The First Snowball Earth?

by Emil Morhardt

When did the first ice on Earth occur? About the only way to find out is to find old rocks with evidence of glaciation then determine exactly how old they are. A type of rock characteristic of glaciation is diamictite, a conglomerate-like mix of rocks with a large range of sizes held together with clay or mud that has been metamorphosed into mudstone. The large range of intermixed sizes in these deposits indicates lack of the size sorting that occurs in a river bed or floodplain, so some other source of disruption must have occurred, one of which is being scraped off and bulldozed along by a glacier. David Zakharov at the University of Oregon with a team of scientists from around the world (Zakharov et al., 2017) reasoned that if they could find examples of this type of rock that had formed near the equator, and could demonstrate that the water the rock encountered during formation came from glacial meltwater, then, they would have proven that at the time there were glaciers near the equator.  Continue reading

Relationships Among Gender, Science, and Glaciers

by Becky Strong

In 2016, Mark Carey, M. Jackson, Alessandro Antonello, and Jaclyn Rushing from the University of Oregon wrote an article discussing the relationships among gender, science, and glaciers, a topic which they believe is understudied. Glaciers play a major role in climate change, and the authors believe that their common representations have removed their social and cultural context, leaving them to be portrayed as nothing more than “simplified climate change yardsticks and thermometers” (Carey et al. 2016). Continue reading

New Model Predicts How Debris-Covered Glaciers Will React to Climate Change

by Lindsay McCord

Glaciers are vulnerable to melting due to climate change, however debris-covered glaciers respond differently to changes in temperature due to insulation from the debris. A new model factors in this variable for debris-covered glaciers in order to predict how these glaciers will react to a changing climate. Focusing on the Khumbu Glacier in the Himalayas of Nepal, the model predicts a loss of 8-10% of total glacial mass by 2100 followed by increased losses as the tongue (frontmost part of the glacier where debris accumulates) separates from the rest of the glacier. This separation process exposes more surface area of the glacier which causes accelerated loss of mass. Continue reading

Will There Be No More Snows of Kilimanjaro?

by Pushan Hinduja

Mount Kilimanjaro is located 300 kilometers south of the equator in Tanzania, and reaches an altitude of almost 20,000 feet. More than half a century ago, Hemingway vividly depicted the beauty and “whiteness” of its glimmering ice sheets in “The Snows of Kilimanjaro”. Today, however, evidence indicates that the famed ice sheets of Kilimanjaro might disappear by 2020. Soon after these scientific reports were released, scientists around the world attributed the decline to global warming, and looked to the ice fields that Hemingway had depicted as a reinforcement to the imminent danger of climate change. Continue reading

Past Polar Ice-Sheet Mass Loss Contributes to Sea-Level Rise

by Grace Stewart

Understanding of global mean sea level during past interglacial periods has greatly improved, but many challenges remain. By using coastal records and oxygen-18 proxy data, Dutton et al. (2015) determined global mean sea level and the contribution from polar ice sheets during three past interglacial periods. Although the results were uncertain, it was determined that global mean sea level was higher than modern day levels in every interglacial period studied—the mid-Pliocene warm period 3,000,000 years ago, the marine isotope stage (MIS) 11 400,000 years ago, and MIS 5e 125,000 years ago. Previous findings were corrected by taking glacial isostatic adjustment (the adjustment of the earth for a long time after a period of deglaciation), dynamic topography, and ice sheet reconstructions into account. Continue reading

Are Glaciers More Than Just Ice in the Human Psyche?

by Jassmin Del Rio

There exist cultures in which glaciers and mountains are associated with deities and hold tremendous spiritual importance to the people that live near them. Climate change itself has cultural and spiritual ties that are, unfortunately, often overlooked by scientific communities. By holding scientific information regarding climate change above all else, spiritual data are left out and, often, not even thought about. Allison points out that there may be considerable value in looking at the climate change issue through humanistic lenses instead of just scientific ones. It is a moral and ethical issue as well as a scientific and economic one, especially for those most directly affected by the changes. Spiritual affiliation could prompt more people to actually take action and educate themselves on the climate change crisis, which would be helpful in alleviating it. Continue reading

July 2012 Greenland Melt Extent Enhanced by Low-Level Liquid Clouds

Increased glacier melting due to global warming can have serious global consequences. Run-off from this rise in melting contributes to sea-level rise around the world which puts communities or even whole countries at risk of permanent flooding in the future. In July of 2012 the Greenland ice-sheet (GIS) experienced an enhanced period of melting that had not been observed in past years. Using various methods to record the melting and local temperature it was determined that low-level liquid clouds were the main factor causing the decrease in the ice-sheet (Bennartz 2013). These clouds were of a particular thickness that allowed them to trap heat while allowing in enough solar radiation to heat the surface of the glaciers. These clouds are part of a positive feed-back loop in which global warming has already contributed to ice melt in the arctic, putting more water into the atmosphere which contributes to the low-level liquid clouds. These clouds then further enhance the melting contributing to more of these types of clouds. Using multi-channel microwave measurements, the researchers were able to determine that these clouds can cover up to 20-50% of the arctic (Bennartz 2013). –Andrew Walnum 

Bennartz, R., Shupe, M., Turner, D., Walden, V., Steffen, K., Cox, C., Kulie, M., Miller, N., Pettersen, C., 2013. July 2012 Greenland melt extent enhanced by low-level liquid clouds. Nature 496, 83-86.

                  R. Bennartz and his colleagues used many different methods for observing melting and the low-level liquid clouds. Ground-based data were collected using “infrared, microwave, radar and lidar remote sensing observation” as part of the ‘Integrated characterization of energy, clouds, atmospheric state, and precipitation at Summit’(ICECAPS). These data were then compiled to plot the amount of ice melt for the Greenland icesheet. Based on cloud data the researchers were able to develop a model to explain the effects of low-level liquid clouds.
                  The results revealed that on days when low-level liquid clouds were present temperatures were able to rise to or above 0 oC. Melting occurred on days when clouds were absent the GIS did not experience surface temperatures above melting temperature. Using a model which takes into account temperature, specific heat, height, air density, infrared flux, and time, the researchers were able to conclude that it was in fact low-level liquid clouds contributing to the rise in temperature and ice clouds. However, the low-level liquid clouds do not always contribute to rising temperatures. The thickness of the clouds determines how much solar radiation is reflected or trapped. When the clouds are thin enough they allow more solar radiation to pass through to the earth while still radiating the heat downwards. When this occurs, surface temperatures are essentially the same temperatures as the clouds.

                  The helps give important insight into future models of climate change in the arctic. The results from this paper show how important low-level liquid clouds are to surface energy balance (the amount of infrared energy that hits the GIS’ surface and is retained or reflected.) Modern climate models do not take into account how changes in the atmosphere will contribute to cloud cover which inhibits the models from recognizing feedback loops that might further contribute glacier and ice-sheet melting in Greenland.

Glaciation Cycles

Milankovitch theory postulates that Earth’s orbital variations are key to the nature of the glacial cycles. Milankovitch believed that 100 thousand year (kyr) forcings drove the glaciation cycle, however that 100 kyr marker is missing at the high latitudes of the Northern Hemisphere’s summer insolation. Earth’s orbit eccentricity does cycle nearly every 100 kyr, so there may be a possible link. Ganopolski and Calov (2011) use ice sheet models coupled with less advanced global climate models to calculate the glacial cycles of the past 800 kyr, in an effort to determine if there is a direct affect on ice sheet changes to 100 kyr eccentricity cyclicity. The authors tested their model until they were confident in its accuracy. They then tested whether holding CO2  constant created a change in glaciation patterns. The results suggested that eccentricity 100 kyr forcings are stronger below CO2 concentrations of 260 ppm. In these scenarios not only do ice volumes differ, but also glacial terminations occur along the 100 kyr cycle. Next, the authors held certain global forcings constant. When obliquity was fixed it was found to have weakened affects on many termination events, making results less robust during periods of low eccentricity. Fixing eccentricity resulted in the model failing in eccentricity levels below 0.02 and then resulting in being dominated by precession intervals when above 0.05. At eccentricity levels of 0.03 and 0.04 with low CO2 concentrations the model correctly aligned with reconstructed records, and also showed accurate termination periods. Overall, the authors determined that there is an underlying forcing of 100 kyr, but are open to the idea that there are many factors that drive glaciation cycles. –Mathew Harreld
Ganopolski A. and Calov, R. 2011. The roloe of orbital forcing, carbon dioxide, and regolith in 100 kyr glacial cycles. Climate of the Past 7, 1415–1425.

            Milankovitch theory postulates that Earth’s orbital variations are key to the nature of the glacial cycles. Milankovitch believed that 100 thousand year (kyr) forcings drove the glaciation cycle, however that 100 kyr marker is missing at the high latitudes of the Northern Hemisphere’s summer insolation. Earth’s orbit eccentricity does cycle nearly every 100 kyr. It has been calculated that the affect of this change is very miniscule, especially compared to other orbital forcings. Eccentricity is also driven at a 400 kyr cycle, but this forcing is completely missing from available ice records. It has been proposed that many factors come into play to drive this 100 kyr cycle, and that those factors hide the true 100 kyr pattern. Ganopolski and Calov use ice sheet models coupled with less advanced global climate models to calculate the glacial cycles of the past 800 kyr, in an effort to determine if there is a direct affect on ice sheet changes to 100 kyr eccentricity cyclicity.
            The model used by the authors was started at 860 kyr to allow for a 60 kyr calibration time. 860 kyr was chosen because it most closely resembled current interglacial levels. If they had started at 800 kyr they would have begun the experiment near the last glacial maximum, making it difficult to start calibration. Using the current condition data the model for each experiment was run from 860 kyr to 800 kyr, and for each experiment the 60 kyr spin-up data was not recorded.
            The first experiment run was their baseline, running realistic changes in all parameters. The significance of this experiment was to test the accuracy of the model over the 800 kyr, comparing it to reconstructed data from the field. The model, overall, supplied accurate changes over the 800 kyr compared to the reconstructed data. Possible issues with the model were found, but were thought to be insignificant in answering their question. The model’s individual parameters were also tested, such as oxygen-18, CO2, and ice volume. Each parameter matched well with reconstructed data, and also matched cyclical peaks found in reconstructed data. Glacier extent maxima matched strongly with current theory, showing that North American glacier extent is dominant and is by a 100 kyr cycle. However, they also suggest that the model underestimates European glacial extents because of incorrectly estimating European glacial sensitivity to orbital forcings.
        The next experiment run was to hold CO2 levels constant to see the change in affect of 100 kyr cycles. CO2 concentrations were run from 200 to 280 parts per million (for every 20 ppm). The results found in this experiment suggest that eccentricity 100 kyr forcings are stronger below CO2 concentrations of 260 ppm. In these scenarios not only do ice volumes differ, but also glacial terminations occur along the 100 kyr cycle. However, it is important to note that glacial terminations can only occur if the deposition of glaciogenic , glacier generated, dust is taken into account. At times of glacial termination dust deposits in North America greatly increase, decreasing ice albedo and increasing ablation, increasing the rate of glacial retreat.
            In the next set of experiments orbital forcings were kept constant by removing each orbital forcing, while all other variables were allowed to change. When obliquity was fixed it was found to have weakened affects on many termination events, making results less robust during periods of low eccentricity. Fixing eccentricity resulted in the model failing in eccentricity levels below 0.02 and then resulting in being dominated by precession intervals when above 0.05. At eccentricity levels of 0.03 and 0.04 with low CO2 concentrations the model correctly aligned with reconstructed records, and also showed accurate termination periods.
            The next step in the study showed the importance of regolith (global sediment) in changing glacial cycles from 40 kyr to 100 kyr. The authors ran one model at set CO2 concentrations while also setting the distribution of terrestrial sediments to a higher level then present. The model supported the hypothesis that the removal of sediments from the North American continent resulted in longer term glaciation cycles—from 40 kyr to 100 kyr. The more terrestrial sediment present means albedo can be reduced sooner and to a greater extent, resulting in shorter glaciation cycles.
            The results presented by Ganopolski and Calov give support to a system that is dominated by 100 kyr eccentricity cycles. However, the authors remain open to the idea that the glaciation cycles are driven by many factors, such as CO2, regolith, other orbital forcings, and other factors. More simulations need to be built upon the findings of this study to further gain understanding in the long term forcings behind glaciations.