kilograms of glacier ice. What’s a kilogram of CO2? It’s the average emission for every 500 meters of driving from a new car in Germany, in 2016. Yeah… the global retreat of glaciers is a bit scary, but it’s also useful. As Marzeion et al. (2017) point out:
“Their [glaciers’] geometric response to changes in atmospheric conditions is slow enough to filter out high-frequency weather and climate variability, but fast enough to provide humans with visible impressions of systematic changes of the environment, without the need for technical or statistical tools. Because of these properties, glaciers have become one of the key indicators of climate change…”
So, glaciers are screaming their giant, frozen canary death songs at us. If we were coal miners we would all be lightheaded and desperately staggering for the exit. This raises some questions. Since we can’t leave our planet, what can we do? Also, given the ever-increasing retreat of Earth’s glaciers, how well can we hope to maximize their preservation in the future?
Good questions. The best answer to the first seems to be improve education and awareness while advancing energy and agricultural practices/technologies. A new study helps answer the latter using clever modelling techniques. Marseion et al. (2018) used temperature and precipitation data to assess the future behaviour of glaciers in Earth’s changing climate. Sadly, their model showed that, given the greenhouse gasses that us dirty, industrious apes have already emitted, our glaciers are already obliged to lose about 36% of their current masses. However, the same model shows that reducing carbon emissions will have strong positive long-term effects. So, what we need to do is act now to reduce CO2 emissions.
Glaciers are retreating. This sucks because glaciers are important. They provide fresh water. They shape the landscape. They contribute to sea-level rise. They even help make the Earth shinny (albedo). Unfortunately, the best estimates show that we will continue to lose a lot of our glacier ice no matter what we do to try and stop it. However, attempts at climate-change mitigation will likely have strong long-term effects on preserving Earth’s glaciers.
Gregory, J. M., White, N. J., Church, J. A., Bierkens, M. F. P., Box, J. E., Van den Broeke, M. R., … & Konikow, L. F. (2013). Twentieth-century global-mean sea level rise: Is the whole greater than the sum of the parts?. Journal of Climate, 26(13), 4476-4499. https://journals.ametsoc.org/doi/10.1175/JCLI-D-12-00319.1
Immerzeel, W. W., Van Beek, L. P., & Bierkens, M. F. (2010). Climate change will affect the Asian water towers. Science, 328(5984), 1382-1385. http://science.sciencemag.org/content/328/5984/1382
Marzeion, B., Cogley, J. G., Richter, K., & Parkes, D. (2014). Attribution of global glacier mass loss to anthropogenic and natural causes. Science, 1254702. http://science.sciencemag.org/content/345/6199/919
Marzeion, B., Champollion, N., Haeberli, W., Langley, K., Leclercq, P., & Paul, F. (2017). Observation-based estimates of global glacier mass change and its contribution to sea-level change. Surveys in geophysics, 38(1), 105-130. https://link.springer.com/article/10.1007/s10712-016-9394-y
Marzeion, B., Kaser, G., Maussion, F., & Champollion, N. (2018). Limited influence of climate change mitigation on short-term glacier mass loss. Nature Climate Change, 8(4), 305. https://www.nature.com/articles/s41558-018-0093-1?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+nclimate%2Frss%2Fcurrent+%28Nature+Climate+Change+-+Issue%29
Roe, G. H., Baker, M. B., & Herla, F. (2017). Centennial glacier retreat as categorical evidence of regional climate change. Nature Geoscience, 10(2), 95. https://www.nature.com/articles/ngeo2863
Shugar, D. H., Clague, J. J., Best, J. L., Schoof, C., Willis, M. J., Copland, L., & Roe, G. H. (2017). River piracy and drainage basin reorganization led by climate-driven glacier retreat. Nature Geoscience, 10(5), 370. https://www.nature.com/articles/ngeo2932
Zemp, M., Frey, H., Gärtner-Roer, I., Nussbaumer, S. U., Hoelzle, M., Paul, F., … & Bajracharya, S. (2015). Historically unprecedented global glacier decline in the early 21st century. Journal of Glaciology, 61(228), 745-762. https://www.cambridge.org/core/journals/journal-of-glaciology/article/historically-unprecedented-global-glacier-decline-in-the-early-21st-century/2F1E3ACB111A03F9BA83D11439F5D681
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