Geochemical Evolution of Meltwater from Glacier Snow to Proglacial Lake

Glaciers around the world are making headlines for their rapid retreat due to warming. Unlike some of these glaciers, however, dry valley glaciers, while accumulating only about 10 cm of snow annually, are neither retreating nor warming. Sarah Fortner, a geochemistry professor at Wittenberg University in Ohio, examined the meltwater of Canada Glacier, a dry valley glacier located in the Taylor Valley of Antarctica, and published a paper focused on two of its proglacial streams, Anderson Creek and Canada Stream.

Canada Glacier flowing into the Taylor Valley, Antarctica (Source: Anthony Powell).

Melting of glaciers develops an important part of a glacier’s anatomy known as “supraglacial streams,” which are conduits of water on top of glaciers. These supraglacial streams often become a source of water for “proglacial streams,” like the Anderson Creek and Canada Stream, narrow channels of rivers that issue from glaciers supply water to lakes located below the glaciers.

Fortner studied the meltwater of Canada Glacier during the 2001 to 2002 austral summer in the southern hemisphere (from November to March) and the contribution of the proglacial stream and glacial surface to water in Lake Hoare, which is located in front of Canada Glacier.

In her study, Fortner determines the crucial role of the wind in redistributing the geochemistry of the glacial surface as well as the two proglacial streams. By looking at the geochemistry of the two proglacial streams and the role of the wind in bringing valley sediments to the supraglacial and ultimately proglacial streams, Fortner found that the glaciers that contributed to the proglacial lakes are not dilute like glacier snow.

Large pond formed from supraglacial melt on the surface of Canada Glacier. (Source: Fortner)

Contrary to expectations, the chemistry between the two streams was quite different. “While they are roughly five miles apart, they were very different,” she told GlacierHub. “Located on the east side of the glacier, Canada Stream was teaming with life, with multiple mosses, lichen, algae, and invertebrates. If you were to press your hand into these, it would feel like a sponge. On the west side of the glacier, Anderson Creek looks barren in comparison. There is life in the stream, but not as abundant or diverse as the Canada Stream.”

In an attempt to find the source of the difference, Fortner and a team of scientists sampled water from supraglacial channels with high discharge for chemical analysis. Through this analysis, Fortner aimed to map the evolution of the chemicals in the meltwater at Canada Glacier from unmelted glacier snow to supraglacial streams to proglacial streams and finally to Lake Hoare located in front of the glacier.

Taylor Valley and Lake Hoare (Source: 77DegreesSouth).

With the chemical mass balance analysis of the samples from the glacier, Fortner first wanted to see whether the chemical composition of the supraglacial stream would be diluted like the unmelted glacier snow, their primary precipitation. According to Fortner, unmelted glacier snow would naturally be very dilute, with a low concentration of any chemical solute, and we would expect the same level of chemical concentration from the supraglacial streams, located on top of the glacier body itself and created as a result of glacier snow melting. However, she found that supraglacial streams were rich in major ions like calcium, sodium, and sulfate. 

“This begins to highlight the importance of wind-blown sediment as control of water chemistry in these Antarctic ecosystems,” Fortner said.

In her paper, she explains that the strong west to east Föhn wind (Foehn wind), a parcel of dry and warm air moving down the lee (downwind side) of the mountain, brought sediments from the floor of Taylor Valley, abundant with carbonate ( CO3(2-)) and gypsum (CaH4O6S) minerals, which are the sources of the high calcium (Ca2+) and sulfate ion (SO2-4) found in the supraglacial streams. In short, the wind delivered sediment that influenced the chemistry of the streams on the surface of the glacier.

Diagram of Föhn wind (Source: ipfs).

“Both sides of the valley floor contributed to the sediment received on the glacier surface which explained major chemical differences found in supraglacial and proglacial streams versus the original unmelted snow. It is also clear that the Föhn wind coming off of the ice sheet had the greatest influence on depositing chemistry,” Fortner explained.

Furthermore, the west to the east direction of the wind causes a difference in chemical composition between the proglacial streams in the western and eastern sides of Canada Glacier, preferentially depositing more sulfate in the western proglacial streams (Anderson Creek) than in the eastern proglacial streams (Canada Stream).

“As a result of the west to east wind, supraglacial streams flowing into Anderson Creek have much higher concentrations of both calcium and sulfate than supraglacial streams flowing into Canada Stream,” Fortner explained.

Map of the Ross Sea. Lake Hoare is located within the Taylor Valley, showing its proximity to Ross Sea. (Sources: USGSantarctic.eu).

The chemical deliveries from the stream channel to the proglacial lake is crucial to examine, as Anderson Creek contributes over 40 percent of the water to Lake Hoare, the final recipient of the meltwater from Canada Glacier, during the low-melt season. However, Fortner said it is just as important to examine the chemical deliveries from the glacial surface (direct runoff).

“While one would think streams would deliver far more chemistry, as glaciers and their direct runoff are typically dilute, glacier surface can be just as important source of chemistry because of the low accumulation and wind delivered sediment,” she added.

Dry valley glaciers are unique in that the glacier surface is an important contributor of chemistry to downstream ecosystems. Unlike many other glaciers, it isn’t just about chemistry from stream channels, but also about glacier surfaces. If more melt continues in response to the wind, this could result in potential changes in the chemical delivery into Lake Hoare. Furthermore, such changes can extend to the continental outline of Antarctica into Ross Sea, the southern extension of the Pacific Ocean.

 

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Small Particles Have Big Impact on Glacial Health

A recent study by Heidi Smith et al. in the desolate McMurdo Dry Valleys of Antarctica has shown that microbial life in biofilms is present across a large part of the region’s ice, suggesting that the stability of polar ice can be influenced by even the smallest of organisms.

Biofilms—thin, slimy bacterial layers that can adhere to a surface—were discovered in conjunction with the windblown dust that accumulates on snow and ice called cryoconite. The research found that a combination of biofilms and cryoconite is capable of enhancing the rate of glacial melting, meaning that the planet may be more vulnerable to sea level rise than previously imagined.

As an important component in the planet’s hydrological and carbon cycles, glacial melting affects sea levels and the chemistry of our oceans. This meltwater enhances the movement of fluids from terrestrial environments to oceans, as well as the transport of nutrients to aquatic ecosystems. In the McMurdo Dry Valleys, the activity of microorganisms on the glacier surface enables the accumulation of organic matter on minerals found in the ice’s dusty cryoconite layers. This relationship results in the darkening of ice over time, making it less efficient at reflecting incoming sunlight than it would be normally. As most of Antarctica’s ice lies atop the continental landmass,  increased melting at the Earth’s southern pole may lead to an appreciable rise in global sea levels.

A view of the Canada Glacier involved in the field study. (Source:Joe Mastroianni, National Science Foundation)
A view of the Canada Glacier involved in the field study (Source: Joe Mastroianni/National Science Foundation).

Prior research in alpine glacial environments and on the Greenland Ice Sheet (Langford et al. 2010) established a correlation between biofilm development and the darkening of cryoconite particles, pointing towards the synergistic possibility of biologically enhanced rates of melting. Until the recent publication of key research by Heidi Smith et al., the role of biofilms in Antarctica was largely unknown.

In conversation with GlacierHub, Smith stated that “the role of biofilms in different glacial locations has not been explored.” She added “due to differences in environmental pressures (temperature extremes, nutrient availability, levels of UV radiation, and rates of flushing), it is possible that the role of biofilms in glacial surface processes varies by location.” Smith’s team was able to establish the precedence of biofilms at extreme southern latitudes in their research and also contributed to the larger body of scientific evidence supporting the role of microbes in influencing reflectivity, otherwise known as albedo, of glaciers.

Smith and her research colleagues employed a variety of methods to investigate the interactions between the biological and mineralogical components of Antarctic ice. Microbial species were identified in the lab via pyrosequencing (which determines the order of nucleotides in DNA by detecting the release of the pyrophosphate ion) as well as epifluorescent microscopy (which utilizes a compound microscope equipped with a high-intensity light source). The team’s research yielded four unique bacterial components in biofilms found in cryoconite holes. Interestingly, Smith told GlacierHub that “while some organisms identified in this study have also been found in cryoconite holes from the Greenland Ice sheet, the relative abundance of individual organisms in each of these locations appears to be geographically distinct.”

transantarctic_mountain_hg
The Trans-Antarctic Mountains, a prominent feature in Northern Victoria Land (Source: Hannes Grobe/Alfred Wegener Institute).

The primary region for fieldwork and sampling for the study was an ice-lidded cryoconite hole on the Canada Glacier, located near Victoria Land, Antarctica. When asked about why the team chose to work in this isolated region, Smith replied: “There are previous studies from this region that have focused on cryoconite hole geochemistry, rates of microbial activity and microbial assemblage composition; therefore, we could place samples from this study into a larger framework.”

Following fieldwork on the glacier, subsequent laboratory analysis showed that enriched levels of nitrogen and carbon isotopes were present when Bacteroidetes (one of the four main bacterial phyla) was incubated in the presence of compounds such as sodium bicarbonate and ammonia. These findings point to the conclusion that the spatial organization within a microbially rich biofilm can promote the transfer of chemical compounds and nutrients. Such a result serves to validate the hypothesis that the formation of biofilms may enhance the accumulation of organic material on cryoconite minerals, thus affecting the color and reflectivity of glacial surfaces.

The study concluded that not only are biofilms present in nearly thirty-five percent of cryoconite holes in Antarctica, but that due to regional differences in the distribution of black carbon between the study region and the Arctic, biofilm may play a heightened role (relative to the northern hemisphere) in promoting biological activity on glaciers. Smith added, “In addition to influencing levels of glacial melt, biofilms have the potential to alter marine ecosystems through glacial runoff.” Additionally, she said, “There is also the potential for increases in CO2 release, which contributes to the rising temperatures globally.”

The research by Smith and her team points to important feedback loops with future increases in temperature, as longer melt seasons will stimulate biofilm communities, which alone have the capacity to increase rates of glacial melt. If temperatures continue to rise, the positive feedback between a warmer climate and lower reflectivity on ice surfaces may lead to exponentially faster rates of glacial melt and sea level rise. Overall, these findings illustrate the environment’s sensitivity to the emissions that human populations generate, suggesting that given enough pressure, Antarctic ice may enter a runaway downward spiral of rapid melting. 

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Photo Friday: The Glaciers of Antarctica

Antarctica, the world’s southernmost continent, is a hostile realm of ice and snow, fictionalized in our popular culture by the likes of H.P. Lovecraft and further romanticized by real-world scientific explorers eager to lay claim to the region.

Humans who venture to the southernmost pole do so by way of the Antarctic Peninsula, where they may visit Port Lockroy, site of a former British research station, or take in by cruise the vast terrain and wildlife of the region. Multiple countries also operate scientific camps and research programs in more remote locales of Antarctica where science teams study awe-inspiring glaciers and ice sheets throughout the year.

The largest ice sheet in the world, Antarctica is composed of around 98% continental ice and 2% barren rock. The ancient ice is incredibly thick, although it has been thinning due to the effects of climate change.

Cotton Glacier flows eastward between Sperm Bluff and Queer Mountain in Victoria Land (Source: Kelly Speelman/National Science Foundation).
Cotton Glacier in Victoria Land (Source: Kelly Speelman/National Science Foundation).

Several nations have made overlapping claims to the Antarctic continent. The Antarctic Treaty, signed in Washington in 1959, attempts to maintain peace, by neither denying or providing recognition to these territorial claims. Today, a total of 53 countries have signed the treaty, including Argentina, Australia, Chile, France, New Zealand, Norway and the United Kingdom, countries that have all made specific claims in the region. The United States and Russia, meanwhile, have maintained a “basis of claim” in the region. Scientists of these nations conduct field research from Antarctica bases to gather greater knowledge about climatic changes affecting the larger world.

The Transantarctic Mountains, glaciers and crevasse fields (Source: Corey Anthony/National Science Foundation).
The Transantarctic Mountains, glaciers and crevasse fields (Source: Corey Anthony/National Science Foundation).

Studying glaciers in Antarctica is of great impact due to the influence of melting glaciers on global sea levels. In addition, Antarctica plays a primary role in the world’s climate. According to Antarcticglaciers.org, “Cold water is formed in Antarctica. Because freshwater ice at the surface freezes onto icebergs, this water is not only cold, it is salty. This cold, dense, salty water sinks to the sea floor, and drives the global ocean currents, being replaced with warmer surface waters from the equatorial regions.”

The Transantarctic Mountains, glaciers and crevasse fields (Source: Corey Anthony/National Science Foundation)
The Transantarctic Mountains, glaciers and crevasse fields (Source: Corey Anthony/National Science Foundation).

Ice sheets in Antarctica are fragile and a number have recently collapsed, causing glacial thinning and threatening a rise in sea levels. Some scientists are concerned that the collapsing ice sheets may not be just a natural occurrence but one more closely linked to a warming planet.

A Tucker tractor has been drifted over at Pine Island Glacier (Source: August Allen/National Science Foundation).
A Tucker tractor has been drifted over at Pine Island Glacier (Source: August Allen/National Science Foundation).

The Pine Island Glacier is one of the “fastest receding glaciers in the Antarctic” and a major contributor to our rising sea levels, according to the U.S. Antarctic Program. Scientists have observed an ice shelf on the Pine Island Glacier that is rapidly thinning, pushing the glacier toward the sea.

A black and white aerial view of Pine Island Glacier Ice Shelf shows its heavily crevassed surface (Source: August Allen/National Science Foundation)
A black and white aerial view of Pine Island Glacier Ice Shelf shows its heavily crevassed surface (Source: August Allen/National Science Foundation).

A team of scientists constructed a field camp in 2012-2013 to study the impacts of climate change on the glacier, also known as PIG.

The first tent erected at the main field camp on Pine Island Glacier (Source: August Allen/National Science Foundation).
The first tent erected at the main field camp on Pine Island Glacier (Source: August Allen/National Science Foundation).

The PIG field camp staff learned to contend with adverse weather conditions in the area and events like windstorms, a common occurrence in this remote and hostile part of the world.

Pine Island Glacier field camp staff attempt to excavate a mountain tent that collapsed during a wind storm (Source: August Allen/National Science Foundation).
Pine Island Glacier field camp staff attempt to excavate a mountain tent that collapsed during a wind storm (Source: August Allen/National Science Foundation).

Helicopters provide support to field projects such as the one conducted in 2012-2013 at the Pine Island Glacier.

(Source: August Allen/ National Science Foundation).
A helicopter is unloaded from an LC-130 at the Pine Island Glacier field project (Source: August Allen/ National Science Foundation).

Elsewhere in Antarctica is the McMurdo Dry Valleys, the largest ice-free area in the region—approximately 15,000-square-kilometers— where science teams perform research projects on glaciers, lakes, and soils, funded by the National Science Foundation. The area is an extreme landscape, but it can also be a useful environment for scientists hoping to study the impacts of climate change.

A glacier pool in the McMurdo Dry Valleys, Antarctica (Source: Peter Rejcek.
A glacier pool in the McMurdo Dry Valleys, Antarctica (Source: Peter Rejcek/National Science Foundation).

In Antarctica, teams of scientists can extract old ice flowing from the ends of glaciers in large quantities rather than by drilling directly into the ancient ice sheet. Around 350 kilograms of ice is then melted into a vacuum-sealed container to capture around 35 liters of ancient air. The ancient air was preserved by the ice for thousands of years. Scientists hope to research the ancient air and examine the impact of methane gas on past climate change, according to the U.S. Antarctic Program.

Scientist Vasilii Petrenko loads an ice melter at Taylor Glacier (Source: Vasilii Petrenko/National Science Foundation).
Scientist Vasilii Petrenko loads an ice melter at Taylor Glacier (Source: Vasilii Petrenko/National Science Foundation).
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Photo Friday: The Dry Valleys of Antarctica

The National Snow and Ice Data Center (NSIDC) houses an excellent Glacier Photograph Collection, including a special collection of photos of the McMurdo Dry Valleys, a row of snow-free valleys in Antartica. However, that doesn’t stop from glaciers from entering into the picture.

About dry valleys and the MucMurdo Dry Valley photo collection, the NSIDC comments:

“While the valleys themselves are notably ice-free, a number of glaciers terminate in the valleys, some acting as outlets to the East Antarctic Ice Sheet. Studies show that the majority of the glaciers in this area are receding. Glaciers were photographed in the course of geologic studies and help document the conditions of the glaciers and how they may have changed.”

Enjoy some of the photos below.

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To view the rest of the collection, click here.

Many thanks to NSIDC and its Glacier Photograph Collection for the use of these photos. These photos are held by the Data Conservancy at Johns Hopkins University.  Please contact Keith Kaneda for further questions about the collection.

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