GlacierHub News Report 05:10:18

GlacierHub News Report 05:10:18

The GlacierHub News Report is a bi-monthly video news report that features some of our website’s top stories. This week, GlacierHub news is featuring an interview with Sophie Elixhauser, a new study on the Atlantic Meridional Overturning Circulation, a discussion of hazardous development in Nepal, and a theory about snowballs and slushies!

 

This week’s news report features:

 

East Greenland’s Iivit Communities: An Interview with Sophie Elixhauser

By: Natalie Belew

Summary: GlacierHub interviewed anthropologist Sophie Elixhauser to discuss her recently published book, “Negotiating Personal Autonomy: Communication and Personhood in East Greenland.” She shared her perspective of her time observing the Inuits in East Greenland. She explained that she began her research in East Greenland with a very broad question about how people relate to their environment.

Read her full interview here.

 

A New Low for the Atlantic Meridional Overturning Circulation

By: Sabrina Ho

Summary: A new paper published in Nature has shown that the Atlantic Meridional Overturning Circulation has decreased drastically in strength, especially in the last 150 years. Increasing freshwater input from melting glaciers and ice sheets in the Nordic and Arctic Seas have contributed to the slowdown. GlacierHub interviewed Wallace Broecker, a well-known geoscience professor in Columbia University’s Department of Earth and Environmental Sciences who coined the term “the great ocean conveyor belt.” He claims that there are dozens of “water hosing experiments” that simulated freshwater input of higher magnitudes coming from Greenland. “Still they failed to shut down the AMOC,” he said.

Read more here.

 

Communities in Nepal Expand to Risk Areas, Despite Hazards

By: Jade Payne

Summary: A recently published study in the journal Land has found that more than a quarter of the new houses in Pokhara, the second-largest city in Nepal, are being built in highly dangerous areas susceptible to multiple natural hazards, including glacier lake outburst floods (GLOFs) and avalanches. The study lists a number of challenges for this rapidly-growing city, located in a region with a number of geological hazards. Most of the newly settled areas are located in agricultural areas, which are attractive to prospective residents because they are flat and have owners who permit construction. However, these locations place new houses at great risk. The researchers indicate that this growth will continue until at least 2035.

Read more here.

 

Was the Earth Frozen Solid

By: Tae Hamm

Summary: Many scientists are coming up with hypotheses about a global ice age during the Cryogenian geologic period that took place between 720 to 635 million years ago. Two main hypotheses are on the table: “Snowball Earth” theory, which argues that ice covered the entire Earth, and “Slushball Earth” hypothesis, where the sea near the equator stayed open, allowing the evaporation and precipitation of water to persist. However, neither of these hypotheses are set in stone, but are rather part of an ongoing debate that requires much clarification. Developing different climate models with many parameters is necessary to better understand what happened during the Cryogenian period, giving flexibility to the ever-unknown complexity of past climate conditions. Moreover, careful study of the organisms that survived during this period could further help us understand the truth behind the Cryogenian ice age.

Read more here.

 

Video Credits:

Presenters: Brian Poe Llamanzares & Sabrina Ho

Video Editor: Brian Poe Llamanzares

Writer: Brian Poe Llamanzares

News Intro: Truyền hình SVOL

Music: iMovie

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Was the Earth Frozen Solid?

The movie “The Day After Tomorrow” depicts a catastrophic climate shift to global cooling, which is referred to as the new ice age. In the movie, melting of polar ice caused by global warming disrupts the North Atlantic current, rapidly dropping the ocean temperature, ultimately leading to the freezing of the ocean on a global scale. Although this over-the-top effect portrayed by this fictional film contains little scientific truth, many scientists are coming up with hypotheses about a global ice age during the Cryogenian, a geologic period that lasted from 720 to 635 million years ago.

Nearly 15 years later, research on glacial refugia has been heating up the debate about this ice age: a contention over the extent to which the glaciation covered the Earth. Two main hypotheses are on the table: “Snowball Earth” theory, which argues that ice covered the entire Earth, and “Slushball Earth” hypothesis, where the band of the sea near the equator stayed open, allowing the hydrologic cycle— evaporation and precipitation of water— to persist.

Image of how “Snowball Earth” might have looked like. (Source: New Atlas).

The term Snowball Earth was first coined by Joe Kirschvink, a geobiologist at CalTech in the late 1980s. The theory was based on the early observation that glacial deposits from this time were widely distributed on nearly every continent, some geologic evidence even suggesting glaciation at tropical latitudes. The abrupt change in the climate is rooted in the positive feedback loop, commonly referred to as the albedo (“whiteness” in Latin) effect. Simply put, as Earth cools and ice forms from the pole down to lower latitudes, the albedo, or the whiteness of the Earth increases, reflecting more solar radiation—just like a black t-shirt under strong sunlight gets hotter as black absorbs more heat, while a white t-shirt reflects all wavelengths of light.

Shortly after the concept of plate tectonics was developed, scientists noticed that, along with the albedo effect, the long-term carbon cycle kicked into high gear, making a double positive feedback. As the ancient supercontinent, Rodinia, broke apart, the newly created coastline in the low latitude intensified the weathering, as there was a more active water cycle assisting the chemical weathering of the rock. Silicate rock, which is a type of rock constituting the majority of the Earth’s crust, goes through a chemical weathering reaction that removes CO2 from the atmosphere. As the atmospheric CO2 was reduced, Earth became colder, as CO2, along with greenhouse gases, worked as blocking shields against the re-emitted heat from escaping the Earth. Moreover, because these broken up continents were in the low latitudes, they could not have prevented the advance of ice that formed in the poles, the coldest region on Earth, which would have created a completely frozen planet.

Simplified five stages of the “Snowball Earth” (Source: Sustainability Corps).

The critics of the Snowball Earth theory— professor Richard Peltier and his fellow colleagues at the University of Toronto and Texas A&M—published a paper refuting the hypothesis, in which they run a series of simulations that resulted in an equatorial belt of open water that may explain the survival of the organisms during the ice age, as well as the subsequent revival of numerous species.

The argument stems from the fact that the process of glaciation not only entailed positive feedback, but also one important negative feedback. As the climate got colder, the atmospheric oxygen would have sunk deeper into the ocean. As atmospheric oxygen spread deep into the sea, it bonded with the layer of old organic matter. This organic matter formed in shallow oceans and later drifted down to deeper waters, where it combined with oxygen, forming CO2. Carbon dioxide, released back into the atmosphere, would have warmed the Earth by the greenhouse effect, which would have defrosted Earth, stopping the ice sheets and glaciers from further advancing. Therefore, such negative feedback would have prevented ice from completely covering the Earth surface.

Model for “Slushball Earth” theory. The color gradient indicates the percentage of the ice coverage. It shows a band of the opened sea along the equator (Source: NASA-GISS/Columbia-CCSR).

Peltier provides another key evidence against Snowball Earth theory, the geographic region that allowed the survival of multicellular fauna and flora referred to as the “glacial refugia.” Had the Earth completely frosted itself, its harsh climate would have killed off many organisms. Moreover, complete reflection of solar radiation would have decimated photosynthetic organisms. Yet, there is no such geological indication that a mass extinction event occurred.

Image of different species that flourished during the Cambrian Explosion (Source: Discover Creation).

The debate of hard versus slushy Snowball Earth becomes more enigmatic at the end of the Cryogenic period and start of Cambrian, when the so-called “Cambrian explosion” of animal life occurs. The Cambrian explosion refers to a short interval during which many multicellular animals in diverse forms appeared on the surface of the Earth. Critics of Snowball Earth argue that such a dramatic increase in biodiversity within a short period of time would not have been able to happen in a hard Snowball Earth scenario, as many organisms prior to the explosion would have gone extinct. The supporters of Snowball Earth, on the other hand, argue that the biodiversity is simply the result of the robust micro-organisms that survived the Snowball Earth, evolving in size as well as anatomical complexity through time.

Neither of these hypotheses is set in stone, but rather are part of an ongoing debate that requires much clarification. To better understand what happened during the Cryogenian period, developing different climate models with many parameters is necessary, giving flexibility to the ever-unknown complexity of past climate conditions. Moreover, careful study of the organisms that survived Snowball Earth could further assist our understanding of this enigmatic period.

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Glaciers Harbor Life Over Millennia

Gyldenlove Glacier, Greenland. Photo by NASA Goddard Space Flight Center.
Gyldenlove Glacier, Greenland. Photo by NASA Goddard Space Flight Center.

Rock samples collected at the base of glaciers in Canada, Norway, Greenland and Antarctica have helped resolve a longstanding mystery: what were the energy sources that supported life in the distant geological past, when the earth was covered with ice?

The microorganisms in subglacial habitats may have taken energy from hydrogen molecules during the harsh Neoproterozoic glaciations, 750 to 580 million years ago, according to a new study in Nature Geoscience. This hydrogen may have been the key to their survival, the authors found.

During the Neoproterozoic glaciations, ice sheets covered the world for millions of years. These ice sheets gave this period its common name, “Snowball Earth.” These environments, previously considered inhospitable to life, have been found to sustain diverse ecosystems over millennia. Subglacial environments lack carbon and light, which usually serve as energy sources for life. In well-lit environments, organisms can use light to produce organic molecules that are used by organisms higher up in the food chain. Darker environments also have organic matter, often from decaying organisms which provide energy for organisms living within them. But in subglacial environments, organic matter is quickly depleted.

“A wide diversity of microbes inhabit vast ‘wetland’ areas beneath ice sheets and many glaciers but life certainly isn’t easy for them,” Jon Telling, lead author of the paper, said in a press release. “They have to contend with cold temperatures, high pressures from overlying ice, dwindling food supplies as washed-in soils and vegetation are consumed, and constant crushing as rocks embedded in glacier beds are ground against bedrock or sediment.”

Bear glacier - Canada. Photo by Dirk Van de Velde/Flickr.
Bear glacier – Canada. Photo by Dirk Van de Velde/Flickr.

Telling and his team reproduced the conditions at the bottom of glaciers in their laboratory to better understand how life survived in these subglacial conditions. They found that some combinations of minerals and physical conditions led to hydrogen being released from rocks.  Microorganisms grab hydrogen molecules, split the bond between the two hydrogen atoms in each molecule and use the energy in the bond for the biological activity, allowing them them to live and to reproduce.

Tests were conducted with six different types of silicate rocks from glacier sites in Canada, Norway, Greenland and Antarctica and scientists regulated experimental variables like the grain size, water content and temperature. The rocks were crushed much as they would be under a glacier, and each  type was found to produce hydrogen under the proper conditions. However, calcite, the rock the researchers tested as a control, did not produce hydrogen. This result confirmed the importance of silicate rock in the survival of microorganisms.

Though the environment in the laboratory is constructed to simulate the natural conditions, there are still many differences between experiment and natural conditions. For instance, the experiment condition is rather stable while the natural conditions vary significantly. The authors pointed out that these differences and other factors are likely to lead to an underestimation of the amount of hydrogen that would be produced in natural environments. In particular, they suggest that the short duration of the experiment and the possibility of escaping gasses during the experiments would add to such an underestimation.

Sediment beneath glacier ice and bedrock at Kiattuut Sermiat Glacier, Greenland. (credit: Eddy Hill)
Sediment beneath glacier ice and bedrock at Kiattuut Sermiat Glacier, Greenland. (credit: Eddy Hill)

The study indicates that hydrogen generated through mashing rocks that can provide a mechanism in support of continued microbial metabolism. The authors note that other researchers have proposed methane as the energy source used by prehistoric microorganisms, but they show that hydrogen could have been far more abundant, and would have been available for longer periods. This hydrogen could have supported food webs in subglacial refugia, in which organic matter produced by bacteria would have provided energy for eukaryotes–organisms whose cells have the nuclei which bacterial cells lack.

Though the ancient eukaryotes were tiny, simple organisms, they are of great importance because they are the ancestors of modern multicellular organisms, from sponges and jellyfish to worms and insects to fish, reptiles birds and mammals. It is remarkable to imagine that they survived planetary glaciations that lasted millions of years by consuming organic matter produced by bacteria—and that these bacteria survived by drawing on the energy in hydrogen molecules released from rocks crushed by ice sheets.

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