Yesterday we learned how poor climate models were because of their over-emphasis on man’s influence. Today we have a guest post on one alternate cause. See what you think.
The last ice age’s peak, known as the Last Glacial Maximum roughly 20,000 years ago, saw average global temperatures approximately 46 degrees Fahrenheit, as determined by a team led by researchers at the University of Arizona. This critical finding helps clarify the connection between greenhouse gases, with a focus on atmospheric carbon dioxide, and the planet’s overall temperature.
To gain a thorough insight into ice age climates, examining the impact of albedo is essential; specifically, the effect of dust-covered ice sheets on albedo sheds light on the complex climate mechanisms that operated during ice ages.
NASA Data defines albedo as the fraction of light that a surface reflects. “If it is all reflected, the albedo is equal to 1. If 30% is reflected, the albedo is 0.3,” explains My NASA. It’s imperative to take into account that albedo can have an impact on the climate, as it’s explained that the albedo of Earth’s surface, including the atmosphere, land surfaces, and ocean, determines how much incoming solar energy (light) is immediately reflected back to space.
According to the ‘ClimateBits: Albedo’ video, bright areas with snow and ice have high albedos, “meaning almost all the sun’s energy is reflected back to space at these locations.” The brightness of clouds and land surfaces contribute to the Earth’s climate — for temperatures to stay within the same range from year-to-year, ClimateBits explains that incoming solar energy must (on average), equal outgoing energy.
Fresh snow can have an albedo of 90%, meaning that 90% of the sunlight hitting a snowy peaked mountain translates to the same percentage reflected out to space. This amount is called the planetary albedo, and is calculated by averaging the albedo of all Earth’s surfaces. The UCAR Center for Science Education notes that understanding how much energy from the Sun is reflected back out to space as well as how much is absorbed becoming heat is valuable in understanding the planet’s climate. “If Earth’s climate is colder and there is more snow and ice on the planet, albedo increases, more sunlight is reflected out to space, and the climate gets even cooler.”
During an ice age, a reduction in the temperature of the Earth’s surface results in the presence of ice sheets and glaciers. There have been (at least) five ice ages within Earth’s history, though the most recent glaciation period reached its peak conditions some 18,000 years ago, “before giving way to the interglacial Holocene epoch 11,700 years ago,” History.com notes.
History delves into what the ice was like at the height of the recent glaciation, explaining that it grew to more than 12,000 feet thick with sheets spreading across Canada, Scandinavia, Russia, and South America. “Corresponding sea levels plunged more than 400 feet, while global temperatures dipped around 10 degrees Fahrenheit on average and up to 40 degrees in some areas.”
The impact of dusty ice sheets
The National Snow and Ice Data Center (NSIDC) explains that extracted ice cylinders show evidence of atmospheric composition in addition to volcanic eruptions, dust storms, and wind patterns, effectively allowing scientists to “reconstruct past worlds.” Measuring past temperatures can also be achieved with an oxygen thermometer, with the NSIDC explaining that ice cores extracted from polar regions reveal past temperatures via the ratio of heavy to light oxygen isotopes. “The fewer heavy isotopes in a polar ice core, the lower the ancient temperature.”
Research published in Geoscience Frontiers in 2016 explores the modulation of ice ages via precession and dust-albedo feedback, presenting a novel proposal for the modulation and rhythm of ice ages and interglacials during the late Pleistocene. From the research comes several key highlights. For example, highlights identify albedo as the primary feedback system regulating ice-age glaciation, and it’s further noted that albedo modulation is “controlled by desertification and dust contamination of ice sheets.” Another highlight of the research points out that low CO2 concentrations result in desertification and dust productions.
A study by Dr. Daniel Baggenstos at the University of Bern and colleagues explored the contribution of different factors during the transition from the last ice age to the current interglacial period, ultimately finding that albedo was the largest and responsible for about half of the warming. Changing CO2 concentrations and other greenhouse gasses were responsible for 37%, and reductions of the amount of reflective dust (and other aerosols) in the atmosphere made up 13%.
The effects of dust on ice sheets today
The American Museum of Natural History cites geologist Ro Kinzler, who points out that we are currently living in an interglacial period in an ice age now, called the Pleistocene Ice Age. Kinzler notes that the Pleistocene Ice Age has been going on since around 2.5 million years ago, though some believe it’s part of an even longer ice age that started “as many as 40 million years ago.” While much of the Earth was covered by ice sheets during the last glacial period, today, there are only two in existence — the Antarctic ice sheet and the Greenland ice sheet.
Winter ice seen around the world is nothing compared to the ice sheets of today. Seasonal ice, for example, can present as a cold weather hazard for businesses in a variety of ways, from a loss of business due to inaccessibility from snow and ice blocking routes to increased employee sick days from injuries due to falls. As such, the safe removal of ice is imperative in order to increase safety on commercial properties, and should serve as part of a winter weather plan. While seasonal ice can include ice that is transparent (thus making it incredibly dangerous when on roads or walkways), the ice sheets of Greenland and Antarctica are incredibly different.
In fact, Antarctica’s ice sheet alone is between 1.6 and 6.4 kilometers thick (equivalent to one and four miles). Regarding the differences between the two, National Geographic notes that the Greenland ice sheet interacts “much more dynamically with the ocean” than the Antarctic sheet, while the annual snow accumulation rate is more than double that of Antarctica. To further address the differences, it’s noted that glacial melt occurs across about half of the Greenland ice sheet, while it is more isolated on the far western part of Antarctica. Additionally, Greenland’s ice shelves are noted to break up faster than those surrounding Antarctica.
A research article published in 2015 by T. Goelles, C. E. Bøggild, and R. Greve explores the impact of dust on ice sheets, particularly in regard to ice sheet mass loss due to dust and black carbon accumulation. The abstract of the article points out that aerosols (such as mineral dust) and black carbon (soot) accumulate on the surface of the ice, resulting in a darker surface and lower albedo. “The darkening effect on the ice surface is currently not included in sea level projections, and the effect is unknown,” states the research, which goes on to present a model framework that includes ice dynamics, aerosol transport and accumulation, as well as ‘the darkening effect on ice albedo and its consequences for surface melt.’ While the model was applied to simplified geometry resembling the conditions of the Greenland ice sheet, the research highlights the need for additional research within the field when it comes to the Earth’s ice post-industrial revolution.
Ice age climates are incredibly complex, with albedo and reflected energy a core component to our planet’s energy balance and climate. Dusty ice sheets further underline the role that albedo plays, by altering the albedo and thus playing a valuable role in aspects of ice age climates where temperature is concerned.
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